WO2025091036A1 - Systems and methods for self-healing power converters - Google Patents

Abstract

Disclosed are self-healing power converter systems and methods including a plurality of converter phase-legs and a control system. The plurality of converter phase-legs include a first converter phase-leg and a second converter phase-leg, each converter phase-leg including a plurality of power converter modules, each power converter module including power switching elements. The control system includes a central controller, a first local controller to control the first converter phase-leg, and a second local controller configured to control the second converter phase-leg. The control system detects a fault with a first power converter module of the plurality of power converter modules of the first phase-leg. In response to detecting the fault, the control system disables a second power converter module of the plurality of power converter modules of the second phase-leg, and continues to drive at least one power converter module of each of the first phase-leg and the second phase-leg.

Description

SYSTEMS AND METHODS FOR SELF-HEALING POWER CONVERTERS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63/593,923, filed on October 27, 2023, titled “SYSTEMS AND METHODS FOR SELF-HEALING POWER CONVERTERS,” which is hereby incorporated by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

[0002] Not applicable.

BACKGROUND

[0003] Power converters of various types have been produced and used in many industries and contexts. Example power converters include alternating current (AC) to direct current (DC) rectifiers, DC to AC inverters, and DC to DC converters. AC to DC rectifiers, also referred to as AC/DC rectifiers, convert AC power to DC power. DC to AC inverters, also referred to as DC/AC inverters, convert DC power to AC power. Power converters can be used for various purposes, such as rectifying AC power from an AC grid power source to DC power for charging a battery, or inverting DC power from a battery to AC power to drive a motor or supply AC power to an AC grid. Further, power converters can be used in various contexts, such as in or connected to an electric vehicle, an engine generator, solar panels, and the like.

SUMMARY

[0004] Power converters may experience faults or failures for various reasons. When such faults are experienced by a power converter, whether at the device level or converter level, the entire power converter may fail and/or be disabled, negatively impacting at least reliability of the power converter.

[0005] Some embodiments disclosed herein address these or other issues. For example, some embodiments disclosed herein are directed to self-healing power converters and methods of power conversion with self-healing power converters that improve reliability of energy conversion systems. The self-healing power converters may use an architecture composed of scalable power modules for each phase and with local regulation for each phase. A self-healing operation enables the self-healing power converters to maintain power operation when power converter modules experience a fault. Thus, the self-healing function can improve reliability.

[0006] In one embodiment, a self-healing power converter system is provided. The system comprises a plurality of converter phase-legs including a first converter phase-leg and a second converter phase-leg, each converter phase-leg including a plurality of power converter modules, each power converter module including power switching elements; and a control system including a central controller, a first local controller configured to control the first converter phase-leg, and a second local controller configured to control the second converter phase-leg. The control system is configured to: detect a fault with a first power converter module of the plurality of power converter modules of the first converter phase-leg; in response to detecting the fault, disabling a second power converter module of the plurality of power converter modules of the second converter phase-leg; and drive, while the second power converter module is disabled, at least one power converter module of each of the first converter phase-leg and the second converter phaseleg to provide output power.

[0007] In one embodiment, a method of power conversion with self-healing power converter is provided. The method comprises driving, by a control system, a plurality of converter phase-legs including a first converter phase-leg and a second converter phase-leg, each converter phase-leg including a plurality of power converter modules, each power converter module including power switching elements; detecting, by the control system, a fault with a first power converter module of the plurality of power converter modules of the first converter phase-leg; and disabling, in response to detecting the fault, a second power converter module of the plurality of power converter modules of the second converter phase-leg; and driving, while the second power converter module is disabled, at least one power converter module of each of the first converter phase-leg and the second converter phase-leg to provide output power.

[0008] The foregoing and other aspects and advantages of the present disclosure will appear from the following description. In the description, reference is made to the accompanying drawings that form a part hereof, and in which there is shown by way of illustration one or more embodiment. These embodiments do not necessarily represent the full scope of the invention, however, and reference is therefore made to the claims and herein for interpreting the scope of the invention. Like reference numerals will be used to refer to like parts from Figure to Figure in the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 illustrates a power converter system according to some embodiments.

[0010] FIGS. 2A-2B illustrate example configurations of the power converter system of FIG. 1.

[0011] FIGS. 3 A-3B illustrate control system diagrams implemented by a power converter (e.g., the power converter of FIG. 1, FIG. 2A, or FIG. 2B), according to some embodiments.

[0012] FIG. 4 illustrates an example of a half-bridge converter, according to some embodiments.

[0013] FIGS. 5A-5J illustrate a operational states of self-healing power converters, according to some embodiments.

[0014] FIG. 6 illustrates a method for self-healing power conversion, according to some embodiments.

[0015] FIG. 7 illustrates a diagram of a self-healing power converter system (e.g., the power converter system of FIG. 1 or power converter of FIG. 2), according to some embodiments. [0016] FIGS. 8A and 8B show waveforms of a self-healing operation by a single-phase grid-connected power converter, according to some embodiments.

[0017] FIG. 9 shows waveforms of an example of a self-healing power converter.

[0018] FIG. 10 shows waveforms that demonstrate transient performance of a self-healing power converter system with a grid side current reference step and using local model predictive control (MPC).

DETAILED DESCRIPTION

[0019] One or more embodiments are described and illustrated in the following description and accompanying drawings. These embodiments are not limited to the specific details provided herein and may be modified in various ways. Furthermore, other embodiments may exist that are not described herein. Also, functions performed by multiple components may be consolidated and performed by a single component. Similarly, the functions described herein as being performed by one component may be performed by multiple components in a distributed manner. Additionally, a component described as performing particular functionality may also perform additional functionality not described herein. For example, a device or structure that is “configured” in a certain way is configured in at least that way, but may also be configured in ways that are not listed.

[0020] As used in the present application, “non-transitory computer-readable medium” comprises all computer-readable media but does not consist of a transitory, propagating signal. Accordingly, non-transitory computer-readable medium may include, for example, a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a ROM (Read Only Memory), a RAM (Random Access Memory), register memory, a processor cache, or any combination thereof. [0021] In addition, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. For example, the use of “comprising,” “including,” “containing,” “having,” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Additionally, the terms “connected” and “coupled” are used broadly and encompass both direct and indirect connecting and coupling, and may refer to physical or electrical connections or couplings. Furthermore, the phase "and/or" used with two or more items is intended to cover the items individually and both items together. For example, “a and/or b" is intended to cover: a (and not b); b (and not a); and a and b.

[0022] Power converters may be described in terms of power conversion efficiency, power density, and cost, among other characteristics. Generally, it is desirable to have power converters with higher power efficiency, higher power density, and lower cost. A highly efficient power converter is able to convert power (e g., AC to DC, DC to AC, and/or DC to DC) without significant losses in energy. A low efficiency power converter experiences higher losses in energy during the power conversion. Such energy losses may manifest as heat generated by the power converter while converting power, for example. Power efficiency for a power converter, inductor, or other electronic component may be expressed as a percentage between 0 and 100% and determined based on the power input to the component and the power output from the component

Power Out using the equation: Power Efficiency — _{power In} ■ A power converter with high power density has a high ratio of power output by the power converter compared to the physical space occupied by the power converter. The power density can be calculated using the equation:

Power Out

Power Density

Volume of Power Converter [0023] Energy costs, including monetary costs and environmental costs, continue to be an important factor across many industries that incorporate power converters. Accordingly, even slight increases (e.g., of tenths of a percent) in power efficiency for a power converter can be significant and highly desirable. Similarly, reductions in materials and size of power converters can be significant and highly desirable, allowing reductions in costs and physical space to accommodate power converters in systems that incorporate power converters.

[0024] Safety and reliability are additional factors that can be important to power converters, particularly as the demand for high power electrified loads and sources are increasing. For example, renewable energy interfaced micro-grid systems are becoming popular energy unit to satisfy either residential or small-scale industrial loads. A renewable energy interfaced microgrid may use one or more different types of renewable sources, such as, for example, solar energy, wind power, and/or battery storage. These various types of renewable energy may be collected in a distributed way and then lumped together with corresponding power converters to be connected back to the grid. Even though the power of an individual energy resource may not be high, the lumped power on the point of common coupling (PCC) can be large. Power converters are also increasing in use in the growing electric vehicle market, for example, to charge electric vehicle batteries. In this setting, the faster of the charging period, the higher the power demand by the EV chargers. These examples suggest rising current ratings and/or voltage ratings of power converters to meet demands. Meanwhile, as current and/or voltage ratings rise, system temperatures and heat dissipation to avoid power failure or faults can increase.

[0025] Power converters may experience faults or failures for various reasons. At a device level, for example, power switching elements or other components of a converter may experience faults due to high (above-rated) voltage, current, frequency, or temperature. At a converter level, faults may arise due to open or short circuits in certain phases, filtering components, or low power areas, or due to high (above-rated) voltage, current, frequency, or temperature (at a converter level). When such faults are experienced by a power converter, whether at the device level or converter level, the entire power converter may fail and/or be disabled, negatively impacting at least reliability of the power converter.

[0026] Some embodiments disclosed herein address these or other issues. For example, some embodiments disclosed herein are directed to self-healing power converters and methods of power conversion with self-healing power converters that improve reliability of energy conversion systems. The self-healing power converters may use an architecture composed of scalable power modules for each phase and with model predictive control (MPC) regulation for each module. The power modules are scalable in that a different number of the power modules can be connected in parallel with the local model predictive control (MPC) for each module to stabilize the output voltage and attenuate the circulating current among different modules. A central-local-level control strategy may be used to manage the self-healing power converter system. Specifically, a central level controller may be responsible for regulating lumped output current (e.g., idq), attenuating the circulating current, and generating target references for the MPC control of each local power module. The self-healing function enables the self-healing power converters to maintain power operation when power converter modules experience fault. Thus, the self-healing function can improve reliability. Additionally, by disabling one or more power converter modules to self-heal and to continue operation after a fault, the power converter may be balanced across phase-legs, enabling simpler controls of the power converter and also operation at a higher efficiency (e.g., because of operation at closer to rated levels).

