APF (active power filter) harmonic current detection method

Abstract

The invention discloses an APF (active power filter) harmonic current detection method. On the basis of an ip-iq harmonic current detection method, a phase-locked loop based on a synchronous coordinate system is adopted to replace a traditional phase-locked loop; fundamental wave sine and cosine components are obtained with an adaptive least mean square algorithm; fixed step size is changed into variable step size, a new step size factor and error nonlinear function model is established on the basis of Sigmoid variable step size adaptive filter function, and contradictions of high convergencespeed and small steady-state error are solved; and finally, angular frequency of fundamental wave phase is substituted into the ip-iq harmonic current detection method to obtain a transformational matrix, and three-phase grid current is subjected to a series of transformation to obtain harmonic components.

Description

technical field [0001] The invention relates to a harmonic current detection method of an active power filter, belonging to the technical field of harmonic current detection. Background technique [0002] With the development of modern industrial technology, the switching action of power electronic devices injects a large number of harmonic components into the power grid, which leads to serious distortion of voltage and current waveforms in the AC power grid, and becomes the most important source of harmonics. Traditional power system harmonic suppression is to prevent the source of harmonic generation, but nowadays, most of them use passive power filter (Passive Power Filter, PPF) or active power filter (Active Power Filter, APF), etc. device to filter out harmonics. In order to effectively detect the harmonic component and reactive current of the power grid and reduce the harm of harmonics, the primary task of the active power filter is to choose a detection method with t...

AI Technical Summary

Problems solved by technology

However, the phase-locked loop structure using low-pass filter, all-pass filter and Hilbert transform has the problems of poor frequency tracking performance and sensitivity to harmonic distortion; the use of Kalman filter requires matrix inversion operation to obtain the optimal The gain factor, so the amount of calculation is large

The patent document with the application number "201110442281.2" discloses the "closed-loop phase-locking method and phase-locker based on the theory of instantaneous reactive power". Although the filter can quickly phase-lock the output in the load power supply environment, the average filter in this method is less effective in filtering out high-frequency harmonic components

In addition, the filtering effect of the phase-locked loop can be improved by cascading some filters with certain characteristics or increasing the order of the filter, but this also increases the computational burden of the system, so a trade-off should be made according to actual needs , to design the most suitable PLL structure

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