Abstract
This thesis develops a motor drive system for condensing unit applications. The system consists of a position sensorless sinewave excited interior permanent-magnet synchronous motor (IPMSM) driven compressor, a square-wave excited surface mounted PMSM (SPMSM) driven fan, and a single-phase boost-type switch mode rectifier (SMR) front end to establish their common DC-link voltage from utility with satisfactory line drawn power quality. All the constituted power stages are fully digitally controlled in a common digital signal processor (DSP). For the compressor IPMSM drive, two types of sensorless control schemes based on the devised internal model based back-EMF estimators are developed and comparatively evaluated. As to the square-wave SPMSM fan drive, its position sensorless control is conducted based on the sensed motor terminal phase voltage. For these two types of PMSM drives, the proper commutation instant shifts are applied to enhance their driving performances, which may be deteriorated due to non-ideal sensorless controls, particularly under higher speeds. In addition, the smooth starting with less current transient is also considered. Finally, in the established single-phase boost SMR front-end, it possesses the inner hysteresis current-controlled PWM (H-CCPWM) scheme and outer voltage control loop. The simple robust control approach is applied to yield improved current and voltage control performances. Moreover, various types of the randomly varying bands for the H-CCPWM schemes are proposed, and their effects on the current harmonic spectral spreading characteristics and the SMR operating performance are observed experimentally.