Indirect stator flux-oriented output feedback control of a doubly fed induction machine

A new indirect stator flux field-oriented output feedback control for doubly fed induction machine is presented. It assures global exponential torque tracking and stabilization of the stator-side power factor at unity level, provided that electric machine physical constraints are satisfied. Based on the inner torque control system, a speed tracking controller, with load torque compensation is designed using passivity approach. In contrast to existing solutions, the stator voltage vector oriented reference frame is adopted in order to improve robustness properties with respect to induction machine parameters variation. To achieve smooth connection of electric machine to the line grid a synchronization algorithm is developed for excitation stage of the doubly fed induction machine operation. The solution proposed requires measurements of line voltages, rotor currents, rotor position and speed. Intensive experimental studies demonstrate high dynamic performance capabilities of the control algorithm proposed.