Rsearch On Position Sensorless Control Technology Of Spmsm For Wide Speed Range

With the development and utilization of rare earth resources,the permanent magnet synchronous motor(PMSM)has developed rapidly.The PMSM has the advantages of small structure,light weight,high power density and easy control.It has gradually replaced the DC motor with commutator in the speed control system.Many problems caused by the commutator can be avoided without using DC motor,but the vector control of the PMSM cannot be separated from the rotor position information,usually obtained by mechanical sensors such as photoelectric encoders,rotary transformers,hall elements,etc.These sensors not only increase the cost of the system,but also reduce the reliability of the system.In recent years,the method of position sensorless control technology has been favored by scholars from all over the world to eliminate the disadvantages caused by position sensors,which can be divided into medium and high speed position sensorless control and low speed or even zero speed position sensorless control according to the applicable speed range.In this paper,the sliding mode observer method is adopted for the medium-high speed range.The highfrequency square wave injection method is adopted for the low-speed range.and the weighted average switching algorithm is used to realize the wide-speed range nonposition sensor control of the permanent magnet synchronous motor.Firstly,the sliding mode observer(SMO)for position sensorless control of PMSM in medium and high speed range is studied.The traditional SMO uses the sign function to reconstruct the back electromotive force(EMF)component in the stationary axis system and uses the low-pass filter(LPF)eliminates the high-frequency harmonics in the back EMF,and the traditional phase-locked loop(PLL)is used to estimate the rotor position information.Due to the high-frequency switching and the use of the LPF in the back EMF,the position observation is inaccurate.In this paper,the structure of the second-order generalized integrator(SOGI)is used to extract the positive sequence component of the back EMF.The harmonics caused by sign function can be eliminated without hysteresis,and the PLL structure based on the tangent function is used for position estimation to obtain better position.The effectiveness of the proposed method is verified by simulation.Secondly,the high-frequency model of the PMSM is introduced for the position sensorless control in the low-speed region.It is realized by the high-frequency square wave injection method.Compared with the traditional high-frequency sine wave injection method,the injected signal frequency can be improved.A new signal separation method is proposed to avoid the use of filters in signal separation,and the Luenberger observer based on the motor model is used for position observation,which improves the position estimation accuracy.For the initial position identification,the injection short-pulse method is used to determine whether the initial position needs to be compensated by detecting the current response time.In order to achieve smooth switching between high and low speed observations,the traditional hysteresis switching method is not used and the weighted average method is adopted to realize the position sensorless control of permanent magnet synchronous motor in wide speed range.The feasibility of the proposed method is verified by simulation.Finally,a PMSM drive control platform was designed and fabricated,including power drive circuit,current conditioning circuit,encoder conditioning circuit and fault handling circuit.The designed platform was used to drive a surface-mounted PMSM with a rated power of 200 W.Experiments show the accuracy and feasibility of the above theoretical analysis...