TWI886569B - Controlling power conversion system with zero current output and method thereof - Google Patents

Abstract

A power conversion system that controls zero-current output, suitable for controlling the output current of the power conversion system to a grid-connected power supply. The power conversion system includes: a DC power supply, an energy storage element, a single-phase full-bridge inverter module, a filter module, phase-locked loop module and control module; wherein, when an output current command value is equal to zero, the control module stops outputting a first-arm pulse width modulation signal, a reverse first-arm pulse width modulation signal, a second-arm pulse width modulation signal, a reverse second-arm pulse width modulation signal to the single-phase full-bridge inverter module, so as to cut off the electrical connection path between the DC power supply and filter module. Therefore, the power conversion system that controls zero-current output of the present invention can be applied to the frequency modulation backup auxiliary service market to solve the problem of power lose. A method of controlling power conversion system that controls zero-current output is also provide.

Description

Power regulation system and method for controlling zero current output

The present invention relates to a power regulation system and method, in particular to a power regulation system and method for controlling zero current output.

As the proportion of intermittent renewable energy increases, the intermittent and uncertain nature of its power generation has an impact on the stability of the power system, and the reliability and stability of the power grid have become important considerations. Microgrids can integrate renewable energy and provide a solution for power stability through energy management and control. The control technology of the power regulation system plays an important role and can effectively provide auxiliary services to the power grid to improve the resilience of the power grid.

Generally speaking, the power conditioning system includes energy storage elements and converters. In independent operation mode, it outputs AC voltage to supply power to the load. In grid-connected mode, it can be connected to the grid and output power to the grid, thereby providing power auxiliary services and helping to stabilize the power supply system. Taipower currently provides qualified traders with day-ahead auxiliary services, including frequency modulation backup auxiliary services, instant backup auxiliary services, and supplementary backup auxiliary services. Among them, frequency modulation backup auxiliary services are the most frequent in power regulation of generator sets. Once the grid frequency shifts, the power regulation system participating in the frequency modulation backup auxiliary service needs to respond within seconds and adjust the output power throughout the day in response to the frequency change to help support the grid frequency.

According to Taipower's frequency modulation auxiliary service specifications, during the frequency modulation auxiliary service output process, when the grid frequency is within the flexible adjustment range, the power regulation system can enter automatic charge and discharge control to maintain the battery state of charge (State Of Charge, SOC) of the energy storage element within the system setting range to respond to the demand for instant power output under the frequency change of the next second. If the battery state of charge of the energy storage element can already respond to the power output demand under the future frequency change, the power regulation system can then perform zero power output to reduce charging and discharging losses. In addition, referring to the revenue settlement specifications of frequency modulation auxiliary services, reducing power losses can also reduce the operating costs of qualified traders' generator sets.

However, when the current power regulation system executes the output current with a current command of zero, the traditional control method will still cause the power switch to be turned on. In addition to the control error, a small current will still be output, resulting in power loss.

In order to solve the above problems, the purpose of the present invention is to provide a power regulation system for controlling zero current output, which is suitable for controlling the output current of the power regulation system to be output to a grid-connected power source. The power regulation system includes: a DC power source; an energy storage element electrically connected to the DC power source; a single-phase full-bridge current conversion module electrically connected to the energy storage element, and used to modulate the first arm pulse width according to the first arm pulse width modulation signal and the reverse first arm pulse width modulation signal. The first arm is connected to the DC power supply via the single-phase full-bridge conversion module to filter out the high-frequency components of the pulse DC power to generate AC power. The second arm is connected to the DC power supply via the single-phase full-bridge conversion module to filter out the high-frequency components of the pulse DC power to generate AC power. The second arm is connected to the DC power supply via the single-phase full-bridge conversion module to filter out the high-frequency components of the pulse DC power to generate AC power. The second arm is connected to the DC power supply via the single-phase full-bridge conversion module to filter out the high-frequency components of the pulse DC power to generate AC power. The second arm is connected to the DC power supply via the single-phase full-bridge conversion module to filter out the high-frequency components of the pulse DC power to generate AC power. The control module is electrically connected to the phase-locked loop module to determine whether the power regulation system outputs the output current to the grid-connected power source according to the output current command value; wherein, when the output current command value is equal to zero, the control module stops outputting the first arm pulse width modulation signal, the reverse first arm pulse width modulation signal, the second arm pulse width modulation signal and the reverse second arm pulse width modulation signal to the single The control module is a single-phase full-bridge converter module, which disconnects the path of electrical connection between the DC power supply and the filter module; wherein, when the output current command value is non-zero, the control module resumes outputting the first arm pulse width modulation signal, the reverse first arm pulse width modulation signal, the second arm pulse width modulation signal and the reverse second arm pulse width modulation signal to the single-phase full-bridge converter module, so as to connect the path of electrical connection between the DC power supply and the filter module.

