A Static Alternative to the Transformer On-Load Tap-Changer

An alternative approach to the conventional on-load tap-change voltage control is described. The proposed solution involves the use of in-phase booster transformers and phase-angle controlled thyristor switching. Any specified range of continuous voltage variation can be achieved and the response is practically instantaneous. Computed and experimental results are presented, illustrating typical voltage and current waveforms as well as their harmonic content.