AC fault ride through of modular multilevel converter VSC-HVDC transmission systems

This paper discusses the AC fault ride through of two terminal modular multilevel converter (MMC) VSC based HVDC integration of combined offshore wind and wave farms. The combined offshore wind and wave farms are modelled as a controllable three phase voltage source connected to a 600MVA, 460kV/370kV transformer. A 31- level MMC has been selected because of acceptable harmonic attributes. Two 300kV DC submarine cables with length of 100km have been employed in this study. A voltage source has been connected in series with an inductive resistive circuit to give a short circuit ratio of 3.5. This paper finally presents a comparative simulation analysis of hysteresis based and PI based DC voltage controller for fault ride through (FRT) capability. The analysis showed that the PI method resulted in smaller overshoots and dips. A high switching frequency PWM based electromagnetic transient (EMT) model in MATLAB/Simulink was developed for the analysis.