Comprehensive Tap and Phase Analysis in a Framework External to the PF

This paper presents a novel and comprehensive method of analyzing transformer taps and phases in power flow (PF) studies. The method is based on constructing a criterion function, which encapsulates physical constraints for the analyzed taps and phases. The root of the criterion function corresponds to the correct solution. To find the root, the Newton method is used. The criterion function is external to the PF routine, and so, the root-finding (and with it, the tap and phase analysis) is done without altering the underlying PF routine. The method is developed for quadrature-boosting-transformers, as well as for regular phase shifting and tap changing transformers. A possibility of accounting for changing impedance is developed and incorporated in the procedure, using real-world phase-impedance relation data of a phase shifting transformer. Generalizing control modes to different types of variables and to non-local variables is illustrated. The method is tested on large benchmark systems: the IEEE118, IEEE300, and Pegase13 659 bus system. Tests show that (since the method is Newtonian) the convergence is normally achieved within 10 iterations.