An Overview Introduction of VSC-HVDC: State-of-art and Potential Applications in Electric Power Systems

High Voltage Direct Current (HVDC) seems going into another booming time since the first test line was developed by Dr. Uno Lamm about seventy years ago in Sweden. The boom of this time can be seen from not only fast increased project number but significant research interests around whole world as well. The major motivation behind comes from new challenges to the conventional ac grid, e.g. increased proportion of renewable power generation, flexibility requirements from power market, and environment impact. The new HVDC technology based on the Voltage Source Converter (VSC) is a feasible and attractive solution that can fulfil almost all above challenges due to its distinct advantages in the areas of controllability and flexibility, e.g. independent control of active and reactive power, fast control response speed, etc. Therefore, much effort is devoted to further extend its advantages and eliminate its drawbacks, such as high losses compared to Current Source Converter (CSC) HVDC and ac system. A new development milestone of VSC-HVDC technology and its application in the power system will be the South-West Link project in Sweden, which will start soon. It will be the first three-terminal VSC-HVDC links embedded in the grid, and marks the practical application of VSC-HVDC going into multi-terminal time. This paper tries to follow and summary the important researches and development of VSC HVDC technology, especially in the VSC topology, modelling and control methods, and potential applications in the power system. All these researches will show profound and significant effects in the development of VSC-HVDC, and even on the future of electric power systems