Reserch On Control Strategy Of PMSM Based On Flux Observer

Direct torque control has the advantages of simple control structure,fast dynamic response and small dependence on parameters,and is widely used in AC speed control systems.The observation of the stator flux linkage is an important part of direct torque control,and the accuracy of the observation results will directly affect the control performance of the system.The traditional flux observer is mainly divided into voltage type and current type.The former uses direct back-electromotive force to integrate,and the latter calculates the stator flux linkage through many parameters of the motor.In this thesis,a novel high-precision voltage-current hybrid model flux linkage observer is proposed based on the amplitude-limited compensation integral algorithm.The variable flux linkage direct torque control strategy based on SVPWM is adopted to weaken the system torque ripple and improve the permanent magnet.Dynamic and static performance of synchronous motors under direct torque control strategy.In this thesis,the structural characteristics of permanent magnet synchronous motor are briefly described and a mathematical model is established.The direct torque control theory is introduced.The effect of flux linkage control on electromagnetic torque is discussed.The influence of flux linkage on the running performance of the motor is deeply studied.Aiming at the performance requirements of the precision and reaction speed of the permanent magnet synchronous motor,the influence of the accuracy of the stator flux linkage on the control performance is studied.The new flux observer of the voltage-current hybrid model is designed.In the low speed case,the system mainly uses the current model flux observer.Therefore,it is less affected by the motor parameters and temperature,and the stator flux linkage can be accurately measured.In the case of medium and high speed,the system mainly adopts the improved voltage model magnet.The chain observer is therefore less affected by the stator voltage and current.And on the basis of the traditional voltage model,the high-pass filter is added,and the amplitude-limited compensation link is introduced,which effectively solves the problems of DC offset,amplitude attenuation and phase shift.The simulation results show that the new observer realizes accurate observation of the stator flux linkage in the full speed range.Aiming at the problems existing in the traditional direct torque control system at low speed,a variable flux linkage direct torque control strategy based on space voltage vector pulse width modulation is proposed,which eliminates the condition of traditional direct torque control to maintain a constant flux linkage.The direct current is zero,the flux amplitude changes with the torque change,and the demagnetization and magnetic circuit saturation are avoided,which can greatly improve the output efficiency of the hidden pole synchronous motor.The control strategy uses spatial voltage vector modulation techniques to synthesize any desired and reversed desired voltage.The simulation results verify that the improved control strategy not only keeps the traditional direct torque control system responsive when the motor is running at low speed,but also suppresses the pulsation of the system and improves the control performance of the system.