All-DC Wind Generation Systems-Slides

Abstract: This webinar will present a case for an all-DC scheme for wind generation systems. The all-DC gird includes: (i) A wind turbine conversion system that is amenable to higher voltages and adaptable for connection to DC collector grids. (ii) A medium voltage DC collector (DC) collector grid. (iii) A high voltage DC (HVDC) transmission grid. The MVDC is stepped-up to HVDC on the offshore substation using solid state transformer (SST), while the wind farm is connected to the AC grid on the shore using multilevel modular converters (MMC). With the advancements in power electronics systems and the flexibility and controllability that they offer the transmission grids in wind power systems have started shifting from high voltage AC systems to HVDC grids. However, the collector grids in wind power systems have stayed largely unchanged, i.e. rated at medium voltage AC levels. This is due to low-voltage conversion systems in wind turbines and particularly the back-to-back voltage source converters (VSCs). The power electronics switches that are building blocks of VSCs are not yet commercially available at higher-voltage and high-current. Therefore, for such applications the VSCs will need to be multilevel and modular by connecting switches in series and parallel. This makes them bulky and costly and hence unsuitable for the confined space within the wind turbine. Therefore, the output of back-to-back VSCs and the wind turbine is rated at low-voltage AC levels and a tower transformer is used to step this voltage up to medium voltage AC levels. In this webinar a high-voltage wind turbine conversion system will be presented that eliminates the VSCs in wind turbines, provides a DC output, and facilitates the connection of wind turbines to a MVDC collector grid.