Extended ZVS-On/ZCS-Off Range for CF-DAB Converter Under DCM Operation for Residential Energy Storage Systems
Edivan Laércio Carvalho, Rafael Cardoso, Carla Aparecida Felipe, Carlos Marcelo de Oliveira Stein, Lucas Vizzotto Bellinaso, Leandro Michels, Dmitri Vinnikov
Abstract
Current-Fed Dual-Active Bridge (CF-DAB) converters are interesting in bidirectional applications when a wide conversion voltage ratio is required, such as residential extra-low voltage energy storage systems, where conventional DAB converters have several limitations. Even though several developments have been made in the last few years to improve the CF-DAB technology for such applications, ensuring a flat efficiency curve is still challenging since it is not easy to ensure high efficiency at very low power. Current solutions include phase-shift modulations (PSM), dual phase-shift (DPSM), and hybrid approaches. This paper proposes an asymmetrical pulse width modulation (a-PWM) strategy to operate the CF-DAB in discontinuous conduction mode (DCM), improving the converter efficiency curve at low power. The DCM operation ensures soft-switching conditions over a wide operation range, providing a simple and effective solution. It is relevant to CF-DAB converter development because conventional modulations have limitations concerning the soft-switching range and usually result in overvoltage problems. A 500 W prototype was built and tested to evaluate this proposal. The experimental results show the a-PWM ensures soft-switching from 2% to 100% of the converter rated power, and the efficiency curve is almost flat due to the improved efficiency at low power level.