DC side short-circuit fault analysis of VSC

HU Jing－jing1，GAO Yi－bo1，YAN Yu－ting2，XV Xi－dong1

（1. School of Electrical Engineering，Zhejiang University，Hangzhou 310027，China；

2. Shenzhen Power Supply Bureau，Shenzhen 518020，China）

Abstract：As the fault voltage and current change raptly in case of DC side fault of voltage source converter（VSC），it's a serious threat to the whole system. Aiming at this problem，the mechanism of DC side short-circuit fault，which is the most serious DC side fault of VSC，was analyzed on power electronics level. The three stages of fault process were presented in detail. Firstly，fault voltage and current expressions of capacitor discharge stage were derived. Then，the existing two cases of the uncontrolled diode rectifier initial stage were

elaborated further. Moreover，the calculation of short-circuit current of the uncontrolled diode rectifier stable stage using switch function was proposed as well. Finally，theoretical analysis of the short-circuit fault process was validated through the PSCAD/EMTDC simulation of ±10 kV DC line. The results indicate that the response of the fault is related to the fault impedance closely. Quick removal of the fault needs to be done by DC circuit breaker instantly when the fault impedance is small，while backup protection could be obtained by dynamic monitoring voltages and currents in ac side using protection devices of ac side when the fault impedance is relatively large.