Virtual Inertia Control of DFIG-based Wind Turbines Based on the Optimal Power Tracking

The increasing penetration of large-scale wind generation in power system will bring a new challenge that the converter based variable speed wind turbines has no contribution to the power system inertia.In this paper,the operation characteristics and control scheme of the doubly fed induction generator(DFIG) was analyzed firstly,and then the relationship between the virtual inertia,the rotor speed regulation and the network frequency variation was investigated.Finally,a novel virtual inertia control strategy of the DFIG based wind turbines was proposed.The proposed strategy can change the maximum power point tracking(MPPT) curve according to frequency deviation monitoring,so as to release the "hidden" kinetic energy and provide dynamic frequency support to the grid.A three-machine system with 20% wind power penetration was used to validate the proposed control strategy.The simulation results show that the DFIG-based wind farms have fast respond ability to the grid frequency deviation caused by the active power disturbances using the virtual inertia control,so that the frequency stability of the power system with large wind power integration is improved.