Abstract
Due to the progress of power electronics technologies in recent years, industrial manufacturing equipments are very sensitive to the power quality events of the utility grid. Voltage sags often cause undervoltage fault in sensitive loads, and interrupt the production process. The series-connected voltage sag compensator has been adopted by industries to maintain the power quality received by sensitive loads. The series coupling transformer of the voltage sag compensator often draws significant inrush current when the compensation voltage is injected. The saturation of the transformer during inrush reduces the output voltage and causes degradation of the compensation voltage, and the inrush current may also trigger the over-current protection of the compensator. In this thesis, an inrush suppression method is proposed. The proposed method can prevent magnetic saturation by limiting the flux-linkage during the starting transient of the compensator. The proposed method can reduce the capacity requirement of the serial coupling transformer, and increase the power density of the compensator system. The proposed inrush suppression method is presented and analyzed in this thesis. Computer simulation and laboratory experimental results are presented to verify the performance of the proposed system.