CN-119448414-B - Photovoltaic grid-connected inverter, modulation method, modulation device, medium, device and product thereof

CN119448414BCN 119448414 BCN119448414 BCN 119448414BCN-119448414-B

Abstract

The invention discloses a photovoltaic grid-connected inverter and a modulation method, a device, a medium, equipment and a product thereof, wherein the inverter comprises a direct current source, an inversion network, a filter inductor and a power grid, the inversion network comprises a flying capacitor, a first power switch tube, a second power switch tube, a third power switch tube, a fourth power switch tube and a fifth power switch tube, the positive electrode of the direct current source is respectively connected with the collector electrodes of the first power switch tube and the third power switch tube, the negative electrode of the direct current source is respectively connected with the emitter electrode of the second power switch tube, the collector electrode of the fifth power switch tube and the power grid, the positive electrode of the flying capacitor is respectively connected with the emitter electrode of the first power switch tube and the collector electrode of the second power switch tube, and the negative electrode of the flying capacitor is respectively connected with the emitter electrode of the third power switch tube, the collector electrode of the fourth power switch tube and the filter inductor. Through the insertion of the fifth power switch tube and the flying capacitor, the direct current source and the alternating current power grid are decoupled when the photovoltaic grid-connected inverter is in a follow current mode, and the common mode voltage is kept unchanged to inhibit leakage current.

Inventors

ZHANG LINGHAO
YU JIANYU
XIE WENQIANG
WANG XINDA
PENG PAI
WANG JIAMING
YUAN YUBO
SHI MINGMING
ZHANG CHENYU
ZHU RUI
LIU RUIHUANG
XIAO XIAOLONG
LI JUAN
GE XUEFENG

Assignees

国网江苏省电力有限公司电力科学研究院
江苏省电力试验研究院有限公司

Dates

Publication Date: 20260505
Application Date: 20241120

Claims (8)

