Research On Direct Torque Control System Of Induction Motors Based On DSP

The direct torque control(DTC) technique is a new kind of high-performance AC frequency conversion timing technique developed after Vector Control Technology. It no need to equivalent the AC motor to DC motor and analyse the mathematical model of the AC motor in stator coordinate, leaves out the complex vector transform. By employing stator-flux-oriented, system control performance out of influence of the changing rotor parameters. With the aid of flux and torque hysteresis controller, DTC has a direct and optimal control to the state of the inverter switch. DTC has got a universal attention and a quick development for its novel control ideas, simple system structure, and excellent static and dynamic performance. However, there are some disadvantages, such as strong ripple of torque, flux and current, and inconstant frequency of switch.This paper gives an analysis to mathematical model of asynchronous motor, provides a thoroughly basic principle of DTC, and also illustated the design of the major modules of DTC system. Three methods used to synthesize voltage vector is introduced, one of the methods called Space Vector PWA, short as SVM, can generate voltage vector of arbitrary size and direction. The flux and torque fuzzy controllers are designed to get reference voltage vector in order to compensate flux and torque ripple. And the introduce of fuzzy logic control technology gives a resolve to the issue of the performance of direct torque that is Susceptible to be affected by systemically changing parameters, and improves robustness of the system. In this paper, two fuzzy controllers are designed in this improved program, therefore it is called double-fuzzy SVM-DTC.The software Matlab/Simulink is used to simulate the conventional DTC system and the double-fuzzy SVM-DTC system, and the establishment of simulation model is specifically presented. The simulated results have proved the improved method is credited with advantages because it can effectively reduce ripple of vector and torque in traditional direct torque control, and the switching frequency of inverter is fixed.In the paper, the experiment is carried out on the platform that using DSP chip TMS320LF2812 as the core, the building of the experiment platform and circuit design are presented in detail, and the experimental procedures based on software CCS3.3 is complied. The feasibility of this new method is verified through the debugging of software and hardware of the system.