A control strategy in Active Power Filter for power quality improvement

In this paper, a new control method for adjusting the zero-sequence current in a three-phase four-wire Voltage-Source Inverter (VSI), used as a Shunt Active Power Filter (SAPF), is presented. Combined with the known instantaneous reactive power theory, the proposed control strategy achieves perfect compensation for harmonics and reactive power when the load currents are non-sinusoidal and severely unbalanced.