Active power filtering apparatus

Abstract

The invention discloses an active power filtering apparatus applicable to a circuit which comprises a system power supply and a harmonic load; the active power filtering apparatus comprises a transformer, an inverter and a modulation signal generation module; a primary side winding of the transformer is connected with the harmonic load in series to be connected to a loop which is formed by the system power supply and the harmonic load; the modulation signal generation module is used for generating a modulation signal of the inverter, wherein the modulation signal is formed by superposition of a reversely amplified transformer primary side fundamental current and positively amplified transformer primary side harmonic current; and the inverter is used for converting a direct current signal into an alternating current signal with the same frequency as the modulation signal to be injected to a secondary side winding of the transformer, so as to enable the transformer primary side fundamental wave equivalent impedance to be Z<1>+(1-<alpha>)Z<m> and to enable the transformer primary side n harmonic wave equivalent impedance to be nZ<1>+(1+<beta>)nZ<m>. Based on fundamental wave and harmonic wave magnetic flux mixed control, the transformer primary side relative fundamental wave short circuit and relative harmonic wave open circuit are realized, and the harmonic current is forced to flow to a passive branch, so that an active filtering effect is played.

Description

technical field [0001] The invention belongs to the technical field of active power filtering, and more specifically relates to an active power filtering device. Background technique [0002] As power electronic nonlinear loads are more and more widely used in industrial and civil fields, the current waveform distortion in the power grid is more serious, and the problems of harmonics and reactive power are becoming more and more significant. For harmonics and power factor problems, the industry has proposed a variety of solutions, the main filtering solutions include traditional passive LC filter, traditional parallel active power filter, series hybrid active power filter, injection hybrid Active power filter and unified power quality conditioner. [0003] Passive filters are large in size and weight, and can only filter out harmonics of specific frequencies. Among all power filters, the series hybrid active power filter has attracted widespread attention because it can gr...

AI Technical Summary

Problems solved by technology

But it only compensates the fundamental magnetic flux, so it can only reduce the fundamental equivalent impedance. When the transformer used is determined, its harmonic equivalent impedance is a fixed value. In order to obtain a better filtering effect, a larger capacity transformer is required. , and a larger-capacity transformer will increase the difficulty of system protection, so there are conflicts between the system protection strategy, capacity and filtering performance of the existing series hybrid active power filter

Images