Active Power Decoupling Control Scheme for Distorted Grids

Recently, the differential buck topology was introduced to compensate the 2^nd order power pulsation of singlephase systems. Specifically, the Common-Mode (CM) operation of the differential buck is utilized for active power ripple mitigation, while the Differential-Mode (DM) operation is used as an active power transporting port. Thus, compared to the available active power ripple mitigation methods in the literature; the differential buck topology does not require supplementary gate drives, power semiconductors, and energy storage elements. Besides, the differential buck converter is suitable for non-isolated systems due to its inherent leakage current suppression characteristic. Therefore, this paper proposes an improved active power decoupling scheme for active rectifiers based on the differential buck topology that are tied to distorted power grids. In addition, it will be shown that for a grid that is distorted to n^th harmonic with a DC component, the DCbus ripple's harmonic components are from 1^st to 2n^th harmonic. The theoretical analyses are validated with a 1 kW rectifier system connected to 120Vrms/50Hz power grid that is distorted by 2^nd, 3^rd, 4^th and 5^th order harmonics with a DC component. The results are aimed to show a ripple free DC-bus voltage with just 30 μF capacitor even when the current supplied from the grid is highly distorted.