Research On The Fast DC Fault Current Limiting Technology

In recent years,with the rapid increase of the number and capacity of converters for flexible DC systems,the DC fault current level is also increasing.As a fast and reliable method of DC fault isolation,it is difficult for DC circuit breakers to meet the requirements of fault isolation.In this case,limiting the DC short-circuit current amplitude with the fault current limiter has become one important means to improve the safety and reliability of the DC power system.The optimized configuration of the resistive-type superconducting fault current limiter is of great significance for enhancing the current limiting effect of the fault current limiter.In this paper,the working principle and parameter design of the resistive-type superconducting fault current limiter are analyzed.The different current limiting effects of the fault current limiter installed at the outlet of the converters and the two ends of the DC line are studied.Based on the artificial immune algorithm,the optimal configuration of the superconducting fault current limiter in the flexible DC system is calculated.Combined with the working process of hybrid DC circuit breaker,a principle of directional longitudinal protection based on fault voltage of superconducting current limiter is proposed,which can quickly and accurately identify the internal fault and external fault.According to the fault current limiting effect analysis of flexible DC system,this paper proposes a hybrid fault current limiter based on the principle of magnetic coupling enhancement.The current limiter utilizes the coupling principle between the two coupled coils: In normal operation,the self-inductance and mutual inductance cancel each other;after the failure occurs,the self-inductance and mutual inductance are mutually enhanced.The simulation results show that the new fault current limiter can play a significant current limiting effect after the DC fault occurs.The optimized configuration method can provide reference for the current limiter configuration in engineering.The proposed current limiter can effectively limit the fault current and has broad application prospects.