Adaptive Filtering Scheme for a Low-Capacitance StatCom

The use of film capacitors to substitute traditionally utilized electrolytic capacitors is a well-known trend in the power electronics industry as it significantly increases the overall reliability of the system. Control challenges arise due to the reduced capacitance of film capacitors with similar volume and weight as electrolytic capacitors. To address these control challenges, previous works have shown the good accuracy and fast dynamic performance of analytical filters to remove low-frequency capacitor voltage ripples. However, as these filters are based on an idealized mathematical model of the system, some harmonic content remains in the filtered signal due to discrepancies between the real system and utilized model, which deteriorates the overall performance of the system. In this paper, an improved adaptive filtering scheme for a low-capacitance static compensator (LC-StatCom) is proposed. The scheme mitigates both time delays and harmonic-contamination in the outer capacitor voltage control loop. Hence, the proposed solution allows the use of a high bandwidth controller and the generation of a current reference free of low-frequency harmonics. The effectiveness of the proposed approach is validated via simulation results on a seven-level 0.35-kVA single-phase LC-StatCom. The results demonstrate that the proposed solution overcomes drawbacks of previous schemes in terms of time response and filtering performance in steady-state operation.