Utilization of embedded VSC-MTDC system for supporting power flow during primary frequency control

This paper deals with the utilization of multi-terminal High Voltage Direct Current (MTDC) system based on Voltage Source Converter (VSC) technology for supporting power flow during primary frequency control in large high voltage transmission system. The investigated MTDC system interconnects synchronous areas within an AC power system. A novel primary frequency support (PFS) controller is incorporated into the standard control scheme of VSC station control to enable VSC- MTDC system taking part in primary frequency control under severe generation outages. An analytical method to determine the PFS gain is also proposed to assure an accurate schedule of exchanged power through VSC-MTDC system according to the residual transferable margin of the parallel HVAC lines. The proposed PFS controller uses feedforward control technique to forestall undesirable effects of transient frequency deviation on system dynamic performance. The PFS controller is then tested on a typical high voltage transmission system.