The amelioration of control strategy of VSC-MTDC based on voltage droop control

The voltage stability of VSC-MTDC depends on the balance between the input power flow and the output power flow. It is significant to optimize power distribution among converters and enhance system voltage stability by adapting the converter voltages to the deviation of the power flow with adequate multi-terminal voltage control strategy. Summarizing the characteristics of the three existing control strategies, including the master-slave control, the voltage margin control and the voltage droop control, an improved control strategy based on voltage droop control is proposed. The theoretical analysis shows that this control strategy could significantly ease the DC bus bar voltage deviation when power flow through converters changes intensely, as well as adapt voltage to the change and distribute the power flow automatically when converter power flow merely changes slightly.