[0027] FIG. 1 illustrates a power converter system 100 in accordance with some embodiments. The power converter system 100 includes a control system 105, a first direct current (DC) load/source 110, a power converter 115, a second source/load 130, and one or more sensors 140. The control system 105 includes a central controller 150 with an electronic processor 155 and a memory 157 and one or more local controllers 160, each having an electronic processor 165 and a memory 167. The power converter system 100, as well as the other power converter systems provided herein, may be non-isolated power converter systems. That is, the power converter system may be coupled to an AC source (e.g., single- or three-phase power grid) or AC load (e.g., single or 3-phase motor) without a transformer. Use of a transformer is common in electrical circuits to provide isolation between the power converter and an AC source or load. However, such a transformer can add inefficiencies and size or volume to the power converter. Accordingly, some examples of the power converter systems provided herein are non-isolated, also referred to as transformerless, to increase efficiency and/or reduce size of the power converter systems. Because the power converters are provided without isolation by a transformer, the power converters may include additional features to prevent transmission of unwanted signals or current (e.g., leakage current) from passing between the power converters and other circuit components (e.g., DC sources, DC loads, AC sources, AC loads, and other structures in contact with or supporting the power converters). These additional features may include LC filters, zero-sequence control of common mode voltage, harmonic injection, model predictive control, variable frequency critical soft switching, and the like. However, in other examples of the power converter systems described herein, the power converter system is isolated and may be coupled to an AC source (e.g., single- or three-phase power grid) or AC load (e.g., single or 3-phase motor) with a transformer.

[0028] In operation, generally, the control system 105 controls power switching elements of the power converter 115 with control signaling (e.g., pulse-width modulated (PWM) signals) to convert power (i) from the DC load/source 110 functioning as a source to the second source/load 130 functioning as a load, or (ii) from the second source/load 130 functioning as a source to the DC load/source 110 functioning as a load. Accordingly, when the DC load/source 110 is functioning as a source for the power converter 115, the second source/load 130 is functioning as a load for the power converter 115. Conversely, when the DC load/source 110 is functioning as a load for the power converter 115, the second source/load 130 is functioning as a source for the power converter 115.

[0029] The DC load/source 110 may be a direct power (DC) load, a DC source, or both a DC load and DC source (i.e., functioning as DC source in some instances and as a DC load in other instances, depending on the mode of the power converter 115). In some examples, the DC load/source 110 is a battery. In other examples, DC load/source 110 may be a capacitor, an ultracapacitor, a DC power supply from rectified AC source (e.g., AC grid power converted to DC power by diode bridge rectifier), or the like. The second source/load 130 may be an AC load, an AC source, both an AC load and AC source (i.e., functioning as an AC source in some instances and as an AC load in other instances, depending on the mode of the power converter 115), a DC load, a DC source, both a DC load and DC source (i.e., functioning as a DC source in some instances and as a DC load in other instances, depending on the mode of the power converter 115). In some examples, the source/load 130 may be an electric (AC) motor, an AC generator, AC power supply grid, a DC battery, a DC capacitor, a DC ultracapacitor, a DC power supply from rectified AC source (e.g., AC grid power converted to DC power by diode bridge rectifier), or the like.

[0030] The DC load/source 110 is coupled to the power converter 115 at a first (DC) side or section of the power converter 115, and the second source/load 130 is coupled to the power converter 115 at a second (AC) side or section of the power converter 115. The first side may also be referred to as an input side or an output side of the power converter 115, depending on the mode of the power converter, or as a DC side of the power converter 115. The second side may also be referred to as an input side or an output side of the power converter, depending on the mode of the power converter, or as an AC side of the power converter 115. In some embodiments, the second side of the power converter 115 may be an AC side having single phase AC power, three-phase AC power, or AC power with another number of phases.

[0031] In some embodiments, the power converter 115 operates with a high DC voltage level. For example, in operation, the DC side of the power converter 115 has a DC voltage (e.g., across input terminals of the power converter 115) of at least 200 V, at least 600 V, at least 800 V, at least 1000 V, at least 1200 V, between 200 V and 1200 V, between 600 V and 1200 V, between 800 V and 1200 V, or another range. Such high DC voltage levels may be desirable in some contexts, such as some electric vehicles. For example, some current electric vehicles (e.g., passenger vehicles and hybrid electric vehicles) operate with a DC bus voltage of between about 200 V and 400 V. This DC bus voltage for passenger electric vehicle may increase in the future. Further, some current electric vehicles (e.g., class 4-8, off-road, or otherwise larger electric vehicles) can operate with a DC bus voltage of more than 1000 V. However, high DC voltage levels may introduce challenges into a typical power converter system, such as an increase in leakage currents, increases in common mode voltage, higher rates of change in common mode voltage, and the like. These challenges can lead to resonance on an LC fdter, shaft voltages, excessive bearing currents (e.g., from discharge events when lubricant dielectric breakdown occurs) that can result in bearing failures, excessive motor shaft currents, excessive motor winding currents (e.g., insulation may be damaged), and excessive geartrain currents (e.g., bearing currents can propagate into the gear train via electromagnetic interference (EMI) or noise, vibration, harshness (NVH) resulting from the damaged bearing race walls). Embodiments described herein, however, can mitigate such challenges through improved LC filters and through control techniques including control techniques that use harmonic injection, cascaded controllers, MPC control, and/or variable frequency critical soft switching (VFCSS).

[0032] The sensor(s) 140 include, for example, one or more current sensors and/or one or more a voltage sensors. For example, the sensor(s) 140 may include a respective current sensor and/or voltage sensor to monitor a current and/or voltage of one or more of the DC load source 110, each phase of the second source/load 130, or other nodes or components of the power converter 115. In some embodiments, additional or fewer sensors 140 are included in the system 100. For example, the sensors 140 may also include one or more vibration sensors, temperature sensors, and the like. In some examples, the control system 105 infers a characteristic (e.g., current or voltage) of the power converter 115, rather than directly sensing the characteristic. The sensor(s) 140 may provide sensor data to the control system 105 indicative of the sensed characteristics of the system 100. Such sensor data may, accordingly, indicate electrical operational characteristics of the system 100. In some examples, the control system 105 infers or estimates a characteristic (e.g., current or voltage) at one or more nodes of the power converter 115 based on the sensor data of a sensor 140 that senses a different type of characteristic or even a different component, rather than directly sensing the characteristic.

[0033] The input-output (I/O) interface 142 includes or is configured to receive input from one or more inputs (e.g., one or more buttons, switches, touch screen, keyboard, and the like), and/or includes or is configured to provide output to one or more outputs (e.g., LEDs, display screen, speakers, tactile generator, and the like). Other electronic devices and/or users may communicate with the system 100 and, in particular, the control system 105, via the I/O interface 142. For example, the control system 105 may receive commands (e.g., from a user or another device) for the power converter system 100 indicating a target torque, target speed, target power level, conversion type, or the like. The control system 105, in response, may drive the power converter 115 to achieve the target and/or conversion type indicated by the command.

[0034] The control system 105 generally monitors the system 100 including the power converter 115 (e.g., based on sensor data from the sensor(s) 140), receives commands (e.g., via the input/output interface 142), and controls the power switching elements of the power converter 115 with control signaling (e.g., pulse-width modulated (PWM) signals) to convert power (e.g., in accordance with the sensor data and/or the commands). In some embodiments, the control system 105 includes a controller (e.g., the central controller 150) that performs this monitoring and control without additional local controllers. In other embodiments, the control system 105 is a cascaded control system including a central controller 150 and one or more local controllers 160. The cascaded control system may communicate in real time (e.g., each control cycle) monitoring information (e.g., sensor data) and control information between the central controller 150 and the one or more local controller 160. In some examples, the local controlled s) 160 each implement model predictive control (MPC) or another regulation control scheme (e.g., PID control, PI control, or the like). Tn some examples, the central controller implements a non-MPC regulation technique, such as proportional integral derivative (PID) control or proportional integral (PI) control.

[0035] Each controller of the control system 105, including the central controller 150 and the local controllers 160, is an electronic controller that may include an electronic processor. Such an electronic controller may further include a memory (e.g., the memory 157 or 167). The memory is, for example, one or more of a read only memory (ROM), random access memory (RAM), or other non-transitory computer-readable media. The electronic processor 155, 165 may be configured to, among other things, receive instructions and data from the memory 157, 167 and execute the instructions to, for example, carry out the functionality of the associated controller described herein, including the processes described herein. For example, the memory may include control software. In some embodiments, instead of or in addition to executing software from the memory to carry out the functionality of the controller described herein, the electronic processor includes one or more hardware circuit elements configured to perform some or all of this functionality. In some examples, the electronic processor is implemented as one or more of an FPGA (field programmable gate array), an ASIC (application specific integrated circuit), a complex programmable logic device (CPLD), a DSP processor, a graphics processing unit (GPU), application processing unit (APU), or the like. Additionally, although a particular controller, electronic processor, and memory may be referred to as a respective, single unit herein, in some embodiments, one or more of these components is a distributed component. For example, in some embodiments, an electronic processor includes one or more microprocessors and/or hardware circuit elements.

