Position-sensorless algorithm for stator-flux-oriented control of single VSC-based DFIG

This paper describes new position-sensorless algorithm for stator flux-oriented control (SFOC) of single voltage source converter (VSC) based doubly fed induction generator (DFIG). The recursive approach proposed here uses modification in estimation of stator flux magnetizing current. It involves recomputation of magnetizing current directly in stator flux reference frame and eliminates the need of transformations of rotor current components in stator reference frame. Compared to previously proposed algorithms, this algorithm does not include complex voltage or flux integration, programmable low pass filters and inverse trigonometric calculations. The algorithm is free from critical machine parameters and hence stable against machine parameter variations. Additionally, the presented work also reaps proven advantages such as starting on the fly and accurate estimation near synchronous speed with varying grid voltage/frequency. The effectiveness of proposed algorithm is validated using MATLAB/Simulink for 2 MW DFIG systems. The simulated results confirm the proposed algorithm with accurate estimations under different operating conditions of DFIG.