Electronic on Load Tap Changer Transformer for DC Electrical Railway Power Supply Systems

Conventional DC railway traction substations present important limitations that complicate the development of more efficient, reliable and economical electrical power supply systems. In this situation, new technological solutions are necessary. Electronic on-load tap changer transformer (OLTC transformer) enable to adapt the voltage on the catenary depending on the traffic conditions. Besides, the use of electronic tap changers can provide a very fast voltage regulation when needed. The objective of the paper is three-fold. Firstly, to describe the principal characteristics and functionalities of OLTC transformers. Secondly, to present the design process of a full-scale OLTC prototype along with its corresponding control. Finally, to perform an experimental validation of the prototype under laboratory conditions.