Comparative analysis of on-load tap changing (OLTC) transformer topologies

On-load tap changing (OLTC) transformers are widely used for voltage control in the distribution network. The paper provides a comparative analysis of different OLTC topologies for the design of a power electronic (assisted) tap changer. Eleven different topologies are compared on the basis of voltage and current rating of the transformer windings and tap switches, using a p.u. methodology. The topologies are designed in such a way that they can provide both positive and negative compensation of the grid voltage. The p.u. comparison is a beneficial tool for OLTC designers to suitably choose the right topology based on the voltage and power levels of the network, type of solid-state switch used and the voltage regulation application.