CN-121984365-A - Photovoltaic inverter and control method thereof

CN121984365ACN 121984365 ACN121984365 ACN 121984365ACN-121984365-A

Abstract

The embodiment of the application discloses a photovoltaic inverter and a control method thereof, which solve the problems of how to reduce the structural complexity and cost of the photovoltaic inverter and reduce the loss of the photovoltaic inverter aiming at the scene of switching between off-grid operation and grid-connected operation of the photovoltaic inverter. The photovoltaic inverter comprises a first bridge arm, a second bridge arm and a third bridge arm, wherein the first bridge arm and the second bridge arm are arranged between a positive direct current bus and a negative direct current bus, and the third bridge arm is arranged between the midpoint of the first bridge arm and the midpoint of the second bridge arm. The controller is used for controlling the first bridge arm and the second bridge arm to work and controlling the third bridge arm to stop working under the condition that the voltage of the power grid is smaller than or equal to the voltage threshold value of the power grid, so that the three output ends of the photovoltaic inverter output electric energy to supply power to the first load. The controller is also used for controlling the first bridge arm, the second bridge arm and the third bridge arm to work under the condition that the voltage of the power grid is larger than the voltage threshold value of the power grid, so that the two output ends of the photovoltaic inverter output electric energy to supply power to the power grid or the second load.

Inventors

SHI HUI
RU YI
MA ZHENG
HU TIANQI
SUN CHENGFEI
TAN XIAOJIN
Hui Libin
CHEN HU

Assignees

华为数字能源技术有限公司

Dates

Publication Date: 20260505
Application Date: 20241030

Claims (15)

