Optimal speed control of induction motor based on Linear Quadratic Regulator theory

In this paper, the optimal speed control, based on Linear Quadratic Regulator (LQR) theory, through stator field orientation (SFO) of an inverter fed induction motor is addressed. The voltage source inverter, behaving as an actuator, is operated using space vector pulse width modulation (SVPWM) technique. The state feedback system is augmented with integral output error to enhance reference tracking and disturbance rejection criteria. In addition, a feed forward gain is introduced to ensure unity dc gain in case of reference tracking. The LQR synthesis is carried out for the whole system considering the integral output error as an additional state. It is interesting to note that the structure of the control law used here resembles the classical proportional integral control law.