多路LLC谐振变换器的光伏均衡器设计与仿真

Design and Simulation of Photovoltaic Equalizer for Multi-output LLC Resonant Converter

为解决串联光伏模块在部分遮蔽情况下的功率失配问题,传统的差分功率处理结构大多采用基于单个光伏模块的多个DC/DC变换器,在解决遮蔽问题的同时带来了复杂性高和成本高的问题。提出了一种LLC型PV组串光伏均衡器,这种单输入-多输出的结构旨在利用LLC多绕组拓扑良好的对称性和输入、输出电压可变的特点实现对不同数量的遮蔽光伏组件的自适应功率分配功能,仅用2个开关就可实现均衡多个模块,使得每个PV模块达到近似最大功率点的效果。对均衡器进行参数设计并给出了软开关条件,同时在PSIM软件中建立PFM模式下的系统仿真模型,在负载切换时实现了变换器的软开关,且能够输出稳定的电压。最后,仿真结果表明均衡器有效提升了光伏组串输出功率的23.78%。

To solve the problem of power mismatch of series photovoltaic(PV)modules under partial shadowing,most of the traditional differential power processing structures are based on multiple DC/DC converters of a single PV module,which brings high complexity and high cost while solving the masking problem.In this paper,a PV string equalizer based on LLC resonant converter is proposed.The purpose of this single-input-multi-output structure is to make use of the satisfying symmetry of the LLC multi-winding topology and the characteristics of variable input and output voltages,thus realizing adaptive power distribution for different numbers of shielded PV modules.Only two switches are used to equalize multiple modules,so that each PV module can achieve the effect of approximate maximum power point.The parameters of the equalizer are designed,and the soft switching conditions are given.At the same time,a system simulation model in PFM mode is established in PSIM software,which realizes the soft switching of the converter during load switching while maintaining the stable output voltage.Finally,simulation results show that the proposed equalizer can effectively improve the output power of PV string by 23.78%.