A PI control algorithm of three-level APF with little static misadjustment for tracking harmonic current

Obviously, tracking harmonic current fast and precisely is one of the keys to design the APF. This paper researches the control method of three-level active power filters. The conventional current state feedback decoupling PI control is analyzed in this paper in detail. This paper pointes out the limitation of the conventional PI conditioner in the research field of APF and presents a novel PI control method. Canceling the delay of one sampling period and the misadjustment for tracking the harmonic current is key problem of this PI control. In this PI control, the predictive output current value is obtained by the state predictor. The delay of one sampling period is remedied in this digital control system by the state predictor. The predictive harmonic command current value is obtained by the repetitive predictor synchronously. The repetitive predictor can achieve better prediction of the harmonic current. By this means, the misadjustment of the conventional PI control for tracking the harmonic current is cancelled. The experiment results indicate that the steady-state accuracy and dynamic response are both satisfying when the proposed control scheme is implemented.