| As an important complementary part of AC transmission in modern electrical grid, HVDC has the advantage of less waste energy, ability to interconnection of asynchronous grids and better system stability. Compared to HVDC, MTDC system can realize multi-power supply and multiple HVDC links, which is more flexible, reliable and convenient. MTDC system is the main development direction in today’s world of HVDC technology. However, there are many bottlenecks which limit the application of MTDC system. One main problem is that the capacity of DC circuit breaker is not enough to meet the requirements of MTDC system. Superconducting fault current limiter(SFCL) is one of the most ideal current limiting devices, which has the advantage of automatic current limiting and short response time. By the combination of SFCL and DC circuit breaker, the difficulty of making DC circuit breaker can be greatly reduced, which is important for the development of MTDC system.This paper explores the application of SFCL in MTDC system. The works completed are listed as followed:(1)A typical loop-type three-terminal DC system is built based on the control strategy of MTDC system. The steady operation and the DC fault feature of the system is simulated and researched. According to the simulation results, the application of SFCL is necessary.(2)An electrical simulation model of resistive-type SFCL id built. The validity and accuracy of this model is verified by experiments.(3)The SFCL model is applied in the three-terminal DC system. The operation state of the system with DC fault is simulated. The simulation results show that SFCL can be an effective limiting device in MTDC system. The fault current can be limited effectively. The normal operation and the recovery of the system will not be affected by SFCLs.(4)Considering the constraints and objectives, an algorithm for multi-objective optimization design of SFCL is presented and applied into the three-terminal DC system. |
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