Phase shifting transformer model for direct approach power flow studies

•A phase shifting transformer model for DA power flow studies is proposed.•The inclusion of medium-length lines in DA power flow studies is formulated.•The inclusion of tap changers in DA power flow studies is formulated.•Case studies for the DA solver including phase shifting transformers are presented.

This proposal is intended to extend the field of application of an extremely efficient power flow algorithm used in radial and weakly meshed grids, the so-called Direct Approach (DA) method. In this work the method is broadened with the possibility of handling shunt admittances, transformers with taps, and phase shifting transformers. While the integration of the two former elements in the DA solver is quite straightforward, the use of phase shifting transformers is far from obvious due to their inherent non-symmetrical admittance matrix. Thus, a model for phase shifting transformers is proposed in this contribution, which allows the use of the DA method in grids that include such devices. A set of case studies is conducted in the contexts of a balanced industrial grid and a standard testbed to demonstrate the validity of the proposal.