FR3161325A1 - BATTERY COMPRISING ELECTROCHEMICAL CELLS DISTRIBUTED IN SEVERAL DISTINCT CLUSTER VOLTAGES - Google Patents

Abstract

The present invention relates to a power battery comprising a plurality of elementary energy storage modules connected in series in at least one current line so as to form a multi-level inverter distributed in the battery and in which the plurality of elementary modules comprises at least a first elementary module in which the electrochemical cells (21) of the cluster (CL1) are interconnected according to a first interconnection configuration determining a first cluster voltage level (VCL1) and a second elementary module in which the electrochemical cells (24) of the cluster (CL4) are interconnected according to a second interconnection configuration determining a second cluster voltage level (VCL4), the second cluster voltage level (VCL4) being the maximum cluster voltage of the battery and the first cluster voltage level (VCL1) being strictly lower than the second cluster voltage level (VCL4). Figure 2.

Description

BATTERY CONTAINING ELECTROCHEMICAL CELLS DISTRIBUTED IN SEVERAL DISTINCT CLUSTER VOLTAGES

The field of the invention relates to a power battery, in particular for electrified vehicles and stationary energy storage systems.

Electrified vehicles are equipped with a traction battery, typically made of lithium-ion electrochemical cells. To date, the costs, electrical efficiency, and energy density of these systems still limit their widespread adoption in these vehicles. Automakers are continuously seeking new solutions to address these technological challenges.

The applicant has developed a distributed multilevel inverter architecture that eliminates the need for voltage converters typically integrated between a battery and the AC power grid. This architecture has been the subject of several patent applications by the applicant. Examples include documents WO-A1-2017/153366 and WO-A1-2021/048477. These documents describe a cell architecture comprising current lines formed by elementary modules, each containing an electrochemical cell, or a cluster of cells, and a switching module forming an H-bridge. These documents further describe innovative control methods for this architecture, enabling the balancing of cell charge states and the generation of polyphase or direct current.

More specifically, in this architecture, power functions are handled by electronic boards performing the DC/AC conversion, located near the cells and based on very low-voltage switching electronics. At any given moment, the cell clusters are indiscriminately activated by current pulses. The voltage waveform produced on each current line is a function of the number of activated clusters. Furthermore, in the case of a stationary application, the distributed multilevel inverter architecture allows for the direct generation of a three-phase network from the battery output, thus eliminating the need for a conventional bidirectional inverter.

There is a need to address the aforementioned problems. In particular, one objective of the invention is to provide an improved architecture for a distributed multilevel inverter battery. Another objective is to offer a control solution that enhances the quality of power waves for exchanges with an electrical grid. Furthermore, another objective is to provide a lower-cost battery.

More specifically, the invention relates to a power battery comprising a plurality of elementary energy storage modules connected in series in at least one current line, each elementary module comprising a cluster of electrochemical cells and a switching module comprising an H-bridge, the electrochemical cells of each cluster being electrically interconnected according to an interconnection configuration within each cluster determining a cluster voltage level and the elementary modules being interconnected in series via the switching modules so as to form a multilevel inverter distributed in the battery capable of generating a selected voltage waveform across the current line by connecting in series a controlled selection of elementary modules from the plurality.

According to the invention, the plurality of elementary modules comprises at least one first elementary module in which the electrochemical cells of the cluster are interconnected according to a first interconnection configuration determining a first cluster voltage level, and a second elementary module in which the electrochemical cells of the cluster are interconnected according to a second interconnection configuration determining a second cluster voltage level. The first and second interconnection configurations are arranged such that the second cluster voltage level is the maximum cluster voltage of the battery, and the first cluster voltage level is strictly lower than the second cluster voltage level. The first and second cluster voltage levels are multiples of the individual voltage of the electrochemical cells, these values being distinct from one another.

According to one variant, the first cluster voltage level is equal to a value between one quarter and three quarters of the second cluster voltage level, or is equal to half of the second cluster voltage level, or is equal to one third of the second cluster voltage level.

According to one variant, the first interconnection configuration includes electrochemical cells electrically connected in series and in parallel within the cluster, or the first interconnection configuration includes all electrochemical cells electrically connected in parallel within the cluster.

