VOLTAGE SAG AND OVER-VOLTAGE COMPENSATION DEVICE WITH PULSE-WIDTH MODULATED TRANSFORMER

摘要

A voltage sag and over-voltage compensation device for an AC electric power distribution system employing cascaded switching devices and a pulse-width modulated transformer. Each stage of the cascaded switching device includes a switching element located within a full-bridge rectifier circuit to allow bi-directional switching through each switching element (i.e., switching through the same switching element during the positive and negative portions of the AC voltage cycle). Each full-bridge rectifier also includes a snubber circuit connected in parallel with a corresponding switching element to absorb the current discharge caused by switching the input power supply to the transformer through the corresponding switching device under non-zero current conditions. On the output side, the voltage sag and over-voltage compensation device includes a filter capacitor to smooth the voltage-corrected AC power supply toward a sinusoidal power supply at the system frequency, and a notch filter to remove noise created by the switching elements.