Research On The Compound Operation Strategy At Full Speed Range Based On Position-Sensorless PMSM

The permanent magnet motor is named for the use of rare earth permanent magnet material as the rotor of the motor.Rare earth permanent magnetic materials have the characteristics of high remanence density,high coercivity and high magnetic energy product,which makes the permanent magnet synchronous motor have higher energy conversion efficiency compared with reluctance motor and asynchronous motor.Under the same volume,the PMSM has stronger load capacity and wider application range.Because of its simplification in mechanical structure,PMSM has a wider application range.The control of sensorless permanent magnet synchronous motor has also become a hot topic.In this paper,a new compound control strategy for the position sensorless SPMSM is proposed,which is applicable to the whole rotational speed range.According to the compound control strategy of SPMSM,after the initial position identification of the rotor is completed,the operation process is divided into low speed process and high speed process according to different parameter characteristics.At present,the compound control strategy is divided into two types.The first one is mainly based on the control mode,and combines two rotor position identification methods suitable for low and high rotational speeds with one control mode,such as the high-frequency injection method of position closed-loop vector control combined with low rotational speed process and the counter potential position identification method of position closed-loop vector control combined with high rotational speed process;The second is the combination of low-speed position open-loop control mode and high-speed position closed-loop control mode,and the combination of compound control with anti-emf type position identification method,such as the combination of low-speed position open-loop V/F control and high-speed position closed-loop vector control.In the two types of compound control strategies,the first kind of method requires high computing power and high consistency of convex polarity of rotor,so the manufacturing cost is high and the mass production is difficult.The second type of method has poor dynamic performance in the process of low speed,and needs to adjust the voltage frequency ratio parameters according to different load conditions to obtain the accurate V/F voltage frequency ratio working area.Although the requirement for computing power is low,the load capacity is poor,which is prone to out-of-step shutdown or the fault of overcurrent protection.Based on this background,a new compound control strategy is proposed in this paper.After the initial position identification of the rotor is completed,the position open-loop I/F control in the low-speed process and the position closed-loop vector control in the high-speed process are adopted,and the rotor position identification in the high-speed process is completed by the anti-electromotive force method.For the initial position identification strategy,the rotor preposition method and the rotor initial position identification method are proposed in this paper.These two kinds of methods can complete the initial position identification operation of the rotor under different conditions.The innovation of this paper is to optimize the switching process of the two control modes.Combined with the inherent mechanical inertia of the rotor,a switching method using the mechanical inertia of the rotor is proposed to optimize the dynamic performance of the switching process by adjusting the average decline slope of the given value of current.The change of key parameters shows that the method is effective.Finally,the operation of the position closed-loop vector control combined with the anti-electromotive force method in the high speed process is simulated and verified by experiments.The current waveform is sampled by the ac servo motor based on DSP28027F U21 control plate.The experiment shows that the compound control strategy proposed in this paper works well for the SPMSM which works at high speed for a long time.