According to one variant, the second interconnection configuration includes all electrochemical cells electrically connected in series within the cluster, or the second interconnection configuration includes electrochemical cells electrically connected in series and in parallel within the cluster.

According to one variant, the plurality of elementary modules further comprises a third elementary module in which the electrochemical cells are interconnected according to a third interconnection configuration determining a third cluster voltage level and in which the third interconnection configuration comprises the electrochemical cells electrically connected in series and in parallel within the cluster such that the third cluster voltage level has an intermediate value between the first voltage level and the second voltage level.

According to one variant, the elementary modules of the plurality all have the same even number of electrochemical cells within the cluster and in which the second and third interconnection configurations are arranged so that the second and third voltage levels are values equal to a power of two multiplied by the value of the first voltage level.

According to one variant, the first elementary module includes the H-bridge switching module consisting of switches having an internal drain-source resistance lower than the internal drain-source resistance of the switches in the H-bridge switching module of the second elementary module.

The invention further provides for an electrical system comprising at least one phase branch and a power battery according to any one of the preceding embodiments, wherein the battery includes at least one current line electrically connected to the phase branch, the current line comprising at least the first and second elementary module of the plurality of elementary modules, the system comprising a control unit configured to connect in series in the current line a controlled selection of elementary modules to generate a selected voltage wave across the terminals of the current line and wherein the controlled selection comprises at least the first and second elementary module.

The invention also provides for a stationary energy storage system comprising such an electrical system.

The invention also provides for an electrified vehicle comprising such an electrical system, for example an electrified motor vehicle with at least partially electrified drivetrain comprising such an electrical system.

The invention further provides a method for controlling a power battery comprising a plurality of elementary energy storage modules connected in series in at least one current line, each elementary module comprising a cluster of electrochemical cells and a switching module comprising an H-bridge, the electrochemical cells of each cluster being electrically interconnected according to an interconnection configuration within each cluster determining a cluster voltage level, and the elementary modules being interconnected in series via the switching modules so as to form a multilevel inverter distributed in the battery capable of generating a selected voltage waveform across the current line by connecting in series a controlled selection of elementary modules from the plurality, the method being implemented by a battery control unit and comprising the following steps:

- determining the voltage setpoint to be generated across the terminals of the current line,

- the series connection among the plurality of elementary modules of at least one first elementary module delivering a first cluster voltage level and at least one second elementary module delivering a second cluster voltage level to generate a voltage wave as a function of the setpoint, the second cluster voltage level being the maximum cluster voltage of the battery and in which the first cluster voltage level is strictly less than the second cluster voltage level.

The invention provides a computer program comprising instructions which, when the program is executed by a power battery control unit, cause the latter to implement such a control method.

The invention provides a power battery control unit comprising means specifically configured to implement the control method according to the invention.

The invention provides a computer-readable recording medium comprising instructions which, when executed by a computer, cause the computer to implement the control method according to the invention.

The invention enables the staggering of voltage jumps, for a battery architecture with a distributed multilevel inverter within the battery, according to different levels during the generation of a voltage waveform in order to improve voltage regulation and the quality of the generated waveform. The invention also makes it possible to reduce the number of switching components in the H-bridge configuration and consequently the cost and energy efficiency of the battery.

Other features and advantages of the present invention will become more apparent upon reading the following detailed description, which includes embodiments of the invention given by way of non-limiting examples and illustrated by the accompanying drawings, in which:

FIG. 1 schematically represents an embodiment of an electrical system comprising a power battery according to the invention.

FIG. 2 schematically represents interconnection configurations of electrochemical cells for clusters integrating a battery according to the invention.

FIG. 3 schematically represents an example of an electrical architecture for an electrified vehicle according to the invention.

FIG. 4 schematically represents an example of an electrical architecture for a stationary energy storage system according to the invention.

The invention applies to electrified vehicles comprising an electric drivetrain powered, at least partially, by an electric machine, i.e., with a fully electric or hybrid motor, preferably motor vehicles, but not exclusively, such as aircraft, trucks, tractors, bicycles, and ships. The invention also finds application in stationary storage systems, for example, renewable energy or grid regulation installations. The power battery comprises elementary modules of electrochemical cells interconnected to form a distributed multilevel inverter structure within the battery, allowing it to be connected to an electrical system operating at direct or alternating voltage without the intermediary of an inverter. The battery system can be connected directly to an extended power grid and to an electric drive machine.

