Study On The Optimal Configuration Method Of Fault Current Limiter And Relay Optimal Coordination In Power Network

With the rapid development of power system,the interconnection between power system is getting much closer,which makes the high level of short-circuit current in power system.The level of short-circuit current may exceed the breaking capacity of circuit breaker and threatens the safe and stable operation of power system.The configuration of fault current limiter(FCL)is one of the important ways to effectively solve the problem of high level of short-circuit current.In order to make good use of the FCL to restrain the short-circuit current,it is necessary to optimize the configuration of FCL.However,the existing research on optimal configuration of FCL does not considering the current limiting effect of FCL on the breaking current of the circuit breaker,which is not conducive to the make full used of FCL.Thus,it is necessary to study on FCL optimal configuration considering breaking current of the circuit breaker.In addition,when the FCL operated during the fault,the measured impedance and current of realy protection will be changed,which may lead to misoperation and refuse to operate of the inverse time overcurrent protection elements and distance protection elements.Thus,it is necessary to optimize the protection parameters to achieve the coordination of the protections.For those reasons,this paper focuses on the optimization of FCL configuration and the parameter setting of inverse time overcurrent protection elements and distance protection elements considering the FCL operation.The main work is as follows:1)In order to accurately evaluate the current limiting effect of the FCL on the maximum breaking current of the circuit breaker in the power system,based on the branch addition method of the node impedance matrix,the node impedance matrix of current limiter and the node impedance matrix with fault point are derived.After that,a mathematical correlation model between the breaking current of the circuit breaker and the configuration of the FCL is established.2)According to the mathematical correlation model,the maximum breaking current of the circuit breaker is calculated.On this basis,the reactance value of the FCL on both sides of each transmission line is taken as the variable,the best current limiting effect of FCL configuration on breaking current of circuit breaker is taken as the objective function,the short circuit current of the bus,the maximum breaking current of the circuit breaker and the reactance of a single current limiter are taken as the constraints to establish the optimal configuration model of FCL.Then,the biogeography-based optimization(BBO)algorithm based on sinusoidal migration model and Cauchy mutation is adopted to solove optimal model.Considering that the adjacent dimensions in optimization variables have similar influence on objective function,the second mutation operation between adjacent dimensions is introduced into the optimal algorithm to improved its optimization ability.The configuration method for FCL based on impproved biogeography-based optimization algorithm with second mutation is proposed.The effectiveness of the proposed method is verified by an example.3)Considering the influence of FCL operation on measured impedance and current of relay protection,this paper analyzes the coordination relationship between inverse time overcurrent protection element and distance protection element at the coordination point.After that,based on the coordination relationship to establishes constraints,and takes the pickup current and time dial setting of inverse time overcurrent relay and time setting of zone II of distance relay as variables,taking the shortest time delay of the whole network protections as the objective function,the optimal coordination model of distance relay and inverse time overcurrent relay is constructed.Using optimal coordination model to obtain the setting of distance relay and inverse time overcurrent relay in test system.Then,c conducting fault simulation of test system in PSCAD/EMTDC,the effectiveness of optimal coordination model are verified.