Decoupled control of natural and power variables of doubly-fed induction generator using feedback linearization

The electromagnetic torque, stator power, and the grid side converter (GSC) power outputs of a double-fed induction generator (DFIG) are differentiated to obtain a feedback linear relationship with the rotor voltage vectors serving as the control inputs. The derived model is such that the torque and power quantities are the state variables of the system, which are insensitive to coordinate system orientation. The steady-state equations from the derived model are used to obtain the optimal operating region with respect to minimal electrical losses. Decoupled torque control is developed by field orientation, while decoupled power control is derived from voltage orientation of the DFIG. Robustness of the decoupled controllers against parameter variation is investigated by locating the poles of its closed-loop transfer function. Results for a 5Hp machine are presented.