1. The photovoltaic inverter is characterized in that an input end of the photovoltaic inverter is used for being connected with a photovoltaic array, and the photovoltaic inverter comprises a controller, a first inductor, a positive bus capacitor, a negative bus capacitor, a first bridge arm, a second bridge arm and a third bridge arm, wherein the positive bus capacitor, the negative bus capacitor, the first bridge arm and the second bridge arm are arranged between a positive direct current bus and a negative direct current bus, and the third bridge arm is arranged between a midpoint of the first bridge arm and a midpoint of the second bridge arm; The positive and negative bus capacitors comprise a first capacitor and a second capacitor which are connected in series, the first bridge arm comprises a first switching tube and a second switching tube which are connected in series, the second bridge arm comprises a third switching tube and a fourth switching tube which are connected in series, the third bridge arm comprises a fifth switching tube and a sixth switching tube, the drain electrode or the collector electrode of the fifth switching tube is connected with the drain electrode or the collector electrode of the sixth switching tube, or the source electrode or the emitter electrode of the fifth switching tube is connected with the source electrode or the emitter electrode of the sixth switching tube; The first inductor is arranged between the first end of the third bridge arm and the first output end of the photovoltaic inverter, the connection point of the positive bus capacitor and the negative bus capacitor is connected with the second output end of the photovoltaic inverter, the second end of the third bridge arm is connected with the third output end of the photovoltaic inverter, and the three output ends of the photovoltaic inverter are used for being connected with a power grid or a load; The controller is used for controlling the first bridge arm and the second bridge arm to work and controlling the third bridge arm to stop working under the condition that the voltage of the power grid is smaller than or equal to a power grid voltage threshold value so as to enable three output ends of the photovoltaic inverter to output electric energy to supply power to a first load; And the controller is further used for controlling the first bridge arm, the second bridge arm and the third bridge arm to work under the condition that the voltage of the power grid is larger than the power grid voltage threshold value, so that the two output ends of the photovoltaic inverter output electric energy to supply power to the power grid or the second load.
2. The photovoltaic inverter of claim 1 further comprising a third capacitance and a fourth capacitance; the third capacitor is arranged between the first output end and the second output end, and the fourth capacitor is arranged between the second output end and the third output end.
3. The photovoltaic inverter of claim 1 or 2 further comprising a second inductance disposed between the second end of the third leg and the third output end, the second inductance magnetically coupled with the first inductance.
4. A photovoltaic inverter according to any of claims 1-3, characterized in that the photovoltaic inverter further comprises a third inductance and a fourth leg arranged between the positive and negative dc bus bars, the fourth leg comprising a seventh and eighth switching tube connected in series, the midpoint of the fourth leg being connected with one end of the third inductance and the other end of the third inductance being connected with the connection point of the positive and negative bus capacitances.
5. The photovoltaic inverter of claim 4, it is characterized in that the method comprises the steps of, The controller is further configured to obtain a current value of the third inductor, a positive bus voltage, a negative bus voltage, and a direct current component of a phase voltage, and output a pulse width modulation signal when the voltage of the power grid is less than or equal to a power grid voltage threshold, where the current value of the third inductor, the positive bus voltage, the negative bus voltage, and the direct current component of the phase voltage are used to determine a duty cycle of the pulse width modulation signal, and the pulse width modulation signal is used to control the fourth bridge arm; The positive bus voltage is the absolute value of the voltage difference between the connection points of the positive direct current bus and the positive bus capacitor, the negative bus voltage is the absolute value of the voltage difference between the connection points of the negative direct current bus and the positive bus capacitor, the phase voltage is the voltage between the first output end and the second output end, or the phase voltage is the voltage between the second output end and the third output end.
6. The photovoltaic inverter of claim 5, it is characterized in that the method comprises the steps of, The controller is further configured to obtain the phase voltage when the voltage of the power grid is less than or equal to a power grid voltage threshold, where the current value of the third inductor, the positive bus voltage, the negative bus voltage, the dc component of the phase voltage, and the phase voltage are used to determine a duty cycle of the pulse width modulation signal.
7. The photovoltaic inverter of any of claims 1-6 further comprising a fifth capacitance disposed between the first end of the second leg and the first output, a sixth capacitance disposed between the first output and the third output, and a seventh capacitance disposed between the second end of the second leg and the third output.
8. A control method of a photovoltaic inverter, characterized by being applied to a photovoltaic inverter, the method comprising: When the voltage of the power grid is smaller than or equal to the voltage threshold of the power grid, controlling the first bridge arm and the second bridge arm to work, and controlling the third bridge arm to stop working so that the three output ends of the photovoltaic inverter output electric energy to supply power to the first load; controlling the first bridge arm, the second bridge arm and the third bridge arm to work under the condition that the voltage of the power grid is larger than the power grid voltage threshold value, so that two output ends of the photovoltaic inverter output electric energy to supply power to the power grid or the second load; The input end of the photovoltaic inverter is used for being connected with a photovoltaic array, and the photovoltaic inverter comprises a first inductor, a positive bus capacitor, a negative bus capacitor, a first bridge arm, a second bridge arm and a third bridge arm, wherein the positive bus capacitor and the negative bus capacitor are arranged between a positive direct current bus and a negative direct current bus; The positive and negative bus capacitors comprise a first capacitor and a second capacitor which are connected in series, the first bridge arm comprises a first switching tube and a second switching tube which are connected in series, the second bridge arm comprises a third switching tube and a fourth switching tube which are connected in series, the third bridge arm comprises a fifth switching tube and a sixth switching tube, the drain electrode or the collector electrode of the fifth switching tube is connected with the drain electrode or the collector electrode of the sixth switching tube, or the source electrode or the emitter electrode of the fifth switching tube is connected with the source electrode or the emitter electrode of the sixth switching tube; The first inductor is arranged between the first end of the third bridge arm and the first output end of the photovoltaic inverter, the connection point of the positive bus capacitor and the negative bus capacitor is connected with the second output end of the photovoltaic inverter, the second end of the third bridge arm is connected with the third output end of the photovoltaic inverter, and the three output ends of the photovoltaic inverter are used for being connected with the power grid or the load.
