Dead-Beat Current Control for Active Filters

The paper discusses the main issues concerning the implementation of digitally controlled parallel active power filters. The considered control strategy is based on the combination of dead-beat control of inverter currents and space vector modulation. For an active filter application, key features of the power converter's control are the achievable harmonic compensation quality (TEC standards compliance) and the robustness of the system's stability (load structure and parameter uncertainty). Both aspects are examined in the paper. As far as the former is concerned, simulations and experimental tests show that even if a high switching frequency is achieved (using a state-of-the-art DSP platform), the intrinsic calculation delay of the dead-beat algorithm represents a serious hurdle for the achievement of a satisfactory compensation quality. From the stability standpoint instead, the effects of parameter mismatches on the system's performance are investigated by means of a complete eigenvalue analysis, which allows to reveal the limits of the system's stability for different possible implementations of the considered control strategy.