With reference to the FIG. 1 A polyphase electrical system is schematically represented and comprises a power bank BAT consisting of a plurality n of elementary modules MCLk forming a multilevel inverter structure distributed throughout the bank. The BAT battery has three current lines LT1, LT2, and LT3 connected to phase branches BP1, BP2, and BP3 of the electrical system. Each current line LT1, LT2, and LT3 has a plurality of elementary modules MCLk interconnected in series. Each elementary module MCLk has a cluster of cells CLk and a switching module COMk forming an H-bridge. The elementary modules are interconnected in series via the switching modules COMk to form the multilevel inverter distributed throughout the BAT battery. This inverter is capable of generating a chosen voltage waveform across each current line by connecting in series a controlled selection of elementary modules from the plurality.

According to the invention, each LT1, LT2, LT3 line comprises a plurality of elementary modules containing CLk clusters of electrochemical cells, which can be interconnected separately within each CLk cluster to deliver a specific cluster voltage to each CLk. A CLk cell cluster can contain two, three, four, five, six, eight, or more cells, forming the cluster voltage Vclk. This allows voltage jumps to be staggered at different levels during the generation of a voltage waveform in order to improve voltage regulation and thus the quality of the generated waveform. The voltage level of a cluster depends on the arrangement of the electrical connections between electrochemical cells. The interconnection connections within a CLk cluster can be in series, in parallel, or in both series and parallel. The cluster voltage level corresponds to the amplitude of the voltage when the COMk switching module of said cluster connects the cell voltage to its connection terminals.

A minimum voltage level is equivalent to the voltage of an individual electrochemical cell, approximately 4.2 volts for a lithium-ion cell. The 4.2-volt value is given as an illustrative example. Other values are possible depending on the chemistry chosen for the electrochemical cell. The minimum possible voltage jump in a current line is therefore dependent on the cell chemistry used for a given module.

The maximum value depends on the interconnection configuration within a cluster, specifically the number of electrochemical cells connected in series; for example, 33.6 volts for eight cells connected in series. Interconnection configurations are configurable according to the desired electrical specifications for capacitance and operating voltage. More detailed examples will be provided later in this description.

Furthermore, it is worth recalling that an electrochemical cell is an electrochemical energy storage device with two electrical connection terminals and a voltage of a few volts, most often between 2.3V and 4.2V. Cells can be of the lithium-ion type (lithiumized nickel manganese cobalt oxide (NMC) or lithium iron phosphate (LFP) are examples of active materials for the positive electrode), nickel cadmium (Ni-Cd), nickel metal hydride (Ni-MH), or sodium-ion, for example. More specifically, a lithium-ion cell is primarily composed of a porous positive electrode, a porous negative electrode, a separator, and an electrolyte (which can be liquid, polymeric, or solid). The operating principle of a lithium-ion cell is based on the reversible exchange of lithium ions between the two porous electrodes.

Returning to the general description of the BAT battery architecture, the phase branches BP1, BP2, and BP3 allow the battery to be connected to various systems designed to use alternating or direct current voltage. The BAT battery system delivers a voltage of several hundred volts at its terminals, for example, with a maximum amplitude of 350, 400, 450, 500, or 1000 volts. However, other voltages are possible, such as lower values like 24 volts, 36 volts, or 48 volts, or higher values of 1500 volts or more, particularly for stationary systems.

In a first branch circuit of phase branches BP1, BP2, and BP3, the battery system BAT includes high-voltage switches Kres, also called high-voltage contactors or relays, for electrically connecting the battery BAT to an extended power supply network RES. Each current line LT1, LT2, and LT3 is connected, via these branches, on one side to a network connection switch, KR1, KR2, and KR3 respectively, and on the other side to a neutral terminal N of the battery. The extended power supply network RES operates at 50 Hz or 60 Hz AC voltage and consists of a three-phase line with three voltage lines P1, P2, and P3. The battery system BAT is adapted to generate three three-phase voltage waves offset by 2π/3. The control of each current line is similar, differing only by a 2π/3 offset between them.