In some embodiments, the single-phase full-bridge converter module further includes: a first power transistor switch, which is turned on or off by the first arm pulse width modulation signal; a second power transistor switch, which forms a first arm electrical path with the first power transistor switch, and the second power transistor switch is turned on or off by the reverse first arm pulse width modulation signal; a third power transistor switch, which is electrically connected to the first power transistor switch, and the third power transistor switch is turned on or off by the second arm pulse width modulation signal; and a fourth power transistor switch, which forms a second arm electrical path with the third power transistor switch, and the fourth power transistor switch is turned on or off by the reverse second arm pulse width modulation signal.

In some embodiments, the first power transistor switch and the second power transistor switch of the first arm electrical path are not turned on at the same time, and the third power transistor switch and the fourth power transistor switch of the second arm electrical path are not turned on at the same time.

In some embodiments, the control module further includes: a subtractor for subtracting the output current command value from the output current of the power regulation system to generate an error signal; a feedback controller electrically connected to the subtractor for receiving the error signal and outputting a feedback voltage signal; a feedforward controller for receiving the output current command value and outputting a feedforward voltage signal; an adder for connecting the feedback controller and the feedforward controller. The adder is electrically connected to the power supply circuit for adding the forward voltage signal and the feedback voltage signal to generate a control signal; and the control chip is electrically connected to the adder for generating a first arm pulse width modulation signal, a reverse first arm pulse width modulation signal, a second arm pulse width modulation signal, a reverse second arm pulse width modulation signal and an output current of the power regulation system according to the control signal and the reverse control signal.

In order to solve the above problems, the purpose of the present invention is to provide a method for zero current output of a power regulation system, which is suitable for controlling the output current of the power regulation system to be output to a grid-connected power source, comprising the following steps: obtaining an output current command value of the power regulation system; and determining the relationship between the output current command value and zero to determine whether the power regulation system outputs the output current to the grid-connected power source; wherein, when the output current command value is equal to zero, the control module stops outputting the first arm pulse width modulation signal, reverses the first arm pulse width modulation signal, and stops outputting the first arm pulse width modulation signal. The control module outputs the first arm pulse width modulation signal, the second arm pulse width modulation signal and the reverse second arm pulse width modulation signal to the phase full-bridge converter module to disconnect the path of the electrical connection between the DC power supply and the filter module; wherein, when the output current command value is non-zero, the control module resumes outputting the first arm pulse width modulation signal, the reverse first arm pulse width modulation signal, the second arm pulse width modulation signal and the reverse second arm pulse width modulation signal to the single-phase full-bridge converter module to connect the path of the electrical connection between the DC power supply and the filter module.

In summary, the power regulation system and method for controlling zero current output of the present invention can be connected in parallel with the grid-connected power supply in the grid-connected mode, and output power to the grid-connected power supply to provide power auxiliary services. When the frequency of the grid-connected power supply V _ac shifts, the power regulation system can adjust the output power in accordance with the frequency change to help support the frequency of the grid-connected power supply V _ac and improve the stability of the power supply system. When the power conditioning system is performing zero power output to reduce charge and discharge losses, the first arm pulse width modulation signal, the reverse first arm pulse width modulation signal, the second arm pulse width modulation signal and the reverse second arm pulse width modulation signal can be immediately disabled to disconnect the power switches in the single-phase full-bridge converter module, so as to achieve a second-level response to stop output, avoid power loss, and thus reduce the operating cost of the generator set.

