Control and reduction of terminal voltage total harmonic distortion (THD) in a hybrid series active and parallel passive filter system

A simple and cost-effective solution to reduce the passive filter terminal voltage total harmonic distortion (THD) is outlined. A modified synchronous reference frame (SRF) based controller for the series active filter allows injection of a controlled percentage of the higher harmonic load currents into the supply, in compliance with the IEEE 519 harmonic current standards, thereby reducing the passive filter terminal voltage THD. This implementation retains all the desirable features of the original SRF controlled hybrid series active filter system. It reduces the rating and size of the passive filter system and allows the use of simpler passive filter system structures such as only a simple high pass passive filter or a simple power factor correction capacitor as the passive filter system. Simulation and experimental results are used to establish the functionality and performance of the SRF controller and the modified SRF controller for the hybrid series active filter system.<>