Reduced-Size Converter in DFIG-Based Wind Energy Conversion System

Induction generators operate in a wide range of speed to accommodate the forced turbine speed tracking required by the MPPT controllers. Consequently, the size of the rotor-side converter needs to be large. This paper introduces a DFIG-based wind power conversion structure that can achieve MPPT in a narrow window of generator speed and consequently reduce the size of the converter. A new hydraulic power transmission system is employed to decouple the shafts of the generator and the turbine, allowing independent control of MPPT and generator speed regulation. The proposed DFIG is investigated by analytical calculations as well as a simulation at different wind speeds to demonstrate the reduced size of the converter and dynamic performance of the power generation.