9. The method of claim 8, wherein the method further comprises: When the voltage of the power grid is smaller than or equal to a power grid voltage threshold value, acquiring a current value of a third inductor, a positive bus voltage, a negative bus voltage and a direct current component of a phase voltage, and outputting a pulse width modulation signal, wherein the current value of the third inductor, the positive bus voltage, the negative bus voltage and the direct current component of the phase voltage are used for determining the duty ratio of the pulse width modulation signal, and the pulse width modulation signal is used for controlling a fourth bridge arm; the positive bus voltage is the absolute value of the voltage difference between the connection points of the positive direct current bus and the positive and negative bus capacitors, the negative bus voltage is the absolute value of the voltage difference between the connection points of the negative direct current bus and the positive and negative bus capacitors, the phase voltage is the voltage between the first output end and the second output end, or the phase voltage is the voltage between the second output end and the third output end; The photovoltaic inverter further comprises a third inductor and a fourth bridge arm arranged between the positive direct current bus and the negative direct current bus, the fourth bridge arm comprises a seventh switching tube and an eighth switching tube which are connected in series, the middle point of the fourth bridge arm is connected with one end of the third inductor, and the other end of the third inductor is connected with a connecting point of the positive and negative bus capacitors.
10. The method according to claim 9, wherein the method further comprises: And under the condition that the voltage of the power grid is smaller than or equal to a power grid voltage threshold value, acquiring the phase voltage, wherein the current value of the third inductor, the positive bus voltage, the negative bus voltage, the direct current component of the phase voltage and the phase voltage are used for determining the duty ratio of the pulse width modulation signal.
11. The photovoltaic power generation system is characterized by comprising a photovoltaic inverter, wherein the input end of the photovoltaic inverter is used for being connected with a photovoltaic array, and the photovoltaic inverter comprises a controller, a first inductor, a positive bus capacitor, a negative bus capacitor, a first bridge arm and a second bridge arm, wherein the positive bus capacitor, the first bridge arm and the second bridge arm are arranged between a positive direct current bus and a negative direct current bus, and a third bridge arm is arranged between the middle point of the first bridge arm and the middle point of the second bridge arm; The positive and negative bus capacitors comprise a first capacitor and a second capacitor which are connected in series, the first bridge arm comprises a first switching tube and a second switching tube which are connected in series, the second bridge arm comprises a third switching tube and a fourth switching tube which are connected in series, the third bridge arm comprises a fifth switching tube and a sixth switching tube, the drain electrode or the collector electrode of the fifth switching tube is connected with the drain electrode or the collector electrode of the sixth switching tube, or the source electrode or the emitter electrode of the fifth switching tube is connected with the source electrode or the emitter electrode of the sixth switching tube; The first inductor is arranged between the first end of the third bridge arm and the first output end of the photovoltaic inverter, the connection point of the positive bus capacitor and the negative bus capacitor is connected with the second output end of the photovoltaic inverter, the second end of the third bridge arm is connected with the third output end of the photovoltaic inverter, and the three output ends of the photovoltaic inverter are used for being connected with a power grid or a load; The controller is used for controlling the first bridge arm and the second bridge arm to work and controlling the third bridge arm to stop working under the condition that the voltage of the power grid is smaller than or equal to a power grid voltage threshold value so as to enable three output ends of the photovoltaic inverter to output electric energy to supply power to a first load; And the controller is further used for controlling the first bridge arm, the second bridge arm and the third bridge arm to work under the condition that the voltage of the power grid is larger than the power grid voltage threshold value, so that the two output ends of the photovoltaic inverter output electric energy to supply power to the power grid or the second load.
12. The photovoltaic power generation system of claim 11, wherein the photovoltaic inverter further comprises a second inductance disposed between the second end of the third leg and the third output, the second inductance magnetically coupled with the first inductance.
13. The photovoltaic power generation system according to claim 11 or 12, wherein the photovoltaic inverter further comprises a third inductor, and a fourth leg disposed between the positive dc bus and the negative dc bus, the fourth leg comprising a seventh switching tube and an eighth switching tube connected in series, a midpoint of the fourth leg being connected to one end of the third inductor, and the other end of the third inductor being connected to a connection point of the positive and negative bus capacitances.
14. The photovoltaic power generation system of claim 13, wherein, The controller is further configured to obtain a current value of the third inductor, a positive bus voltage, a negative bus voltage, and a direct current component of a phase voltage, and output a pulse width modulation signal when the voltage of the power grid is less than or equal to a power grid voltage threshold, where the current value of the third inductor, the positive bus voltage, the negative bus voltage, and the direct current component of the phase voltage are used to determine a duty cycle of the pulse width modulation signal, and the pulse width modulation signal is used to control the fourth bridge arm; The positive bus voltage is the absolute value of the voltage difference between the connection points of the positive direct current bus and the positive bus capacitor, the negative bus voltage is the absolute value of the voltage difference between the connection points of the negative direct current bus and the positive bus capacitor, the phase voltage is the voltage between the first output end and the second output end, or the phase voltage is the voltage between the second output end and the third output end.
15. The photovoltaic power generation system of claim 14, wherein, The controller is further configured to obtain the phase voltage when the voltage of the power grid is less than or equal to a power grid voltage threshold, where the current value of the third inductor, the positive bus voltage, the negative bus voltage, the dc component of the phase voltage, and the phase voltage are used to determine a duty cycle of the pulse width modulation signal.

