Modelling and controller design for VSC-HVDC attached to an AC network

In this paper a model and a controller design method for controlling the power and line voltage of a voltage source converter (VSC) in VSC HVDC (High Voltage Direct Current Transmission) attached to an AC system are introduced. The control structure proposed consists of a cascade from power and AC voltage onto a VSC current controller. The controller for the VSC current loop is designed using a standard low order model and the power and voltage controllers are designed using a model extended to included power and AC voltage behaviour. A good validation of the extended model against a rigorous PSCAD model is demonstrated for SCR=4.0.