一种新颖的ZVZCS-PWM三电平变换器研究

A Novel ZVZCS-PWM Three-level Converter using Coupled Output Inductor

由于三电平变换器的主开关管电压应力为输入电压的50%,因而该变换器在高电压输入场合获得了广泛的应用。三电平变换器采用移相控制可实现超前桥臂的零电压开通,但与通常的移相桥式变换器一样,其滞后桥臂较难实现软开关。针对这一问题,提出了一种利用变压器次级辅助电路实现滞后桥臂零电流关断的零电压零电流开关脉宽调制(Zero-Voltage and Zero-Current-Switching Pulse Width Modulation,简称ZVZCS-PWM)半桥式三电平变换器,该变换器在宽负载范围内实现了滞后桥臂的零电流软开关(Zero-Current-Switching,简称ZCS-PWM),解决了难以实现滞后管软开关的难题。详细分析了该变换器工作原理及超前桥臂和滞后桥臂软开关的工作条件,在此基础上设计并制作了一台实验样机,得出令人满意的实验结果。

Voltage stress of each main switch in three-level converter is reduced to half of the input voltage,which makes the converter quite suitable for high input voltage applications.The phase-shifting control can provide ZVS easily for leading switches,but difficultly for lagging switches which is similar to traditional phase-shifting control full bridge converter,thus it becomes a focus problem.A Zero-Voltage and Zero-Current-Switching （ZVZCS） PWM three-level converter using an auxiliary circuit in the secondary is proposed, which can provide ZCS for lagging switches and solve the problem.The principle of operation and working conditions for realizing soft switching of both leading and lagging switches are analyzed.An experimental prototype is designed and built, which gives satisfying results.