| Permanent magnet synchronous motor(PMSM)has good application prospects in aerospace,industrial control,advanced manufacturing and electric drive due to its advantages of high torque density,high power density and high efficiency.For PMSM control,speed measurement and rotor position positioning are very important.In some cases,the environment is bad,so it is not suitable to install sensors to measure speed and rotor position.In the estimation of rotor position of permanent magnet synchronous motor,the method based on back EMF model is often used in medium and high speed region;In the low-speed or even zero speed region,the value of back EMF is too small to extract the position signal.Usually,the method of high-frequency signal injection is used to observe the rotor position by using the salient pole effect generated by PMSM itself or during operation.At present,the sensorless control technology of PMSM is only realized on the basis of two-level inverter.In this paper,this technology is applied to three-level inverter.This paper studies the rotor position identification of permanent magnet synchronous motor.High frequency signal injection method and sliding mode observation method are adopted in the very low / zero speed region and medium high speed region respectively to realize the rotor position identification of the motor,which is verified by simulation and experiment.In this paper,the mathematical model of permanent magnet synchronous motor in dq coordinate system is established through coordinate transformation,and the vector control strategy of zero direct axis and space voltage vector modulation strategy are adopted.The motor control system based on speed double closed loop is built and verified by simulation and experiment.The high frequency model of PMSM is established,and the principle of high frequency sine wave injection method is analyzed.In order to reduce the use of low-pass filter,the high-frequency square wave injection method is used to extract the rotor position,and its feasibility in the vector control of permanent magnet synchronous motor is verified.Aiming at the disadvantages of poor robustness,low accuracy and sensitivity to noise caused by extracting position angle from arctangent function,the vector cross multiplication method is used to decouple the position error information,and the control strategy of high-frequency signal injection is realized through phase-locked loop extraction,simulation and experiment.Aiming at the serious dead time problem in the control system of three-level inverter,a method combining dead time elimination and compensation is adopted to eliminate the nonlinear influence caused by dead time.Based on the analysis of the mechanism of dead time effect of three-level converter,the influence of dead time effect on permanent magnet synchronous motor vector control system is deduced and verified.When the stator three-phase current is near the zero crossing point,the harmonic of stator current is eliminated through the introduction of dead time compensation to improve the accuracy of rotor position identification,and its effectiveness is verified by simulation.In order to realize the sensorless full speed domain control of permanent magnet synchronous motor,the sliding mode observer method is used to identify the corresponding rotor position information in the medium and high speed region.Based on the chattering problem of sliding mode motion,the second-order sliding mode observation control is further designed and verified by theoretical analysis and simulation.In order to solve the problem of the dependence of the second-order sliding mode on the upper bound of the boundary function,a second-order sliding mode control algorithm combined with fuzzy control is adopted,which not only effectively eliminates the system chattering,but also avoids the problem.The effectiveness of this method is verified by simulation. |
