A novel configuration to eliminate dominant Harmonic frequency (DHF) by using FFT in series active filters

Abstract

This paper investigates the operation of an active filter configuration to eliminate the dominant harmonics from a low frequency (50 Hz) square wave Voltage Source Inverter (VSI). VSIs are playing a vital in industry for medium voltage high power drive applications. For high power drives the inverter switching frequency should be less to minimize the switching losses of power semiconductor devices. The Total Harmonic Distortion (THD) of the inverter output voltage should be less. In this work a series configuration of active filter with main square wave inverter is studied. The output of each H-bridge inverter is connected to the input mid-point of previous inverter which provides an added advantage in the circuit. The control signal of low frequency square wave inverter is synchronized with the control signals of the H-bridge series inverters. The estimation of the harmonic voltage of the main square wave inverter is carried out using 16 point FFT algorithm in a PIC microcontroller. Simulation and hardware results are demonstrated to validate the operation of the active filter.