Voltage support in hybrid AC-DC grid by wind power plants and VSC

Previously, the large conventional fossil fuel plants were in charge of supporting the grid voltage by supplying the reactive power. They will be gradually replaced with renewable energy sources (RES), leading to a more volatile power system with low inertia. This paper investigates the performance of voltage source converters (VSC) in establishment of voltages in a future power system featured with hybrid AC-DC grids and wind power plants. An optimal power flow (OPF) model for multiple planning periods is developed to optimally dispatch the reactive power of different available reactive power sources, including wind power plants, HVDC converters and traditional generators. The developed OPF model is ready to work at the top level of a hierarchical voltage control scheme. Case studies demonstrated that the developed model was able to reduce active power losses and improve the voltage profiles in the overall system.