10: Energy storage element

20: Single-phase full-bridge converter module

22: Electrical path of the first arm

24: Second arm electrical path

30: Filter module

40: Phase-locked loop module

50: Control module

51: Subtraction device

52: Feedback controller

53: Feedforward controller

54: Adder

55: Control chip

100: Power regulation system

Er: Error signal

I _o : output current

I _{o_cmd} : Output current command value

SW1: First power transistor switch

SW2: Second power transistor switch

SW3: The third power transistor switch

SW4: Fourth power transistor switch

T _A+ : First arm pulse width modulation signal

T _A- : Reverse first arm pulse width modulation signal

T _B+ : Second arm pulse width modulation signal

T _B- : Reverse second arm pulse width modulation signal

u: Feedback voltage signal

V _ac : Grid-connected power

V _c : Feedback voltage signal

V _control : control signal

V _dc : DC power supply

S100, S102, S104, S106: Steps

FIG1 is a block diagram showing a power regulation system for controlling zero current output according to an embodiment of the present invention.

Figure 2 is a circuit diagram of a single-phase full-bridge converter module according to an embodiment of the present invention.

FIG3 is a block diagram showing a control module of an embodiment of the present invention.

FIG4A is a schematic diagram showing a current signal simulation without zero current output control.

FIG4B is a schematic diagram showing a current signal simulation with zero current output control.

FIG5 is a flow chart showing a method for controlling zero current output of a power regulation system according to an embodiment of the present invention.

Please refer to FIG1, which shows a block diagram of a power regulation system 100 for controlling zero current output according to an embodiment of the present invention. The power regulation system 100 for controlling zero current output is suitable for controlling the output current I _o of the power regulation system 100 to the grid-connected power source V _ac . The power regulation system 100 includes: a DC power source V _dc , an energy storage element 10, a single-phase full-bridge converter module 20, a filter module 30, a phase-locked loop module 40 and a control module 50. In addition, the power regulation system 100 for controlling zero current output can be applied to the frequency modulation backup auxiliary service market to enhance the competitiveness of the energy storage industry.

The DC power source V _dc can generate a DC voltage signal and/or a DC current signal. The DC power source V _dc can be, for example, a battery power source or a DC power supply.

The energy storage element 10 is electrically connected to the DC power source V _dc . The energy storage element 10 may be, for example, a capacitor or a battery.

The single-phase full-bridge converter module 20 is electrically connected to the energy storage element 10 and the DC power source V _dc . The single-phase full-bridge converter module 20 can be turned on or off according to the first arm pulse width modulation signal TA ₊ , the reverse first arm pulse width modulation signal _TA- , the second arm pulse width modulation signal TB ₊ and the reverse second arm pulse width modulation signal _TB- to output pulse DC power.

The filter module 30 is electrically connected to the energy storage element 10 and the DC power source V _dc through the single-phase full-bridge converter module 20. The filter module 30 can receive the pulse DC power output by the single-phase full-bridge converter module 20. The filter module 30 can be used to filter out the high-frequency components of the pulse DC power to generate AC power. The filter module 30 can be, for example, a filter composed of an inductor and a capacitor.

The phase-locked loop module 40 is electrically connected to the filter module 30, the control module 50, and the grid-connected power source V _ac . The phase-locked loop module 40 can receive the AC power source output by the filter module 30. The phase-locked loop module 40 can be used to make the angular frequency ω _s of the AC power source equal to the angular frequency ω of the grid-connected power source V _ac . The phase-locked loop module 40 can measure the voltage signal of the grid-connected power source V _ac , and transmit it to the analog-to-digital converter (not shown) for sampling after attenuation, and then calculate the synchronous angular frequency ω _s through the control module 50 to ensure that the synchronous angular frequency ω _s of the AC power source is close to or equal to the angular frequency ω of the grid-connected power source V _ac . For example, the voltage signal of the grid-connected power V _ac after attenuation can be shifted 90 degrees by equation (1), and equation (1) is as follows:

The input signal e of the PI controller (not shown) in the phase-locked loop module 40 is then designed using equation (2), and equation (2) is as follows: e = V _m { sin (ω t ) cos (ω _s t )- cos (ω t ) sin (ω _s t )} (2)

Wherein, e is the signal at the input of the PI controller, Vm is the amplitude _of the voltage signal after the grid-connected power supply _Vac is attenuated, ω is the angular frequency of the grid-connected power supply _Vac , and _ωs is the synchronous angular frequency of the AC power supply.

