Study of voltage source converter-based HVDC system during DC side faults

Recently voltage source converter-based HVDC technology has witnessed a remarkable development due to the several advantages it exhibits over the conventional HVDC systems. However, one of the main remaining challenges is the behavior of the system under DC side faults where the VSC protection is a priority. In this paper, the effect of changing the inductance in the AC side and the capacitance in the DC side of the voltage source converter on the converter DC current during fault is investigated. A 500MW/400kV HVDC system is simulated using Matlab/Simulink. Results showed that both capacitance and inductance values have a significant effect on the intensity and timing of the DC current flowing from the AC side to the DC side through the converter freewheeling diodes. Increasing the capacitance increases the blocking time of this current while high inductances decrease its amplitude. However, it is not possible to increase indefinitely the values of the capacitance and inductance where an appropriate compromise must be attained during the design of the system.