Robust Observer Design for Sensorless Voltage and Frequency Control of a Doubly Fed Induction Generator in Standalone Mode

The paper proposes a rotor speed observer for sensorless voltage and frequency control of a standalone doubly fed induction generator (DFIG) system. The proposed speed estimator is designed based on the sliding mode observer (SMO) technique, which makes the estimation algorithm robust under parametric variations and external disturbances. The position of the rotor is computed directly by the integration of the estimated speed by the designed observer. The proposed observer requires the measurements of stator voltage and current to estimate the speed. The design procedure of the observer does not require the mechanical parameters of the DFIG, which makes the observer design independent of the mechanical parameters. Lyapunov stability criteria are used to formulate the sliding gains for the observer. Simulation and experimental results are demonstrated to show the efficacy of the designed observer in terms of accuracy and convergence rate under different steady-state and dynamic conditions. The estimated rotor speed and position are utilized for controlling the magnitude of the stator voltage of a standalone DFIG system, which validates the performance of the observer.