A control method of the three-phase four-leg active power filter

This paper present a novel all-digital approach applied to three-phase four-wire active power filters, which is made up of a three-phase four-leg voltage source converters. The controller just detects main current and DC side capacitor voltage and duty cycle of the switches can be calculated simply. This controller has fewer measurement, higher robustness and simpler calculation as comparing to traditional controllers. Calculation method of the switch duty cycle is deducted on the base of mathematics model formed. Simulation result verify that the APF with proposed controller can compensate the harmonics, reactive power current and zero sequence current effectively.