Zero-current through compensation method and device for grid-connected inverter

Abstract

The invention provides a zero-current through compensation method for a grid-connected inverter. In the method, when output current of the grid-connected inverter is in a zero-point compensation area, the grid-connected inverter is subjected to zero-point compensation in the following modes, namely the pulse width of a high-frequency switching tube in a high-frequency bridge arm of the grid-connected inverter is adjusted, so that the output current of the grid-connected inverter is not clamped at the zero point, and another high-frequency switching tube in the high-frequency bridge arm is adjusted to complementarily connect the high-frequency switching tube; meanwhile, a corresponding low-frequency switching tube in a low-frequency bridge arm is subjected to the same pulse width, and another low-frequency switching tube in the low-frequency bridge arm is adjusted to complementarily connect the low-frequency switching tube. Correspondingly, the invention provides a zero-current through compensation device. Due to the invention, the grid-connected current is not clamped at the zero point, so that grid-connected current zero-point distortion is eliminated; moreover, the output voltage and output current of the grid-connected inverter can accurately reflect modulation information provided by a grid-connected circuit closed-loop control system.

Description

technical field [0001] The invention relates to the technical field of grid-connected inverters, in particular to a zero-current ride-through compensation method and device for a grid-connected inverter. Background technique [0002] In order to ensure the quality of the power grid, the power sector has very strict regulations on the total harmonic distortion (THD, directly related to the harmonic content) of the grid-connected current of distributed generation, and there are many related international standards, such as IEEE Std929-2000 , UL1741, etc., strictly limit the maximum current harmonic content of grid-connected inverters. Therefore, analyzing the causes of the grid-connected current waveform distortion of the grid-connected inverter and reducing the harmonic content of the grid-connected current are of great significance to ensure the quality of the grid. [0003] In the case of a low grid voltage distortion rate, there are three main reasons affecting the grid-c...

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Problems solved by technology

[0005] However, in addition to the current zero crossing effect caused by the traditional linear PWM control strategy, the conduction duty cycle of the switch is too small, that is, the modulation pulse width is too narrow is also a factor leading to the current zero crossing effect

Specifically, in the grid-connected inverter, due to the influence of the grid-source parasitic capacitance, it takes a certain time for the switch to be turned on and off. Small, that is, if the modulation pulse width is too narrow, it often causes the switch tube to be turned off before it is fully turned on, which leads to the following two problems: one is that the switch tube is too narrow in the output voltage and output current. The pulse width is modulated, so it cannot accurately reflect the modulation information given by the closed-loop control system of the grid-connected circuit; second, the output current is embedded at the zero point, and the grid-connected current waveform is distorted at the zero point, and the current harmonic content increases. Time system power cannot be effectively transmitted, grid-connected output power quality is poor, and switching loss is increased

However, there is currently no solution to this problem

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