Distribution Generation Case Study: Electric Wind Farm with Doubly Fed Induction Generators

The paper presents simulation results regarding the operation of an electric generation wind farm connected to the grid. A load is also connected at the middle of the power line that joins the grid to the wind farm. The wind farm is equipped with Doubly Fed Induction Generators (DFIG). Two configurations, grid and load alone, and grid, load, and the wind farm, were simulated at different conditions, such as wind speed close to zero, nominal wind speed, load close to zero, and nominal load. The DFIG could operate as a rotating capacitor, similar to a synchronous machine. Therefore, there are no capacitor banks operating with the wind farm. The steady state voltage profile and active power losses could be obtained. Furthermore, voltage stability (PV or nose characteristics) and transient stability (three-phase symmetrical short circuit and one phase-to-ground short circuit) are studied. It is seen that the distributed generation could increase the voltage stability. Moreover, the DFIG rotor voltages control could change the reactive power the DFIG takes or supplies to the grid. The rotor converter dc voltage would affect the reactive power flow toward the DFIG, similar to the under- or over-excitation effects present in a synchronous machine.