1. A modulation method of a photovoltaic grid-connected inverter is characterized in that the photovoltaic grid-connected inverter comprises a direct current source, an inversion network, a filter inductance L f and a power grid, The inverter network comprises a flying capacitor C 1 , a first power switching tube S 1 , a second power switching tube S 2 , a third power switching tube S 3 , a fourth power switching tube S 4 and a fifth power switching tube S 5 ; The positive electrode of the direct current source is respectively connected with the collector electrode of the first power switch tube S 1 and the collector electrode of the third power switch tube S 3 , the negative electrode of the direct current source is respectively connected with the emitter electrode of the second power switch tube S 2 , the collector electrode of the fifth power switch tube S 5 and one end of a power grid, and the other end of the power grid is connected with one end of a filter inductor L f ; The anode of the flying capacitor C 1 is respectively connected with the emitter of the first power switch tube S 1 and the collector of the second power switch tube S 2 , the cathode of the flying capacitor C 1 is respectively connected with the emitter of the third power switch tube S 3 , the collector of the fourth power switch tube S 4 and the other end of the filter inductor L f , and the emitter of the fourth power switch tube S 4 is connected with the emitter of the fifth power switch tube S 5 ; the current flowing through the power grid is grid-connected current i g , the voltage at two ends of the power grid is power grid voltage v g , and the modulation method of the photovoltaic grid-connected inverter comprises the following steps of: The direction of the grid-connected current i g and the direction of the grid voltage v g are obtained and judged, wherein the grid-connected current i g flowing from the filter inductor L f to the grid is in the positive direction; If the grid-connected current I g and the grid voltage v g are both in the positive direction, the photovoltaic grid-connected inverter is in the working interval I, and switching between the M1 mode and the M2 mode is performed; If the grid-connected current i g is positive, and the grid voltage v g is negative, the photovoltaic grid-connected inverter is in a working interval II, and switching between an M3 mode and an M4 mode is performed; If the grid-connected current i g and the grid voltage v g are both in the negative direction, the photovoltaic grid-connected inverter is in the working interval III, and switching between the M5 mode and the M6 mode is performed; If the grid-connected current i g is in a negative direction and the grid voltage v g is in a positive direction, the photovoltaic grid-connected inverter is in a working interval IV, and switching between an M7 mode and an M8 mode is performed; When the photovoltaic grid-connected inverter is in an M1 mode, the first power switching tube S 1 , the third power switching tube S 3 and the fifth power switching tube S 5 are conducted, the second power switching tube S 2 and the fourth power switching tube S 4 are cut off, and therefore a direct current source charges the filter inductor L f through the third power switching tube S 3 ; When the photovoltaic grid-connected inverter is in an M2 mode, the first power switch tube S 1 , the fourth power switch tube S 4 and the fifth power switch tube S 5 are conducted, the second power switch tube S 2 and the third power switch tube S 3 are cut off, so that a direct current source charges a flying capacitor C 1 through the first power switch tube S 1 , and a filter inductor L f discharges through the fourth power switch tube S 4 and the fifth power switch tube S 5 ; When the photovoltaic grid-connected inverter is in an M3 mode, the second power switching tube S 2 and the fourth power switching tube S 4 are conducted, the first power switching tube S 1 , the third power switching tube S 3 and the fifth power switching tube S 5 are cut off, and therefore the power grid charges the flying capacitor C 1 and the filter inductor L f through the second power switching tube S 2 ; When the photovoltaic grid-connected inverter is in an M4 mode, the first power switching tube S 1 , the fourth power switching tube S 4 and the fifth power switching tube S 5 are conducted, the second power switching tube S 2 and the third power switching tube S 3 are cut off, and therefore current flows through the fourth power switching tube S 4 , the fifth power switching tube S 5 , the filter inductor L f and a power grid; When the photovoltaic grid-connected inverter is in an M5 mode, the second power switching tube S 2 and the fourth power switching tube S 4 are conducted, the first power switching tube S 1 , the third power switching tube S 3 and the fifth power switching tube S 5 are cut off, and therefore the flying capacitor C 1 supplies power to a power grid through the second power switching tube S 2 ; When the photovoltaic grid-connected inverter is in an M6 mode, the first power switch tube S 1 , the fourth power switch tube S 4 and the fifth power switch tube S 5 are conducted, the second power switch tube S 2 and the third power switch tube S 3 are cut off, so that a direct current source charges a flying capacitor C 1 through the first power switch tube S 1 , the fourth power switch tube S 4 and the fifth power switch tube S 5 , and the filter inductor L f discharges through the fourth power switch tube S 4 and the fifth power switch tube S 5 ; When the photovoltaic grid-connected inverter is in an M7 mode, the first power switching tube S 1 , the third power switching tube S 3 and the fifth power switching tube S 5 are conducted, and the second power switching tube S 2 and the fourth power switching tube S 4 are cut off, so that a power grid supplies power to a direct current source; when the photovoltaic grid-connected inverter is in an M8 mode, the first power switch tube S 1 , the fourth power switch tube S 4 and the fifth power switch tube S 5 are conducted, the second power switch tube S 2 and the third power switch tube S 3 are cut off, and therefore the direct current source charges the flying capacitor C 1 through the first power switch tube S 1 , the fourth power switch tube S 4 and the fifth power switch tube S 5 .
2. The method for modulating a grid-connected photovoltaic inverter according to claim 1, wherein the inverter network further comprises a parasitic capacitance to ground C pv , one end of the parasitic capacitance to ground C pv is connected with the negative electrode of a direct current source, the other end of the parasitic capacitance to ground C pv is grounded and connected with one end of a power grid, and the negative electrode of the direct current source is directly connected with one end of the power grid to form a common-ground topology structure, so that the parasitic capacitance to ground C pv is short-circuited, and common-mode leakage current is eliminated.
3. The method for modulating a photovoltaic grid-connected inverter according to claim 1, wherein the first power switching tube S 1 , the second power switching tube S 2 , the third power switching tube S 3 , the fourth power switching tube S 4 and the fifth power switching tube S 5 are switching components with symmetrical parasitic parameters.
