Flexible DC Distribution Line Protection Method Considering Instantaneous Power
In order to avoid misoperation during the protection of flexible DC distribution lines,it is necessary to accurately identify the fault location.However,it is difficult to grasp the fault characteristics of DC distribution lines and locate the fault.The protection method of flexible DC distribution line considering instantaneous power is studied.A modular multilevel converter(MMC)is used to commutate the ports,and the dynamic model of dis-tribution line in three-phase static coordinate system is obtained by calculation.According to the frequency domain information in the voltage step signal,the fault information in the time domain is converted,and the fault features are extracted by wavelet transform.Considering the instantaneous power characteristics,the protection device is installed at the port of the flexible DC power network line.According to the instantaneous power change of the end point,the fault location in the DC transmission line is determined.Based on the fault voltage characteristics,the fault pole selection criterion is designed to judge the direction of the current mutation,and the flexible DC dis-tribution line protection is realized.The experimental results show that the protection action of the proposed method is correct,and the DC voltage change rate of the fault outside the area is almost the same as that of the fault inside the area,which makes the protection action reliable and realizes the good application of the flexible DC distribution line protection method considering instantaneous power.
instantaneous powerflexible DCdistribution line protectionwavelet transform
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