AC System Frequency Support Method of the MTDC System Connected with Wind Farms

Large-scale offshore wind farms integrating into onshore AC systems through the multi-terminal DC (MTDC) system would cause the overall inertia of AC system being substantially reduced, i.e. the AC system frequency is more susceptible to changes in load. In order to solve this problem, this paper proposes a frequency support method by regulating DC voltage in MTDC system so as to offset the load imbalance, and larger frequency events caused by larger load imbalances between multi-terminal systems can be solved by using wind turbine inertia response in conjunction. Finally, with simulation models of MTDC system with AC interconnected AC systems on MATLAB/Simulink platform, the correctness and applicability of the frequency support method are verified by simulation.