Secondary-Side Phase-shift Controlled ZVS DC/DC Converters

With the global energy crisis intensifying, renewable energy development and utilization become more and more important. On the input side of a Distributed PV energy storage power generation system, the output voltage of solar photovoltaic cells is usually low, so a high step-up DC/DC convener is needed to realize step-up, then the power can be transferred to the power grid. While a step-down DC/DC converter is often required to achieve step-down on the output side to DC load power supply. In this paper, a step-up and a step-down type soft switch DC/DC converter with secondary-side phase-shift control scheme are presented and thorough researched.First of all, a step-up DC/DC converter with secondary side phase-shift control scheme is presented. A full-bridge structure is employed in the primary side to handle large input current and an improved three-level configuration is adopted in the secondary side to achieve a high output voltage conversion for grid-connected applications. Moreover, the phase shift angle between the primary and secondary power switches is used as the control freedom to regulate the output voltage. Furthermore, a tri-mode operation including Balance, Boost and Buck modes can be realized to achieve a wide voltage conversion. In addition, Zero-voltage-Switching (ZVS) operation can be achieved during a wide voltage range and the voltage stress across the secondary diodes is reduced compared with the conventional primary phase shift control strategy. Finally, the experimental results from a2.5kW250～350V input and800V output prototype are provided to verify the effectiveness of the proposed converter. The experimental results show that the converter has higher application prospect in Distributed PV energy storage power generation system.Next, a step-down DC/DC converter with secondary side phase-shift control scheme is presented by alter of the step-up DC/DC converter, and further verified the advantages of the Secondary-Side Phase-shift Controlled ZVS DC/DC Converter by theoretical analysis and prototype experiments.