When the input signal e is suppressed to zero, as shown in equation (3), the synchronous angular frequency ω of the AC power source will be equal to the angular frequency ω _s of the grid-connected power source V _ac , so as to complete the output of the phase-locked phase-locked loop module 40, and equation (3) is as follows:

Thus, once the angular frequency _ωs of the grid-connected power source V _ac shifts, the phase-locked loop module 40 can immediately respond to the frequency change for regulation to help support the required frequency of the grid-connected power source V _ac , thereby improving the control speed of the power regulation system 100.

The control module 50 is electrically connected to the phase-locked loop module 40. The control module 50 can receive an output current command value I _{o_cmd} . The output current command value I _{o_cmd} can be obtained through a data calculation program, a data measurement program, or a user command, but is not limited thereto. The control module 50 can be used to determine whether the power regulation system 100 outputs the output current I _o to the grid-connected power source V _ac according to the output current command value I _{o_cmd} . For example, when the output current command value I _{o_cmd} is equal to zero, the control module 50 stops outputting the first arm pulse width modulation signal TA ₊ , the reverse first arm pulse width modulation signal _TA- , the second arm pulse width modulation signal TB ₊ and the reverse second arm pulse width modulation signal _TB- to the single-phase full-bridge converter module 20 to disconnect the path of the electrical connection between the DC power source Vdc and the filter module 30. In this way, the power regulation system 100 will not output the output current I _o to the grid-connected power source V _ac .

When the output current command value I _{o_cmd} is non-zero, the control module 50 resumes outputting the first arm pulse width modulation signal TA ₊ , the reverse first arm pulse width modulation signal _TA- , the second arm pulse width modulation signal TB ₊ and the reverse second arm pulse width modulation signal _TB- to the single-phase full-bridge converter module 20 to conduct the path of the electrical connection between the DC power source Vdc and the filter module 30. In this way, the power regulation system 100 can output the output current I _o to the grid-connected power source V _ac . In addition, generally speaking, the output current command value I _{o_cmd} is an AC time-varying signal. Therefore, in the embodiment of the present invention, the output current command value I _{o_cmd} may have “positive value”, “negative value”, and “zero value”, and the non-zero value refers to “positive value” or “negative value”.

Please refer to FIG. 2, which shows a circuit diagram of a single-phase full-bridge converter module 20 of an embodiment of the present invention. The single-phase full-bridge converter module 20 further includes: a first power transistor switch SW1, a second power transistor switch SW2, a third power transistor switch SW3, and a fourth power transistor switch SW4.

The first power transistor switch SW1 is driven by the first arm pulse width modulation signal TA ₊ to be turned on or off. For example, when the first arm pulse width modulation signal TA ₊ is at a high voltage level, the first power transistor switch SW1 is in a turned-on state. When the first arm pulse width modulation signal TA ₊ is at a low voltage level, the first power transistor switch SW1 is in a turned-off state.

The second power transistor switch SW2 is electrically connected to the first power transistor switch SW1. The second power transistor switch SW2 and the first power transistor switch SW1 form a first arm electrical path 22. The second power transistor switch SW2 is driven by the reverse first arm pulse width modulation signal _TA- to be turned on or off. For example, when the reverse first arm pulse width modulation signal _TA- is at a high voltage level, the second power transistor switch SW2 is in a conducting state. When the reverse first arm pulse width modulation signal _TA- is at a low voltage level, the second power transistor switch SW2 is in a disconnected state.

The third power transistor switch SW3 is driven by the second arm pulse width modulation signal TB ₊ to be turned on or off. For example, when the second arm pulse width modulation signal TB ₊ is at a high voltage level, the third power transistor switch SW3 is in a conducting state. When the second arm pulse width modulation signal TB ₊ is at a low voltage level, the third power transistor switch SW3 is in a disconnected state.

The fourth power transistor switch SW4 is electrically connected to the third power transistor switch SW3. The fourth power transistor switch SW4 and the third power transistor switch SW3 form a second arm electrical path 24. The fourth power transistor switch SW4 is driven by the reverse second arm pulse width modulation signal _TB- to be turned on or off. For example, when the reverse second arm pulse width modulation signal _TB- is at a high voltage level, the fourth power transistor switch SW4 is in a conducting state. When the reverse second arm pulse width modulation signal _TB- is at a low voltage level, the fourth power transistor switch SW4 is in a disconnected state.

