Stator-flux-linkage-referenced control and online optimization of a doubly-fed induction generator

A trajectory-tracking controller with shaft load torque estimator is presented for a doubly-fed induction generator using the backstepping approach. Trajectory generation is straightforward since the nominal system model is flat. The machine controller is designed in stator-flux-linkage-referenced coordinates to exploit the relationship between a single rotor current component and generated torque. While the stator flux linkage is not explicitly controlled, it is shown to converge to a reference due to inherent internal system damping. As such, its angle may be used for loss minimization purposes since it is shown to influence the distribution of reactive currents in the system. The presented approach is evaluated with numerical simulations.