Digital Anti-Windup PI Controllers for Variable-Speed Motor Drives Using FPGA and Stochastic Theory

The windup phenomenon occurs when the output of a proportional-integral (PI) controller is saturated, which results in performance degradation or even instability. In this letter, three new anti-windup algorithms are proposed for a digital PI-speed controller to improve the control performance of variable-speed motor drives. These designs are implemented in a field programmable gate array (FPGA) device and stochastic theory is employed to enhance the computational capability of FPGA. Compared with conventional digital anti-windup techniques, the proposed methods offer several advantages: large dynamic range, easy digital design, minimal scaling of digital circuits, reconfigurability, and direct hardware implementation, while maintaining high control performance. The developed controllers are applied to the speed control of a field-oriented controlled induction motor drive using a hardware-in-the-loop test bench. The improved speed responses confirm the effectiveness of the proposed anti-windup schemes