| Project members: Lidong Zhang, Hans-Peter Nee The conventional high-voltage direct-current (HVDC) transmission system (i.e., HVDC with thyristor converters) has difficulty to maintain operation in very weak AC systems. This is inherent for thyristor valves, where commutation is dependent on the sinusoidal waveform of the alternating voltage. The newly-developed HVDC system based on voltage-source converter (VSC) technique has overcomed such weakness. The project goal is to develop a synchronous-machine-emulated controller for grid-connected VSCs. The VSC-HVDC using this type of control does not have requirement on short-circuit capacity of the ac system. Moreover, the voltage-source converter gives the weak ac system strong voltage support, just like a synchronous machine does. The possible application of the research is to use VSC-HVDC as inter-tie for connecting two very weak ac systems. |