In addition, the first arm pulse width modulation signal TA ₊ and the reverse first arm pulse width modulation signal _TA- are complementary signals. The second arm pulse width modulation signal TB ₊ and the reverse second arm pulse width modulation signal _TB- are complementary signals to prevent the second power transistor switch SW2 and the first power transistor switch SW1 from being turned on at the same time or the fourth power transistor switch SW4 and the third power transistor switch SW3 from being turned on at the same time. In other words, the first power transistor switch SW1 and the second power transistor switch SW2 of the first arm electrical path 22 will not be turned on at the same time, and the third power transistor switch SW3 and the fourth power transistor switch SW4 of the second arm electrical path 24 will not be turned on at the same time.

Please refer to FIG. 3, which shows a block diagram of the control module 50 of the embodiment of the present invention. The control module 50 further includes: a subtractor 51, a feedback controller 52, a feedforward controller 53, an adder 54 and a control chip 55.

The subtractor 51 may receive the output current command value I _{o_cmd} . The subtractor 51 may be configured to subtract the output current command value I _{o_cmd} from the output current I _o of the power conditioning system to generate an error signal Er.

The feedforward controller 53 can be used to receive the output current command value I _{o_cmd} and output a feedforward voltage signal. The feedforward controller 53 can be designed according to the rules or equations between the input and output of the control chip 55. For example, equation (4) is the relationship between the voltage of the DC power supply of the power regulation system 100 and the voltage of the AC power supply, and equation (4) is as follows:

為交流電源的電壓之峰值，m _a 為調變係數，V_dc為直流電源的電壓值。在正常調變下，調變係數m _a 小於1，故直流電源V_dc的電壓值須大 於交流電源的電壓之峰值

，當交流電源與直流電源V_dc大小選定後，調變係數值即可由式(4)產生。 in

is the peak value of the AC power voltage, mA is the modulation _factor , and V _dc is the DC power voltage. Under normal modulation, the modulation _factor mA is less than 1, so the DC power voltage V _dc must be greater than the peak value of the AC power voltage.

Once the AC power source and DC power source V _dc are selected, the modulation coefficient value can be generated by equation (4).

與三角波訊號之峰值

的比值，而式(5)如下：

Then, by substituting the modulation coefficient into equation (5), we can get the peak value of the feedforward voltage signal V _c

and the peak value of the triangle wave signal

The ratio of, and formula (5) is as follows:

為前饋控制器53輸出的前饋電壓訊號V之峰值，

為三角波訊號之峰值。當選定三角波訊號之峰值

時，前饋電壓訊號V_c的大小即可知悉，並可產生前饋電壓訊號V_c，如下式(6)：

in

is the peak value of the feedforward voltage signal V output by the feedforward controller 53,

is the peak value of the triangle wave signal.

When , the magnitude of the feedforward voltage signal V _c can be known, and the feedforward voltage signal V _c can be generated, as shown in the following formula (6):

The feedback controller 52 is electrically connected to the subtractor 51. The feedback controller 52 can be used to receive the error signal Er and output the feedback voltage signal u to the adder 54. This embodiment adopts a proportional integral controller as the feedback controller 52. The input signal of the feedback controller 52 is the error signal Er, as shown in the following formula (7): Er = I _{o_cmd} - I _o (7)

The output signal of the feedback controller 52 is the feedback voltage signal u, which is expressed as follows:

The adder 54 is electrically connected to the feedback controller 52 and the feedforward controller 53. The adder 54 can receive the feedback voltage signal u output by the feedback controller 52 and the feedforward voltage signal V _c output by the feedforward controller 53. The adder 54 can be used to add the feedforward voltage signal V _c and the feedback voltage signal u to generate a control signal V _control .

