Grid-Forming and Active Power Flow Control of a Three-Terminal VSC-HVDC System

The use of high-voltage direct current (HVDC) transmission technology based on voltage source converters has been validated in applications involving renewable energy generation and long-distance transmission. For multi-terminal direct current (MTDC) transmission technology, this paper investigates the case of renewable energy generation delivered by a three-terminal de system. The matching control is employed at each terminal to support the voltage at each port while stabilizing the frequency at the ac side. By incorporating an outer power flow control loop, the inverter station at each terminal can not only achieve voltage support but also maintain active power flow balance throughout the entire system, enabling precise control of port power.