Additional improved adaptive frequency control strategy in VSC-MTDC systems with wind turbines

Since the additional frequency control of multi-terminal flexible DC transmission system is easy to property DC voltage abnormality, this paper investigates the mathematical relationship from AC system frequency and DC voltage, and proposes an improved adaptive frequency regulation strategy. This strategy connects VSC-MTDC systems containing wind energy to make sure that the DC voltage is stable during system frequency tuning. Finally, A three-terminal flexible DC transmission system containing wind power is constructed at PSCAD/EMTDC, and the results show that the proposed method is able to reduce voltage swings while achieving mutual power support between AC systems.