Low voltage ride through capability enhancement of wind turbine generator system during network disturbance

The energy capacitor system (ECS), composed of power electronic devices and electric double layer capacitor to enhance the low voltage ride through (LVRT) capability of fixed speed wind turbine generator system (WTGS) during network disturbance, is discussed. Control scheme of ECS is based on a sinusoidal pulse width modulation voltage source converter and DC-DC buck/boost converter composed of insulated gate bipolar transistors. Two-mass drive train model of WTGS is adopted because the drive train system modelling has great influence on the characteristics of wind generator system during network fault. Extensive analysis of symmetrical fault is performed with different voltage dip magnitudes and different time durations. Permanent fault because of unsuccessful reclosing is also analysed, which is one of the salient features of this study. A real grid code defined in the power system is considered and LVRT characteristic of WTGS is analysed. Finally, it is concluded that ECS (20 MW) can significantly enhance the LVRT capability of grid connected WTGS (50 MW) during network disturbance, where simulations have been carried out by using PSCAD/EMTDC.