One-cycle control for three-phase four-leg active power filter

This paper presents a three-phase four-leg active power filter design based on one-cycle control. We extend the constant-frequency integration control method to three-phase four-wire systems. The control circuit is composed of four integrators with reset along with several flip-flops, comparators and some linear components. The proposed APF does not require load current and phase voltage sensing, nor the harmonics and reactive current calculation, and does not use any multipliers. Moreover, it employs constant switching frequency modulation, which is desirable for industrial applications. Simulation results demonstrate that the proposed active power filter is capable of compensating current harmonics and reactive power, and reducing the neutral current in an effective and robust manner.