Short-circuit current calculation and performance requirement of HVDC breakers for MMC-MTDC systems

To evaluate the performance requirement of high-voltage direct current (HVDC) breakers for modular multilevel converter (MMC)-MTDC (multi-terminal high voltage direct current) systems with high efficiency, the equivalent model for calculating the maximum short-circuit current is presented in this paper. First, the short-circuit current is decomposed into the steady-state component and the fault component according to its physical dynamics. Second, the steady-state component is determined by solving the direct current (DC) network; the fault component is calculated by an equivalent network in which the converters are replaced by a reactance, a resistance, and a capacitance in series. Then, the complete procedure for evaluating the performance requirement of HVDC breakers is described based on short-circuit current calculation. Verifications have been carried out based on a three-terminal 800 MW/+/- 400 kV bipolar MMC-MTDC system. The results show that the proposed methodology is efficient and effective. Lastly, based on the same system, the performance requirement of HVDC breakers and the influence by the sub-module (SM) capacitance and the smoothing reactor have been studied with the proposed methodology. (c) 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.