Abstract
ABSTRACT This thesis is mainly concerned with the position sensorless control and the acoustic noise reduction studies for permanent-magnet synchronous motor (PMSM) drive. First, an experimental digital signal processor (DSP) based PMSM drive is established. A robust current control and back-EMF estimation scheme are proposed to yield close and robust current tracking performance. And the motor back electromagnetic force (EMF) can be observed and employed for performing the proposed sensorless control. Secondly, the suitable front-end switch-mode rectifiers (SMRs) are developed and utilized to establish boostable and well-regulated DC-link voltage for the followed PMSM inverter. In addition to the control and performance evaluation of the SMR-fed motor drive, the vibration and acoustic noise reductions for the SMR and the inverter-fed PMSM are also studied. In vibration and acoustic noise reductions of SMR, the important audible vibration modes of the inductor employed in the low-frequency (LF) SMR are first identified from measurements. Then the controls for eliminating one specific vibration mode and two vibration modes simultaneously via deterministic and stochastic three-stage excitation approaches are studied. As to the HF SMRs, a random switching frequency ramp-comparison current-controlled PWM (RC-CCPWM) scheme and a randomly band hysteresis CCPWM scheme are developed. Theoretical bases of all proposed control approaches are derived and their comparative performances are evaluated experimentally. On the other hand, the acoustic noise reduction for the PMSM drive via random PWM approach is also conducted. As to the sensorless control aspect, the motor back-EMF estimated using the proposed scheme, which contains the absolute rotor position information, is used to perform the position sensorless control of PMSM. The nonideal position estimation is then improved by an intelligent tuning scheme, wherein the estimated rotor position is tuned to yield minimum torque current component and thus better sensorless vector control performance. In addition, the motor can be automatically and quickly started under the preset torque current limit. Moreover, to achieve unidirectional starting under position sensorless control, a simple and practical initial rotor position estimation and starting scheme is further developed. Key words: Permanent-magnet synchronous motor, position sensorless control, acoustic noise, robust current control, switch-mode rectifier, low-frequency switching, random switching, three-stage excitation, back-EMF estimation, intelligent tuning, initial rotor position estimation, unidirectional starting.