Research On Key Problems Of The Quenching Fluxcoupling Type Superconducting Fault Current Limiter Applied To Power System

With the gradual expansion of the power system in China,the level of short circuit current has been increasing,which exceeds the breaking capacity of existing commercial circuit breakers.How to limit the short circuit current to the breaking level of circuit breakers is an important issue in the power system.Superconducting fault current limiter(SFCL)is an effective method to prevent short circuit current from exceeding the standard capacity.Flux-coupling type superconducting fault current limiter(FC-SFCL)adopts a superconducting coupling inductance and the structure of parallel circuit breaker,which can effectively limit the level of short circuit current in the power grid,realize automatic current sharing and current limiting functions,and improve the overall breaking level.Based on the research status of SFCL,this paper discusses the operating characteristics of FC-SFCL which considers quenching,and studies its influence on the relay protection and transient stability of the power system.The main work accomplished is as follows:(1)The overall parameter design process of quenching FC-SFCL is studied.Considering its quenching characteristics of current limiting and arc resistance characteristics of circuit breakers,a simulation model of the high-voltage transmission line containing FC-SFCL is built to verify the current sharing and current limiting effects.(2)Based on the current-sharing and current-limiting operating modes,the transient recovery voltage characteristics of the circuit breaker are theoretically studied,and the fault removal process is simulated.The influence of FC-SFCL’s quenching and inductance parameters on the transient recovery voltage characteristics of breakers is studied,and measures to suppress the rise rate of the transient recovery voltage are proposed.(3)The branch current characteristics of quenching FC-SFCL in the closing process of breaks are studied.The influence of the quenching resistance on the direct current(DC)component of the short circuit current is analyzed.Some methods of suppressing the DC component of short-circuit current are explored.(4)The influence of quenching FC-SFCL on different types of relay protection is evaluated,and a simulation model is built to verify the theoretical analysis.Aiming at the types of relay protection which are impacted,corresponding coordination methods are proposed.(5)The influence of FC-SFCL on the transient stability of the power system is studied and a mathematical model of transient stability is built.The power-angle characteristics of power system are theoretically analysed considerding quenching and non-quenching of FCSFCL respectively in the operation.A transient stability simulation model is built to verify the influence of the quenching resistance and inductance on the power-angle characteristics of the generator.