A new non-characteristic harmonic compensation method in three-phase active power filters equipped with a small DC capacitor

This paper proposes a new control method suitable for active power filters equipped with a small dc capacitor. The proposed method can achieve not only suppressing the dc capacitor voltage fluctuation in transient states but also compensating all harmonic components in steady states. The proposed method employs a harmonic detection method based on the 7-step compensator and a repetitive controller with a comprehensive harmonic detection method. The experimental results using the active power filter with a small dc capacitor of 300-μF have confirmed that the proposed method has the capability to compensate non-characteristic harmonics produced by a 15-kW diode rectifier in steady states without any voltage fluctuations in transient states.