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.