Research on Fuzzy Direct Torque Controlling System of Induction Machine with Fuzzy Speed Regulator

To reduce traditional direct torque control (DTC) system low speed control precision and the large torque ripple in low speed, a fuzzy control system of DTC was proposed. On the basis of conventional PI regulator, a fuzzy speed PI regulator was designed according to speed error and its rate of change, which could adjust the proportional coefficient kp and integral coefficient k_p dynamically to adapt the system to the speed variations, and advanced the self-adaptation of speed. In voltage vector fuzzy controller model, the stator flux angle, the stator flux error, and the torque error are reasonably fuzzified into several fuzzy subsets to optimize selection of the voltage vector and decrease the torque ripple. The experimental results show that the proposed fuzzy control system not only can ensure swift speed response, small overshooting, and high steady speed precision, but also can effectively decrease torque ripple in low speed. Additionally, the system improves the observation precision of the stator flux and enhances the robustness of the whole system