Linear-quadratic regulator of torque and reactive power of a doubly fed induction generator operating in an unbalanced grid

The paper presents a state controller for torque and reactive power tracking of a doubly fed induction generator operating in an unbalanced grid. The state feedback gain is tuned using linear-quadratic optimization. Reference stator currents are calculated using instantaneous power theory and precisely tracked by the current controller. In the paper there are presented simulation results of an electrical model of doubly fed induction machine with the proposed control algorithm operating in either balanced and unbalanced grid.