Abstract
This paper shows the dynamic behavior of the HVDC system which uses forced commutation converter when an AC fault occurs in it. The model HVDC system is unidirectional transmission into a load system without any AC voltage source. Computer simulation program using transient analysis has been developed to perform many runs changing several parameters. First, the results of computer simulation when load impedance changes in the receiving system are shown and they indicate the superiority of voltage-source converter in dynamic behavior. Then, the results of computer simulation when an AC fault occurs in the receiving system are shown. Simulated AC faults are 1 Line-to-Ground (1 LG), 2 Line-Short-Circuit (2 LS) and 3 Line-to-Ground (3 LG). The results of computer simulation indicate that the voltage-source converter must be turned off quickly to protect the switching devices while the current-source converter has no severe problem in the AC fault condition. The overcurrent and overvoltage for the voltage-source converter are shown with the parameters of AC reactance and turn-off delay.
