A Method for Detecting Damage of Network-side Filter Capacitor of Double-fed Frequency Converter

Abstract

The invention discloses a method of detecting damage of a filter capacitor on a doubly-fed frequency converter grid side. The method comprises the following steps in sequence: S1, acquiring current of a three-phase grid side filter capacitor; S2, conducting 3s / 2s conversion; S3, conducting Z conversion on two transfer functions of an SOGI phase-shift circuit; S4, calculating output values of two coordinate components after Z conversion of the transfer functions of the SOGI phase-shift circuit is conducted; S5, solving positive and negative sequence components of the current; S6, calculating positive and negative sequence values of the current of the grid side filter capacitor; and S7, calculating the degree of unbalance. According to the method, the SOGI phase-shift circuit is utilized to fully filter current shifts and high-frequency signals, time delays caused by filter links are avoided, the grid connection time of the doubly-fed frequency converter is shortened, and the grid side filter capacitor can be accurately detected whether to be damaged without increases of hardware.

Description

technical field [0001] The invention belongs to the technical field of capacitor damage detection, and in particular relates to a method for detecting damage to a network-side filter capacitor of a doubly-fed frequency converter. Background technique [0002] At present, in wind power generation, double-fed wind turbines and back-to-back dual PWM converters are mainly used to realize variable-speed and constant-frequency power generation; LCL filters are usually used on the grid side of the grid to reduce the high-order harmonic content of the grid current; during the operation of the inverter, the capacitors in the LCL filter that mainly play a filtering role are prone to failure. [0003] Most of the existing LCL filter capacitor fault detection methods rely on hardware, which increases the cost of the inverter virtually. Accurate situation, and there are 5 / 7th harmonics on the capacitor current, so that it is impossible to judge whether the filter capacitor on the grid s...

AI Technical Summary

Problems solved by technology

[0002] At present, in wind power generation, double-fed wind turbines and back-to-back dual PWM converters are mainly used to realize variable-speed and constant-frequency power generation; The power grid side usually uses LCL filters to reduce the high-order harmonic content of the grid current; during the operation of the inverter, the capacitor in the LCL filter that mainly plays a filtering role is prone to failure

[0003] Most of the existing LCL filter capacitor fault detection methods rely on hardware, which increases the cost of the inverter virtually. Accurate situation, and there are 5 / 7 harmonics on the capacitor current, so that it is impossible to judge whether the filter capacitor on the grid side is faulty through the conventional method of calculating the effective value of the capacitor current

Images