4. The method of claim 1, wherein the DC source comprises a photovoltaic cell PV and a DC regulated capacitor C dc , The positive pole of the photovoltaic cell PV is connected with the positive pole of the direct current voltage stabilizing capacitor C dc , and the negative pole of the photovoltaic cell PV is connected with the negative pole of the direct current voltage stabilizing capacitor C dc .
5. The modulating device of the photovoltaic grid-connected inverter is characterized in that the photovoltaic grid-connected inverter comprises a direct current source, an inversion network, a filter inductance L f and a power grid, The inverter network comprises a flying capacitor C 1 , a first power switching tube S 1 , a second power switching tube S 2 , a third power switching tube S 3 , a fourth power switching tube S 4 and a fifth power switching tube S 5 ; The positive electrode of the direct current source is respectively connected with the collector electrode of the first power switch tube S 1 and the collector electrode of the third power switch tube S 3 , the negative electrode of the direct current source is respectively connected with the emitter electrode of the second power switch tube S 2 , the collector electrode of the fifth power switch tube S 5 and one end of a power grid, and the other end of the power grid is connected with one end of a filter inductor L f ; The anode of the flying capacitor C 1 is respectively connected with the emitter of the first power switch tube S 1 and the collector of the second power switch tube S 2 , the cathode of the flying capacitor C 1 is respectively connected with the emitter of the third power switch tube S 3 , the collector of the fourth power switch tube S 4 and the other end of the filter inductor L f , and the emitter of the fourth power switch tube S 4 is connected with the emitter of the fifth power switch tube S 5 ; The current flowing through the power grid is grid-connected current i g , the voltage at two ends of the power grid is power grid voltage v g , and the modulating device comprises the following modules: The current voltage module is used for acquiring and judging the direction of the grid-connected current i g and the direction of the grid voltage v g , wherein the grid-connected current i g flowing from the filter inductor L f to the grid is in the positive direction; The working interval I module is used for switching between an M1 mode and an M2 mode when the grid-connected current I g and the grid voltage v g are both in the positive direction and the photovoltaic grid-connected inverter is in the working interval I; The working interval II module is used for switching between an M3 mode and an M4 mode when the grid-connected current i g is in a positive direction and the grid voltage v g is in a negative direction and the photovoltaic grid-connected inverter is in the working interval II; The working interval III module is used for switching between an M5 mode and an M6 mode when the grid-connected current i g and the grid voltage v g are in the negative direction and the photovoltaic grid-connected inverter is in the working interval III; The working interval IV module is used for switching between an M7 mode and an M8 mode when the grid-connected current i g is in a negative direction and the grid voltage v g is in a positive direction and the photovoltaic grid-connected inverter is in the working interval IV; When the photovoltaic grid-connected inverter is in an M1 mode, the first power switching tube S 1 , the third power switching tube S 3 and the fifth power switching tube S 5 are conducted, the second power switching tube S 2 and the fourth power switching tube S 4 are cut off, and therefore a direct current source charges the filter inductor L f through the third power switching tube S 3 ; When the photovoltaic grid-connected inverter is in an M2 mode, the first power switch tube S 1 , the fourth power switch tube S 4 and the fifth power switch tube S 5 are conducted, the second power switch tube S 2 and the third power switch tube S 3 are cut off, so that a direct current source charges a flying capacitor C 1 through the first power switch tube S 1 , and a filter inductor L f discharges through the fourth power switch tube S 4 and the fifth power switch tube S 5 ; When the photovoltaic grid-connected inverter is in an M3 mode, the second power switching tube S 2 and the fourth power switching tube S 4 are conducted, the first power switching tube S 1 , the third power switching tube S 3 and the fifth power switching tube S 5 are cut off, and therefore the power grid charges the flying capacitor C 1 and the filter inductor L f through the second power switching tube S 2 ; When the photovoltaic grid-connected inverter is in an M4 mode, the first power switching tube S 1 , the fourth power switching tube S 4 and the fifth power switching tube S 5 are conducted, the second power switching tube S 2 and the third power switching tube S 3 are cut off, and therefore current flows through the fourth power switching tube S 4 , the fifth power switching tube S 5 , the filter inductor L f and a power grid; When the photovoltaic grid-connected inverter is in an M5 mode, the second power switching tube S 2 and the fourth power switching tube S 4 are conducted, the first power switching tube S 1 , the third power switching tube S 3 and the fifth power switching tube S 5 are cut off, and therefore the flying capacitor C 1 supplies power to a power grid through the second power switching tube S 2 ; When the photovoltaic grid-connected inverter is in an M6 mode, the first power switch tube S 1 , the fourth power switch tube S 4 and the fifth power switch tube S 5 are conducted, the second power switch tube S 2 and the third power switch tube S 3 are cut off, so that a direct current source charges a flying capacitor C 1 through the first power switch tube S 1 , the fourth power switch tube S 4 and the fifth power switch tube S 5 , and the filter inductor L f discharges through the fourth power switch tube S 4 and the fifth power switch tube S 5 ; When the photovoltaic grid-connected inverter is in an M7 mode, the first power switching tube S 1 , the third power switching tube S 3 and the fifth power switching tube S 5 are conducted, and the second power switching tube S 2 and the fourth power switching tube S 4 are cut off, so that a power grid supplies power to a direct current source; when the photovoltaic grid-connected inverter is in an M8 mode, the first power switch tube S 1 , the fourth power switch tube S 4 and the fifth power switch tube S 5 are conducted, the second power switch tube S 2 and the third power switch tube S 3 are cut off, and therefore the direct current source charges the flying capacitor C 1 through the first power switch tube S 1 , the fourth power switch tube S 4 and the fifth power switch tube S 5 .
6. A computer readable storage medium having stored thereon a computer program/instruction, which when executed by a processor, implements the steps of the method of modulating a photovoltaic grid-tie inverter of any of claims 1-4.
7. A computer device, comprising: A memory for storing computer programs/instructions; a processor for executing the computer program/instructions to implement the steps of the method of modulating a photovoltaic grid-tie inverter of any of claims 1-4.
8. A computer program product comprising computer programs/instructions which, when executed by a processor, implement the steps of the method of modulating a photovoltaic grid-connected inverter of any of claims 1-4.

