Three level hysteresis control of 3-phase, 4-wire shunt active power filter for harmonic compensation under unbalanced non stiff source

In this paper the proposed control algorithm for three phase four wire shunt active power filter (APF) compensate the unbalanced and non-linear loads. The control algorithm is implemented in MAT LAB environment to improve the power quality in distribution system. In this algorithm the theory of instantaneous symmetrical component used to extract a positive sequence of supply voltage to generated reference compensator currents under the assumptions of unbalanced and non stiff source voltages. The active power filter is implemented with pulse width modulation based current controlled voltage source inverter. The switching signals for VSI are generated through proposed three level hysteresis current controllers. The simulation results showing that the shunt active power filter is effectively compensating the supply current harmonics and reactive power at the point of common coupling.