It should be noted that, thanks to this multilevel inverter architecture distributed in the battery, the electrical system does not include an AC/DC voltage converter between the LT1, LT2 and LT3 power lines and the BP1, BP2 and BP3 phase branches operating on alternating current.

Furthermore, in an embodiment for an electrified vehicle, the battery system BAT is the vehicle's traction battery and also includes high-voltage switches Kmel for electrically connecting the battery BAT to a drive electric machine MEL. Each current line LT1, LT2, and LT3 is connected, via a second set of phase branch connections BP1, BP2, and BP3, on one side to a drive electric machine connection switch, KM1, KM2, and KM3 respectively, and on the other side to a neutral terminal N of the battery. The drive electric machine can be an asynchronous or synchronous machine, possibly a DC machine, since the battery system is capable of generating any voltage waveform, AC or DC.

Alternatively, for a renewable energy installation, the second phase branch connection can be connected to a photovoltaic or wind turbine system. Alternatively, the battery is connected to the power grid for grid regulation purposes.

Furthermore, another set of connections is planned to connect the battery to a DC voltage bus, also called a high-voltage bus, for the needs of an electrified vehicle, among other things. This latter set of connections includes, for example, high-voltage systems and a DC/DC voltage converter for the requirements of an on-board network operating at 12 volts.

The BAT battery system also includes a BMS control unit, one of whose functions is to control the voltage waveform of each line LT1, LT2, LT3 according to a reference setpoint Vref from the MCLk element modules. The COMk switching module is capable of configuring the MCLk element module in three different states to deliver the Vmclk voltage, which is respectively the cluster voltage Vclk, a zero voltage, and the inverted cluster voltage Vclk to the MCLk module's connection terminals.

The COMk switching module, for example, consists of two switching sections forming an H-bridge that can be controlled in three different states by a control signal from the battery management system (BMS) (BAT) specifically addressing the MCLk module. These states are represented by a control variable (uik) that can take, for example, the values 1, 0, and -1, representing the three different states that respectively control the cluster voltage (Vclk), a zero voltage, and the inverted voltage (-Vclk) at the connection terminals of the MCLk element module addressed by the control signal (uik). Each COMk switching module includes electronic components, such as power transistors, possibly MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) or HEMTs (High Electron Mobility Transistors), driven by the control signals from the BMS.

Thus, an example of a control mode for the voltage Vmclk across each elementary module MCLk within a set n of modules can be implemented based on a control signal uik according to the following relationship:

Thus, the BMS control unit can control, on each voltage line LT1, LT2, and LT3, any voltage waveform consisting of amplitude steps composed of the cluster voltages Vclk of each activated cluster, according to a reference voltage setpoint Vref, by connecting the cells in series via the COMk switching modules. The reference voltage setpoint Vref can be a sinusoidal waveform with a frequency of 50 Hz, any alternating waveform, for example a square wave, or it can be a constant voltage, for example.

Other control variants are conceivable taking into account other criteria, such as the state of charge of the electrochemical cells of a cluster, their temperature, their state of aging, or even a defective state of the switching module possibly.

Furthermore, preferably, line switches are also provided to allow the three current lines LT1, LT2, LT3 to be connected in series. Alternatively, alternative embodiments of the BAT battery are envisaged, comprising a single current line LT1 including all the elementary modules MCLk connected in series.

In FIG. 2 A non-limiting embodiment of clusters CL1, CL2, CL3, and CL4 of electrochemical cells forming the battery according to the invention has been schematically described. Each cluster comprises eight electrochemical cells, in this example of the lithium-ion type, and each cell has an individual voltage of approximately 4.2 volts. According to the principle of the invention, the plurality of elementary modules of the battery comprises at least a first elementary module in which the electrochemical cells 21 of cluster CL1 are interconnected according to a first interconnection configuration determining a first cluster voltage level VCL1 of 4.2 volts, and a second elementary module in which the electrochemical cells 24 of cluster CL4 are interconnected according to a second interconnection configuration determining a second cluster voltage level VCL4 of 33.6 volts.

The first and second voltage levels have distinct, non-equal values. More precisely, the first and second interconnection configurations are arranged so that the second cluster voltage level is the maximum cluster voltage of the battery, and the first cluster voltage level is strictly lower than the second cluster voltage level. Both the first and second voltage levels are multiples of the individual electrochemical cell voltages.