[0036] FIGS. 2A and 2B illustrate example configurations of the power converter system 100, identified as power converters 200 and 250, respectively. In other examples, the power converter system 100 is implemented in another configuration. In FIGS. 2A and 2B, the DC source 110, sensors 140, and input/output 145 are not illustrated to simplify the diagrams. In FIG. 2A, the power converter 200 is a full-bridge single phase converter. The power converter 200 includes a central controller 150, two local controllers 160, and a self-healing power converter 115. In this example, the self-healing power converter 115 includes two scalable power converter modules 205 (also referred to as scalable power converter circuits 205). In some examples, each scalable power converter module 205 includes a half-bridge single phase converter circuit (see, e.g., FIG. 4 coupled to a respective terminal of a (single phase) AC load 130. One of the scalable power converter modules 205 may be driven to output an AC signal that is 180 degrees out of phase with respect to the other scalable power converter module 205.

[0037] In FIG. 2B, the power converter 250 is a three-phase converter. The power converter 250 includes a central controller 150, three local controllers 160, and a self-healing power converter 115. In this example, the self-healing power converter 115 includes three scalable power converter modules 205. In some examples, each scalable power converter module 205 includes a half-bridge single phase converter circuit (see, e.g., FIG. 4 coupled to a respective phaseleg 130a, 130b, 130c of a (three-phase) AC load 130). Each of the scalable power converter modules 205 may be driven to output an AC signal that is 120 degrees out of phase with respect to the other scalable power converter modules 205.

[0038] FIG. 3A-3B illustrate control system diagrams for a converter system 300. The converter system 300 may be an example of, for example, the power converter system 100, the power converter 200, the power converter 220, and/or the power converter 250.

[0039] FIG. 3 A illustrates a converter system 300 including a central controller 150, three local controllers 160a, 160b, 160c (each being an instance of the local controller 160 previously introduced), and scalable power converter modules 205a, 205b, and 205c (each being an instance of the scalable power converter module 205 previously introduced). The local controllers 160a-c may be referred to generically as the local controllers 160 or each local controller 160. The scalable power converter modules 205a-c may be referred to generically as the scalable power converter modules 205 or each scalable power converter module 205. When implemented by the power converter 200 (full bridge, single phase), the converter system 300 may include the local controllers 160a and 160b and the scalable power converter modules 205a and 205b, while the remaining dashed components of the converter system 300 (local controller 160c and module 205c) may not be present. When implemented by the power converter 250 (three-phase), the converter system 300 may include the local controllers 160a, 160b, and 160c and the scalable power converter modules 205a, 205b, and 205c.

[0040] The diagram of FIG. 3 A illustrates communications between the components of the converter system 300 during operation (e.g., when a power converter utilizing the converter system 300 is operating to convert power). As illustrated, each scalable power converter module 205 provides sensor data to a respective local controller 160. The scalable power converter module 205 may have incorporated therein one or more sensors of the previously described sensors 140 (see FIG. 1). In some examples, the sensor data includes one or more of inductor current for an LC fdter of the module 205, capacitor voltage for a capacitor of the LC fdter of the module 205, output current output by the LC filter of the module 205, and/or temperature indicating temperature of or surrounding one or more components of the scalable power converter 205 (e.g., a power switching element, capacitor, inductor, etc.). Each local controller 160 further provides the sensor data to the central controller 150. Accordingly, the central controller 150 receives sensor data for each scalable power converter module 205 present in the converter system 300. The central controller 150, in turn, generates a reference target for each local controller 160. The reference target is specific to each local controller 160.

[0041] The central controller 150 may be, for example, a PID controller that generates the reference target(s) based on the sensor data received and an overall power demand or command (e g., received via I/O interface 142 or a memory). In some examples, the central controller 150 includes a grid current controller block 302 that translates the sensor data from a stationary reference frame (e.g., abc reference frame) to a rotational reference frame (e.g., a direct-quadrature (DQ or DQ0) reference frame). For example, the controller block 302 may translate, via translator 304, grid current (i_g) provided as sensor data (e.g., Sensor Dataa,b,c) from i_g,abc to i_g,dq. To translate, the translator 304 may use Park and Clarke transformations. The central controller 150 may then generate reference targets for each leg of the rotational reference frame (e.g., a voltage target for the D component, a voltage target for the Q component, a voltage target for the 0 (zero) component)). The reference targets may be set based on the sensed values (i.e., values indicated by sensor data) relative to desired values for these characteristics to cause the sensed values to approach the desired values (e.g., using PID techniques). For example, a regulator 306 may receive the grid current (i_g,d_q) and a command (e.g., a current command in the DQ reference frame received from a memory or the I/O interface 142), and may output a voltage target (v_c,dq)to cause the grid current to approach the current command. The voltage target (v_e,dq) may be referred to as a global reference target. The controller block 302 may output the voltage target in the stationary reference frame by translating, via translator 308, the voltage target from the rotational reference frame to the stationary reference frame (e.g., v_c,d_q to v_c,abc). The translator 308 may translate from the DQ0 reference frame to the stationary (abc) reference frame using Park and Clark inverse transformations. The voltage targets in the stationary reference frame may be referred to as local reference targets. [0042] In some examples, the central controller 150 includes zero-sequence control. For example. The central controller 150 may include a zero-sequence control block 310 where the zero sequence (0-axis of the DQ0 reference frame) is set to half a DC link voltage to control leakage current in the system. In some embodiments, the central controller further injects a harmonic eO* (e.g., a sinusoidal or triangular wave voltage signal as a harmonic injection) into the 0 component (e.g., summed with the half DC link voltage). The harmonic may be a 3^rd order harmonic of the fundamental frequency of an output AC signal or AC grid to which the converter is coupled. The central controller 150 may then, via a reference generation block 312, add the zero sequence component (v_c,o*) to the voltage targets (v_c_abc). In other examples, the zero sequence component may be provided to the translator 308 as the zero sequence component (v_e,o*) of the voltage target in the rotational DQ0 reference frame that is translated to the voltage target in the stationary (abc) reference frame (v_c abc).

[0043] The central controller 150 may then generate and output a reference target (Ref) for each local controller 160 present in the converter system 300 (e.g., Refa, Refb, Refc to the local controllers 160a, 160b, 160c). For example, Refa may be set to v_c,a*, Refb may be set to v_c,b*, and Refc may be set to v_c,c* as output by the reference generation block 312 or as output by the current control block 302. In examples in which three phases are not present (e.g., full bridge, single phase), the “c” components of the grid current (i_g,_c) and target voltage (v_g,c) may be omitted from the central controller reference generation process described with respect to FIG. 3A.

[0044] As described with respect to FIG. 3 A, the reference target is a voltage value for the voltage across a capacitor of an LC filter of the scalable power converter module 205. In other examples, the reference target is another electrical characteristic of the scalable power converter module 205 (e.g., another voltage or a current target).

[0045] Each local controller 160 receives the corresponding reference target from the central controller 150. Each local controller 160, in turn, generates control signals, based on the received reference target, for controlling the corresponding scalable power converter module 205. By generating appropriate control signals, each local controller 160 may thereby regulate the electrical characteristic of the reference target (e.g., capacitor voltage) to approach the value indicated by the reference target. [0046] Turning to FIG. 3B, a more detailed diagram 320 of the local controller 160a and the scalable power converter module 205a is provided. The diagram similarly applies to the other local controllers 160b and 160c and scalable power converter modules 205b and 205c.

[0047] As illustrated, the local controller 160a includes the electronic processor 165 and a gate driver 330; the scalable power converter modules 205a each include a switching circuit 335 and are associated with sensors 340. The scalable power converter modules 205a include N modules, where N is an integer that is greater than or equal to two. With reference to FIG. 3B, the scalable power converter modules 205a are individually identified as scalable power converter modules 205a-l, 205a-2, 205a-3, ... 205a-N. Generally, the more modules (i.e., the greater the value of N), the higher the output current may be by the power converter system (i.e., the higher the output current rating)., Additionally, generally, the more modules (i.e., the greater the value of N), the more resilient the power converter system may be because, as explained further, more power modules may experience faults or be disabled and the system may continue to operate via the self-healing capabilities described herein.

[0048] In operation, the electronic processor 165 receives the reference target (Refa) from the central controller 150 and sensor data 345 (Sensor Data_a) from the sensors 340. The sensor data 345 may be as previously described with respect to FIG. 3A. From the reference target and sensor data, the electronic processor 165 determines a duty cycle reference (d_a*) and a switching frequency (fsw).

[0049] The gate driver 330 receives the duty cycle reference (d_a*) and the switching frequency (fsw) and generates variable frequency soft switching (VFSS) control signals 350. The VFSS control signals 350 may include, for each scalable power converter module 205a, a first pulse width modulated (PWM) signal having a frequency equal to the switching frequency (fsw) and a duty cycle equal to the duty cycle reference (d_a*) and a second PWM signal that is an inversion of first PWM signal. Although inverter gates that provide the control signals 350 are shown external to the gate driver 330 in FIG. 3B, the inverter gates may be internal to the gate driver 330 and/or may represent virtual inverter gates where the gate driver 330 produces an inverted signal through control techniques without a separate hardware inverter gate.

