CN-115720056-B - Concentrated suppression method for leakage current of platform-level photovoltaic inverter

CN115720056BCN 115720056 BCN115720056 BCN 115720056BCN-115720056-B

Abstract

The invention is suitable for the field of photovoltaic inverter leakage current suppression, and provides a concentrated suppression method for the photovoltaic inverter leakage current at a transformer area level, which comprises the steps of counting the number of photovoltaic inverters in a transformer area, and setting the carrier phase initial value of each photovoltaic inverter; the method comprises the steps of obtaining leakage current signals of each photovoltaic inverter in a platform area, monitoring the whole leakage current condition of the platform area in real time, optimizing carrier phase shift angles according to the whole leakage current condition of the platform area through a simulated annealing algorithm to obtain carrier phase compensation values of each photovoltaic inverter, sending generated carrier phase compensation instructions to each photovoltaic inverter local control unit, and adjusting each carrier phase by each photovoltaic inverter local control unit according to the received instructions so as to realize centralized suppression of the leakage current of the platform area level inverter.

Inventors

CHENG YUNPENG
CHEN JIANSHAN
ZHANG XUEBO
ZHANG JITAO
WANG YONG
WANG FEI
LI XIAOQIANG
ZHANG QUANQUAN

Assignees

国网江苏省电力有限公司响水县供电分公司
中国矿业大学

Dates

Publication Date: 20260508
Application Date: 20221114

Claims (7)

1. A method for concentrated suppression of leakage current of a photovoltaic inverter at a station level, the method comprising the steps of: s01, counting the number of photovoltaic inverters in a platform area, and setting the carrier phase initial value of each photovoltaic inverter; S02, obtaining leakage current signals of all photovoltaic inverters in the transformer area, and monitoring the integral leakage current condition of the transformer area in real time; S03, optimizing a carrier phase shift angle through a simulated annealing algorithm according to the whole leakage current condition of the station area to obtain carrier phase compensation values of all photovoltaic inverters; And S04, sending the generated carrier phase compensation instruction to each photovoltaic inverter local control unit, and adjusting each carrier phase by each photovoltaic inverter local control unit according to the received instruction so as to realize centralized suppression of the leakage current of the transformer area level inverter.
2. The concentrated suppression method for district-level photovoltaic inverter leakage current according to claim 1, wherein in step S01, each photovoltaic inverter carrier phase initial value is that a first photovoltaic inverter carrier phase is unchanged, a second photovoltaic inverter carrier phase is shifted from the first one The carrier phase of the third photovoltaic inverter is offset from that of the first photovoltaic inverter Analogize in the first place The carrier phase of the photovoltaic inverter is offset from the first phase Wherein the method comprises the steps of The total number of the photovoltaic inverters in the transformer area is calculated.
3. The concentrated suppression method for a cell-level photovoltaic inverter leakage current according to claim 2, wherein the set carrier phase initial value is substituted into each inverter leakage current expression, then the first The table inverter leakage current expression is: , Wherein, the Not less than 2, mr being modulation ratio, ωsw being angular frequency of triangular carrier wave, ω0 being angular frequency of modulated wave, vdc being DC side voltage, amp being harmonic amplitude, K being loop passive parameter expression, its specific form being: , Wherein L1 is a photovoltaic inverter side filter inductor, lg is a photovoltaic inverter network side filter inductor, cf is a photovoltaic inverter filter capacitor, and Cpv is a photovoltaic unit parasitic capacitor.
4. The concentrated suppression method for the leakage current of the platform-level photovoltaic inverter according to claim 1, further comprising the step of sending leakage current information of each platform inverter to a monitoring center in real time so as to monitor the whole leakage current condition of the platform.
5. The concentrated suppression method for the leakage current of the photovoltaic inverter of the transformer area level according to any one of claims 1 to 4, wherein in step S03, the leakage current information of each photovoltaic inverter in the transformer area and the overall leakage current condition of the transformer area are determined, and the carrier phase of the leakage current is optimized by a simulated annealing algorithm.
6. The concentrated suppression method for the leakage current of the platform-level photovoltaic inverter according to claim 5, wherein optimizing the carrier phase of the leakage current by the simulated annealing algorithm specifically comprises: S11, initializing parameters, wherein the parameters comprise an initial temperature T, a termination temperature Ttop, an annealing rate alpha and iteration times k at each temperature; S12, randomly generating an inverter carrier phase data set between [0,2 pi ], substituting each phase data into a leakage current expression, calculating the sum of the leakage currents of the inverters in the transformer area, judging whether to accept the inverter carrier phase data set according to a Metropolis criterion, wherein the Metropolis criterion is set as follows: , Where p represents the probability of accepting the set of inverter carrier phase data; S13, comparing the p with the random number generated in [0,1], if the p is smaller than the random number, the algorithm receives the current carrier phase data, compares the sum of the current transformer area inverter leakage currents with the standard maximum value of the total transformer area leakage currents, if the sum of the current transformer area inverter leakage currents is smaller than the standard maximum value, exits the circulation, designates the group of the transformer area inverter carrier phase data as a carrier phase compensation value, and if the p is not smaller than the random number, abandons the current phase data, and continues to circulate until an ideal carrier phase compensation value appears.
7. The concentrated suppression method for the leakage current of the photovoltaic inverter of the district level according to claim 1, wherein in S04, each local control unit of the photovoltaic inverter adjusts the respective carrier phase according to the received carrier phase compensation value command, so that the leakage current is lower than the set standard maximum value of the leakage current of the district level, thereby achieving concentrated suppression of the leakage current of the photovoltaic inverter of the district level.