The control chip 55 is electrically connected to the adder 54. The control chip 55 can receive the control signal V _control output by the adder 54. The control chip 55 can be used to generate the first arm _pulse width _modulation signal TA _{+, the reverse first arm pulse width modulation signal TA-} , the second arm pulse width modulation signal TB ₊ , the reverse second arm pulse width modulation signal _TB- and the output current _Io of the power regulation system 100 according to the control signal _V control and the reverse control signal -V control (not shown). In addition, the reverse control signal -V _control can be obtained by the control chip 55 processing the control signal V _control , but is not limited thereto. For example, the control chip 55 can compare the control signal V _control and the reverse control signal with the triangle wave signal to generate the first arm pulse width modulation signal TA ₊ , the reverse first arm pulse width modulation signal _TA- , the second arm pulse width modulation signal TB ₊ , the reverse second arm pulse width modulation signal _TB- and the output current _Io of the power regulation system 100.

It is worth noting that when the output current command value I _{o_cmd} = 0, the PWM signals of the first power transistor switch SW1, the second power transistor switch SW2, the third power transistor switch SW3 and the fourth power transistor switch SW4 are disabled (Disable), which can ensure that each power switch on the first arm electrical path 22 and the second arm electrical path 24 is in the disconnected state. When the output current command value I _{o_cmd} ≠ 0, the PWM signals of the first power transistor switch SW1, the second power transistor switch SW2, the third power transistor switch SW3 and the fourth power transistor switch SW4 are enabled (Enable), and the normal switching of each power switch on the first arm electrical path 22 and the second arm electrical path 24 is restored, as shown in equations (10) and (11):

Since all power switches in the single-phase full-bridge converter module 20 are in the disconnected state when the output current command value I _{o_cmd} is zero, the problem of power switches still being turned on in the traditional SPWM control method is solved, which not only causes power loss but also causes control errors.

Please refer to FIG4A, which shows a current signal simulation diagram without zero current output control. The horizontal axis is time, and the vertical axis is the current signal. As shown in FIG4A, the simulation presents the output current command value _{Io_cmd} and the actual output current _Io . When the output current command value _{Io_cmd} is zero, the output current _Io will still output a small current to the grid-connected power source _Vac , causing power loss and increasing the operating cost of the generator set.

Please refer to FIG. 4B , which shows a current signal simulation diagram with zero current output control. The simulation shows that when the output current command value I _{o_cmd} is zero, the output current I _o can be effectively reduced to zero, and when the output current command value I _{o_cmd} is restored to a non-zero value, the current output can be quickly restored and the output current I _o can be output to the grid-connected power source V _ac , thereby improving the control accuracy of the power regulation system 100 and achieving zero current output.

Please refer to FIG5 , which shows a flow chart of a method for controlling zero current output of the power regulation system 100 according to an embodiment of the present invention. Step S100 , obtaining an output current command value I _{o — cmd} of the power regulation system 100 .

In step S102, the relationship between the output current command value I _{o_cmd} and zero is determined to determine whether the power regulation system 100 outputs the output current I _o to the grid-connected power source V _ac .

In step S104, when the output current command value I _{o_cmd} is equal to zero, the control module 50 stops outputting the first arm pulse width modulation signal TA ₊ , the reverse first arm pulse width modulation signal _TA- , the second arm pulse width modulation signal TB ₊ and the reverse second arm pulse width modulation signal _TB- to the single-phase full-bridge converter module 20 to disconnect the path of the electrical connection between the DC power source V _dc and the filter module 30, so that the power regulation system 100 stops outputting the output current I _o to the grid-connected power source V _ac , and then returns to step S100. For example, the single-phase full-bridge converter module 20 operates as follows: the first power transistor switch SW1 is driven to be turned on or off according to the voltage level of the first arm pulse width modulation signal TA ₊ ; the second power transistor switch SW2 is driven to be turned on or off according to the voltage level of the reverse first arm pulse width modulation signal _TA- ; the third power transistor switch SW3 is driven to be turned on or off according to the voltage level of the second arm pulse width modulation signal TB ₊ ; and the fourth power transistor switch SW4 is driven to be turned on or off according to the voltage level of the reverse second arm pulse width modulation signal _TB- . When the control module 50 receives the output current command value I _{o_cmd} and confirms that it is equal to zero, it can immediately stop outputting the first arm pulse width modulation signal T _A+ , the reverse first arm pulse width modulation signal T _A- , the second arm pulse width modulation signal T _B+ and the reverse second arm pulse width modulation signal T _B- to the single-phase full-bridge converter module 20, thereby improving the overall control speed and accuracy of the power regulation system 100 and achieving the effect of stopping output in seconds.

