Multi-Timescale Control of Variable-Speed Wind Turbine for Inertia Provision

Abstract

The increasing deployment of power converters has led to a significant reduction in the power system inertia and consequently resulted in frequency stability issues. To improve the robustness of the grid against frequency disturbances, it is becoming more expected in many countries that renewable energy generation, such as wind turbine power systems, should provide equivalent inertia support to the power system. This can be achieved through advanced control of power converters, in addition to adding extra energy storage devices, e.g., batteries. In wind turbine systems, although the ancillary service of inertia provision can be realized by coupling the rotor speed with the grid frequency, the rotor speed recovery process affects the inertia response if the controller is not properly designed or well-tuned. To address this issue, in this paper, we propose a multi-timescale control strategy for a doubly fed induction generator (DFIG) wind turbine system. Synthetic inertia control and speed recovery control are simultaneously incorporated into the controller of the rotor-side converter, whereas their dynamics are decoupled under different timescales to avoid control conflict. Extensive simulation results are provided, which validate the efficacy of the proposed inertia emulation scheme.