A new control strategy of shunt active filters for power quality improvement of highly and randomly varying loads

This paper presents a new control strategy for the shunt active filter in three-phase three-wire systems with zero sequence voltages. An extended method based on instantaneous power theory in a rotating reference frame is developed for extracting the compensating signals for highly/randomly varying loads. Since voltages at the point of common coupling contain low frequency interharmonics, conventional methods can not he used for dc voltage regulation. Therefore, a new method is introduced for this purpose. A three-phase electric arc furnace model is used to show power quality improvement through reactive power and harmonic compensation by a shunt active filter using the proposed method. Simulation results are provided to verify the system performance.

I. INTRODUCTION

Application of nonlinear loads such as adjustable speed drives electric arc furnaces and power conversion devices in power system results in power quality problems such as harmonics, inter-hannonics and voltage fluctuations that force the utilities and consumers to take countermeasure actions. Due to the variety of nonlinear loads and their problems, different compensation systems have been used. Passive filters are conventional solutions to mitigate harmonics. The limitation of passive filters for compensating complex problems such as noninteger harmonics and flicker has made active filters attractive.