Research On Key Technologies Of Drive And Control For High-speed Permanent Magnet Synchronous Motors

With the advantages of high power density, high work efficiency, and high response speed, the high-speed permanent magnet synchronous motor (PMSM) has been widely applied in the high-speed electric spindle systems. Lots of harmonic currents are generated in the stator winding currents due to the small number of stator windings in the high-speed PMSM system as well as the small value of inductances, which would have a great influence on the system’s operating efficiency and torque stationarity. Therefore, the research on the stator current harmonic suppression method for high-speed PMSM is of great importance. In addition, the sensors applied to rotor position detection of high-speed and ultra high-speed PMSMs are rare, thus the sensorless control technique is needed in most cases to estimate rotor position and speed. The characteristics of high speed and high frequency of this system put forward higher requirements for sensorless control technique. So it is of certain theoretical and application value to develop the research on sensorless control technique for high-speed PMSM. This paper will mainly probe into some key techniques applied in the high-speed PMSM’s drive and control system, such as stator current harmonic suppression and sensorless control.Firstly, in this paper, the high-speed PMSM’s model is established. The stator current harmonic suppression scheme is established based on three-phase LC filter circuit for high-speed PMSM. Through the rational design of the resonant frequency and harmonic peak of the LC filter circuit, the high-frequency harmonics in the stator currents could be reduced obviously. In order to suppress the low-frequency harmonics in the stator currents, the method based on the low-frequency voltage distortion compensation is proposed. By setting both the fundamental frequency coefficients of PWM voltage and reference phase voltage equal, this method can reduce the low-frequency harmonic distortion of PWM voltage waveform and consequently suppress the low-frequency current harmonics generated from PWM control. The permanent magnet flux linkage harmonics has an effect on the stator current harmonics, and the study of this influence shows the relationship between each permanent magnet flux linkage harmonic and stator currents, thereby a harmonic voltage feedforward compensation scheme is proposed to suppress the stator current harmonics. Secondly, the sensorless control method for high-speed PMSM based on Luenberger observer is adopted, the estimation expressions of the rotor speed and position could be derived according to the phasor diagram of Luenberger observer and the rotor’s rotation direction could be judged by backward difference and normalization processing. Besides, when there are errors in system parameters, the variation rules of parameter’s errors are analyzed and the relationship between the rotor speed, position estimation results, and parameter’s errors could be derived according to the phasor diagram of Luenberger observer. The influence of parameter’s errors on the estimation results could be overcome through the compensation of estimation errors. When the motor is running in the transient states such as load sudden change, acceleration or deceleration, a Luenberger observer algorithm is proposed which is suitable for the motor’s transient operations, the estimation expressions of the rotor speed and position in the motor’s transient operations could be derived at last, which could achieve the precise speed control in the motor’s transient operations.Thirdly, two-degree-of-freedom control method is adopted to design the speed loop. Under the circumstances of different reference speeds and different load disturbances, the two-degree-of-freedom control system could be evaluated by selecting the proper linear quadratic performance index. The two-degree-of-freedom controller’s parameters could be designed by using the complex integral numerical computation method, which could achieve both the reference speed tracking ability and the load disturbance suppression ability. The robustness of the parameters of this controller is analyzed as well.Finally, the experimental platform of high-speed PMSM drive control system is set up while the hardware circuit structures and software programs are designed respectively. Through software programming and selecting the appropriate discretization methods, the practical experiments are conducted to test the current harmonic suppression method based on minimum current harmonic PWM control, the sensorless control method based on Luenberger observer, and the robust speed control method based on two-degree-of-freedom control respectively. The results of the practical experiments verifies the effectiveness of these control methods.