[0050] Each noninverted and inverted signal pair of the VFSS control signal 350 controls the switching of a pair of power switching elements of a respective switching circuit 335. In some examples, the switching frequency (fsw) is varied during operation such that each pair of power switching elements is controlled to soft switch (zero voltage switching). By soft switching, the converter may reduce switching losses and increase conversion efficiency. In some examples, current ripple through an inductor of an LC filter of the switching circuit 335 should or must be above a certain minimum threshold to enable soft switching. The amplitude of current ripple may vary according to switching frequency, where the higher the switching frequency, the smaller the current ripple. Accordingly, in some examples, the local controller may determine the largest switching frequency (fsw) that will still enable soft switching, potentially limited by a maximum switching frequency associated with high switching loss. Generally, the duty cycle of the PWM control signals controls the output voltage of the converter, while frequency does not. Accordingly, the duty cycle may be determined based on the desired voltage conversion ratio to achieve the desired output voltage, while the frequency may be used to adjust current ripple (and thereby achieve soft switching).

[0051] To generate the duty cycle reference (da*) from the reference target and sensor data, the local controller 160a (e.g., via the electronic processor 165) may implement model predictive control (MPC). As used herein, MPC can refer to a control algorithm that relies on or is aware of a system dynamic (e.g., implements or uses a dynamic model representing the converter under control) and predicts, through computation based on electrical characteristics of the converter and the dynamic model, input commands or reference values to control the system's behavior. Accordingly, MPC, as used herein, may refer to a model predictive control algorithm in a stricter use of the term (such as described in further detail below) as well as other dynamic prediction algorithms (e.g., a linear-quadratic regulator (LQR) control algorithm).

[0052] In one example, to implement the MPC algorithm, the electronic processor 165 may, in each control period, solve a cost function using the electrical characteristics and the control reference target for that phase. By solving the cost function, the electronic processor 165 can predict future steps of control signaling to actuate the power switching elements to control power on that phase of an AC voltage section of the power converter to trend towards the control reference target. The electronic processor 165 may then generate the control signaling for that particular phase based on a first step of the future steps of control signals. Accordingly, in contrast to a PI control algorithm, the MPC algorithm derives an optimal duty cycle by processing a state variable and tracking error in a linear way with specific coefficients. Because no integration procedure is needed in MPC, the dynamic performance of MPC may be improved relative to a PI technique with less overshoot and higher tracking speed. Additionally, because MPC has higher control bandwidth, the electronic processor 165 can provide an active damping term to mitigate (reduce or eliminate) LC or LCL resonance that may otherwise be present in a filter circuit in the AC section of the power converter 115.

[0053] In some examples, to implement MPC, the electronic processor 165 receives sensor data (e.g., the inductor current, i_{L a}, lower capacitor voltage, v_Cf_iCl, grid current, i_{g a}) and the reference target (Refa). The electronic processor 165 may execute the MPC algorithm explicitly with a pre-configured piecewise affine function to generate the desired duty cycle for the per phase switching modulation. For the digital execution of the MPC algorithm, the state space equations can be configured as

[0054] The standardized matrix format can be expressed as xk+i = X_k + Bu_k + Ee_k (3) where A = [1, ~T_s/L_fs- T_s/C_f, 1], B = [T_s/L_fs; 0], E = [0; -T_s/C_f], X_k = [i_L(fc); v_cf (fc)], u_k = [v_DCd(k)] and e_k = [i_gk].

[0055] The cost function can be composed of two items

represent the weighting matrices for the tracking error and input variable terms in the cost function. In some examlpes, the weighting of Vc

v_Cf (k~) in X_k may be configured to be 100-500 times larger than other terms to track the lower output capacitor voltage references more accurately.

[0056] In other examples, the local controller 160 implements a non-MPC control technique, such as, for example, a PID control technique.

[0057] Generally, and as illustrated in FIG. 4, each pair of power switching elements includes a first transistor receiving a first (non-inverted) control signal (e.g., PWM) and a second transistor receiving an inversion of the first control signal (e.g., inverted PWM). Accordingly, during operation, when the first transistor of the pair is enabled (ON), the second transistor of the pair is disabled (OFF), and vice versa. The terms power switching element and transistor are used interchangeably herein. In some examples, the transistors may be a type of field effect transistor (FET), such as, for example, a metal oxide semiconductor (MOS) FET, silicon carbide (SiC) FET, or Gallium Nitride Transistors (GaN) FET.

[0058] FIG. 4 illustrates an example of a switching circuit that may serve as the switching circuit 335 in one or more of the scalable power converter modules 205 that may be present in a power converter (e.g., the power converter system 100, power converter 200, 250). More particularly, FIG. 4 illustrates an example of a half-bridge converter 400 that may serve as the switching circuit 335. As illustrated, the converter 400 includes DC terminals 420 (also referred to as DC nodes, DC links, DC rails, etc.) having a positive DC terminal 422 and a negative DC terminal 424. The converter 400 further includes interface terminals 425 (also referred to as interface nodes) having a positive interface terminal 427 and negative interface terminal 429. The converter 400 may be operated as a bidirectional converter or as a unidirectional converter (in either direction), depending on the configuration and control of the system in which it is implemented. Accordingly, the DC terminals 420 may be input terminals and the interface terminals 425 may be output terminals in some examples (e.g., DC/DC conversion and DC/AC inversion), and the DC terminals 420 may be output terminals and the interface terminals 425 may be input terminals in some examples (e.g., AC/DC rectification). Additionally, the interface terminals 425 may be AC input terminals (e.g., for AC/DC rectification), may be AC output terminals (e.g., for a DC/AC inverter), or may be DC output terminals (e.g., for DC/DC conversion).

[0059] The converter 400 further includes a DC link capacitor (CDC) 430, a, a high side (upper) power switching element (Ml) 435 (also referred to as upper switch or upper FET 435), a low side (lower) power switching element (M2) 440 (also referred to as lower switch or lower FET 440), a midpoint node 442 connecting a drain terminal of upper switch 435 and a source terminal of lower switch 440, and an LC filter 445.

[0060] The power switching elements 435 and 440 may be field effect transistors (FETs), each having a respective gate, source, and drain terminal. The FETs may be, for example, a MOSFET, a silicon carbide (SiC) FET, a gallium nitride (GaN) FET, among other types of FETs. [0061] The LC filter 445 includes a switch-side inductor Lsw 450, a lower capacitor CB 455, and an upper capacitor CA 415. The switch-side inductor Lsw 450 is coupled between the midpoint node 442 and a filter node 260. For example, a first end of the switch-side inductor Lsw 450 is coupled to the midpoint node 442, and a second end is coupled to the filter node 460. The lower capacitor CB 455 is coupled between the filter node 406 and the negative DC terminal 424. For example, a first end of the lower capacitor CB 455 is coupled to the filter node 460, and a second end is coupled to the negative DC terminal 424. The upper capacitor CA 415 is coupled between the filter node 460 and the positive DC terminal 422. For example, a first end of the lower capacitor CA 415 is coupled to the filter node 460, and a second end is coupled to the positive DC terminal 422.

[0062] In some examples, the LC filter 445 is an LCL filter (an LC filter with an additional inductor (L)), in which an additional (interface) inductor is coupled between the filter node 460 and the positive interface terminal 427.

[0063] The upper capacitor 415 allows for the ripple currents at both input nodes and output nodes (nodes 422, 427) of the power converter 200 to be shared. Because the ripple currents on the input nodes and the ripple currents on the output nodes have some correlation, differential mode currents of these input and output nodes can be canceled through this capacitance. This reduction in differential mode current can result in improved EMI performance and decreased total capacitor ripple current when compared with a typical half-bridge converter (e.g., when the total capacitance between the two converters is held constant). Furthermore, the reduction in total capacitor ripple current can allow for a decrease in capacitor size, for example, when capacitor ripple current drives capacitor sizing.

[0064] The converter further includes drain-source capacitors CDS 465a and 465b, each respectively coupled across one of the switches 435, 440. In particular, a first drain-source capacitor 465a is provided across a source terminal 470a and drain terminal 475a of the upper switch (Ml) 435, and a second drain-source capacitor 465b is provided across a source terminal 470b and drain terminal 475b of the lower switch (M2) 440. The drain-source capacitors (CDS) 465a-b may be generically and collectively referred to herein as drain-source capacitor(s) (CDS) 465.

[0065] The drain-source capacitors (CDS) 465 can slow a voltage rise during an ON-to- OFF transition of the switches 435 and 440. This slowed voltage rise can, in turn, reduce the switching losses of the switches 435 and 440.

[0066] In some examples of the converter 400, one or both of the upper capacitor CA 415 and the drain-source capacitors CDS are not included in the converter 400. [0067] In some examples, N instances of the power converter 400 are paralleled to serve as the scalable power converter modules 205a, N instances of the power converter 400 are paralleled to serve as the scalable power converter modules 205b, and, if a third phase is present, N instances of the power converter 400 are paralleled to serve as the scalable power converter modules 205c (see FIG. 3A). Accordingly, because the modules are paralleled, the DC link voltage across nodes 420 and DC link capacitor 430 may be shared by each of the N power converter modules of a phase-leg or all phase-legs. Additionally, because the modules are paralleled, each of the N power converter modules of a phase-leg may connect to an interface or grid node 425 via a respective LC filter 445 of that power converter module. Thus, the current output by each power converter module of a phase-leg may be summed at the interface or grid node 425. The power converter 400 is one example of a circuit that may serve as the switching circuit 335. In other examples of the converter system 300, other converter circuits are used.

