Virtual flux direct power control of the three-level NPC shunt active power filter based on backstepping control

Abstract

In this paper, a novel control strategy of multilevel shunt active power filter is presented. The idea behind the proposed control scheme is to combine the backstepping control and direct power control with virtual flux concept into one controller able to improve the performance of active power filter. The choice of the multilevel topology leads to a clear enhancement in the compensation of the polluting load harmonics. To take full benefit of this choice, the task of balancing voltages of dc-link capacitors is assigned to the multilevel space vector modulation with balancing ability. For this reasons, the adopted multilevel active power filer is proposed to reduce harmonic currents flowing into the power system and to draw a nearly sinusoidal current with unity power factor. Complete simulation of the resultant active filtering system validates the efficiency of the proposed backstepping control law. Compared to the traditional control, the used of backstepping control allows to exhibit excellent transient response during large load variations.