Abstract
The major purposes of this thesis lie in the development of switch-mode rectifier (SMR) fed modular digital inverters and making their controls. After exploring the comparative features of some existing SMRs, a simple three-phase single-switch SMR is designed and employed as an AC/DC front-end converter for the followed inverters. And the suitable control scheme is developed to establish the boostable and well-regulated DC-link voltage. It follows that the inverter output performance is improved with line drawn power quality are obtained. As to the development of modular digital inverters, the design and implementation of high performance digital signal processor (DSP) based single-phase inverter module are first made. The proposed sophisticated current and voltage waveform control schemes consist of feedback, command feedforward and simple robust disturbance cancellation controls. Moreover, a simple robust compensation control approach is proposed to reduce the nonlinear effects caused by transformer flux imbalance. With the developed single-phase inverter module, the establishment of three-phase inverters using two or three modules is studied. The studied three-phase inverters include Y-, -, V- and Scott-T connected inverters. Finally, after establishing the inverters having good waveform tracking characteristics, the arbitrary waveform tracking control is studied. Some measured results show that the designed inverters possess good and robust waveform tracking performance under unknown and varying loads, and they also possess good programmable waveform tracking capability. Moreover, some comparative performance evaluations of the inverters fed by the conventional rectifier and the developed SMR are made. Key words: Inverter, single-phase, three-phase, digital control, DSP, waveform control, robust control, transformer flux imbalance, switch-mode rectifier, Delta-connected, Y-connected, V-connected, Scott-T connected.