On-Grid Operation of BESS assisted DFIG-WECS

This paper proposed a battery (in battery energy storage system (BESS)) state-of-charge (SoC-based control strategy to address the power imbalance issue in the wind energy conversion system (WECS), especially for the doubly-fed induction generator (DFIG)-based WECS, keeping the battery safe under any condition. Unlike the latest reported work, where a fixed rotor-current-gain or manual operation-based strategy (to reduce the DFIG power generation or power export to the grid) is presented, this work has automated the DFIG-BESS-WECS operation, using a reconfigurable control strategy based on real-time battery-SoC condition. If the battery-SoC approaches the maximum limit, the BESS immediately stops charging the battery further. The DC bus is then maintained by the DFIG-rotor side converter, operating the DFIG in the off-MPP (maximum power point) mode. If the battery-SoC approaches the minimum limit, the BESS immediately stops discharging the battery further, and the DC bus is then maintained by the grid-side interlinking converter, reducing the grid-power export to a lower maximum permissible value. To validate this strategy, the DFIG-BESS-WECS is modeled in MATLAB/Simulink environment and simulated in Opal-RT real-time simulator. Simulation results show that regardless of wind velocity and load variations, the battery SoC is maintained within a safe range while utilizing the maximum possible wind energy. The DC bus voltage is also regulated throughout the operation.