In this example, cluster CL2 determines a third cluster voltage level, VCL2, with an intermediate value of 8.4 volts, and cluster CL3 determines a fourth cluster voltage level, VCL3, with an intermediate value of 16.8 volts. For cluster CL1, the electrochemical cells are interconnected in parallel. For cluster CL4, the electrochemical cells are interconnected in series. For cluster CL2, the 22 electrochemical cells are interconnected in series and parallel in a configuration where two blocks of cells are interconnected in series, each containing four cells in parallel. For cluster CL3, the 23 electrochemical cells are interconnected in series and parallel in a configuration where four blocks of cells are interconnected in series, each containing two cells in parallel. Other interconnection configuration variations are conceivable by those skilled in the art to provide a desired cluster voltage level depending on the number of electrochemical cells available.

The electrical interconnections between cells within the same block are fixed. Each cluster is electrically connected to an individual H-bridge switching module.

Furthermore, in this battery embodiment, each cluster comprises eight electrochemical cells, ensuring that the maximum voltage per cluster does not exceed 40 volts. Consequently, the resistance of the MOSFET switches in each switching module can achieve Drain Source Resistance (RDSon) values as low as 0.2 milliohms when the transistor is conducting. Moreover, for lower-voltage clusters, MOSFET technology can be adapted to achieve even lower RDSon values, thereby reducing losses and improving the battery's energy efficiency.

Compared to a battery architecture of this type described in the prior art, the number of H-bridge switching modules is reduced for a battery of the same capacity and order of magnitude of voltage. Furthermore, the minimum voltage jumps can be reduced to the voltage of a single lithium-ion cell. However, this is not mandatory. The battery may comprise a combination of clusters with different voltage levels, ranging from the voltage of an individual cell to a maximum desired cluster voltage permitted by the number of cells in each cluster. The battery includes at least one cluster with a voltage level between one-quarter and three-quarters of the maximum voltage. Preferably, the battery includes at least one cluster with a voltage level equal to half the maximum cluster voltage, or at least one cluster with a voltage level equal to one-third of the maximum cluster voltage.

The invention offers the following technical advantages. In automotive applications, the control function is improved, particularly during vehicle start-up, due to the ability to more precisely control the power supply to the electric motor, ranging from a voltage amplitude of a few volts to approximately ten volts. The current and voltage waveform quality is also improved due to the reduction of harmonics and, consequently, the reduction in the number of filtering components.

Furthermore, for stationary energy storage systems, current regulation is improved due to the reduction of current oscillations around a given setpoint. In addition, the architecture allows for a decrease in recirculation current between interconnected lines in the case of an installation with multiple interconnected batteries.

A first method of distributing the electrochemical cell clusters of a power battery according to the invention is now described by way of non-limiting example. This method comprises eleven electrochemical cell clusters, each defining several distinct cluster voltage levels. A voltage level corresponds to the voltage of an individual electrochemical cell. In this example, each current line comprises eleven elementary modules, i.e., eleven cell clusters that can be connected in series. Voltage jumps are controllable for values ranging from 4.2 volts to 33.6 volts. Each cluster comprises eight cells whose interconnection configurations are arranged such that the cells are electrically connected all in parallel (CL1), in series and parallel (CL2, CL3), or all in series (CL4, CL5, CL6, CL7, CL8, CL9, CL10, CL11). Cluster identification reference Number of voltage levels in series Cluster voltage in volts CL1 1 4.2 volts CL2 2 8.4 volts CL3 4 16.8 volts CL4 8 33.6 volts CL5 8 33.6 volts CL6 8 33.6 volts CL7 8 33.6 volts CL8 8 33.6 volts CL9 8 33.6 volts CL10 8 33.6 volts CL11 8 33.6 volts Total number of cells:
88 Maximum controllable voltage amplitude:
298.2 volts

In the preferred variant of this first distribution method, each cluster contains the same number N of electrochemical cells, where N is an even number; in this example, N equals eight. Other quantities of cells per cluster are possible, for example, four, six, ten, twelve, or more. In one of these variants, the interconnection configuration for the maximum voltage clusters is arranged so that the cells are connected in series and parallel. For example, the voltage of 33.6 volts is achieved from two blocks of eight cells in series connected in parallel, the number N then being equal to 16. The other cluster voltage levels are formed by adding additional blocks in parallel. This variant doubles the battery's electrical capacity.

