面向城市灵活供电的高频隔离双向DC/DC变换器的启动分析与优化

Startup Analysis and Optimization of High Frequency Isolated Bidirectional DC/DC Converter for Urban Flexible Power Supply

高频隔离双向DC/DC变流器是基于直流配电的城市灵活供电系统的重要枢纽设备。CLLC变换器作为典型的拓扑,具有效率高、功率对称性强等优点,但由于其启动过程较为复杂,接入直流配电系统时需要进行分析与优化。针对CLLC启动时可能直接接入直流母线,或带电阻型、电容型负载等工况,首先对已有的软启动方法进行了研究,然后针对现有方法存在的问题提出了一种不对称改变占空比的新软启动方法,最后通过Matlab/Simulink对不同软启动方法进行对比。仿真结果表明,所提方法能有效抑制启动瞬间的电流尖峰,避免了由寄生电容充放电引起的谐振电流高频波动,且始终保证整流侧一半的二极管实现ZCS关断。所提方法具有工作模态简单、容易实现的优点,可有效指导工程实践。

High frequency isolated bidirectional DC/DC converter is an important hub equipment of urban flexible power supply system based on DC distribution.As a typical topology,CLLC converter has the advantages of high efficiency and strong power symmetry.However,due to its complex startup process,it needs to be analyzed and optimized when connecting to DC distribution system.In view of the fact that CLLC may be directly connected to the DC bus during startup,or live resistive or capacitive loads,the existing soft start methods are first studied.Then,a new soft start method with asymmetric duty cycle is proposed to solve the problems of the existing methods.Finally,different soft start methods are compared through Matlab/Simulink.Results show that the proposed method can effectively suppress the current spike at the starting moment,avoids the high frequency fluctuation of resonant current caused by charging and discharging of parasitic capacitors,and always ensures that half of the rectifier diodes can turn off ZCS.The proposed method can effectively guide engineering practice with its simple working mode and easy realization.