Photovoltaic inverter and control method thereof

1 . A photovoltaic inverter comprising:

a conversion circuit comprising:

a positive direct current bus;

a negative direct current bus;

a switching transistor;

a conversion circuit input configured to couple to a power supply through the positive direct current bus and the negative direct current bus; and

a conversion circuit output configured to couple to a load;

a collection circuit configured to obtain a positive direct current bus voltage of the conversion circuit and a negative direct current bus voltage of the conversion circuit; and

a controller configured to:

generate an even-order harmonic voltage regulation signal based on the positive direct current bus voltage, the negative direct current bus voltage, and a first phase of an output voltage of the photovoltaic inverter;

generate a drive control signal based on the even-order harmonic voltage regulation signal; and

control the switching transistor to be turned on or off to control the conversion circuit output to output a target voltage and reduce a difference between the positive direct current bus voltage and the negative direct current bus voltage.

2 . The photovoltaic inverter of claim 1 , wherein the conversion circuit further comprises:

a neutral point;

at least one switching bridge arm comprising switching transistors; and

two groups of capacitors coupled in series with each other and coupled in parallel with the at least one switching bridge arm between the positive direct current bus and the negative direct current bus, wherein a series connection point of the two groups of capacitors is the neutral point,

wherein the collection circuit comprises a collection circuit input coupled to the positive direct current bus, the negative direct current bus, and the neutral point, and

wherein the collection circuit is further configured to obtain the positive direct current bus voltage and the negative direct current bus voltage based on a first potential of the positive direct current bus, a second potential of the negative direct current bus, and a third potential of the neutral point.

3 . The photovoltaic inverter of claim 1 , wherein the controller is further configured to:

generate an even-order harmonic amplitude signal based on the positive direct current bus voltage and the negative direct current bus voltage;

generate an even-order harmonic phase signal based on the first phase; and

further generate the even-order harmonic voltage regulation signal based on the even-order harmonic amplitude signal and the even-order harmonic phase signal.

4 . The photovoltaic inverter of claim 3 , wherein the collection circuit is further configured to obtain the first phase and a second phase of an output current of the photovoltaic inverter, and wherein the controller is further configured to:

determine a type of the load based on the first phase and the second phase, wherein the type is at least one of an inductive load, a capacitive load, or a resistive load; and

further generate the even-order harmonic phase signal based on the type.

5 . The photovoltaic inverter of claim 4 , wherein the controller comprises:

a signal generation circuit coupled to the collection circuit and configured to:

generate the even-order harmonic amplitude signal based on the positive direct current bus voltage and the negative direct current bus voltage;

generate the even-order harmonic phase signal based on the first phase; and

generate the even-order harmonic voltage regulation signal based on the even-order harmonic amplitude signal and the even-order harmonic phase signal;

a voltage control circuit coupled to the signal generation circuit and configured to generate a voltage instruction signal of the conversion circuit based on the even-order harmonic voltage regulation signal; and

a drive control circuit configured to:

couple the voltage control circuit to the conversion circuit;

generate the drive control signal based on the voltage instruction signal; and

control the switching transistor to be turned on or off based on the drive control signal.

6 . The photovoltaic inverter of claim 5 , wherein the voltage control circuit is further configured to:

obtain a fundamental wave instruction of an external central control system; and

superimpose the fundamental wave instruction and the even-order harmonic voltage regulation signal to obtain the voltage instruction signal of the conversion circuit.

7 . The photovoltaic inverter of claim 6 , wherein the controller further comprises:

a voltage feedback circuit coupled to the collection circuit and the voltage control circuit and configured to:

obtain the output voltage through the collection circuit; and

set the output voltage as a voltage feedback signal,

wherein the voltage control circuit is further configured to generate a level-1 voltage instruction signal based on the voltage feedback signal and the voltage instruction signal, and

wherein the drive control circuit is further configured to generate the drive control signal based on the level-1 voltage instruction signal.

8 . The photovoltaic inverter of claim 7 , wherein the controller further comprises:

a current feedback circuit coupled to the collection circuit and configured to:

obtain the output current through the collection circuit; and

set the output current as a current feedback signal; and

a current control circuit coupled to the voltage control circuit, the drive control circuit, and the current feedback circuit and configured to generate a level-2 voltage instruction signal based on the level-1 voltage instruction signal and the current feedback signal,

wherein the drive control circuit is further configured to generate the drive control signal based on the level-2 voltage instruction signal.

9 . The photovoltaic inverter of claim 8 , wherein the drive control circuit is further coupled to the signal generation unit; circuit and is further configured to:

obtain the even-order harmonic voltage regulation signal; and

generate the drive control signal based on the even-order harmonic voltage regulation signal and the level-2 voltage instruction signal.

10 . A photovoltaic inverter control method comprising:

detecting a positive direct current bus voltage of a conversion circuit of a photovoltaic inverter and a negative direct current bus voltage of the conversion circuit;

generating an even-order harmonic voltage regulation signal based on the positive direct current bus voltage, the negative direct current bus voltage, and a first phase of an output voltage of the photovoltaic inverter;

generating a drive control signal based on the even-order harmonic voltage regulation signal; and

controlling a switching transistor in the conversion circuit to be turned on or off to control the conversion circuit to output a target voltage and reduce a difference between the positive direct current bus voltage and the negative direct current bus voltage.

