A modification to the fast decoupled load flow for power system with low X/R ratio branches

For solving load flow problems, the fast decoupled load flow method (FDLF) is probably the most popular because of its efficiency. Reliability in convergency for most power systems is very high but it does have difficulties in convergence for ill-conditioned system with low X/R ratio branches. A modification to the FDLF is presented in this paper, named MFDLF. It is shown that its convergency is much better than that of FDLF for ill-conditioned systems. In essence, it is done by multiplying unitary (rotation) operators to the bus injection complex power and each row of the admittance matrix. In the literature, other methods have been proposed for improving FDLF´s convergency. But these methods suffer from slower convergency if a transmission line is a part of a loop. In addition, when there are a large number of low X/R branches in the system, the analysis complexity will be greatly increased by the many intermediate dummy buses and branches