A hysteretic current controller for active power filter with constant frequency

In accordance with the advantage of conventional hysteretic current control method, this paper advances a novel control method for active power filter (APF). In conventional hysteretic current control, the hysteretic band (HB) is fixed and actual compensating current is limited in a fixed hysteretic band. When the voltage source inverter (VSI) works in high-frequency state, as the switching frequency changes the problems such as increasing switching losses and audible noise will appear. In response to this problem, the constant frequency hysteretic current control method based on variable hysteretic band is advanced in this paper. Firstly, the connection between hysteretic band and switching frequency must be found correctly. Then, the variable hysteretic band current controller is designed according to the connection. Finally, the Matlab simulation results show that the switching frequency of VSI is held nearly constant and the proposed controller can track reference current well. The problems of increasing switching losses and audible noise which happened in high-frequency state can be resolved in conventional hysteretic current control.