A Seamless Modulation Strategy for Step-up/down Partial Power Processing Converter (SUD-P3C)

This paper proposes a seamless modulation strategy for a step-up/down partial power processing converter (SUD-P3C), to realize smooth mode transition and continuous output regulation. Due to the implementation of zero volt switching (ZVS) on the high voltage side, the proposed method effectively suppresses voltage spikes caused by hard switching of the high voltage side switches, resulting in improved system reliability. Moreover, according to the small-signal analysis, the two operating modes have the same output-to-control transfer function, so the converter can adopt only one unified controller rather than two dedicated ones and reduce controller design complexity. A 400 V-3 kW prototype has been built, and the experimental results verified the effectiveness of the proposed modulation strategy. Compared to the conventional modulation strategy, the power losses are reduced by up to 14 % due to ZVS switching.