Description

Photovoltaic grid-connected inverter, modulation method, modulation device, medium, device and product thereof Technical Field The invention relates to a photovoltaic grid-connected inverter and a modulation method, a modulation device, a medium, equipment and a modulation product thereof, belonging to the technical field of photovoltaic grid-connected inverters. Background In a distributed photovoltaic power generation system, the non-isolated photovoltaic grid-connected inverter (Transformerless Grid-connected Inverter, TLI) has the advantages of small volume, low cost, high efficiency and the like. However, because the TLI topology and the grid have no effective electrical isolation, the common-mode voltage generates common-mode leakage current through parasitic capacitance of the photovoltaic array to the ground, which increases grid-connected current harmonics, affects the quality of the grid-in current, and also causes safety problems. The half-bridge TLI topology directly connects a neutral point of a power grid with a midpoint of a direct current bus, clamps voltage on a parasitic capacitor, and can inhibit leakage current. However, the half-bridge TLI topology has obvious buck characteristics, the input voltage requirement is 2 times that of the full-bridge TLI topology, and the half-bridge TLI topology is not applicable to a low-power scene. The full-bridge TLI topology adopting unipolar sinusoidal pulse width modulation also has the capability of suppressing leakage current, but can generate high-frequency common-mode voltage, and grid-connected current harmonic is larger, and meanwhile, 2 filter inductors are needed to increase the cost. Disclosure of Invention The invention aims to overcome the defects in the prior art and provides a photovoltaic grid-connected inverter, a modulation method, a modulation device, a medium, a device and a product thereof, wherein the photovoltaic grid-connected inverter decouples a direct current source from an alternating current power grid in a follow current mode through the insertion of a fifth power switching tube S 5 and a flying capacitor C 1, and keeps a common-mode voltage unchanged so as to inhibit leakage current. In order to achieve the above purpose, the invention is realized by adopting the following technical scheme: In a first aspect, the invention discloses a photovoltaic grid-connected inverter, which comprises a direct current source, an inverter network, a filter inductor L f and a power grid, The inverter network comprises a flying capacitor C 1, a first power switching tube S 1, a second power switching tube S 2, a third power switching tube S 3, a fourth power switching tube S 4 and a fifth power switching tube S 5; The positive electrode of the direct current source is respectively connected with the collector electrode of the first power switch tube S 1 and the collector electrode of the third power switch tube S 3, the negative electrode of the direct current source is respectively connected with the emitter electrode of the second power switch tube S 2, the collector electrode of the fifth power switch tube S 5 and one end of a power grid, and the other end of the power grid is connected with one end of a filter inductor L f; The positive electrode of the flying capacitor C 1 is respectively connected with the emitter of the first power switch tube S 1 and the collector of the second power switch tube S 2, the negative electrode of the flying capacitor C 1 is respectively connected with the emitter of the third power switch tube S 3, the collector of the fourth power switch tube S 4 and the other end of the filter inductor L f, and the emitter of the fourth power switch tube S 4 is connected with the emitter of the fifth power switch tube S 5. Further, the inverter network further comprises a ground parasitic capacitor C pv, one end of the ground parasitic capacitor C pv is connected with the negative electrode of the direct current source, the other end of the ground parasitic capacitor C pv is grounded and connected with one end of the power grid, and the negative electrode of the direct current source is directly connected with one end of the power grid to form a common-ground topological structure, so that the ground parasitic capacitor C pv is short-circuited, and common-mode leakage current is eliminated. Further, the first power switch tube S 1, the second power switch tube S 2, the third power switch tube S 3, the fourth power switch tube S 4 and the fifth power switch tube S 5 are all switching components with symmetrical parasitic parameters. Further, the direct current source comprises a sum direct current stabilizing capacitor C dc of a photovoltaic cell PV, The positive pole of the photovoltaic cell PV is connected with the positive pole of the direct current voltage stabilizing capacitor C dc, and the negative pole of the photovoltaic cell PV is connected with the negative pole of the direct current voltage stabilizing cap