Research On Rotor Position Estimation Method Of Permanent Magnet Synchronous Motor Considering Dead-time Effect Compensation

Permanent magnet synchronous motor has many advantages,such as small volume,high efficiency,high torque density,strong robustness and excellent speed regulation performance.In recent years,it has been widely used in national defense,electric vehicles,household appliances and other fields.In vector control of permanent magnet synchronous motor,it is necessary to install mechanical position sensor to obtain real-time rotor position information of the motor.However,the installation of traditional mechanical position sensor not only increases the system cost,lessens the system reliability,but also limits the use of motor control system in special environment.Therefore,the research on sensorless control technology based on rotor position estimation has become a hot issue.In the medium and high speed range of permanent magnet synchronous motor,the rotor position estimation based on extended back electromotive force is often used.Due to the dead-time effect of the inverter,a large number of harmonic components appear in the stator voltage and current of the motor,which seriously affects the accuracy of rotor position observation based on the model method,resulting in harmonic errors in the estimated rotor position and deteriorating the control performance of the system.For the purpose of improving the accuracy of rotor position estimation,this paper mainly studies the compensation method of inverter dead-time effect.Firstly,the structure and classification of permanent magnet synchronous motor are introduced,establish the mathematical model of the motor in three coordinate systems under ideal conditions,and the commonly used vector control methods are analyzed to lay the foundation for the position estimation method.Secondly,based on the theory of sliding mode control,this paper studies the method of rotor position estimation using sliding mode observer.For the purpose of reducing chattering in sliding mode system,sigmoid function is used instead of traditional sign function,and normalized orthogonal phaselocked loop is used to extract rotor position information.Simulation results show that the sliding mode observer can estimate rotor position effectively.Thirdly,aiming at the problem that(6k±1)th harmonics appear in the stator current caused by the dead-time effect of the inverter,and then(6k)th harmonics appear in the estimated rotor position,a new dead-time compensation method based on harmonic observer was proposed,which effectively suppressed the harmonic pulsation of the estimated rotor position.In this method,a second-order generalized integrator was used to construct a(6k±1)th harmonic current compensator,which was connected in parallel with the fundamental current controller.Under the premise of not affecting the fundamental current control objective,the(6k±1)th harmonic in the stator current was effectively suppressed,and then the(6k)th harmonics in the estimated rotor position was suppressed.Compared with the traditional deadtime compensation method based on harmonic injection,which can only suppress the designated harmonic,the proposed method can effectively suppress the all(6k)th harmonic in the estimation of rotor position,and requires no complex transformation process and less computation.Simulation results show that the proposed dead-time compensation method is effective in improving the accuracy of rotor position estimation.Finally,the bench experiments are carried out on the 1.5kW PMSM experimental platform,including steady-state experiments and dynamic experiments of acceleration and deceleration,loading and unloading.The experimental results indicate that the proposed method can effectively compensate the rotor position estimation error caused by the inverter deadtime effect and has higher rotor position estimation accuracy than the traditional compensation method.