Optimized virtual inertia of wind turbine for rotor angle stability in interconnected power systems

Abstract In the power system with virtual inertias, the current dynamic analysis of frequency stability is insufficient to ensure grid security because the virtual inertia control also has a significant effect on the first swing stability of the rotor angle. This paper investigates a novel virtual inertia control strategy for wind turbines to improve the first swing stability of the rotor angle in the interconnected power grid. The virtual energy provided by the virtual inertia control of the wind turbines is calculated. Considering that the rotor angle swings in the forward and backward directions, the effect of virtual energies in two different coherent generator groups on system transient energy conversion is evaluated. Moreover, a novel control method is proposed to provide more reliable inertia support. A typical two-area interconnected power system with a high wind penetration of 35%, which consists of four conventional power plants and two doubly fed induction generator (DFIG)-based wind farms, is simulated. The simulation results demonstrate that in the transient events, the rotor angle difference between the coherent generator groups can be reduced by regulating the variable inertias, significantly improving the reliability of the virtual inertia support of wind turbines.