A thyristor based series power flow control device for multi-terminal HVDC transmission

This paper achieves flexible power flow control by inserting a DC voltage to a line of MTDC transmission. A thyristor based power flow control device is designed to generate this inserted DC voltage. Three-phase six-pulse rectifier using thyristor can convert an AC voltage from AC generator or AC grid to a DC voltage. Power exchange occurs between the AC voltage terminal and DC grids without causing extra power losses which would be found if an inserted resistance is used. A control system is designed for the device and for the power flow control. This design is simulated by using PSCAD/MTDC and evaluated under different operation conditions. The control system is evaluated. Power flow control method is evaluated. This simulation proves the capability of the device to control the power flow effectively.