SOLVING THE NONLINEAR POWER-FLOW EQUATIONS WITH AN INEXACT NEWTON METHOD USING GMRES

This paper presents a detailed investigation into the effectiveness of iterative methods in solving the linear system subproblem of a Newton power flow solution process. An exact Newton method employing an LU f actorization has been one of the most widely used power flow solution algorithms, due to the efficient minimum degree ordering techniques th at attempt to minimize fill-in. However, the LU factorization remains a computationally expensive task that can be avoided by the use of an iterative method in solving the linear subproblem. An inexact Newton m ethod with a preconditioned Generalized Minimal Residual (GMRES [12]) linear solver is presented as a promising alternative for solving the power flow equations. When combined with a good duality preconditioner , the Newton-GMRES method achieves a better than 50% reduction in comp utation, compared to Newton-LU, for two large-scale power systems: one with 3493 buses and 6689 branches, another with 8027 buses and 13765 branches.