[0068] FIGS. 5A-5J illustrate simplified block diagrams of examples of the self-healing power converter 115, described above, in various states of operation. As described above, the power converter 115 may include a plurality of scalable power converter modules 205. In FIGS. 5A to 5H, the power converter 115 is illustrated as a full bridge, single phase converter (see, e.g., FIG. 2A) having two phase-legs (OA and B), each with three scalable power converter modules 205. The scalable power converter modules 205 are identified in FIG. 5A-5H as associated with one of the phase-legs (OA and B) and as module #1, #2, or #3 for each phase-leg. In FIG. 5 A, the modules 205 are more particularly identified as modules 205a-l, 205a-2, and 205a-3 for the phase-leg OA and as modules 205b- 1, 205b-2, and 205b-3 for the phase-leg OB. The individual labels 205a-l, 205a-2, 205a-3, 205b-l, 205b-2, and 205b-3 similarly apply to the modules 205 of FIGS. 5B-5H, but are not individually labeled as such to simplify the diagrams. In FIGS. 51 to 5J, the power converter 115 is illustrated as a three-phase converter (see, e.g., FIG. 2B) having three phase-legs (OA, OB, and OC), each with three scalable power converter modules 205. The scalable power converter modules 205 are identified in FIG. 5I-5J as associated with one of the phase-legs (OA, OB, and OC) and as module #1, #2, or #3 for each phase-leg. In FIG. 51, the modules 205 are more particularly identified as modules 205a-l, 205a-2, and 205a-3 for the phaseleg OA, as modules 205b-l, 205b-2, and 205b-3 for the phase-leg OB, and as modules 205c-l, 205c-2, and 205c-3 for the phase-leg OC. The individual labels 205a-l, 205a-2, 205a-3, 205b-l, 205b-2, 205b-3, 205c-l, 205c-2, 205c-3 similarly apply to the modules 205 of FIG. 5J, but are not individually labeled as such to simplify the diagrams. Tn other examples, the power converter 1 15 may have more or fewer phase-legs and more or fewer scalable power converter modules 205 compared to the examples of FIGS. 5A-5J.

[0069] The block diagrams of the power converter 115 of FIGS. 5A-5J are described in conjunction with a method 600 of FIG. 6 for self-healing power conversion. That is, the block diagrams assist in illustrating the self-healing functions and operation of the self-healing power converters 115 and the self-healing power converter system 100. By self-healing, the power converter 115 (and power converter system 100 of which the power converter 115 is a part) may have increased reliability as operation may continue despite a fault in a power converter module. Additionally, by disabling one or more power converter modules to self-heal and to continue operation after a fault, the power converter 115 may be balanced across phase-legs, enabling simpler controls and operation at a higher efficiency (e.g., because of operation at closer to rated levels).

[0070] FIG. 6 illustrates a method 600 for self-healing power conversion. The method 600 is described as being carried out by the power converter system 100 and with respect to diagrams of FIGS. 5A-5J. However, in some examples, the method 600 may be implemented by another power converter system. Additionally, although the blocks of the method 600 are illustrated in a particular order, in some embodiments, one or more of the blocks may be executed partially or entirely in parallel, may be executed in a different order than illustrated in FIG. 6, or may be bypassed.

[0071] In FIG. 6, at block 605 of the method 600, a control system drives a plurality of converter phase-legs that each include a plurality of power converter modules (e.g., power converter modules 205), and each power converter module including power switching elements. The plurality of converter phase-legs may include a first converter phase-leg and a second converter phase-leg. For example, with reference to FIG. 5A and/or FIG. 5H, the first converter phase-leg may be phase QA including converter modules (or circuits) 205a-l, 205a-2, and 205a- 3, and the second converter phase-leg may be phase B including converter modules (or circuits) 205b- 1, 205b-2, and 205b-3. As previously described, each converter module 205 may include a switching circuit 335 including at least two power switching elements (see FIG. 3B). Additionally, as previously described, each switching circuit 335 may be implemented as the half-bridge converter 400 of FIG. 4. [0072] The control system driving the plurality of converter phase-legs in block 605 may be the control system 105 of FIG. 1. As previously described, the control system 105 may include a central controller 150 and local controllers 160, which may be arranged and operated as described with respect to FIGS. 2A, 2B, 3A, and/or 3B.

[0073] In some examples, for the control system 105 to drive the plurality of converter phase-legs, the central controller 150 generates a reference target for each local controller 160, where each local controller 160 is associated with one of the plurality of converter phase-legs. For example, the central controller 150 may generate reference targets Refa and Refb (or Refa, Refb, and Refc, if three-phase), for the local controllers 160a and 160b, respectively (or 160a, 160b, and 160c, respectively, if three-phase), as described above with respect to FIG. 3 A. Further, each local controller 160 may control the plurality of power converter modules of the phase-leg associated with the local controller 160 based on the respectively received reference targets. For example, with reference to FIG. 3B, the local controller 160a may generate control signals 350 to drive each power converter module 205a, and the other local controlled s) 160 may similarly generate control signals for their corresponding power converter modules 205. As described with respect to FIG. 3B, the local controllers 160 may generate the control signals 350 based on the received reference target and sensor data (e.g., from sensors 340).

[0074] FIG. 5A illustrates an example of the converter modules 205 of a first phase-leg ( A) and of a second phase-leg ( B) being driven by a control system (e.g., the control system 105), as described with respect to block 605 of FIG. 6. In some examples, the converter modules 205 of a third phase (if present) are also being driven by the control system.

[0075] Returning to FIG. 6, at block 610, the control system detects a fault with a first power converter module of the plurality of power converter modules of a first converter phase-leg. For example, with reference to FIG. 5B, the control system (e.g., the control system 105 of FIG. 1) detects a fault with power converter module #3 of phase A. As another example, with reference to FIG. 51, the control system (e.g., the control system 105 of FIG. 1) detects a fault with power converter module #3 of phase A.

[0076] The control system 105 may detect the fault based on sensor data from one or more sensors (e.g., the sensors 140 (FIG. 1) or 340 (FIG. 3B)). To detect a fault, a local controller 160 or the central controller 150 of the control system 105 may compare sensor data to a threshold. For example, the central controller may detect the fault based on a comparison of a sensed parameter value (indicated by the sensor data from sensors 140 or 340) to a threshold, where the comparison indicates that the sensed parameter value is outside of a (non-fault) parameter range. In response to the comparison indicating that a particular parameter of a particular converter module is outside of the parameter range, the control system 105 may detect the fault. For example, the control system 105 (e.g., either one of the local controllers 160 or the central controller 150) may receive a temperature from the sensors 140 or 340 indicating a temperature of the first converter module (e.g., of the first converter module overall, of an environment of the first converter module, and/or of a particular component (e.g., power switching element, capacitor, or inductor) of the first converter module). The control system 105 may compare the received temperature to a temperature threshold. When the received temperature exceeds a temperature threshold (e.g., a high or maximum temperature threshold), the control system 105 may, in response, detect the fault with the first converter module. In another example, the control system 105 may receive an electrical characteristic (e.g., a current, voltage, or power value) of the first converter module. With reference to the circuit of the converter 400 of FIG. 4, which is an example of one of the converter modules 205, the electrical characteristic may be, for example, output or grid current (i_g), capacitor voltage (v_c), or inductor current (it) through inductor Lsw). The control system 105 may compare the received electrical characteristic to one or more thresholds (e.g., an upper threshold, a lower threshold, and upper and lower threshold). When the received electrical characteristic is below a lower threshold or above an upper threshold (e.g., indicating low voltage, low current, high voltage, or high current)), the control system 105 may, in response, detect the fault with the first converter module. In some examples, the control system 105 may detect a fault with one or more converter modules using other techniques or parameters.

[0077] FIG. 5B illustrates an example of a control system detecting a fault with the converter module #3 of a first phase-leg (OA), as described with respect to block 610 of FIG. 6. FIG. 51 illustrates another example of a control system detecting a fault with the converter module #3 of a first phase-leg (QA), as described with respect to block 610 of FIG. 6.

[0078] In block 615 of FIG. 6, in response to detecting the fault with the first converter module of the first phase-leg, the control system disables a power converter module of the plurality of power converter modules of each other phase-leg of the power converter 115. For example, FIG. 5C illustrates an example of a control system (e.g., the control system 105) disabling the converter module #3 of a second phase-leg ( B), as described with respect to block 615 of FIG. 6. FIG. 5J illustrates an example of a control system (e.g., the control system 105) disabling the converter module #3 of a second phase-leg ( B) and disabling the converter module #3 of a third phase-leg ( C), as described with respect to block 615 of FIG. 6.

[0079] To disable the power converter module(s) 205, the control system 105 may configure a control signal to disable the power switching elements of the power converter module(s) that are to be disabled. For example, the central controller 150 may provide to the local controller(s) 160 of the other phase-leg(s) a command to disable a power converter module 205. In response, the local controller(s) 160 may set the duty cycle of the control signals 350 (see FIG. 3B) to zero for the power converter module(s) that are to be disabled.

[0080] In block 620, while the power converter module of each other phase-leg is disabled, the control system drives at least one power converter module of each of the phase-legs to provide output power. For example, the control system 105 may drive the enabled (non-disabled) and operational (non-faulted) power converter modules 205 of each of the phase-legs. FIG. 5C illustrates an example of a control system (e.g., the control system 105) that, while the converter module #3 of the second phase-leg ( B) is disabled, drives the converter modules #1 and #2 of both the first phase-leg ( A) and the second phase-leg (OB). Additionally, FIG. 5 J illustrates an example of a control system (e.g., the control system 105) that, while the converter module #3 of the second phase-leg (OB) is disabled, drives the converter modules #1 and #2 of the first phaseleg (OA), the second phase-leg (OB), and the third phase-leg (OC). In this example, the converter module #3 of the third phase-leg (OC) is also disabled.

