Implementation of Three-Phase Bidirectional Isolated DC-DC Converter with Improved Light-Load Efficiency

Phase-Shift Modulation (PSM) strategy had been widely used in Three-Phase Bidirectional Isolated DC-DC Converter (3P-BIDC). Nevertheless, this conventional high frequency PSM method is more suitable for medium and rated load application. In light-load conditions (0-0.3 p.u.), the power efficiency may drop to less than 65%. Thus, this paper proposes an enhanced switching strategy by introducing a low frequency burst-mode signal to control the number of active PSM cycle over one burst cycle. A 150-V, 1.5-kW, 3P-BIDC prototype is developed for laboratory testing. This prototype is first evaluated with the conventional PSM strategy for wide range of loads. Then the proposed method is applied for light-load condition evaluation. The experimental results prove that an average of 90% power efficiency could be achieved under light load condition.