Abstract
A novel approach for the 120 Hz ripple power mitigation in a single-phase, three-level dc/ac inverter is proposed. In the traditional approach, a bulk electrolytic capacitor is used to eliminate the low frequency ripples in a dc-link capacitor, however, this solution is not due to the low frequency components and large energy is stored. A new active filtering technique without an external circuit or extra switching power devices is proposed. As a result. a small dc-link capacitor can be realized through controlling the phase angle between different inverter ports modulating reference waveforms. Additionally, the circuit takes advantage of the superior features of GaN power switching devices, as a result cooling size will be reduced, and with faster switching speed, small size passive components can be realized. Theoretical analysis and control algorithms are provided to verify the proposed low ripple mitigation technique and the control strategy of the converter.