[0081] In some examples, to drive the enabled (non-disabled) and operational (nonfaulted) power converter modules 205 of each of the phase-legs, the control system 105 may operate in a similar manner as described with respect to block 605, except that the disabled and faulted power converter modules 205 are not driven. Accordingly, the central controller may generate a reference target for each local controller 160, where each local controller 160 is associated with one of the plurality of converter phase-legs. For example, the central controller 150 may generate reference targets Refa and Refb (or Refa, Refb, and Refc, if three-phase), for the local controllers 160a and 160b, respectively (or 160a, 160b, and 160c, respectively, if three- phase), as described above with respect to FIG. 3A. Further, each local controller 160 may control the enabled and operational power converter modules of the phase-leg associated with the local controller 160 based on the respectively received reference targets. For example, with reference to FIG. 3B, the local controller 160a may generate control signals 350 to drive each enabled and operational power converter module 205a, and the other local controller(s) 160 may similarly generate control signals for their corresponding enabled and operational power converter modules 205. As described with respect to FIG. 3B, the local controllers 160 may generate the control signals 350 based on the received reference target and sensor data from the sensors 340 (e.g., using an MPC algorithm or another control technique).

[0082] In some examples, to drive the enabled and operational power converter modules 205 in block 620, the control system 105 determines a new reference current (I<Dnew,ref) for each converter phase-leg. To determine the new reference current, the control system 105 determines whether a total output current (Lew, ref) for the plurality of converter phase-legs exceeds a current limit (Imax). The current limit (Imax) may be the sum of current limits of each converter phase-leg (lOmax). For example, the converter 115 may be requested to provide a total output current (IOnew,ref) at each converter phase-leg (e.g., as indicated, at least indirectly, by the CMDDQ input to the regulator 306 in FIG. 3A). Additionally, each phase-leg may have a current limit (l max), which may be the sum of the current limits of each enabled and operational power converter module 205 of the phase-leg. The current limit of each power converter module 205 may be a predetermined value or threshold (e.g., a current rating) below which the power converter module 205 is expected to remain (e.g., given particular limits of components making up the power converter module 205).

[0083] In response to determining that the total output current (Lew, ref) exceeds the current limit (Imax), the control system 105 may provide reduced reference targets to the local controllers 160 corresponding to the phase-legs. For example, with reference to FIG. 3A, the control system 105 may reduce the CMDDQ input to the regulator 306, to ultimately reduce the reference targets (Refa and Refb, or Refa, Refb, and Refc) to the local controllers 160. To reduce the CMDDQ, the control system 105 may set CMDDQ input to the current limit (Imax) or may set CMDDQ input to a portion of the total output current that is based on the ratio of enabled to total power converter modules 205 of the phase-legs (e.g., Lew, ref = p*Lew,ref, where p = enabled power converter modules 205 of a phase-leg / total power converter modules 205 of the phase-leg). For example, with reference to FIG. 5C, p = 2/3.

[0084] In response to determining that the total output current (Lew, ref) does not exceed the current limit (Imax), the control system 105 may provide normal or nonreduced reference targets to the local controllers 160 corresponding to the phase-legs. For example, with reference to FIG. 3 A, the control system 105 may use the CMDDQ input to the regulator 306 as normal to produce, via the central controller 150, the reference targets (Refa and Reft, or Reft, Reft, and Reft) to the local controllers 160.

[0085] For example, with reference back to FIG. 5 A, initially, the three power converter modules of each phase are all operating to provide the rated current, I, to the output side. Accordingly, the total output current is 31 for each phase-leg. When the power failure happens to converter module #3 of <|>A (see FIG. 5B), the control system disables the converter module #3 in each phases (see FIG. 5C) and adjusts the output current to Lew for each module based on the comparison with the module output current limitation. If the remaining paralleled modules (#1 and #2) cannot maintain the same total output current 31 as before the fault, the control system 105 can reduce the total output current reference to maintain the per module output current value (e.g., Lew = p*3I). Otherwise, the control system can maintain the same total output current (e.g., Lew = 31) and the per module output current value will be increased accordingly.

[0086] The diagrams of FIGS. 5D-5H illustrate additional operational states of the power converter 115 as a full bridge, single phase converter after the block 620 of FIG. 6 is completed (e.g., after the operational state shown in FIG. 5C).

Second Fault in Phase A (FIGS. 5D to 5F)

[0087] In some examples of the method 600, the control system 105 continues to drive the power converter modules as described with respect to block 620 until, returning to block 610 (via optional dashed line path of FIG. 6), the control system 105 detects a second fault with a second power converter module of the first converter phase-leg. As illustrated in FIG. 5D, the control system (e.g., the control system 105 of FIG. 1) may detect the second fault with power converter module #2 of phase A. As another example, although not illustrated, the control system may detect a fault with power converter module #2 of phase A in a three-phase system (see, e.g., FIG. 51). The control system 105 may detect the second fault with the second power converter module using similar techniques as described above with respect to detecting the first fault with power converter module #1 of phase <t»A. For example, the control system 105 may detect the fault based on sensor data (e.g., indicating temperature or an electrical characteristic) exceeding or falling below a threshold. [0088] After detecting the second fault, the control system 105 may proceed as illustrated in FIG. 5E or as illustrated in FIG. 5F. In the example of FIG. 5E, the control system 105 proceeds by disabling another converter module of the each other phase-leg (e.g., converter module #2 of phase OB, and, if present, of phase OC). The control system 105 may disable the converter module #2 of the other phase-legs using similar techniques as described above with respect to block 615 of method 650 and disabling the converter module #3 of the phase B. Then, while the power converter module #2 and #3 of each other phase-leg is disabled, the control system 105 drives at least one power converter module of each of the phase-legs to provide output power. For example, the control system 105 may drive the enabled (non-disabled) and operational (non-faulted) power converter modules 205 of each of the phase-legs. FIG. 5E illustrates an example of a control system (e.g., the control system 105) that, while the converter module #2 and #3 of the second phase-leg ( B) are disabled, drives the converter module #1 of both the first phase-leg ( A) and the second phase-leg (OB). Additionally, in examples with three phases, the control system 105 may drive the converter module #1 of the first phase-leg ( A), the second phase-leg (OB), and the third phase-leg (OC), while the other converter modules #2 and #3 are disabled or faulted.

[0089] As an alternative to disabling a further converter module of the second phase-leg (OB), the control system 105 may control a switch network to reassign one of the power converter modules of the plurality of power converter modules of the second phase-leg to the first phase-leg. For example, with reference to FIG. 5F, a switch network 505 may interface with the outputs of the converters 205 of the phase-legs of the power converter 115. The switch network 505 may include one or more switches or relays to redirect the output of a converter module 205 of one phase-leg to be an output of another phase-leg. By controlling the switch network 505, a power converter module 205 that is enabled and operational may be reassigned to a second phase-leg to replace a faulted power converter module 205 of a first phase-leg. For example, with reference to FIG. 5F, the switch network 505 may be controlled (by control system 105) to disconnect the output of converter module #1 of the second phase-leg ( B) from a phase-leg B output node (that connects each of the converter modules of the second phase-leg OB) and to connect the output of the converter module #1 of the second phase-leg (OB) to a phase-leg OA output node (that connects each of the converter modules of the first phase-leg OA). Thus, effectively, each of the first phase-leg OA and the second phase-leg OB will have two enabled and operational power converter modules 205. In such examples, the control system 105 may also provide the control signals originally intended for converter module #2 of the first phase-leg (QA) to the reassigned converter module #1 of the second phase-leg ( B). For example, the switching network 505 may include additional switches to re-route control signals from a local controller 160 associated with the first phase-leg (QA) to the converter module #1 of the second phase-leg (OB). The control system 105 may then continue to drive at least one power converter module of the first phase-leg (e.g., converter modules #1 originally of phase-leg OA and converter module #2 originally of phase-leg OB) and of the second phase-leg (e.g., converter modules #2 and 3 originally of phaseleg OB).

Second Fault in Phase OB (FIGS. 5G-5H)

[0090] In some examples of the method 600, the control system 105 continues to drive the power converter modules as described with respect to block 620 until, returning to block 610 (via optional dashed line path of FIG. 6), the control system 105 detects a second fault with a power converter module of the second converter phase-leg ( B). As illustrated in FIG. 5G, the control system (e.g., the control system 105 of FIG. 1) may detect the second fault with power converter module #2 of phase QB. The control system 105 may detect the second fault with the power converter module using similar techniques as described above with respect to detecting the first fault with power converter module #1 of phase QA. For example, the control system 105 may detect the fault based on sensor data (e.g., indicating temperature or an electrical characteristic) exceeding or falling below a threshold.

[0091] After detecting the second fault, the control system 105 may proceed as illustrated in FIG. 5H. In the example of FIG. 5H, the control system 105 proceeds by re-enabling converter module #3 of phase-leg QB. The control system 105 may reenable converter module #3 of phaseleg QB by providing normal control signals (e.g., control signals 350 of FIG. 3B) to the converter module #3 of phase-leg QB similar to the control signals being provided to converter module #1 of phase-leg QB. As shown in FIG. 5H, by re-enabling the converter module #3 of phase-leg QB, the converter 115 continues to have balanced phase-legs QA and QB, each with two enabled and operational converter modules.

[0092] Thus, while the power converter module #2 of phase QA and converter module #3 of phase QB are faulted, the control system 105 drives at least one power converter module of each of the phase-legs to provide output power. For example, the control system 105 may drive the enabled (non-disabled) and operational (non-faulted) power converter modules 205 of each of the phase-legs. FIG. 5H illustrates an example of a control system (e.g., the control system 105) that, while the power converter module #2 of phase A and converter module #3 of phase B are faulted, drives the converter modules #1 and #2 of the first phase-leg ( A) and converter modules # 1 and #3 of the second phase-leg (OB).

