Anti-Windup PID Controller With Integral State Predictor for Variable-Speed Motor Drives

The windup phenomenon appears and results in performance degradation when the proportional-integral-derivative (PID) controller output is saturated. Integral windup is analyzed on the PI plane, and a new anti-windup PID controller is proposed to improve control performance of variable-speed motor drives and is experimentally applied to the speed control of a vector-controlled induction motor driven by a pulse width-modulated voltage source inverter. The steady-state value of the integral state is predicted while the PID controller output is saturated, and this value is utilized as an initial value of the integral state when the PID controller begins to operate in a linear range. Simulation and experiments result in more similar speed responses against load conditions and step reference change over conventional anti-windup schemes. Control performance, such as overshoot and settling time, is very similar to that determined by PID gain in the linear range.