Effects of two-area variable inertia on transient stabilisation in interconnected power system with DFIG-based wind turbines

This study investigates a novel operating method of the interconnected power grid to improve dynamic stability using variable inertia control of large wind farms. In this scheme, the system inertia is considered as an adjustable operating parameter which can be regulated for inter-area power oscillation control and frequency support. Based on the linear state equations derived from a two-area interconnected power system, the effect of the controlled inertia on power oscillation damping is evaluated theoretically considering the different cases of power feeding and receiving networks. The respective wind turbine variable inertia control strategies for the feeding and receiving regional networks are proposed to enhance both inter-area power oscillation damping and frequency stability. A typical two-area interconnected power system with a high 30% wind penetration is simulated, which consists of four conventional power plants and two doubly fed induction generator (DFIG)-based wind farms. The results demonstrate that by using the proposed control scheme, the frequency stability and the inter-area oscillation damping are both significantly improved for the more effective inertia support in the interconnected power system.