Furthermore, the interconnection configuration of the electrochemical cells in the clusters follows an architectural relationship in which, relative to a cluster voltage delivered by a reference cluster (for example, the one with the maximum value), another cluster delivering half the reference voltage comprises parallel cell blocks with doubled capacitance. This distribution mode corresponds to the example illustrated in FIG. 2 In other words, voltage levels above the lowest level, corresponding to an individual cell voltage, are values equal to a power of two multiplied by the individual cell voltage.

Furthermore, for the purpose of optimizing battery performance, the battery preferably has a greater number of high-voltage clusters (e.g., 33.6 volts) than low-voltage clusters (e.g., 4.2 volts or 8.4 volts). In one variant configuration, the battery has a plurality of clusters delivering a desired maximum cluster voltage and at least one cluster with a lower voltage, equal to half the maximum voltage, or equal to one-third of the maximum voltage.

In another variant of this first distribution mode, we consider that the number of electrochemical cells per cluster is not identical for all clusters.

A second distribution method for the electrochemical cell clusters of a power battery according to the invention, comprising eight electrochemical cell clusters, is now described by way of non-limiting example. With this distribution, the battery can generate any voltage level between 0 volts and 415.8 volts for a configuration comprising 99 cells, a number of cells close to that of the first distribution method. This second distribution method reduces the number of elementary modules and therefore the number of H-bridge switching modules. Consequently, the cost of the architecture is reduced. Cluster identification reference Number of voltage levels in series Cluster voltage in volts CL1 1 4.2 volts CL2 1 4.2 volts CL3 2 8.4 volts CL4 5 21 volts CL5 10 42 volts CL6 10 42 volts CL7 20 84 volts CL8 50 210 volts Total number of cells:
99 Maximum controllable voltage amplitude:
415.8 volts

A third method of distributing the electrochemical cell clusters of a power battery according to the invention, comprising seven electrochemical cell clusters, is now described by way of non-limiting example. Each cell cluster delivers a specific voltage level distinct from the other clusters. The voltage levels vary according to a power-of-two geometric progression of ^2k, where k is a positive integer.

In this example, for seven clusters and following this geometric sequence, the power line voltage can range from 0 volts to 533 volts for 95 cells, a number of cells close to that of the first distribution method. This third distribution method reduces the number of elementary modules and therefore the number of H-bridge switching modules. Cluster identification reference Number of voltage levels in series Cluster voltage in volts CL1 1 4.2 volts CL2 2 8.4 volts CL3 4 16.8 volts CL4 8 33.6 volts CL5 16 67.2 volts CL6 32 134.4 volts CL7 64 268.8 volts Total number of cells:
127 Maximum controllable voltage amplitude:
533 volts

Furthermore, in one architectural variant, the type of chemistry used for the different clusters can vary between clusters. Therefore, it is possible to adapt the cluster voltage level by choosing the appropriate chemistry for the desired cluster voltage.

Furthermore, in the event of a cluster failure, this architecture allows for the replacement of a faulty cluster with one containing cells of an updated version or a different chemistry. Thus, cells of several types can coexist within the same battery.

There FIG. 3 This schematically illustrates an electrified vehicle. The term "electrified" should be understood to mean that the vehicle has a fully electric or hybrid powertrain incorporating the power battery according to the invention. The vehicle includes an electric drive machine 34 capable of transmitting torque to the drive wheels 32 of the vehicle through a transmission 31. The electric drive machine 34 may be three-phase. The vehicle includes an electrical system comprising the battery 30 according to the multilevel inverter architecture distributed throughout the battery as described in FIG. 1 The battery has three current lines capable of generating three-phase and single-phase voltage waves. The vehicle also includes a battery charging interface 38 for charging from an AC power supply. The charging interface 38 is an on-board charger that electrically connects the battery 30 to the charging station for AC charging in single-phase or three-phase current. The charging interface 38 is also capable of fast DC charging.

Each current line of the battery 30 comprises separate cluster voltage modules according to the invention. The vehicle further comprises a monitoring system 36 cooperating with a control unit 35 of the battery system 30. The battery system 30 can be directly electrically connected to the electric drive machine 34, thereby improving its energy efficiency in traction.

