A DC capacitor voltage control method for active power filters using modified reference including the voltage ripple derived from a theoretical analysis

This paper proposes a new dc capacitor voltage control method suitable for active power filters equipped with a small dc capacitor. The proposed control method calculates the theoretical energy stored in the dc capacitor and provides it to the dc capacitor voltage feedback controller as its energy reference. As a result, the proposed method has capability to regulate the mean value of the dc capacitor voltage without any degradation in harmonic compensation even when a small dc capacitor and a high feedback gain are applied. Furthermore, application of a high feedback gain to the proposed method makes it possible to suppress the capacitor voltage fluctuations effectively without any performance deterioration in the harmonic compensation. Experimental results confirm a good harmonic compensating performance when applying a high-gain feedback controller to an active power filter with a small dc capacitor. The results also demonstrate a significant improvement in the capacitor voltage regulation even when a sudden load change occurs.