Double closed-loop cascade control for active power filter

A cascade control method for active filter based on recursive integrator is proposed. Because the dynamics of filter current are much faster than DC voltage, cascade control can be implemented with the voltage loop outside the inner current loop. A current loop controller based on recursive integral is introduced to eliminate the steady state error caused by the reference sinusoidal current. The expected supply current is directly calculated by the supply voltage and the output of the voltage loop controller. As a result, the detection algorithm is simplified. Discussions on the design of the current and voltage control loops are presented and offer a significant theory basis for designing the controller parameters of active filter. The proposed method is simple and easy for engineering application. The experiment results demonstrate the effectiveness of the proposed method.