Design Of The SVM-DTC For Asynchronous Motor Based On STM32

As a new method of AC speed regulating system, Direct Torque Control is widely spread with its simple control structure, fast torque response and low demands on the motor parameters. However, torque ripple exists at low speed situations of the Direct Torque Control, how to improve the torque ripple is the starting point of this paper.This paper elaborates a mathematical model of asynchronous motor and two common coordinate systems, and introduces the principles of space vector pulse width modulation (SVPWM) and direct torque control. With analyzing the causes of torque ripple, this paper focuses on a program:based on SVPWM of the direct torque control, and using PID controller instead of the hysteresis comparator, which is called SVM-DTC control strategy. On the other hand, the exact solution of the stator flux has a great significance to overcome the torque ripple. As the pure integrator observation method is simple, and does not involve rotor parameters, so it can be widely used. However, there exists offset, or saturation in the flux observed by the pure integrator observation method. Therefore, this paper focuses on a new kind of the flux observer:an improved integrator with saturated and feedback. This flux observer not only inhibits the flux saturation, but also is effective of the flux offset, closes to the theoretical value of flux.In order to achieve the SVM-DTC control strategy and the observed effect of the improved integrator with saturated and feedback, I build the hardware testing platform of the asynchronous motor control system based on STM32, this hardware testing platform includes the power supply module, the power module, the driver module, the detection module and the control module. The software program based on STM32, has achieved the SVPWM module, the solution of stator flux and torque, the improved digital integrator with saturated and feedback, the digital achievement of PID controller and the FIR low-pass filter.Finally, by debugging the SVM-DTC for asynchronous motor control system which is based on STM32, the experimental results show that the control strategy has a better control performance with good dynamic performance, small torque ripple and stable stator flux waveform. The results meet the expected experimental purposes.