Stator Flux Observation and Speed Estimation of a Doubly Fed Induction Generator

This paper developed the theory of decoupled control of active and reactive power for a doubly fed induction generator and discussed the methods to determine the stator flux and the rotor position. A closed-loop observer of stator flux is constructed, to which the deviations of the observed and measured rotor current were fed back. The observer constructed in the paper can eliminate the original errors of flux and restrain the errors arisen from the deviation of machine´s parameters. The rotor speed observation model is derived based on Lypunov´s stability theory. The observers were implemented in a DSP excitation control device and the tests of rotor exciting current control without position sensors are developed. The results prove that the observers have good astringency and the rotor speed observation is effective.