Research On Weak Magnetic Control Strategy Of Less-Rare-Earth Spoke-type Hybrid Permanent Magnet Motor

Rare earth permanent magnet synchronous motors are widely used in electric vehicles for its high power density,wide speed range and simple structure.However,with the rising price of REPMSM,the manufacturing cost of Rare earth permanent magnet synchronous motors is also increasing,limiting the development of permanent magnet synchronous motor to a certain extent.A motor called HPMM is studied in this paper,its excitation magnetic field is formed by the non rare-earth material ferrites and rare-earth material NdFeB.By reasonably designing the location and magnetizing direction of the two permanent magnets,the two magnetic fields can be reasonably complementary to each other in space and increase the air gap flux of the motor.This novel design method not only reduces the rare earth material and the manufacturing cost of the motor,but also ensures the power density and torque output capacity of the motor,which makes the performance of the motor as good as that of the rare earth permanent magnet synchronous motor.In order to verify the actual performance of HPMM and realize the high-performance operation of the motor,this paper focuses on the MTPA control below the base speed and the weak field control above the base speed of the motor.Firstly,the structure,operation principle and mathematical model of HPMM are introduced in detail,and the control system of the motor is designed based on space vector pulse width modulation control algorithm.PI controller is used in the both speed loop and current loop of the system.Then the actual performance of HPMM and the designed driving control system are verified by simulation and experiment with MATLAB/Simulink.Secondly,the maximum torque per ampere control is introduced.Compared with i_d=0 control,this method can output more electromagnetic torque with the same stator current.An engineering approximation method of maximum torque per ampere control is proposed for engineering application.The simulation results show that the method can achieve the same effect as the formula method of maximum torque per ampere control,and the method is simple and easy to implement.Aiming at the influence of inductance parameter variation on control accuracy,a maximum torque per ampere control based on inductance parameter identification is proposed.Experimental results show that the method can effectively solve the influence of inductance parameter variation and has strong practicability.Finally,the principle of flux-weakening control is analyzed from three aspects:voltage limit trajectory,current limit trajectory and operation area.A kind of flux-weakening control based on voltage regulation method is introduced.The simulation and experiment verify that the weak magnetic control of HPMM under different working conditions has good dynamic response.