A Method to Analyze the Transient Angle Stability of OMIB System with DFIG-Based Wind Farm

The increasing amount of the integration of doubly-fed induction generator (DFIG) will bring about some adverse effects on the transient stability, or even threaten the reliability and the safety of the whole power grid. By analyzing the equivalent external characteristic of DFIG, it can be regarded as constant negative resistance and time-varying negative impedance during steady period and transient period. Using this segmented model for analyzing the transient stability of one machine infinite bus (OMIB) system with DFIG integration, it concludes that DFIG integration increases SG's initial rotor angle, which decreases the stability. In the period of fault duration and initial stage after clearing of fault, the DFIG is equivalent to time-varying impedance. The impact on transient stability depends on the reactive power of DFIG, which can be derived through the segmented DFIG equivalent model.