Description

Photovoltaic inverter and control method thereof Technical Field The application relates to the technical field of energy, in particular to a photovoltaic inverter and a control method thereof. Background The photovoltaic inverter may include a high efficiency reliable inverter concept (HIGHLY EFFICIENT AND reliable inverter concept, heric) inverter that includes the circuit topology of an H4 bridge inverter that is used to convert direct current to single phase alternating current. In the off-grid operation scene and the grid-connected operation scene of the photovoltaic inverter, the driving mode of the Heric inverter can be adopted to drive the Heric inverter, or the driving mode of the H4 bridge inverter can be adopted to drive the Heric inverter. However, aiming at the off-grid operation of the photovoltaic inverter, a scene of outputting alternating current by adopting a single-phase three-wire system is needed, the driving mode of the Heric inverter is adopted to drive the Heric inverter, and a split-phase transformer is needed to be arranged in the photovoltaic inverter, so that the photovoltaic inverter is complex in structure and high in cost. Aiming at the grid-connected operation of the photovoltaic inverter, a scene of outputting alternating current by adopting a single-phase two-wire system is needed, the H4 bridge inverter in the Heric inverter is driven by adopting a driving mode of the H4 bridge inverter, and the loss of the photovoltaic inverter is high due to higher voltage born by each switching tube. Therefore, aiming at the scene that the photovoltaic inverter is switched between off-grid operation and grid-connected operation, how to reduce the structural complexity and cost of the photovoltaic inverter and reduce the loss of the photovoltaic inverter is a problem to be solved. Disclosure of Invention The embodiment of the application provides a photovoltaic inverter and a control method thereof, which solve the problems of how to reduce the structural complexity and cost of the photovoltaic inverter and reduce the loss of the photovoltaic inverter aiming at the scene of switching between off-grid operation and grid-connected operation of the photovoltaic inverter. In order to achieve the above purpose, the embodiment of the application adopts the following technical scheme: In a first aspect of an embodiment of the present application, a photovoltaic inverter is provided, an input end of which is used for connecting a photovoltaic array, the photovoltaic inverter including a controller, a first inductor, a positive and negative bus capacitor disposed between a positive dc bus and a negative dc bus, a first bridge arm and a second bridge arm, and a third bridge arm disposed between a midpoint of the first bridge arm and a midpoint of the second bridge arm. The positive and negative bus capacitors comprise a first capacitor and a second capacitor which are connected in series, the first bridge arm comprises a first switching tube and a second switching tube which are connected in series, the second bridge arm comprises a third switching tube and a fourth switching tube which are connected in series, the third bridge arm comprises a fifth switching tube and a sixth switching tube, the drain electrode or the collector electrode of the fifth switching tube is connected with the drain electrode or the collector electrode of the sixth switching tube, or the source electrode or the emitter electrode of the fifth switching tube is connected with the source electrode or the emitter electrode of the sixth switching tube. The first inductor is arranged between the first end of the third bridge arm and the first output end of the photovoltaic inverter, the connection point of the positive bus capacitor and the negative bus capacitor is connected with the second output end of the photovoltaic inverter, the second end of the third bridge arm is connected with the third output end of the photovoltaic inverter, and the three output ends of the photovoltaic inverter are used for being connected with a power grid or a load. The controller is used for controlling the first bridge arm and the second bridge arm to work and controlling the third bridge arm to stop working under the condition that the voltage of the power grid is smaller than or equal to the voltage threshold value of the power grid, so that the three output ends of the photovoltaic inverter output electric energy to supply power to the first load. The controller is also used for controlling the first bridge arm, the second bridge arm and the third bridge arm to work under the condition that the voltage of the power grid is larger than the voltage threshold value of the power grid, so that the two output ends of the photovoltaic inverter output electric energy to supply power to the power grid or the second load. Based on the scheme, compared with the driving mode of the Heric inverter, the driving mode of the Heric inverter is adopted to d