Abstract
Survey results suggest that 92% of interruption at industrial facilities is voltage sag related. the unexpected shut-downs of production lines often result in substantial economic losses. Voltage sag compensators, which are connected in series with critical loads, have been considered the most cost-effective ride-through solution against voltage sags.Transformers are often installed in front of critical loads for electrical isolation. When voltage sags happen, the transformers are exposed to disfigured voltages and a DC offset will occur in its flux linkage. When the compensator restores the load voltage, the flux linkage will be driven to the level of magnetic saturation and severe inrush current occurs . The compensator is likely to be interrupted because of its own over-current protection, and eventually the compensation fails, and the critical loads are interrupted by the voltage sag.This thesis proposes an inrush current mitigation technique together with a state feedback controller for the voltage sag compensator. The operation principle of the proposed method is presented in detail, simulation, and experimental results are provided validate the proposed approach.