A novel DC voltage control strategy for multiterminal HVDC system with offshore wind farms integration

DC voltage control and power distribution are significant requirements for multi-terminal HVDC control system. The common voltage droop control has the drawback of failing to keep the dc voltage at a fixed value if active power is fluctuating, and voltage margin method actually controls dc voltage only by one converter at a time. A novel control strategy-Coordinated DC Voltage Control-is thus proposed. This strategy utilizes telecommunication technology to coordinate all the grid side converters to control dc voltage. A stable dc voltage as well as accurate power distribution according to the minimization of power loss or other optimal power flow algorithm can be achieved. The control effects are validated based on a five-terminal HVDC system modeling in PSCAD/EMTDC with three different scenarios, including steady state and dynamic state. The satisfactory simulation results prove the feasibility and robustness of the proposed control strategy.