DC Voltage Regulation and Frequency Support in Pilot Voltage Droop-Controlled Multiterminal HVdc Systems

This paper presents an improved pilot voltage droop based control for the multiterminal high-voltage dc (MTDC) systems. The proposed control strategy maintains adequate power sharing and efficient voltage regulation among the converter stations. The incorporation of the average voltage sharing loop enables achieving superior dynamic performance while avoiding dc system average voltage deviation from nominal value. Furthermore, the frequency consensus algorithm is used for modifying the power reference of converters to achieve the desired frequency deviation sharing between the ac areas connected through the droop controlled voltage source converters. Finally, the incorporation of the frequency locked loop enables achieving fast grid synchronization and superior dynamic performance for the control of the converter stations. The simulations carried out in the MATLAB/Simulink environment revealed the effectiveness of the controller to provide enhanced dc voltage regulation and frequency deviation sharing during disturbances in the MTDC system.