Simulation of three-phase four-wire shunt active power filter using novel switching technique

The control circuit of the active power filter used for power quality improvement has several basic functional blocks, out of which the reference current generator and the switching pulses generator are considered as most important blocks. This paper presents a novel switching technique for three phase four wire shunt active power filter. The switching pulses are derived by using the three dimensional space vector modulation technique with null vector eliminated. The switching algorithm presented here simplifies the switching strategy. The focus is on the implementation of a pulse width modulation scheme with less number of switch commutations per period and maximum DC bus voltage utilisation. A digital controller is used to provide dead beat current control. The combination of the digital controller and the modulation scheme gives the four leg active power filter the capability to independently track reference current waveforms in three phases. This four leg active power filter can be used for harmonic compensation, reactive power compensation, and load balancing and neutral current compensation. Simulation results are given to show the validity of the proposed switching control strategy.