Abstract
This thesis presents the development and control of a position sensorless permanent-magnet synchronous motor (PMSM) drive for freezer applications. First, a digital signal processor (DSP) based PMSM drive with necessary sensing devices and control schemes is designed and implemented. The off-the-shelf intelligent power module is employed to construct the inverter, and the auxiliary power supplies for the constituted subsystems are properly designed. Secondly, a single-phase front-end switch mode rectifier is established to provide the well-regulated and/or boostable DC-link voltage for the motor drive with good line drawn power quality. To further enhance the operating performance of the SMR, a robust hysteresis current-controlled pulse width modulation (HCC-PWM) scheme is proposed to yield closer current waveform tracking around zero-crossing points of AC cycles. Moreover, the random switching methods for classical fixed-band and sinusoidal-band HCC-PWM schemes are developed to yield more uniformly distributed current harmonic spectrum. Thirdly, an internal model following controller based PMSM back electromotive force (EMF) estimator is devised for performing the sensorless vector control of PMSM. As the motor is started in synchronous motor mode and reaches a sufficient speed, the estimated and suitably compensated back-EMF is utilized for making the PMSM vector control. Through proper mode operation arrangement, very stable operation and good driving performance are obtained. Finally, the application of the developed sensorless PMSM drive in freezer compressor driving is studied with some experimental results being provided to evaluate its driving performance. To enhance the performance in high-speed of a freezer, the voltage boosting and commutation advanced shift control strategies and their effectiveness are also explored. In the realization of control schemes, all the developed control algorithms of SMR and motor drive are implemented in a command DSP to facilitate the miniaturization of whole motor drive system.