计及行波折反射的柔性直流电网故障限流器参数优化

Parameter optimization of a fault current limiter in a flexible DC power grid considering refraction and reflection of a traveling wave

行波的折反射过程对故障暂态响应有重要影响,目前对故障限流器(FaultCurrentLimiter,FCL)参数优化配置时,均未考虑故障行波折反射过程对FCL参数选取的影响。因此,提出了一种计及行波折反射的故障暂态响应时域分析方法,并用此方法对混合阻感并联型FCL进行了参数优化。首先,建立换流器故障等效模型,对比不同限流阻抗类型的FCL对故障电流的抑制能力。其次,推导了故障行波的频域和时域表达式,根据彼得逊法则建立各个时序的等效模型从而准确求得故障电流。并以故障电流和FCL两端的电压应力为优化目标,利用粒子群算法对FCL参数进行优化配置,得到限流阻抗最优匹配值。最后,通过在PSCAD/EMTDC仿真软件中搭建三端直流电网模型进行仿真对比。仿真结果验证了计及行波折反射的故障电流计算方法以及优化模型的准确性。

The refraction and reflection process of traveling waves has an important influence on the fault transient process.Studies up to now,while optimizing the parameters of the fault current limiter(FCL),have not considered the influence brought by the refraction and reflection process of the fault traveling wave on the selection of FCL parameters.This paper proposes a time-domain analysis method of fault transient response considering traveling wave refraction and reflection and optimizes the parameters of the FCL with parallel resistance-inductance.First,an equivalent converter fault model is established,then the suppression effect on the fault current of the FCL using different current-limiting impedance types is compared.Secondly,the expressions of the fault traveling wave in the frequency and time domains are derived,and the equivalent models of each time sequence are established according to Peterson’s rule to accurately calculate the fault current.The fault current and the voltage stress at both ends of the FCL are taken as the optimization objectives,and the parameters of the FCL are optimized using a particle swarm optimization algorithm to obtain the optimal matching value of the current limiting impedance.Finally,a three-terminal DC grid model is built in PSCAD/EMTDC for simulation comparison.The simulation results verify the accuracy of the fault current calculation method as well as the optimized model considering the traveling wave refracted reflection.This work is supported by the National Natural Science Foundation of China(No.U2066208).