The fast-decoupled power flow algorithm is derived from the Newton-Raphson load-flow method by exploiting the physical property of well-operated transmission networks that real power flow is strongly coupled to voltage phase angle while reactive power flow is strongly coupled to voltage magnitude, with only weak cross-coupling between the two pairs; this justifies neglecting the corresponding off-diagonal Jacobian submatrices and, under further approximations (small angular differences, line susceptance dominant over conductance, reactive injection small relative to a bus's short-circuit reactive capacity), replacing the remaining Jacobian blocks with a constant susceptance-based matrix that need not be recomputed or refactorized each iteration. This decoupling and constant-matrix property substantially reduces the computation per iteration relative to full Newton-Raphson, at the cost of requiring more iterations, and is a core method within iterative numerical solution theory for power-flow analysis in power system engineering.
The fast-decoupled power flow algorithm is derived from the Newton-Raphson load-flow method by exploiting the physical property of well-operated transmission networks that real power flow is strongly…