Study Of Sensorless Drive Forpermanent Magnet Synchronous Motor Based On High Frequency Signal Injection

Permanent magnet synchronous motor is more and more widely used as its smallvolume, light weight and smallinertia. The control strategies of permanent magnetsynchronous motor used mostly now arevector control and direct torque control, and bothof the control strategies need the rotor position, but the use of the position sensorlimits thescope of use.Currently,sensorless control strategies of permanent magnet synchronousmotorfall into two categories, the back emf estimation which is suitable for high speedapplicationand the saliency-tracking methods whichare suitable for low speedapplication.Ofthe saliency-tracking methods, the high frequency voltage injection method is used mostly,by injecting high frequency voltage vectors, the rotor position can be got after thedemodulation of the high frequency current response.In this paper, the mathematical model of permanent magnet synchronous motor indifferent coordinates is analyzed, andon the MATLAB/Simulink platform, the mathematicalmodel is established.Through theanalysis of the traditional SVPWM modulation method,improved SVPWM fast realization method is put forward, and the digital implementationof the proposed method is given.Based on the mathematical model of PMSM built before,the simulation of vector control of PMSM is conducted on the MATLAB/Simulink platform,and the experiment of vector control is conducted on a PMSM control system.According to mathematical model of PMSM established, the current response of themotor under high frequencyrotating voltage injection is analyzed, through the extracting ofthe current response, the initial rotor position detection based on the direct calculate methodis studied.According to the traditional initial position estimation method, the influencingfactors of rotor position estimation precision areanalyzed, and an improved method basedon the Synchronous Frame Filter is proposed.During low speed running, the currentresponse of PMSM under high frequencyrotatingvoltage is deduced,and the fundamentalcomponent of the currentproduced by the vector control will not affect the estimation of therotor position.The heterodyne method for the extractionofthe rotor position estimation erroris studied, and the Luenberger observer is constructed to estimate the rotorposition.On the platform built before, the simulation of estimating the initial position of PMSMunder high frequency rotating voltage injection method is conducted. The effectiveness andfeasibility of the improvedmethod proposed in this paper is proved through the contrastexperiments of the traditional direct calculation method and the improved method. Then, the simulation of the rotor position estimation at low speed is conducted through theheterodyne method and the Luenberger observer, and the method studied in this paper isproved feasible and effective.Finally, based on the DSP56F8346produced by FreeScale, a hardware platform isbuilt to experiment the sensorless vector control of PMSM, through properdigital DSPsoftware algorithm, the control strategy studied in this paper is proved feasible andeffective, and the system has realized the estimate of the rotor position at both zero speedand low speed.