Research On The Sensorless Control Of The Permanent Magnet Synchronous Motor

The permanent magnet synchronous motor (PMSM) has been widely used because of its excellent features such as simple structure, high power density, high efficiency and high reliability. In order to achieve high-performance vector control, it is necessary to detect the rotor position and speed. Installation of mechanical sensors, the system will bring a lot of problems, such as the high cost of large volume, high complexity, decreased robustness, maladjustment to environmental changes. Therefore, sensorless control technology of PMSM has become one of the hot researches at home and abroad.This dissertation introduces the three-phase stationary coordinate system, the two-phase stationary coordinate system, the synchronously rotating coordinate system and the transformation relation between them, and establishes the mathematical model of permanent magnet synchronous motor in both of the α-β coordinate system and the d-q coordinate system. This dissertation points out that the traditional back-EMF observer based state estimation of amplitude-frequency characteristics is equivalent to first-order low-pass filter, which will cause a natural phase error in the estimation of the back-EMF. To solve this problem, an improved back EMF observer is proposed. There is no phase error between observed value and the true value using the improved back-EMF observer.This dissertation discusses the second order generalized integrator-frequency-locked loop (SOGI-FLL) structure. It is pointed out that it has the characteristics of band pass at the frequency resonance point, and has no phase shift. Analysis of the frequency response characteristics of the Dual SOGI-FLL (DSOGI-FLL) structure indicates that DSOGI-FLL structure can eliminate two octave interference, while doubling the response speed of the frequency. The twice SOGI-FLL (TSOGI-FLL) is studied, and the conclusion that TSOGI can enhance the filtering effect to low-order harmonics is drawn. The composite SOGI-FLL (CSOGI-FLL) method is designed, on this basis the rotor position and speed estimation method based on CSOGI-FLL method is proposed.The frequency response of SOGI and reduced order resonant regulator (ROR) to the positive and negative angle frequency signals are compared. SOGI structure with the two order cannot distinguish the positive and negative angular frequency, while the ROR with the first order can. The method of realizing ROR by using the orthogonality of signal is given. To solve the low harmonic problems of PMSM, the ROR cross feedback network is designed to eliminate the harmonics. The rotor position and speed estimation method based on ROR-MSHE-FLL is proposed as well.This dissertation discusses the magnetic saturation salient principle of surface mounted PMSM (SPMSM). The principle of the high frequency voltage injection method is described. SOGI instead of the band-pass filter is used to solve amplitude attenuation and phase shift of bandpass filter, possible system instability is avoided, and the estimation of rotor position as well as rotor speed is realized. The rotor position of the pre-estimated rotor position is modified by the method of comparing the magnitude of the response current peak value. A sensorless starting and low speed operation method of PMSM based on the improved high frequency voltage injection method is proposed, which can improve the running scheme of no position and speed sensor in full speed range.Finally, experimental platform of PMSM is established, and the experimental results show that the method proposed in this dissertation is effective.