Research On Fault Tolerant Control Strategy Of Permanent Magnet Synchronous Motor

With the development of the country in the field of new energy,the popularity of electric vehicles has gradually increased,and the core component of electric vehicles is the motor.In the field of motor control,the efficiency of permanent magnet synchronous motor is high,and due to its high reliability,the application field of this kind of motor is continuously expanding.In order to make the motor run smoothly under various adverse conditions,more stringent requirements are put forward for safety.Moreover,in order to improve the efficiency of electric vehicles,the motor must be controlled more effectively and accurately.The main contents of this paper are as follows:Firstly,various expressions of motor model are introduced,and the mathematical model is established based on the open circuit fault of one phase;The current vector trajectory method is introduced to determine which phase of the motor has fault by judging the slope of the vector,and then the fault model is simulated.Secondly,the characteristics of the three fault-tolerant topologies are analyzed.SVPWM modulation is carried out when the equipment fault occurs.Detailed simulation experiments are carried out on the three topologies.According to the simulation results,it is known that the three-phase four switch scheme has faster response speed and less ripple after the speed reaches stability.Then the capacitor neutral point voltage of two-phase four switch and three-phase four switch are compared.It is concluded that the neutral point voltage fluctuation of three-phase four switch is small,which shows that this structure has good control effect.Although the traditional three-phase four switch vector control scheme can effectively control the neutral point voltage,it will complicate the operation.Then,because the three-phase four switch topology charges and discharges the DC capacitor during operation,the voltage at the midpoint will be unbalanced.The traditional vector control will complicate the operation.In order to simplify the operation,MPC(predictive control algorithm)is used based on the three-phase four switch structure.The simulation results show that MPC method has obvious effect on restraining the neutral point voltage,and the torque jitter after adding MPC algorithm is 50% lower than the traditional three-phase four switch vector control,which proves that MPC method can also limit the torque ripple.Finally,the principle of ILC(iterative learning)algorithm is introduced.ILC module is added on the basis of MPC algorithm,and ILC learning module is connected in parallel on the basis of PI controller.ILC learning law is used to suppress the jitter of speed,and this method is simulated.From the simulation results,this scheme can effectively suppress the fluctuation of speed.This method can reduce the accumulated error of electric vehicle during long-distance operation and avoid driving deviation of electric vehicle.