级联H桥型电力电子变压器隔离级高频电流波动抑制策略

High-frequency Current Fluctuation Suppression Strategy for Isolation Stage of Cascaded H-Bridge Based Power Electronic Transformer

串联谐振型双有源桥变换器(DABSRC)由于具有控制简单及软开关范围宽的特点,可用在级联H桥型电力电子变压器隔离级DC-DC电能变换环节中。考虑电力电子变压器各相单元存在二倍电网工频瞬时功率波动,导致隔离级DABSRC高频电流幅值呈现相同波动,且过大波动将会增加隔离级开关器件导通损耗和电流应力。为解决该问题,文中以优化高频电流有效值为目标,提出一种零序电压注入控制策略,通过在交流侧级联H桥变换器中注入零序电压,降低了隔离级DABSRC开关器件电流应力。最后,利用苏州同里10 kV交流/750 V直流3 MVA级联H桥型电力电子变压器工程示范样机进行验证,仿真及样机测试结果证明了控制方法的有效性。

Due to the simple control and wide soft switching range of dual active bridge series resonant converter(DABSRC),it can be used in the isolation DC-DC stage of the cascaded H-bridge(CHB)converter based power electronic transformer(PET)in power transformer link.Considering there exists instaneous power fluctuation of twice power grid frequency at each phase of PET,it causes the high-frequency current fluctuation in the DABSRC with the same frequency at isolation stage.In addition,it would increase the conduction loss and current stress of power semiconductor devices in the isolation stage DABSRC.In order to solve this issue,aiming at optimizing the valid values of high-frequency current,a zero sequence voltage injection(ZSVI)control strategy is proposed.By injecting zero sequence voltage into AC side of the CHB converter,the current stress of switching device for isolation stage DABSRC is reduced.Finally,simulation and experimental results on a demonstration prototype of 10 kV AC/750 V DC 3 MVA PET in Tongli,Suzhou city of China verify the feasibility of the control method.