Impact of fixed and variable speed wind turbine systems on power system voltage stability enhancement

This paper investigates the effect of fixed speed and variable speed grid-connected wind generators on the voltage stability of a power system network. The wind generators considered are the squirrel cage induction generator (SCIG), which is fixed speed, the doubly-fed induction generator (DFIG) and the direct driven synchronous generator (DDSG) which are variable speed. Studies were conducted on a standard five machine, 14-bus system augmented by a radially connected wind power plant (WPP), which contains 215 wind turbine generators (WTG).The studies include examining the voltage magnitude, loading margin and voltage collapse of the system. These studies are conducted for the normal state as well as for line contingencies. It is found that large scale integration of WTG (direct drive synchronous generator) at the transmission level has the potential to improve the long term voltage stability of the grid by injecting reactive power.