Reactive power characteristics analysis on emergency stop of doubly fed induction generator

This paper analyzes the reactive power characteristics of the doubly-fed induction generator (DFIG) during the emergency off-grid process caused by the crowbar protection action. Since the action of the crowbar is much faster than the stator switching, the DFIG would be running with a short-term squirrel cage asynchronous operation. The mathematical model of the DFIG under above situation was proposed in this paper, based on which detailed analysis was given on reactive power demands during squirrel-cage asynchronous state of the DFIG. It is achieved that the amount of reactive power absorption was associated with the initial operating conditions such as the terminal voltage and speed before disconnection, which can be prescribed as the s-Q characteristic of DFIG. Finally, analysis on the measured data of the wind farm disconnected event verified the validity of the model. (paper)