级联型电力电子变压器分级解耦控制

应用于交直流混合配电网的级联型电力电子变压器(PET)能够实现柔性互联、电压变换、电气隔离和功率控制等多种功能.由于级联型PET内部的级联H桥级和双有源桥级之间电气耦合程度高且控制目标不同,提出一种分级解耦控制方案,在简化控制架构的同时可实现各级的独立灵活控制.此外,针对级联型PET采用多个功率单元输入串联输出并联的拓扑结构,提出一种基于分级解耦控制的串联均压并联均流控制策略,以降低参数差异的影响.研制了一台额定交流电压为10 kV、额定直流电压为750 V、额定容量为500 kVA的级联型PET.实验结果验证了该控制方案工程应用的可行性及有效性.

Hierarchical Decoupling Control of Cascaded Power Electronic Transformer

Cascaded power electronic transformer (PET) for hybrid AC/DC distribution networks can realize multiple functions such as flexible interconnection, voltage conversion, electrical isolation and power control. Due to the high degree of electrical coupling between the cascaded H-bridge and the dual active bridge stage in the cascaded PET with different control objectives, a hierarchical decoupling control scheme is proposed to simplify the control architecture and achieve independent flexible control at all levels. Since the topology of cascaded PET adopts input-series output-parallel (ISOP) of multiple power units, a control strategy of series voltage equalization and parallel current equalization based on hierarchical decoupling control is proposed to reduce the influence of parameter differences. A cascaded PET with rated AC voltage of 10 kV, rated DC voltage of 750 V and rated capacity of 500 kVA is developed, and the experimental results verify the feasibility and effectiveness of the engineering application of the control scheme.