Instant voltage compensator based on a three-leg converter

This study proposes an instant voltage compensator (IVC)-based on a three-leg converter. It provides single ac-ac power conversion without large energy storage elements, so the size and cost are reduced. It operates as a boost converter when the line voltage is lower than the rated output voltage and as a buck converter when the line voltage is higher than the rated output voltage. Only one leg among the three legs is switched at a high frequency, whereas the other legs are switched at the line frequency. Therefore the power conversion efficiency is higher than that of a conventional IVC where all of the legs are controlled by a high switching frequency. The output voltage is regulated faster using a weighted-error proportional and integral controller. Experimental results are obtained with a 3 kW prototype to verify that the proposed IVC quickly compensates for the voltage sag and swell of the line voltage.