Research On Off-line Parameter Identification Of Permanent Magnet Synchronous Motor With Load

Permanent magnet synchronous motor(PMSM)is applied in various fields due to its advantages such as small volume,light weight,high efficiency,good control performance and no fever of rotor.Permanent magnet synchronous motor has the characteristics of high coupling nonlinearity.Both vector control and direct torque control(DTC)need to rely on the parameters of the motor to achieve a stable control effect.So it is necessary to identify the off-line parameters of the motor before the motor drive control.Firstly,this paper introduces the structure classification of permanent magnet synchronous motor and its influence on electrical parameters.After analyzing the theory and significance of coordinate transformation,three transformation matrixes between coordinate systems are given.The PMSM mathematical model is derived in two-phase rotating coordinate system.The vector control principle and SVPWM modulation technology based on rotor field oriented are introduced.Secondly,on the basis of the analysis of the existing parameter identification methods,an off-line parameter identification method based on voltage pulse injection is proposed to identify the stator resistance,the axis inductor and the rotor flux of the rotor,combining with the experimental conditions and the needs of the project.Then,the mathematical model of the vector control current loop is analyzed and deduced,and then the PI parameters of the current loop are calculated and set by the identification of the stator resistance of the motor parameters and the inductor of the direct axis.Then,the necessity and engineering significance of the initial position angle identification of permanent magnet synchronous motor rotor are introduced.Based on the analysis of the relationship between the magnetic circuit saturation with inductance value of permanent magnet synchronous motor,the relationship between the rotor position and the winding current,design a current difference detection method,Arbitrarily selected two phase winding,the other phase winding is disconnected,the voltage pulses are injected in the forward and reverse directions of the winding,the rotor position is calculated and the NS poles are distinguished.In order to eliminate the impact of the current sampling accuracy result from the residual magnetic flux generated by voltage pulse,a method of pulse injection which can eliminate the influence of residual flux is proposed in this paper.It can improve the accuracy of the initial rotor position angle detection.The experimental results verify that the method is simple and reliable,and is not limited by the salient pole structure of the rotor,and it can be applied to both surface mount and embedded motor.The detection process remains the rotor completely static and has great value of practical engineering.On the basis of identifying the initial position angle of the rotor,a method is designed to identify the rotating angle of the rotating transformer without load,but the engineering field motor has been coupled to the load,and it is not easy to disconnect.The friction force of the rotor is larger in the case of the load of the motor.The method of identifying the rotating angle of the rotating transformer without load is not applicable,so a method is proposed to identify the rotating angle of the rotating transformer under the load of the motor.Finally,the software and hardware design of the system is completed,and a simulation model is built based on the MATLAB/SIMULINK platform to verify the correctness of the identification algorithm.Then,a 2.2kW permanent magnet synchronous motor is taken as the object.The TMS320F28034 DSP chip of TI is used to control the system.Experimental verification is carried out to verify the validity and feasibility of the off-line parameter identification method for PMSM.