[0093] A similar approach may be taken in three-phase system, such as illustrated in FIG. 51 and 5J. For example, if converter module #2 of phase OB or of phase OC faulted, the control system may reenable the converter module #3 of phase OB or of phase OC, as the case may be.

[0094] In some examples, after executing the method 600 of FIG. 6, the faulted power converter module is reset or the fault is otherwise resolved such that the power converter module may again be enabled and operational. In some examples, the control system (e.g., the control system 105) may return to block 605 of the method 600 and drive each of the power converter modules 205 of the power converter 115 (see, e.g., FIG. 5 A and FIG. 51).

[0095] FIG. 7 provides a diagram 700 applicable to some examples of the self-healing power converter system 100 and the power converter 200. This diagram 700, like FIG. 2A, illustrates a full bridge, single phase architecture including two phase-legs: phase-leg A and phaseleg B, each having parallel converter modules 205.

[0096] FIGS. 8A and 8B show respective waveforms 800, 810 of a self-healing operation by a single-phase grid-connected power converter, for example, the power converter system 100 having, for each phase-leg, two parallel converter modules 205 (FIG. 8A) and three parallel converter modules 205 (FIG. 8B), where one power converter module 205 faults. As shown, with one parallel converter module 205 in fault, the total phase output current can be maintained at the same value without the need to shut down the power operation. The reliability of the power converter system 100 is improved accordingly.

[0097] FIG. 9 shows waveforms 900 of an example of a self-healing power converter, as described herein, including: inductor current, grid side output current, module side output current, DC bus voltage, and output capacitor voltage with two scalable modules.

[0098] FIG. 10 shows waveforms 1000 that demonstrate transient performance of output capacitor voltage, grid side current, and inductor side current for the power converter system 100 with a grid side current reference step and using local MPC control as described above. As illustrated, using the local level MPC control, the dynamic performance of the transient has a short response time and small oscillation. [0099] As noted above, the power converter system 100 (and power converter 115), may function as a DC-AC inverter, as a AC -DC rectifier, and/or as a DC-DC converter. In some examples, the power converter system 100 operates only as an inverter, only as a rectifier, or only as a DC-DC converter. In other examples, the power converter system 100 operates as two or more of an inverter, a rectifier, or a DC-DC converter. In some examples, at various moments in time, the power converter system may operate in an inverter mode to converter DC to AC, in a rectifier mode to converter AC to DC, or in a DC converter mode to convert DC at one voltage level to another voltage level. Accordingly, in some examples, (e.g., when used in an electric vehicle), the power converter system 100 may be used in one or more of the following modes: in an inverter mode to drive a motor with an AC signal generated from a received DC signal from a battery; in a rectifier mode to implement regenerative breaking and converter AC power from the (braking) motor to charge a battery; in a rectifier mode to charge converter AC power from an external source (e.g., grid) to charge a battery; in an inverter mode to inverter DC power from a battery to an AC signal for output to other AC loads (e.g., on a local microgrid or utility grid). The self- healing functionality described with respect to FIGS. 5A-5I and FIG. 6 applies to the power converter system 100 (and the power converter 115) in each of these modes of operation, including as an inverter, rectifier, and/or DC-DC converter.

[00100] The present specification describes one or more electronic controllers (e.g., the central controller 150, the local controller(s) 160). An electronic controller includes one or more processors configured to facilitate power conversion (e.g., by controlling the switching devices of, for example, a scalable power converter system as described herein) and one or more memories or storage devices. The storage device(s) may thus include a computer program product that when executed on the electronic controller (which, as noted, may be a processor-based device) causes the processor-based device to perform operations to facilitate the implementation of procedures and operations described herein. The electronic controller may further include peripheral devices to enable input/output functionality. Such peripheral devices may include, for example, flash drive (e.g., a removable flash drive), or a network connection (e.g., implemented using a USB port and/or a wireless transceiver), for downloading related content to the connected system. Such peripheral devices may also be used for downloading software containing computer instructions to enable general operation of the respective system/device. Alternatively and/or additionally, in some embodiments, special purpose logic circuitry, e.g., an FPGA (field programmable gate array), an ASIC (application specific integrated circuit), a complex programmable logic device (CPLD), a DSP processor, a graphics processing unit (GPU), application processing unit (APU), etc., may be used in the implementations of the electronic controller or electronic processor. Other modules that may be included with the electronic controller may include a user interface to provide or receive input and output data. The electronic controller may include an operating system.

[00101] Computer programs (also known as programs, software, software applications or code) include machine instructions for a programmable processor, and may be implemented in a high-level procedural and/or object-oriented programming language, and/or in assembly/machine language. As used herein, the term “machine-readable medium” refers to any non-transitory computer program product, apparatus and/or device (e.g., magnetic discs, optical disks, memory, Programmable Logic Devices (PLDs)) used to provide machine instructions and/or data to a programmable processor, including a non-transitory machine-readable medium that receives machine instructions as a machine-readable signal.

[00102] In some embodiments, any suitable computer readable media can be used for storing instructions for performing the processes / operations / procedures described herein. For example, in some embodiments computer readable media can be transitory or non-transitory. For example, non-transitory computer readable media can include media such as magnetic media (such as hard disks, floppy disks, etc.), optical media (such as compact discs, digital video discs, Blu- ray discs, etc ), semiconductor media (such as flash memory, electrically programmable read only memory (EPROM), electrically erasable programmable read only Memory (EEPROM), etc ), any suitable media that is not fleeting or not devoid of any semblance of permanence during transmission, and/or any suitable tangible media. As another example, transitory computer readable media can include signals on networks, in wires, conductors, optical fibers, circuits, any suitable media that is fleeting and devoid of any semblance of permanence during transmission, and/or any suitable intangible media.

[00103] Although particular embodiments have been disclosed herein in detail, this has been done by way of example for purposes of illustration only, and is not intended to be limiting with respect to the scope of the appended claims, which follow. Features of the disclosed embodiments can be combined, rearranged, etc., within the scope of the invention to produce more embodiments. Some other aspects, advantages, and modifications are considered to be within the scope of the claims provided below. The claims presented are representative of at least some of the embodiments and features disclosed herein. Other unclaimed embodiments and features are also contemplated.

FURTHER EXAMPLES

[00104] Example 1 : A method, apparatus, and/or non-transitory computer-readable medium storing processor-executable instructions for a self-healing power converter system comprising: a plurality of converter phase-legs including a first converter phase-leg and a second converter phase-leg, each converter phase-leg including a plurality of power converter modules, each power converter module including power switching elements; and a control system including a central controller, a first local controller configured to control the first converter phase-leg, and a second local controller configured to control the second converter phase-leg, the control system configured to: detect a fault with a first power converter module of the plurality of power converter modules of the first converter phase-leg; in response to detecting the fault, disabling a second power converter module of the plurality of power converter modules of the second converter phase-leg; and drive, while the second power converter module is disabled, at least one power converter module of each of the first converter phase-leg and the second converter phase-leg to provide output power.

[00105] Example 2: The method, apparatus, and/or non-transitory computer readable medium of Example 1, wherein the central controller is configured to generate a first reference target and a second reference target based on sensed characteristics of the first and second converter phase-legs; wherein the first local controller is configured to control the plurality of power converter modules of the first converter phase-leg based on the first reference target; and wherein the second local controller is to control the plurality of power converter modules of the second converter phase-leg based on the second reference target.

[00106] Example 3: The method, apparatus, and/or non-transitory computer readable medium of any of Examples 1 to 2, wherein the central controller is configured to: in response to detecting the fault, determine whether a total output current for the plurality of converter phaselegs exceeds a current limit; in response to determining that the total output current exceeds the current limit, providing reduced reference targets to the local controllers; and in response to determining that the total output current does not exceed the current limit, providing nonreduced reference targets to the local controllers. [00107] Example 4: The method, apparatus, and/or non-transitory computer readable medium of any of Examples 1 to 3, wherein the reduced reference targets are a portion of the nonreduced reference targets, the portion being based on a ratio of enabled converter modules to total converter modules of the plurality of converter phase-legs.

[00108] Example 5: The method, apparatus, and/or non-transitory computer readable medium of any of Examples 1 to 4, wherein the central controller is configured to: detect a second fault with a third power converter module of the plurality of power converter modules of the first converter phase-leg; and in response to detecting the second fault, disable a fourth power converter module of the plurality of power converter modules of the second converter phase-leg, and continue to drive at least one power converter module of each of the first converter phase-leg and the second converter phase-leg.

[00109] Example 6: The method, apparatus, and/or non-transitory computer readable medium of any of Examples 1 to 5, wherein the central controller is configured to: detect a second fault with a third power converter module of the plurality of power converter modules of the first converter phase-leg; and in response to detecting the second fault, control a switch network to reassign one of the power converter modules of the plurality of power converter modules of the second converter phase-leg to the first converter phase-leg, and continue to drive at least one power converter module of each of the first converter phase-leg and the second converter phase-leg.

[00110] Example 7: The method, apparatus, and/or non-transitory computer readable medium of any of Examples 1 to 6, wherein the control system is configured to: detect a second fault with a third power converter module of the plurality of power converter modules of the second converter phase-leg; and in response to detecting the fault, enable the second power converter module of the plurality of power converter modules of the second converter phase-leg, and continue to drive at least one power converter module of each of the first converter phase-leg and the second converter phase-leg.

[00111] Example 8: The method, apparatus, and/or non-transitory computer readable medium of any of Examples 1 to 7, wherein each power converter module includes an LC filter and is configured to connect to a grid node via the LC filter.

[00112] Example 9: The method, apparatus, and/or non-transitory computer readable medium of any of Examples 1 to 8, wherein each local controller is a model predictive controller that implements model predictive control to drive the power switching elements of the converter phase-leg corresponding to the local controller.