The battery can also be connected to a high-voltage DC bus, for example operating at a nominal voltage between 100 and 800 volts, for example 450 volts, and to a low-voltage on-board network 37 operating at a nominal voltage of type 12 volts. For this purpose, the electrical system includes power electronics 39 comprising a DC/DC converter connecting the voltage bus to the on-board network 37 (450 volts/12 volts) which includes a service battery.

There FIG. 4 This schematically illustrates a stationary energy storage system 40 comprising the power battery according to the invention. In this type of application, the power lines of the power battery 40 are directly connected to a transformer 41. The transformer 41 is connected to an electrical network 42.

Furthermore, a method for controlling the power battery, implemented by its control unit, is provided. The control unit is equipped with an integrated circuit computer and electronic memory, the computer and memory being configured to execute the control method. However, this is not mandatory. Indeed, the computer could be external to the control unit, while still being coupled to it. In this latter case, it could itself be arranged as a dedicated computer including, for example, a dedicated program. Consequently, the control unit, according to the invention, can be implemented in the form of software modules, electronic circuits, or hardware, or a combination of electronic circuits and software modules.

The control unit is adapted to monitor battery-specific parameters in cooperation with current and voltage sensors, such as the State of Charge (SOC), which designates the battery's state of charge level expressed as a ratio between the amount of energy stored at a given time and the maximum amount of energy that can be stored at a given time; the Open Circuit Voltage (OCV), expressed in volts; the charging current, expressed in amperes; and the State of Health (SOH), which designates the battery's aging level parameter, expressing a ratio between the maximum amount of electricity that can be stored at a given time and the maximum amount of electricity that can be stored when the battery was new.

According to the invention, the battery control unit is configured to generate a chosen voltage waveform across the terminals of the current line(s) by connecting in series a controlled selection of elementary modules from a plurality of modules. More specifically, the method comprises a step of determining a voltage setpoint to be generated across the current line, and a step of connecting in series, from among the plurality of elementary modules, at least one elementary module delivering a first cluster voltage level and at least one elementary module delivering a second cluster voltage level to generate a voltage waveform according to the setpoint. The second cluster voltage level is the maximum cluster voltage of the battery, and the first cluster voltage level is strictly lower than the second cluster voltage level. The selection of modules is configured by the control unit so that the combination of the chosen cluster voltages is regulated as closely as possible to the voltage setpoint. A voltage regulator is provided to perform this function. The voltage wave generated by the control unit can be a sinusoidal wave, a peak sinusoidal wave, a square wave, a triangular wave, a pulsed signal, or even a DC voltage signal, for example.

For example, at least one first module delivers a cluster voltage between 3 volts and 4.5 volts, and at least one second module delivers a cluster voltage between 30 volts and 35 volts. A voltage waveform can be generated from a combination comprising several 33.6-volt cluster voltage modules, one or two 16.8-volt cluster voltage modules, and one 4.2-volt voltage module.

Furthermore, according to a preferred variant, the selection is configured to maintain the charge state balance of cell clusters between clusters of a current line. To this end, the control unit includes means for estimating the charge state of each electrochemical cell cluster and means for selecting or prioritizing clusters based, moreover, on their charge state.

In addition, the selection is configured to maintain thermal homogeneity within all electrochemical cell clusters.

The invention is described above by way of example. It is understood that a person skilled in the art is able to carry out different variants of the invention by combining, for example, the different features above taken alone or in combination, without departing from the scope of the invention.

Claims (11)

