| Distributed PV system is one of the hot study of power electronics in recent years. Distributed PV system has a number of characteristics that the conventional distributed power 'system does not have, such as the power output not being constant, maximum power point tracking (MPPT) and so on. So the DC/DC converter which can be used in distributed PV systems, not only have the conventional distributed DC/DC converters features, but also meet the special requirements of PV systems.For the demand of the DC/DC conversion in PV system, the technical solution of a soft-switching converter (LLC resonant DC/DC converter) has been seleeted to outspread reaearch and design work in this paper. The study shows that the scheme which have some good characteristics, such as high efficiency, good controlling-characteristics, can commendably fulfil the demand of high power density and high-efficiency within a certain power range. However, the converter, which has poor adaptability in a wide range of power, can not satisfy the requirement of a wide range of power in PV system.The LLC resonant fundamental equivalent circuit model is built by analyzing the transient work process of the LLC resonant DC/DC converter in this Paper; and by analyzing the fundamental equivalent circuit model, the control characteristics, load characteristics and output characteristics of the converter can be known. The master of the Converter operation rules can lay the foundation for formulating control strategies. Then A simple parameter optimization design method is summarized by efficiency analysis. The advantages and disadvantages and the application of occasions of the LLC resonant DC/DC converter are elaborated by simulation analysis. Finally, a 400V/510W prototype converter is built in the lab to verify the effectiveness of the proposed converter.
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