Circuit Configuration and Control of a Grid-Tie Small-Scale Wind Generation System for Expanded Wind Speed Range

In this paper, a grid-tie small-scale wind generation system is proposed with innovations in both of the topology and the controller. A novel high step-up zero-current turning-on soft-switching rectifier and a storage branch are employed to improve the low-wind-speed (LWS) and high-wind-speed (HWS) performances. The optimized LWS operation is guaranteed by the rectifier, the battery pack, and film capacitors. The enhanced HWS performance is fulfilled by parallel operation of the inverter and the battery charge converter. Furthermore, the control strategy aiming at improving overall system efficiency and extending battery lifespan and exploitable wind speed range is adopted. A state-of-charge (SOC) control method is used and ensures SOC is most frequently within a range of 20-80%. The proposed method not only slows down the battery capacity fading by SOC scope limitation and by charge/discharge current restriction, but also provides safety capacity margin in case of extreme HWS condition. Also, a simple but reliable dead-zone controller is applied on the battery charge/discharge converter to control the dc-link voltage. Finally, the theoretical analysis and the control method are verified by simulations, experiments, and are tested in the real wind field.