Series-shunt Multi-port Flexible Interconnection Switch for Distribution Network

The increasing penetration of distributed generation, widespread adoption of electric vehicles, and diversity of users' load have caused problems such as voltage violation, feeder congestion and bi-directional power flow in distribution network (DN). Flexible interconnection switch can be exploited to take place of normally open point, enhancing the control capability of DN. Besides, under the trend of meshed and complicated framework of DN, an economic and scalable multi-feeder flexible interconnection technology is urgently needed. Nevertheless, the conventional back-to-back scheme is not suitable for wide application for its high price and huge volume caused by adopting full-power-rating topology. This paper proposed a series-shunt multi-port flexible interconnection switch (S²-MFIS), which was able to control power flow of multiple feeders and provide reactive power support, with advantages of low cost, modularity, high power density and scalability. First, the power flow regulation principle was analyzed and corresponding power flow control strategy was proposed. Then, the inner energy mechanism was established and voltage balance control method was offered. Next, the design method for key parameters in main circuit was given and comparison between S²-MFIS and full-power-rating back-to-back scheme was performed from multiple aspects including device quantity, device parameters, etc. At last, the feasibility and effectiveness of S²-MFIS under multi-feeder flexible interconnection scenario were verified by digital simulation and protype experiment.