采用定频移相控制的宽输出范围多电平LLC谐振变换器

Wide Output Range Multi-level LLC Resonant Converter With Fixed-frequency Phase-shift Control

针对电动汽车车载充电器的后级DC-DC环节,提出一种具备宽输出范围的多电平LLC谐振变换器。该变换器通过增加一组半桥和辅助变压器,构造出高于输入电压的多电平结构,结合定频移相脉宽调制控制,实现两倍电压增益拓展。该方案避免了变频控制下增益范围对谐振参数的制约,简化了参数设计过程。工作于串联谐振点使变换器在整个充电工作过程中均可实现功率管的零电压开关和整流管的零电流开关,有利于系统效率的提升。搭建一台输入380V、功率3.3kW的实验样机,验证所提拓扑与控制方案的可行性。经测试,变换器能为动力电池提供250~420V的充电电压,其峰值效率达到了97.1%。

A multi-level LLC resonant converter with a wide output voltage range is proposed for the rear stage DC-DC of the on-board charger for electric vehicles(EVs).To achieve a higher level than the input voltage,one more half-bridge and auxiliary transformer is introduced with the control of pulse width modulation based on fixed-frequency phase-shift to extend twice the voltage gain range.The presented scheme avoids the restriction of gain range on resonance parameters under traditional frequency modulation(FM)control,and simplifies the parameter design process.Furthermore,by operating under the nature resonant frequency,the converter can realize ZVS of MOSFETs and ZCS of rectifier during the full charging process and a high efficiency can be achieved.A prototype with input of 380V and output power of 3.3kW is built to verify the feasibility of the proposed configuration and control scheme.The experiment results show that the converter provides a charging range of 250~420V for the traction battery,and the peak efficiency reaches 97.1%.