微电网中电力电子变压器的电压质量控制策略研究

摘要

电力电子变压器(PET)中多个直流环节的存在使得其替代固态开关作为微电网接口后实现了微电网与主电网在频率与电气上的隔离,此时微电网内部的电能质量与PET的控制策略密切相关.本文首先分析了PET接入后对微电网PCC点电压质量影响的差异,研究了PET输出侧PCC点电压质量劣化的机理,指出不采取任何电压质量调节措施时,基于PET的微电网PCC电压易受非线性负荷影响而出现谐波劣化.然后,针对微电网存在的电流型与电压型谐波,分析了PET调节微电网PCC点电压质量的本质,综合考虑PET采样特点、容量限制等因素提出了一种直接电压控制与虚拟阻抗控制相结合的高供电电压质量控制策略.最后,仿真与实验验证了本文理论分析与所提策略的正确性与有效性.%The harmonic distribution of power electronic transformer ( PET) based microgrid is different from the microgrid with solid-state switch.And the voltage quality of the point of common coupling ( PCC) is related to PET's control strategy at this time.Considering the PET based microgird is more like an independent small rating power system which has been isolated by multiple DC link, a voltage quality control strategy for PET based micro-gird has been proposed.Firstly, the voltage quality characters of PET based microgrid have been discussed, and it is found that the voltage of PCC will distort when PET is working without any voltage quality control strategy.Then, the feasibility of PET to improve the PCC voltage quality is analyzed, and a control strategy which is consisted by a voltage control loop and a virtual impedance loop has been proposed for PET.Experimental results verified the va-lidity and effectiveness of the presented control strategy to enhance the voltage quality issues of PET based micro-grid.