[00113] Example 10: The method, apparatus, and/or non-transitory computer readable medium of any of Examples 1 to 9, wherein the plurality of converter phase-legs include a third converter phase-leg, and each of the first converter phase-leg, the second converter phase-leg, and the third converter phase-leg corresponds to a respective phase of a three-phase power converter, or wherein the first converter phase-leg and the second converter phase-leg correspond to a singlephase power converter and the first converter phase-leg is configured to be coupled to a first terminal of a single-phase grid and the second converter phase-leg is configured to be coupled to a second terminal of the single-phase grid.

[00114] Example 11: The method, apparatus, and/or non-transitory computer readable medium of any of Examples 1 to 10, wherein the central controller is configured to: generate global reference targets in a rotational reference frame; translate the global reference targets to local reference targets in a stationary reference frame; and generate reference targets for the local controllers based on the local reference targets.

[00115] Example 12: The method, apparatus, and/or non-transitory computer readable medium of any of Examples 1 to 11, wherein the central controller is configured to generate the reference targets for the local controllers based on the local reference targets and a zero-sequence control target that is based on half a DC link voltage of the plurality of converter modules.

[00116] Example 13: The method, apparatus, and/or non-transitory computer readable medium of any of Examples 1 to 12, wherein the central controller is configured to detect the fault based on a comparison of a sensed parameter value to a threshold that indicates the sensed parameter value is outside of a parameter range.

Claims

WHAT IS CLAIMED IS:

1. A self-healing power converter system comprising: a plurality of converter phase-legs including a first converter phase-leg and a second converter phase-leg, each converter phase-leg including a plurality of power converter modules, each power converter module including power switching elements; and a control system including a central controller, a first local controller configured to control the first converter phase-leg, and a second local controller configured to control the second converter phase-leg, the control system configured to: detect a fault with a first power converter module of the plurality of power converter modules of the first converter phase-leg; in response to detecting the fault, disabling a second power converter module of the plurality of power converter modules of the second converter phase-leg; and drive, while the second power converter module is disabled, at least one power converter module of each of the first converter phase-leg and the second converter phaseleg to provide output power.

2. The self-healing power converter system of claim 1, wherein the central controller is configured to generate a first reference target and a second reference target based on sensed characteristics of the first and second converter phaselegs; wherein the first local controller is configured to control the plurality of power converter modules of the first converter phase-leg based on the first reference target; and wherein the second local controller is to control the plurality of power converter modules of the second converter phase-leg based on the second reference target.

3. The self-healing power converter system of claim 1, wherein the central controller is configured to: in response to detecting the fault, determine whether a total output current for the plurality of converter phase-legs exceeds a current limit; in response to determining that the total output current exceeds the current limit, providing reduced reference targets to local controllers including the first and second local controllers; and in response to determining that the total output current does not exceed the current limit, providing nonreduced reference targets to the local controllers.

4. The self-healing power converter system of claim 3, wherein the reduced reference targets are a portion of the nonreduced reference targets, the portion being based on a ratio of enabled converter modules to total converter modules of the plurality of converter phase-legs.

5. The self-healing power converter system of claim 1, wherein the central controller is configured to: detect a second fault with a third power converter module of the plurality of power converter modules of the first converter phase-leg; and in response to detecting the second fault, disable a fourth power converter module of the plurality of power converter modules of the second converter phase-leg, and continue to drive at least one power converter module of each of the first converter phase-leg and the second converter phase-leg.

6. The self-healing power converter system of claim 1, wherein the central controller is configured to: detect a second fault with a third power converter module of the plurality of power converter modules of the first converter phase-leg; and in response to detecting the second fault, control a switch network to reassign one of the power converter modules of the plurality of power converter modules of the second converter phase-leg to the first converter phase-leg, and continue to drive at least one power converter module of each of the first converter phase-leg and the second converter phase-leg.

7. The self-healing power converter system of claim 1, wherein the control system is configured to: detect a second fault with a third power converter module of the plurality of power converter modules of the second converter phase-leg; and in response to detecting the fault, enable the second power converter module of the plurality of power converter modules of the second converter phase-leg, and continue to drive at least one power converter module of each of the first converter phase-leg and the second converter phase-leg.

8. The self-healing power converter system of claim 1, wherein each power converter module includes an LC filter and is configured to connect to a grid node via the LC filter.

9. The self-healing power converter system of claim 1, wherein each local controller of the control system, including the first local controller and the second local controller, is a model predictive controller that implements model predictive control to drive the power switching elements of a converter phase-leg corresponding to the local controller.

10. The self-healing power converter system of claim 1, wherein the plurality of converter phase-legs include a third converter phase-leg, and each of the first converter phase-leg, the second converter phase-leg, and the third converter phase-leg corresponds to a respective phase of a three-phase power converter, or wherein the first converter phase-leg and the second converter phase-leg correspond to a single-phase power converter and the first converter phase-leg is configured to be coupled to a first terminal of a single-phase grid and the second converter phase-leg is configured to be coupled to a second terminal of the single-phase grid.

11. The self-healing power converter system of claim 1, wherein the central controller is configured to: generate global reference targets in a rotational reference frame; translate the global reference targets to local reference targets in a stationary reference frame; and generate reference targets for local controllers, including the first and second local controllers, based on the local reference targets.

12. The self-healing power converter system of claim 11, wherein the central controller is configured to generate the reference targets for the local controllers based on the local reference targets and a zero-sequence control target that is based on half a DC link voltage of the plurality of power converter modules.

13. The self-healing power converter system of claim 1, wherein the central controller is configured to detect the fault based on a comparison of a sensed parameter value to a threshold that indicates the sensed parameter value is outside of a parameter range.

14. A method of power conversion with a self-healing power converter, the method comprising: driving, by a control system, a plurality of converter phase-legs including a first converter phase-leg and a second converter phase-leg, each converter phase-leg including a plurality of power converter modules, each power converter module including power switching elements; detecting, by the control system, a fault with a first power converter module of the plurality of power converter modules of the first converter phase-leg; and disabling, in response to detecting the fault, a second power converter module of the plurality of power converter modules of the second converter phase-leg; and driving, while the second power converter module is disabled, at least one power converter module of each of the first converter phase-leg and the second converter phase-leg to provide output power.

15. The method of claim 14, further comprising: generating, by a central controller of the control system, a first reference target and a second reference target based on sensed characteristics of the first and second converter phaselegs; controlling, by a first local controller of the control system, the plurality of power converter modules of the first converter phase-leg based on the first reference target; and controlling, by a second local controller of the control system, the plurality of power converter modules of the second converter phase-leg based on the second reference target.

16. The method of claim 14, further comprising: in response to detecting the fault, determining, by a central controller of the control system, whether a total output current for the plurality of converter phase-legs exceeds a current limit; in response to determining that the total output current exceeds the current limit, providing, by the central controller, reduced reference targets to local controllers of the control system; and in response to determining that the total output current does not exceed the current limit, providing, by the central controller, nonreduced reference targets to the local controllers.

17. The method of claim 16, wherein the reduced reference targets are a portion of the nonreduced reference targets, the portion being based on a ratio of enabled converter modules to total converter modules of the plurality of converter phase-legs.

18. The method of claim 14, further comprising: detecting, by the control system, a second fault with a third power converter module of the plurality of power converter modules of the first converter phase-leg; and in response to detecting the second fault, disabling a fourth power converter module of the plurality of power converter modules of the second converter phase-leg, and continuing to drive at least one power converter module of each of the first converter phase-leg and the second converter phase-leg.

19. The method of claim 14, further comprising: detecting, by the control system, a second fault with a third power converter module of the plurality of power converter modules of the first converter phase-leg; and in response to detecting the second fault, controlling a switch network to reassign one of the power converter modules of the plurality of power converter modules of the second converter phase-leg to the first converter phase-leg, and continuing to drive at least one power converter module of each of the first converter phase-leg and the second converter phase-leg.

20. The method of claim 14, further comprising: detecting, by the control system, a second fault with a third power converter module of the plurality of power converter modules of the second converter phase-leg; and in response to detecting the fault, enabling the second power converter module of the plurality of power converter modules of the second converter phase-leg, and continuing to drive at least one power converter module of each of the first converter phase-leg and the second converter phase-leg.

21. The method of claim 14, wherein each power converter module includes an LC filter and is configured to connect to a grid node via the LC filter.

22. The method of claim 14, further comprising: driving, by each local controller implementing model predictive control, the power switching elements of the converter phase-leg corresponding to the local controller.

23. The method of claim 14, wherein the plurality of converter phase-legs include a third converter phase-leg, and each of the first converter phase-leg, the second converter phase-leg, and the third converter phase-leg corresponds to a respective phase of a three-phase power converter, or wherein the first converter phase-leg and the second converter phase-leg correspond to a single-phase power converter and the first converter phase-leg is configured to be coupled to a first terminal of a single-phase grid and the second converter phase-leg is configured to be coupled to a second terminal of the single-phase grid.

24. The method of claim 14, further comprising: generating, by a central controller of the control system, global reference targets in a rotational reference frame; translating, by the central controller, the global reference targets to local reference targets in a stationary reference frame; and generating, by the central controller, reference targets for local controllers of the control system based on the local reference targets.

25. The method of claim 24, wherein the central controller generates the reference targets for the local controllers based on the local reference targets and a zero-sequence control target that is based on half a DC link voltage of the plurality of power converter modules.

26. The method of claim 14, wherein the central controller detects the fault based on a comparison of a sensed parameter value to a threshold that indicates the sensed parameter value is outside of a parameter range.