UDE-based Harmonic Suppression Strategy In The Weak Field Of Permanent Magnet Synchronous Motors

Permanent Magnet Synchronous Motor(PMSM)has the advantages of small size,high efficiency,wide speed range,and large power density.It is widely used in many fields such as electric vehicles,space vehicles,and industrial equipment.The PMSM rotor uses permanent magnets,and the excitation magnetic field is fixed and not adjustable.Therefore,when the motor terminal voltage increases with the rotation speed up to the maximum voltage that the inverter can provide,in order to further increase the speed of the PMSM,flux-weakening control is required.However,when the PMSM is operating in the field weakening region,current harmonics are introduced,causing torque fluctuations and affecting the field weakening control performance of the permanent magnet synchronous motor system.Therefore,it is important to suppress the current harmonics in the PMSM flux weakening region.This paper studies the mathematical model of permanent magnet synchronous motors,introduces the PMSM classic vector control combined with the principles of coordinate transformation,further details the basic principles and common methods of PMSM flux weakening control.In addition,by analyzing the effects of inverter dead zone effect,inverter power tube voltage drop,PMSM permanent magnet harmonics and other factors,the cause and harmonic distribution of current harmonics in the field weakening zone are explained.On this basis,the Uncertainty and Disturbance Estimator(UDE)algorithm is used to design the current loop controller,combined with a delay filter with high gain characteristics to suppress the 6th harmonic of the current loop.In addition,in view of the problem that there may be large fluctuations in the transition of the permanent magnet synchronous motor from the constant torque region to the field weakening region,a field weakening switching strategy considering both the PMSM speed and the stator voltage value is designed.Finally,a simulation model is built by MATLAB and Simulink,and the effectiveness of the proposed flux-weakening harmonic suppression strategy and good anti-interference performance are verified by comparing with the traditional fluxweakening control method.The algorithm program is written with DSP28335 as the controller,and experimental verification is carried out on a set of 20 k W built-in permanent magnet synchronous motor system experimental platform.Simulation and experimental results show that the proposed PMSM field weakening harmonic suppression strategy based on uncertainty and disturbance estimation can not only reduce the current harmonic content of the field weakening region,but also effectively avoid the torque ripple that may exist during the switching between the constant torque region and the flux-weakening region,improves the stability of PMSM field weakening control.