Research On Direct Torque Control Strategy Of High Performance Contra-rotating Permanent Magnet Synchronous Motor

Nowadays,the world has faced a major challenge of energy shortages.Therefore,how to efficiently utilize the existing resources and develop new energy resources has become a key issue to be solved.Due to the structure of single electrical input dual mechanical output and the motor style of permanent magnet synchronous motor,the contra-rotating permanent magnet synchronous motor(CR-PMSM)improves the energy utilization and the efficiency of the motor.Meanwhile,the CR-PMSM could drive underwater vehicle by connecting the inner and outer axes with the rotating propeller,and then it could further promote the development and utilization of marine resources.Therefore,the research on the control method of the CR-PMSM has farreaching significance for improving the crisis of energy shortages.In the thesis,the control performance of the CR-PMSM is mainly studied under special working conditions,namely heave unbalanced load and large sudden load.On the basis of the literature,the superior control method is summarized and proposed.Then,in the above working conditions,the problems of the method are improved by improving the method and proposing a new control method.At first,the superior method is proposed and studied,which is the dynamic master-slave direct torque control method with sliding mode control.However,as shown in the simulation results of the method,the following problems exist.Specifically,the slave rotor has large torque and speed ripples under heavy unbalanced load,and the rotor has poor robustness under large sudden load torque change.Then,the novel method is proposed to improve the above problems.On the basis of the more accurate mathematical model of the CR-PMSM,the relationship between the torque angle of two rotors and the stator voltage of the motor is discussed.Then,a dual-rotor direct torque control strategy is designed to realize the control of the two rotors' torques.Moreover,a high-order sliding mode load torque observer is designed and made compensation to the system,in order to improve the robustness of the system under the sudden change of large load torque.Finally,the results of the simulations and experiments show that,compared with the dynamic master-slave control with sliding mode control,the above problems are improved by adopting the new method in the thesis.Specifically,under heavy unbalanced loads,the proposed dual-rotor direct torque control could not only avoid the large torque and speed ripples problem of dynamic master-slave control,but also realize the performance that dual rotors of the CR-PMSM could synchronously track for a given speed.What is more,the load observer could quickly and accurately track the change of the load,so the robustness of the rotor is improved in the case of large sudden load changes by compensating for the load torque.