Mathematical Modeling and Position-Sensorless Algorithm for Stator-Side Field-Oriented Control of Rotor-Tied DFIG in Rotor Flux Reference Frame

The rotor-tied doubly fed induction generator (DFIG) configuration has the advantages of higher efficiency and reduced size as compared to stator-tied DFIG for the same power rating. This article presents a mathematical modeling of rotor-tied DFIG in rotor-flux reference frame considering the observer at stationary reference frame. Furthermore, position-sensorless algorithm for the rotor-tied DFIG is proposed to estimate the rotor position, which is based on simple algebraic equations. The proposed position-sensorless algorithm is independent of critical machine parameters which makes the algorithm robust against parameter variations. The algorithm works accurately for different wind speed conditions and thus, useful for wind energy conversion system (WECS) which necessitates the constant frequency operation against variable wind speed. The effectiveness of the proposed position-sensorless algorithm is verified using hardware-in-loop (HIL) set up. OPAL-RT and STM32F407VG micro controller are used in the HIL. Simulation and experimental results for a 250 kW rotor-tied DFIG-based WECS are shown under different wind speed conditions.