Research On The Optimal Current Control Strategy Of Synchronous Reluctance Motor

Synchronous reluctance machine(SynRM)is a kind of simple,efficient and reliable synchronous machine with the characteristic of reluctance.Because of the no windings on the rotor,SynRM has higher efficiency compared with the same levels of the ac motor;as there is no permanent magnet on the rotor compared with PMSM,the problem of irreversible demagnetization caused by excessive demagnetization effect doesn't have to be considered,so the SynRM has a stronger ability of flux-weakening.The optimal control scheme of SynRM is studied from the perspective of efficiency optimization and flux-weakening speed-expansion,to promote its application in the field of drive.First of all,the structure characteristics and operation principle of SynRM,and the four kinds of traditional vector control strategy are analyzed in this paper.The four control strategies are derived in the linear model which ignores the influence of magnetic circuit saturation to affect the control performance.Therefore,based on the magnetic field analysis of SynRM's rotor by the finite element simulation software,the nonlinear relationship between the inductance and current and the torque characteristics considering magnetic circuit saturation are obtained.The mathematical model considering the saturation of magnetic circuit is established,and the track of the optimal stator current with the change of torque is obtained to achieve the maximum torque per ampere(MTPA)control.In addition,as to the coupling problem of traditional current loop,decoupling control considering magnetic saturation is proposed to improve the dynamic and static performance.Secondly,in order to further improve the speed range of the SynRM,the stable operating range of the motor under the maximum voltage and current limit is analyzed.And the current optimization allocation principle in the constant torque,flux-weakening I area and flux-weakening II area is derived to realize the maximum torque.And combining the flux-weakening with the efficiency optimization,the motor optimal operating point is defined to make the input current minimal in the process of load change.Furthermore the single voltage closed-loop control is designed to realize the smooth running of the optimal current trajectory.Finally,the performance of the control system carried out in this paper is verified by Matlab/Simulink simulation.With the TMS320F2812 of the TI company as the control core,the hardware circuit of the control system is designed to finish the adjustment of the program of the control method.The experiments including steady-state output characteristic comparison experiment of MTPA control considering magnetic circuit saturation and constant 45° current angle control,maximum load capacity test for full speed range,and load mutation and rotational speed mutation experiment to verify the effectiveness of the control method.