Credible Reactive Power Regulation Capacity Assessment of DFIG Wind Farms

Doubly-fed induction generator (DFIG) wind turbines can provide reactive power to participate in grid reactive power control, however the reactive power regulation capability provided by DFIG is uncertain due to the uncertainty of the active power output and terminal voltage of the generator. In this paper, we investigate the credible reactive power regulation capability of the wind farm considering the limit of all the reactive power compensation devices, also the uncertainty of the active power output from the wind turbines and the limit of the power flow is also considered to obtain a reliable reactive power regulation capability from the wind farm. First, the reactive power limit of the DFIG wind turbines is derived considering the limit of the power converter capacity and parameters of the wind turbine. Then the constraints considered to evaluate the credible reactive power regulation capability are investigated, and the method to evaluate the reactive power regulation capability of the wind farm is proposed. Finally, simulation study is presented with a power system model connected with a DFIG wind farm. The result shows a stricter reactive power regulation capability can be obtained considering all the constraints compare with the simple superposition method, which is more reliable and it can be used for further investigate on the reactive power control strategy.