Sequence Coordination of Power Network Protection Based on Fault Current Limiting Equipment Action

With continuous increase of society's demand for energy, higher requirements have been placed on the supply of electricity. While field of power grids continues to introduce more new energy sources, it also requires power grid to provide stable and sustainable energy supply chain. According to equipment response and fault protection caused by grid faults, protection sequence coordination methods for multiple types of fault current-limiting equipment including fault current limiters, DC circuit breakers, hybrid MMCs and converters are proposed in this paper. In addition, for DC circuit breaker to isolate the fault, there is rejection to act, and fault current limiter and DC circuit breaker are required to cooperate after DC line failure in upper-layer ring network system so that half-bridge converters can block faults on both sides of converter during DC line faults. What's more, reliability of DC circuit breaker is determined by detecting the rate of change in fault current, and different fault current limiting devices need to cooperate with each other according to different fault areas in composite DC grid. Reasonable timing coordination strategy can effectively isolate the effect of faults. Finally, it is verified by simulation that upper-layer ring network system needs to trigger the start of fault current limiter, Meanwhile, backup line DC circuit breaker in faulty line and adjacent line as well as exit side of converter station needs to be triggered too. Moreover, lower multi-terminal system is set to require lockout signal for converter, and hybrid MMC converter station needs to be put in lock-free ride-through control mode, which realizes the rationality of research content in this paper.