Coordinated Virtual Inertial Control of DFIG with BESS for Frequency Support

As the installed capacity of wind turbines increases, the overall inertia of the system decreases, which reduces the ability of the system to support the frequency. Due to the tendency to operate in a maximum power tracking state and the lack of an active power reserve, doubly-fed induction generator (DFIG), a type of the current popular wind turbine, are unable to efficiently utilize the rotor kinetic energy to engage in frequency regulation in the face of grid frequency variations. To address this issue, virtual inertia control (VIC) is introduced to release the kinetic energy of the DFIG provide dynamic frequency support to the grid. In addition, a properly designed control strategy for the battery energy storage system (BESS) can store the excess energy of the DFIG system and release it as needed to assist frequency regulation. In this paper, we propose a coordinated control strategy for virtual inertial regulation with BESS for DFIG frequency support. We design a charge-discharge switching control strategy for the BESS. Time-domain simulations are conducted to verify the effectiveness of the proposed method in suppressing frequency disturbances.