Unipolar/Bipolar Mixed Modulation for Discontinuous Current Mode Single-Phase Grid-tied Inverter with Off-time Discrete Control

This paper proposes a mixed modulation combining unipolar and bipolar modulations with the off-time discrete control for the discontinuous current mode (DCM) grid-tied inverters to improve the efficiency. The proposed method has the advantages of the two conventional modulation. The off-time discrete control, which discretely adjusts the oscillation cycles during the zero-current period of the DCM, enables zero-voltage switching (ZVS). This paper presents a strategy to mix both modulations for achieving ZVS and the peak current reduction. The performance of the proposed method was validated by experiments with a 400 W class prototype.