Influence of Integrated DFIG on Transient Angle Stability of Power System

Increasing integration of DFIGs is leading to more quantities of transient angle stability patterns. To theoretically catch those patterns, a DC power flow-based extended equal area criterion method is presented. At the outset, DFIG is modelled via constant power source, thanks to its fast recovery property of active generation conveyed in electromechanical transient timescale. Then, to allow us to deduce analytical expression of rotor angle of synchronous machines, DC power flow is introduced. Upon the above approximation tricks, a generic and analytical two-end transmission system involving two-machine and two-DFIG is presented. By further incorporating extended equal area criterion, impacts of DFIG power generation on transient angular stability are analyzed, such that an intuitive stability criterion taking steady operational variables as input is rendered. Time-domain simulations executed on the given two-end system justified the precision and effectiveness of the released stability criterion.