DECOUPLED POWER FLOW SOLUTION METHOD FOR WELL-CONDITIONED AND ILL-CONDITIONED POWER-SYSTEMS

A decoupled power flow solution method for well- and ill-conditioned power systems is derived. The proposed method is simple, has no mathematical approximations and requires less storage and computational time than either the Newton-Raphson (NR) method for ill-conditioned systems, or the Fast Decoupled (FD) method for well-conditioned systems. In the derived method, the power flow is decoupled into P and Q power models without any approximations and the P model is decomposed into a generator active power model and a load active power model. The difference between the load active power model matrix and the reactive power model is combined with the mismatch power and the second-order vectors, which enables the same matrix triangulation to be used to solve the load active and load reactive power flow models. The proposed method is adjusted with the optimal multiplier to improve the convergence and decrease the computational time of the ill-conditioned systems. To examine their effectiveness, two ill-conditioned systems, i.e., 11- and 43-bus systems and a well-conditioned 90-node German utility network are studied using the proposed method and compared with the FD and NR methods. The results show that the proposed method has greater computational speed, smaller memory requirements and better convergence than the FD method for well-conditioned systems and gives a convergent solution for ill-conditioned systems while the FD gives a divergent solution.