Description

Concentrated suppression method for leakage current of platform-level photovoltaic inverter Technical Field The invention belongs to the field of photovoltaic inverter leakage current inhibition, and particularly relates to a concentrated leakage current inhibition method for a transformer area-level photovoltaic inverter. Background With the rapid development of economy, the demand for energy in the society of today is increasing. The traditional fossil fuel has limited reserves and brings about various environmental problems, and the solar energy is one of clean energy sources, has the advantages of small pollution, rich energy storage, convenient collection and the like, is widely used at present, and the total amount of the photovoltaic installation is steadily increased in recent years. The distributed photovoltaic inverter is used as core equipment for energy conversion and electric energy quality control in the photovoltaic grid-connected system, plays an important role in the whole photovoltaic grid-connected system, and various indexes of the distributed photovoltaic inverter directly or indirectly influence the electric energy quality. The photovoltaic inverter is classified into an isolated photovoltaic inverter and a non-isolated photovoltaic inverter by taking the electrical isolation of a direct current side and an alternating current side with or without a transformer as a standard, wherein the non-isolated photovoltaic inverter has the advantages of simple structure, small volume, light weight and the like, and has wider application prospect. However, unlike isolated photovoltaic inverters, non-isolated photovoltaic inverters, when in use, have a direct electrical connection between the photovoltaic unit and the ac grid. Because larger parasitic capacitance exists between the photovoltaic cell panel and the ground, a loop is formed among the photovoltaic cell panel, the parasitic capacitance and the ground and the power grid, the parasitic capacitance is stimulated by a common mode voltage with high frequency variation, and larger leakage current is caused in the common mode loop. The occurrence of leakage current seriously affects the output power quality of the photovoltaic grid-connected system and even endangers personal safety. Disclosure of Invention The embodiment of the invention aims to provide a concentrated suppression method for leakage current of a platform-level photovoltaic inverter, which aims to solve the problems in the background technology. The embodiment of the invention is realized in such a way that the method for intensively inhibiting the leakage current of the platform-level photovoltaic inverter comprises the following steps: s01, counting the number of photovoltaic inverters in a platform area, and setting the carrier phase initial value of each photovoltaic inverter; S02, obtaining leakage current signals of all photovoltaic inverters in the transformer area, and monitoring the integral leakage current condition of the transformer area in real time; S03, optimizing a carrier phase shift angle through a simulated annealing algorithm according to the whole leakage current condition of the station area to obtain carrier phase compensation values of all photovoltaic inverters; And S04, sending the generated carrier phase compensation instruction to each photovoltaic inverter local control unit, and adjusting each carrier phase by each photovoltaic inverter local control unit according to the received instruction so as to realize centralized suppression of the leakage current of the transformer area level inverter. According to the concentrated suppression method for the leakage current of the district-level photovoltaic inverter, provided by the embodiment of the invention, the concentrated suppression of the leakage current of the district-level inverter is realized by reasonably configuring the carrier phases of all inverters based on the inverter control strategy of carrier phase shifting. In addition, the overall leakage current condition in the transformer area is monitored in real time, and the carrier phase is adjusted and compensated in time, so that the leakage current suppression precision of the transformer area-level photovoltaic inverter is improved. Drawings Fig. 1 is a schematic diagram of a system architecture of a photovoltaic inverter in a method for centralized suppression of leakage current of the photovoltaic inverter at a bay level; FIG. 2 is a graph of a photovoltaic inverter leakage current common mode equivalent model used in a concentrated suppression method of the photovoltaic inverter leakage current at a station level; FIG. 3 is a schematic diagram of carrier phase shifting of a photovoltaic inverter used in a centralized suppression method of leakage current of a photovoltaic inverter at a station level; FIG. 4 is a flow chart of carrier phase shift control used in a centralized suppression method for leakage current of a photovoltaic in