11 . The photovoltaic inverter control method of claim 10 , wherein detecting the positive direct current bus voltage and the negative direct current bus voltage comprises: detecting the positive direct current bus voltage and the negative direct current bus voltage based on a first potential of the positive direct current bus, a second potential of the negative direct current bus, and a third potential of a neutral point of the conversion circuit.

12 . The photovoltaic inverter control method of claim 10 , wherein generating the even-order harmonic voltage regulation signal comprises:

generating an even-order harmonic amplitude signal based on the positive direct current bus voltage and the negative direct current bus voltage;

generating an even-order harmonic phase signal based on the first phase; and

further generating the even-order harmonic voltage regulation signal based on the even-order harmonic amplitude signal and the even-order harmonic phase signal.

13 . The photovoltaic inverter control method of claim 12 , wherein generating the even-order harmonic phase signal comprises:

detecting the first phase and a second phase of an output current of the photovoltaic inverter;

determining a type of a load based on the first phase and the second phase, wherein the type is one or more of an inductive load, a capacitive load, or a resistive load; and

further generating the even-order harmonic phase signal based on.

14 . The photovoltaic inverter control method of claim 13 , wherein generating the drive control signal comprises:

generating a voltage instruction signal of the conversion circuit based on the even-order harmonic voltage regulation signal; and

further generating the drive control signal based on the voltage instruction signal.

15 . The photovoltaic inverter control method of claim 14 , wherein generating the voltage instruction signal comprises:

detecting a fundamental wave instruction of an external central control system; and

superposing the fundamental wave instruction and the even-order harmonic voltage regulation signal to obtain the voltage instruction signal.

16 . A power supply system comprising:

a power supply configured to supply power to a load; and

a photovoltaic inverter comprising:

a conversion circuit comprising:

a positive direct current bus;

a negative direct current bus;

a switching transistor;

a conversion circuit input configured to couple to the power supply through the positive direct current bus and the negative direct current bus; and

a conversion circuit output configured to couple to the load;

a collection circuit configured to obtain a positive direct current bus voltage of the conversion circuit and a negative direct current bus voltage of the conversion circuit; and

a controller configured to:

generate an even-order harmonic voltage regulation signal based on the positive direct current bus voltage, the negative direct current bus voltage, and a first phase of an output voltage of the photovoltaic inverter;

generate a drive control signal based on the even-order harmonic voltage regulation signal; and

control the switching transistor to be turned on or off to control the conversion circuit output to output a target voltage and reduce a difference between the positive direct current bus voltage and the negative direct current bus voltage.

17 . The power supply system of claim 16 , wherein the conversion circuit further comprises:

a neutral point;

at least one switching bridge arm comprising switching transistors; and

two groups of capacitors coupled in series with each other and coupled in parallel with the at least one switching bridge arm between the positive direct current bus and the negative direct current bus, wherein a series connection point of the two groups of capacitors is the neutral point of the conversion circuit,

wherein the collection circuit comprises a collection circuit input coupled to the positive direct current bus, the negative direct current bus, and the neutral point, and

wherein the collection circuit is further configured to obtain the positive direct current bus voltage and the negative direct current bus voltage based on a first potential of the positive direct current bus, a second potential of the negative direct current bus, and a third potential of the neutral point.

18 . The power supply system of claim 16 , wherein the controller is further configured to:

generate an even-order harmonic amplitude signal based on the positive direct current bus voltage and the negative direct current bus voltage;

generate an even-order harmonic phase signal based on the first phase; and

further generate the even-order harmonic voltage regulation signal based on the even-order harmonic amplitude signal and the even-order harmonic phase signal.

19 . The power supply system of claim 18 , wherein the collection circuit is further configured to obtain the first phase and a second phase of an output current of the photovoltaic inverter, and wherein the controller is further configured to:

determine a type of the load based on the first phase and the second phase, wherein the type is one or more of an inductive load, a capacitive load, or a resistive load; and

further generate the even-order harmonic phase signal based on the type.

20 . The power supply system of claim 19 , wherein the controller comprises:

a signal generation circuit coupled to the collection circuit and configured to:

generate the even-order harmonic amplitude signal based on the positive direct current bus voltage and the negative direct current bus voltage;

generate the even-order harmonic phase signal based on the first phase; and

generate the even-order harmonic voltage regulation signal based on the even-order harmonic amplitude signal and the even-order harmonic phase signal;

a voltage control circuit coupled to the signal generation circuit and configured to generate a voltage instruction signal of the conversion circuit based on the even-order harmonic voltage regulation signal; and

a drive control circuit configured to:

couple the voltage control circuit to the conversion circuit;

generate the drive control signal based on the voltage instruction signal; and

control the switching transistor to be turned on or off based on the drive control signal.