In addition, in this embodiment, the single-phase full-bridge converter module 20 further operates as follows: the first power transistor switch SW1 and the second power transistor switch SW2 of the first arm electrical path 22 are prohibited from being turned on at the same time; and the third power transistor switch SW3 and the fourth power transistor switch SW4 of the second arm electrical path 24 are prohibited from being turned on at the same time. In this way, a short circuit is avoided to affect the operation of the single-phase full-bridge converter module 20 or cause danger.

In step S106, when the output current command value I _{o_cmd} is a non-zero value, the control module 50 resumes outputting the first arm pulse width modulation signal TA ₊ , the reverse first arm pulse width modulation signal _TA- , the second arm pulse width modulation signal TB ₊ and the reverse second arm pulse width modulation signal _TB- to the single-phase full-bridge converter module 20 to conduct the path of the electrical connection between the DC power source V _dc and the filter module 30, so that the power regulation system 100 resumes outputting the output current I _o to the grid-connected power source V _ac , and then returns to step S100.

In summary, the power regulation system and method for controlling zero current output of the present invention can be connected in parallel with the grid-connected power source V _ac in the grid-connected mode, and output power to the grid-connected power source V _ac , thereby providing power auxiliary services. When the frequency of the grid-connected power source V _ac shifts, the power regulation system can adjust the output power in accordance with the frequency change to help support the frequency of the grid-connected power source V _ac and improve the stability of the power supply system. When the power conditioning system 100 is performing zero power output to reduce charge and discharge losses, the first arm pulse width modulation signal TA ₊ , the reverse first arm pulse width modulation signal _TA- , the second arm pulse width modulation signal TB ₊ and the reverse second arm pulse width modulation signal _TB- can be immediately disabled to disconnect the power switches in the single-phase full-bridge converter module 20, thereby achieving a second-level response to stop output, avoiding power loss, and thereby reducing the operating cost of the generator set.

10: Energy storage element 20: Single-phase full-bridge converter module 30: Filter module 40: Phase-locked loop module 50: Control module 100: Power regulation system Io: Output current Io_cmd: Output current command value TA+: First arm pulse width modulation signal TA-: Reverse first arm pulse width modulation signal TB+: Second arm pulse width modulation signal TB-: Reverse second arm pulse width modulation signal Vac: Grid-connected power supply Vdc: DC power supply

Claims (8)

