Practical Fine Tuning of Cascaded Loop Control of AC Motors

The PI regulator is not the most effective linear controller for regulating the speed of AC motors. This paper demonstrates that linear system design can achieve superior performance in terms of load-torque rejection and reference tracking. Two analytical tuning methods are suggested. The first method improves speed regulation and load-torque rejection simultaneously based on the well-known Texas Instruments (TI)’s tuning method. The second proposed method employs an equivalent structure to the first, but designs the speed loop with a novel approach. This demonstrates that by employing zero-pole cancellation, the speed loop turns to be a linear second-order system which is only about the damping ratio and natural frequency. Meanwhile the controller’s parameters can be calculated based on the chosen damping ratio and natural frequency.