A method for suppressing leakage current of a three-phase four-leg photovoltaic grid-connected inverter

Abstract

The invention discloses a method for restraining a leakage current of a three-phase four-bridge-arm photovoltaic grid-connected inverter. The method is characterized in that modulating waves Va*, Vb* and Vc* and triangular carrier waves VC are compared through comparators to obtain logic signals Sa, Sb and Sc, then a communication signal ST1, a communication signal ST2 and a communication signal ST3 corresponding to an A phase, a B phase and a C phase respectively are communicated in turns, and the logic signals Sa, Sb and Sc are controlled to obtain three-phase four-bridge-arm photovoltaic grid-connected inverter switching signals through a logic circuit. The three-phase four-bridge-arm photovoltaic grid-connected inverter leakage current restraining method has the advantages that complex space vector modulation is not needed for generating the system switching signals, only a basic logic circuit is needed for serving as a switching signal generating circuit, the method can be achieved through simulation elements, and the achieving process is simple and practicable; meanwhile, the system common-mode voltage can be constant, and active suppression on the system leakage current is accordingly achieved.

Description

technical field [0001] The invention belongs to the field of power electronic conversion, and relates to an inverter control technology from DC power input to AC power output, in particular to a method for suppressing leakage current of a three-phase four-arm photovoltaic grid-connected inverter. Background technique [0002] Non-isolated three-phase photovoltaic grid-connected inverters are small in size and high in efficiency, and have good application prospects. However, using the traditional three-phase four-leg photovoltaic grid-connected inverter topology and modulation method will lead to a large leakage current in the system. The German VDE-0126-1-1 standard stipulates that if the peak leakage current of the photovoltaic system is greater than 300mA, the photovoltaic grid-connected inverter must be disconnected from the grid within 0.3S. Because the leakage current will cause many hazards, such as causing electromagnetic interference, it will also pose a potential t...

AI Technical Summary

Problems solved by technology

The Chinese patent application number is 201210108752.5, and its title is "A Modulation Method for Reducing Common Mode Voltage of Three-phase PWM Converter". The application uses space vector modulation technology to improve system common mode voltage performance, although the common mode voltage decreases One-sixth of the DC bus voltage, but cannot guarantee a constant common-mode voltage

Although this method can improve the output waveform and reduce the harmonic content, it still cannot guarantee the constant common mode voltage of the system, so it cannot effectively suppress the leakage current

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