Abstract
This thesis develops a digital signal processor (DSP) based air-conditioning system, it consists of a sensorless permanent-magnet synchronous motor (PMSM) driven compressor, a sensorless PMSM driven cooling fan and a common switch mode rectifier (SMR) front end. The system compactness is achieved through power circuit modularization and common digital control environment. Besides, for making comparative driving performance evaluation, the standard PMSM drives for the compressor and the fan are also established. In the developed PMSM driven compressor, both high-frequency signal injection (HFI) and the extended-EMF (EEMF) sensorless control methods are applied and evaluated to comprehend their distinct merits and weak points. Then accordingly, a hybrid sensorless control scheme combining these two methods is developed to yield improved driving performance within wide speed range. In the developed control scheme, while the motor is started and driven under lower speed using HFI method, it is changed smoothly and operated using EEMF method as the speed is increased to a preset value. As to the PMSM driven cooling fan, the direct duty-ratio voltage-mode PWM scheme is adopted for the less stringent performance requirements. The standard and sensorless controls for sine-wave and square-wave PMSM drives are all studied and evaluated. In the proposed sensorless control schemes, only one-phase motor terminal voltage is sensed and properly signal processed. Better driving performance is further achieved via commutation advanced shift technique. Finally, a common front-end switch-mode rectifier (SMR) is formed to establish the boostable and well-regulated DC-link voltage for the followed two PMSM drives. Both the standard and the newly evolved bridgeless boost type SMRs are comparatively assessed. Owing to the limitation of pulse width modulation (PWM) channel number of the DSP TMS320F28335, the analog PWM circuit is employed as an alternative for realizing the front-end SMR.