Adaptive Voltage Droop Method of Multiterminal VSC-HVDC Systems for DC Voltage Deviation and Power Sharing

Voltage source converter based multiterminal HVDC (VSC-MTDC) technology has shown many advantages. However, following a large disturbance, the dc voltage and the output power of the VSC station with fixed droop control may hit their limits, thereby reducing the dc voltage control ability of the whole MTDC system. Here an adaptive droop control scheme is proposed on the basis of both the dc voltage deviation factor and the power sharing factor. It contributes to ensure the dc voltage and the power loading rate of each converter within their limits during large disturbances, and the power sharing capability of the whole MTDC system remain high. The working principle of the proposed adaptive droop control is discussed in details. Case study and simulations are performed based on the PSCAD/EMTDC model of a ±320 kV four-terminal VSC-HVDC system to validate the effectiveness of the proposed adaptive droop method.