Simulation studies on a control and protection scheme for hybrid multi-terminal HVDC systems

In this paper a control and protection scheme for hybrid multi-terminal HVDC systems is proposed and its performance is studied by means of analog and digital simulation. Hybrid multi-terminal HVDC systems consist of forced commutated voltage source converter (VSC) stations, line commutated current source converter (CSC) stations and DC transmission lines. A control and protection scheme which combines DC voltage control and power control for VSC stations with DC voltage control and DC current control for CSC stations is studied. Performance of this control and protection scheme in case of startup, normal state operations, and faults in the HVDC system and AC system is confirmed by means of the AC-DC power system simulator and Electro-magnetic Transients Program.