Abstract:In view of the fact that a large number of 500/220kV electromagnetic loop networks in Guizhou power grid can not be operated in a short time, the open-loop operation is easy to reduce the reliability of power supply, and the closed-loop operation is faced with the contradiction of power flow control difficulty and short-circuit current exceeding the standard. The operation of the system is mainly aimed at improving the reliability of local power grid. A flexible HVDC system installed in the low-voltage side channel of electromagnetic loop network is proposed to realize loop closing operation. Many advantages such as injecting short-circuit current into flexible and direct non-directional system, active and reactive power can be used to realize independent decoupling control. The basic strategy of the flexible and direct control and protection system under this scheme is studied, including the basic protection strategy of the flexible HVDC transmission system, the design principles and design schemes of different control levels based on the overall control and protection of Guizhou power grid ring network. Finally, the flexible DC back-to-back device installed at 220 kV voltage level of Liuzhi and Puding transformers in Guizhou Province is taken as the simulation object. The simulation results show that the design scheme can effectively protect the safe and stable operation of flexible direct current in the electromagnetic loop network application scenario.