The Research Base On Two-Fuzzy Control For Induction Motor Direct Torque Control

The direct torque control (DTC) is another high performance control technique after vector control theory in AC control field. Compared with vector control theory, DTC discard the decouple idea of vector control and directly controls flux and torque in stationary reference, so that it has the advantage of rapid torque response and less relying on motor parameters. A new two-fuzzy control algorithm is proposed in this paper and the simulation experiments are done to prove that the performance of DTC system is increased in low and high speed. The paper is combined with two parts as follows:In the fist part, this paper systemically introduces the fuzzy logic control and the fuzzy self-adaptive control method and analyzes the design method of fuzzy control system (FCS) according to features of FCS. A strategy to greatly decrease the electromagnetic torque ripple is presented through designing a fuzzy DTC system with fuzzy self-adaptive speed PI regulator. In outer loop control, a new kind of speed control model is designed which utilizes fuzzy self-adaptive speed PI regulator instead of the conventional PI regulator. In inner loop control, the novel fuzzy controller is used to replace the traditional two-level flux and three-level torque of bang-bang controller in order to overcome the drawback of select right voltage vector by torque and flux error in basic DTC control system. The new algorithm is realized in this paper through large error is large regulated and small error is small regulated.In the second part, simulation model is established by MATLAB/Simulink software for validating superior performance in DTC. The basic DTC and the new method are simulated and the results are compared for their performance. The simulation results show that the new control method has rapid dynamic response while great reduction of torque ripple is achieved, and the track of steady stator flux is nearly equal to the expected circular one. On the other hand, these results demonstrate this method improves performance in low-speed range.