A power battery (BAT) comprising a plurality of elementary energy storage modules (MCLk) connected in series in at least one current line (LT1), each elementary module (MCLk) comprising a cluster of electrochemical cells (CLk) and a switching module (COMk) comprising an H-bridge, the electrochemical cells of each cluster (CLk) being electrically interconnected according to an interconnection configuration within each cluster determining a cluster voltage level (Vclk), and the elementary modules (MCLk) being interconnected in series via the switching modules (COMk) so as to form a multilevel inverter distributed within the battery (BAT) capable of generating a selected voltage waveform across the current line (LT1) by connecting in series a controlled selection of elementary modules (MCLk) from the plurality, characterized in that the plurality of elementary modules (MCLk) comprises at least a first elementary module in which the electrochemical cells (21) of the cluster (CL1) are interconnected according to a first interconnection configuration determining a first cluster voltage level (VCL1) and a second elementary module in which the electrochemical cells (24) of the cluster (CL4) are interconnected according to a second interconnection configuration determining a second cluster voltage level (VCL4) and in that the first and second interconnection configurations are arranged such that the second cluster voltage level (VCL4) is the maximum cluster voltage of the battery and in which the first cluster voltage level (VCL1) is strictly less than the second cluster voltage level (VCL4). Battery according to claim 1 wherein the first cluster voltage level (VCL1) is equal to a value between one quarter and three quarters of the second cluster voltage level (VCL4), or is equal to half of the second cluster voltage level (VCL4), or is equal to one third of the second cluster voltage level (VCL4). Battery according to any one of claims 1 to 2 wherein the first interconnection configuration comprises the electrochemical cells (22) electrically connected in series and in parallel within the cluster (CL1), or comprises all the electrochemical cells (21) electrically connected in parallel within the cluster (CL1). Battery according to any one of claims 1 to 3 wherein the second interconnection configuration comprises all electrochemical cells (24) electrically connected in series within the cluster (CL4), or comprises electrochemical cells (24) electrically connected in series and in parallel within the cluster (CL4). Battery according to any one of claims 1 to 4 wherein the plurality of elementary modules further comprises a third elementary module in which the electrochemical cells (22) of the cluster (CL2) are interconnected according to a third interconnection configuration determining a third cluster voltage level (VCL2) and in which the third interconnection configuration comprises the electrochemical cells (22) electrically connected in series and in parallel within the cluster (CL2) such that the third cluster voltage level (VCL2) has an intermediate value between the first voltage level (VCL1) and the second voltage level (VCL4). Battery according to claim 5, wherein the elementary modules (MCLk) of the plurality all have the same even number of electrochemical cells within the cluster and wherein the second and third interconnection configurations are arranged such that the second and third voltage levels (VCL4, VCL2) are values equal to a power of two multiplied by the value of the first voltage level (VCL1). Battery according to any one of claims 1 to 6 in which the first elementary module comprises the H-bridge switching module consisting of switches having an internal drain-source resistance lower than the internal drain-source resistance of the switches of the H-bridge switching module of the second elementary module. Electrical system comprising at least one phase branch (BP1) and a power battery (BAT) according to any one of claims 1 to 7 wherein the battery (BAT) comprises at least one current line (LT1) electrically connected to the phase branch (BP1), the current line (LT1) comprising at least the first and second elementary module of the plurality of elementary modules (MCLk), the system comprising a control unit (BMS) configured to connect in series in the current line (LT1) a controlled selection of elementary modules (MCLk) to generate a selected voltage wave across the terminals of the current line and wherein the controlled selection comprises at least the first and second elementary module. Stationary energy storage system comprising an electrical system according to claim 8. Electrified vehicle with at least partially electrified drivetrain comprising an electrical system according to claim 8. A method for controlling a power battery comprising a plurality of elementary modules (MCLk) for energy storage connected in series in at least one current line (LT1), each elementary module (MCLk) comprising a cluster (CLk) of electrochemical cells and a switching module (COMk) comprising an H-bridge, the electrochemical cells of each cluster (CLk) being electrically interconnected according to an interconnection configuration within each cluster determining a cluster voltage level (Vclk), and the elementary modules being interconnected in series via the switching modules (COMk) so as to form a multilevel inverter distributed in the battery (BAT) capable of generating a selected voltage waveform across the current line (LT1) by connecting in series a controlled selection of elementary modules from the plurality, the method being implemented by a battery control unit and being characterized in that it comprises the following steps:
- determining a voltage setpoint to be generated across the terminals of the current line (LT1),
- the series connection among the plurality of elementary modules of at least one first elementary module delivering a first cluster voltage level (VCL1) and at least one second elementary module delivering a second cluster voltage level (VCL4) to generate a voltage wave as a function of the setpoint, the second cluster voltage level (VCL4) being the maximum cluster voltage of the battery and the first cluster voltage level (VCL1) being strictly less than the second cluster voltage level (VCL4).