Design and implementation of a fast on-load tap changing regulator

The on-load tap changing (OLTC) regulators have been widely used since the introduction of electric energy. They ensure a good regulation of the output voltage in presence of large variations of the input voltage with typical response time from 100 ms to several seconds. On the other hand, the continuous growth of power semiconductor devices, such as the insulated gate bipolar transistor (IGBT), permits the development of fast OLTC regulators, being able to fix other problems in the AC mains, like the sags, flicker and harmonic distortion. This paper reports the design and implementation of a fast OLTC regulator, including the power and control stages, and presents several experimental results.