Control of Multi-Terminal VSC-HVDC System to Integrate Large Offshore Wind Farms

This paper presents operation and control strategies of multi-terminal HVDC transmission system (MTDC) using voltage source converters (VSCs) for integrating large offshore wind farms. The framework and operation principles of the proposed system are described and control strategies for coordinating various VSCs are proposed. DC voltage control based on the DC voltage-current (V-I) droop characteristic of grid side converters is implemented, to ensure stable system operation and flexible power dispatch between various onshore AC grids. To validate the performance of the proposed control strategies, a typical four terminal MTDC networks, which connecting two offshore wind farms with two onshore AC grids, is established in PSCAD/EMTEC. Simulation results under normal and abnormal operation conditions verify the satisfactory performance of the proposed control strategy and accuracy of the theoretical analysis.