| Due to the easy implementation,high efficient and stable driving of the asynchronous motor,it is widely used in electric vehicles.The direct torque control(DTC)technology has the advantages of strong robustness against motor parameters,simple structure and quick dynamic response.It has become a high-performance control scheme.However,the control effect of the DTC is not good under the larger disturbance.DTC technology for the asynchronous motor is further studied in the thesis,the main works and conclusions are listed as follow:First,the working principles of DTC technologies are analyzed,in which the implementation method and control method for DSC system DTC system are discussed.Aiming at the problem of large torque pulsation,a novel torque control method is proposed.By using the root trajectory method to determine the parameters of each PI regulator and introducing the method of space vector modulation(SVM),the control technology of SVM-DTC is formed.Second,the models of DSC system,DTC system and SVM-DTC system are established with MATLAB package.Simulation results indicate that the control effect of the SVM-DTC system is better than other two methods.Then,a 180W/380 VAC asynchronous motor is chosen as control target and STM32F103-C8T6 MCU is adopted as controller.The hardware for the experimental platform is designed,in which the control module,power supply module and driving and isolating module are realized.The software design is also finished.The developed programs include main program,braking operation and SVPWM waveforms generating subprograms.Final,the verification experiments on the SVM-DTC method are implemented.The control effects with the motor without loading and under load are testified.Results indicate that SVM-DTC system switching frequency is constant,torque pulsation is low,system speed regulation performance is excellent.The control effect of the SVM-DTC method proposed in the thesis is ideal and a good application prospect can be expected. |
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