Abstract
The wide-spread use of sophiscated equipments and computer systems in the industrial and the commercial sectors leads to higher demand on the quality of electric power. Survey shows that most of the power quality problems are associated with voltage sags and momentary interruptions. Such problems often result in the shutdown of industrial processes, or even equipment damages in some extreme cases.A new voltage sag compensator system for sensitive industrial loads will be proposed in this thesis. The proposed system consists of a voltage source inverter connected in series with the load via a coupling transformer. The inverter operates in pulse-width modulation mode to produce three-phase AC voltages. Upon detection of voltage sags, the inverter instantly injects compensation voltages to maintain the voltage at the sensitive load. A special mechanism to attenuate system transient disturbances like voltage spikes is also included to avoid any false triggering of the compensator.The proposed system will be verified by computer simulation and prototype experimental results. A design process for sizing the energy storage capacitor of the system is also presented.