Variable Inertias of Wind Turbines in Interconnected Power System for Transient Stability Enhancement

The virtual energy generated by the variable speed wind turbine with virtual inertia control not only changes the frequency response of the system, but also has a significant effect on the transient stability of rotor angle. In this paper, the equivalent model of interconnected system with wind turbines is derived. According to the extended equal area criterion, the conversion between the virtual energy of wind turbine and the transient energy of synchronous generator (SG) is calculated, and the first swing stability of rotor angle is evaluated. The integral manifold method is then adopted to reduce the order of the system model, and the influence of variable inertia control on system damping is analyzed. A variable inertia optimization control strategy is proposed to reduce rotor angle variation by exchanging transient energy with SG while providing rapid inertia response. Finally, a two-area interconnected power system with high wind power penetration is established. The results demonstrate that under the proposed control strategy, the transient stability of system frequency and rotor angle can be both significantly improved.