| The entry of new elements into the network,such as high percentage and high penetration of new energy sources and large-scale new loads,greatly impacts the structure and operation mode of the existing distribution network.The flexible interconnection device(FID),represented by flexible power electronic switch and multi-state flexible switch,is applied to the distribution network by replacing the contact switch,effectively improving the system’s real-time regulation and control ability and the flexibility of the topology.However,many connected converters and large capacities make the construction cost and the return on investment low,making it difficult to promote the application in practice.This paper proposes a new technical path to reconfigure the distribution network from the physical level based on maintaining a traditional distribution network’s stock power supply form,i.e.,embedded flexible interconnected distribution network(EDC-FIDN)formed flexibly embedding multi-terminal DC network into AC distribution network.How to use EDC continuous regulation capability and DAS real-time information interaction capability to achieve rapid power supply restoration and effectively improve the operational resilience of the distribution network.In this paper,the research of flexible interconnected distribution network power supply restoration technology is carried out with EDC-FIDN as the research object,and the specific research contents are as follows:(1)A flexible interconnected distribution network topology with embedded DC composition is proposed.The components and topological features of this topology are described;the EDC-FIDN is divided into three regions: AC feeder region,EDC region,and AC direct interface-MMC converter,and its mathematical model is established respectively;the topology,working principle,and traditional control strategy of MMC,the core equipment of EDC-FIDN,are elaborated.(2)Considering the synergy between EDC and DAS in the fault handling process,an EDC-based fault handling technology for flexible interconnected distribution networks is proposed.Based on the traditional DAS,the DAS communication structure of EDC-FIDN is designed;based on analyzing the information interaction contents of DAS in EDC-FIDN,the general idea of EDC-FIDN operation based on DAS is designed;for the case of EDC-FI DN AC feeder fault,the whole fault handling process is analyzed in terms of the main station of distribution network automation,feeder sub-station and The information interaction between the main station,feeder sub-station,and EDC sub-station during the whole fault handling process is analyzed.The power supply restoration architecture of EDC-FIDN is designed.(3)Considering the EDC-FIDN power restoration effect and power supply reliability,a two-stage EDC-FIDN power restoration strategy based on DAS is proposed,i.e.,the fast and optimized restoration stages.In the fast emergency power restoration stage,the VSG-based EDC smooth switching control is proposed to support the fast power restoration of the MMC converter to the power loss side;in the optimal restoration stage,the EDC-FIDN optimization model is established to optimize the power restoration path,and the simultaneous grid connection control strategy of EDC is designed to support the feeder switch powered switching in the network reconfiguration stage;a 58-node flexible distribution network with embedded DC was constructed using PSCAD/MTDC and Matlab software to restore power supply to the case,and the results verified the reasonableness and effectiveness of the proposed strategy. |
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