电力电子变压器中LLC谐振变换器的研究

摘要

针对传统移相全桥两电平变换器低耐压能力且轻载时不利于软开关实现而导致的低效率问题,提出了一种应用于电力电子变压器中的双向对称半桥三电平LLC谐振变换器结构,该结构利用电感电容的谐振原理,当系统工作在感性区域时,可实现全负载范围内初级开关管的零电压导通(ZVS)和次级二极管的零电流关断(ZCS),进而提高系统效率,且该结构能实现能量的双向传输,应用灵活.最后根据基波近似等效法得到了半桥三电平LLC谐振变换器的等效模型,由仿真和实验结果共同验证了理论分析的正确性与该结构的可行性.此外,根据LLC的增益特性和阻抗特性所得的谐振网络参数也使系统得到了较好的稳定性和较强的鲁棒性.%The efficiency of traditional phase-shift full bridge two level converter is not high,because the voltage endurance capacity is low,and it is not conducive to achieve soft switching under the light load condition.A bidirection al symmetrical half bridge three level LLC resonant converter is put forward,which is applied to power electronic transformer.The three level LLC resonant converter uses the resonance principle of inductance and capacitance,when the system is working in sensitive area,which can realize zero voltage switching(ZVS) of all primary switches and zero current switching(ZCS) of all secondary rectifier diodes over the full load range,and improve the system efficiency.This converter can realize bidirectional energy-transform and enhance the flexibility in application.The equivalent model of the symmetrical half bridge three level LLC resonant converter is obtained according to the first harmonic approximation.Both the simulation and experimental results validate the correctness of the theoretical analysis and the feasibility of the structure.The LLC resonant network parameters,which are gotten based on the gain characteristics and impedance characteristics,make the system have better stability and stronger robustness.