A power regulation system for controlling zero current output is suitable for controlling the output current of the power regulation system to be output to a grid-connected power supply. The power regulation system includes: A DC power supply; An energy storage element electrically connected to the DC power supply; A single-phase full-bridge converter module electrically connected to the energy storage element, for switching on or off according to a first arm pulse width modulation signal, a reverse first arm pulse width modulation signal, a second arm pulse width modulation signal and a reverse second arm pulse width modulation signal to output a pulse DC power; A filter module is electrically connected to the DC power source through the single-phase full-bridge converter module to filter out the high-frequency components of the pulse DC power to generate an AC power source; A phase-locked loop module is electrically connected to the filter module and the grid-connected power source to make the angular frequency of the AC power source equal to the angular frequency of the grid-connected power source; and A control module is electrically connected to the phase-locked loop module to determine whether the power regulation system outputs the output current to the grid-connected power source according to an output current command value; Wherein, when the output current command value is equal to zero, the control module stops outputting the first arm pulse width modulation signal, the reverse first arm pulse width modulation signal, the second arm pulse width modulation signal and the reverse second arm pulse width modulation signal to the single-phase full-bridge current conversion module to disconnect the path of the electrical connection between the DC power source and the filter module; Among them, when the output current command value is a non-zero value, the control module resumes outputting the first arm pulse width modulation signal, the reverse first arm pulse width modulation signal, the second arm pulse width modulation signal and the reverse second arm pulse width modulation signal to the single-phase full-bridge current conversion module to conduct the path of the electrical connection between the DC power source and the filter module. A power regulation system for controlling zero current output as described in claim 1, wherein the single-phase full-bridge converter module further comprises: a first power transistor switch, which is turned on or off by the first arm pulse width modulation signal; a second power transistor switch, which forms a first arm electrical path with the first power transistor switch, and the second power transistor switch is turned on or off by the reverse first arm pulse width modulation signal; a third power transistor switch, which is electrically connected to the first power transistor switch, and the third power transistor switch is turned on or off by the second arm pulse width modulation signal; and A fourth power transistor switch forms a second arm electrical path with the third power transistor switch. The fourth power transistor switch is driven by the reverse second arm pulse width modulation signal to be turned on or off. A power regulation system for controlling zero current output as described in claim 2, wherein the first power transistor switch and the second power transistor switch of the first arm electrical path will not be turned on at the same time, and the third power transistor switch and the fourth power transistor switch of the second arm electrical path will not be turned on at the same time. A power regulation system for controlling zero current output as described in claim 1, wherein the control module further comprises: a subtractor for subtracting the output current command value from the output current of the power regulation system to generate an error signal; a feedback controller electrically connected to the subtractor for receiving the error signal and outputting a feedback voltage signal; a feedforward controller for receiving the output current command value and outputting a feedforward voltage signal; an adder electrically connected to the feedback controller and the feedforward controller for adding the feedforward voltage signal to the feedback voltage signal to generate a control signal; and A control chip is electrically connected to the adder, and is used to generate the first arm pulse width modulation signal, the reverse first arm pulse width modulation signal, the second arm pulse width modulation signal, the reverse second arm pulse width modulation signal and the output current of the power regulation system according to the control signal and a reverse control signal. A method for controlling the zero current output of a power regulation system, suitable for controlling the output current of the power regulation system as described in claim 1 to be output to a grid-connected power source, comprising the following steps: Obtaining an output current command value of the power regulation system; and Determining the relationship between the output current command value and zero to determine whether the power regulation system outputs the output current to the grid-connected power source; Wherein, when the output current command value is equal to zero, the control module stops outputting the first arm pulse width modulation signal, the reverse first arm pulse width modulation signal, the second arm pulse width modulation signal and the reverse second arm pulse width modulation signal to the single-phase full-bridge current conversion module to disconnect the path of the electrical connection between the DC power source and the filter module; Among them, when the output current command value is a non-zero value, the control module resumes outputting the first arm pulse width modulation signal, the reverse first arm pulse width modulation signal, the second arm pulse width modulation signal and the reverse second arm pulse width modulation signal to the single-phase full-bridge current conversion module to conduct the path of the electrical connection between the DC power source and the filter module. A method for controlling zero current output of a power regulation system as described in claim 5, wherein the single-phase full-bridge converter module further comprises: a first power transistor switch and a second power transistor switch constituting a first arm electrical path, and a third power transistor switch and a fourth power transistor switch constituting a second arm electrical path, and the single-phase full-bridge converter module operates as follows: The first power transistor switch is driven to turn on or off according to the voltage level of the first arm pulse width modulation signal; The second power transistor switch is driven to turn on or off according to the voltage level of the reverse first arm pulse width modulation signal; The third power transistor switch is driven to be turned on or off according to the voltage level of the second arm pulse width modulation signal; and The fourth power transistor switch is driven to be turned on or off according to the voltage level of the reverse second arm pulse width modulation signal. A method for controlling zero current output of a power regulation system as described in claim 6, wherein the single-phase full-bridge converter module further operates as follows: The first power transistor switch and the second power transistor switch of the first arm electrical path are prohibited from being turned on at the same time; and The third power transistor switch and the fourth power transistor switch of the second arm electrical path are prohibited from being turned on at the same time. A method for controlling the zero current output of a power regulation system as described in claim 5, wherein the control module further comprises: a subtractor for subtracting the output current command value from the output current of the power regulation system to generate an error signal; a feedback controller electrically connected to the subtractor for receiving the error signal and outputting a feedback voltage signal; a feedforward controller for receiving the output current command value and outputting a feedforward voltage signal; an adder electrically connected to the feedback controller and the feedforward controller for adding the feedforward voltage signal to the feedback voltage signal to generate a control signal; and A control chip is electrically connected to the adder, and is used to generate the first arm pulse width modulation signal, the reverse first arm pulse width modulation signal, the second arm pulse width modulation signal, the reverse second arm pulse width modulation signal and the output current of the power regulation system according to the control signal and a reverse control signal.