Design Considerations for DSP-Controlled 400 Hz Shunt Active Power Filter in an Aircraft Power System

A multiresolution control strategy is proposed for a digital signal processor (DSP)-controlled 400 Hz active power filter (APF) to reduce the real-time computational requirements. By rearranging the computational elements into high- and low-frequency control groups, the proposed control strategy takes best advantages of the DSP computation resources to increase the control frequency for the high computational group, which mainly determines the APF performance. Based on bandwidth features of different control plants in APF, detailed analysis is given to determine the control and sampling frequencies for these plants. Anti-aliasing filters are designed to avoid aliasing when downsampling scheme is used to further reduce computation resource. A 20 kVA prototype is set up to verify the validity of the proposed strategy and analysis. Experimental results show that the proposed control strategy meets the computational requirements for the control system using a DSP. The proposed control strategy achieves the total harmonic distortion as low as 5.7%, which meets the avionic DO-160F standard, and also exhibits good dynamic performance.