Control method for three-phase three-wire active filtering apparatus

Abstract

The invention relates to a control method for a three-phase three-wire active filtering apparatus. The control method comprises: a load current detection and analysis portion analyzes a current generated in a load to obtain contents of each subharmonic and sizes of various components in a fundamental wave; a compensation instruction current calculating synthesis portion, first according to a compensation requirement, calculates a frequency domain signal of a compensation instruction current , then, converts the frequency domain signal into a time domain signal, and obtains a present instruction current; and a compensation current tracking control portion compares a present instruction current signal with a detected practical compensation current signal and calculates to generate a control voltage vector signal, then, converts the control voltage vector signal into a driving signal to drive a semiconductor power switching device to obtain the goal of tracking and controlling a compensation current. According to the method, no interphase coupling exists, so current tracking control is more accurate; and the method can easily detect active and reactive components, and positive and negative sequence currents of a load fundamental current with simple calculation, thereby greatly reducing the expenditure of a CPU.

Description

technical field [0001] The invention relates to the field of harmonic control in power systems, and more particularly to a novel harmonic detection and tracking control method for a three-phase three-wire parallel active power filter. Background technique [0002] With the increasing non-linear load in the power grid, the harmonics generated by it will pollute the power grid more and more seriously. At present, the harmonic suppression devices mainly using passive filters and active power filters are mainly used to control grid pollution. [0003] Passive filters are widely used because of their simple structure, low cost and mature technology, but they have many inherent shortcomings that are difficult to overcome. The active power filter (APF), as a fast and dynamic power electronic device for harmonic compensation, has many advantages compared with passive filters: the filtering performance is not affected by the system impedance; it will not be affected by the system im...

AI Technical Summary

Problems solved by technology

The problem with this detection method is: this detection method needs to undergo multiple coordinate transformations; it cannot easily detect the negative sequence current; it can only detect the total harmonic current, but cannot obtain the information of each harmonic current

However, to detect harmonics in this way, it is necessary to perform FFT transformation and inverse transformation on the three-phase load current one by one (at least two phases), which requires a large amount of calculation.

When tracking and controlling the compensation current, due to the direct coupling of the three phases, it cannot be decoupled, which affects the compensation effect and reduces the control accuracy.

In addition, if you need to use space vector control (SVPWM), you need to do another coordinate transformation, which further increases the amount of calculation

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