Problems of Power Flow Computations for a Power System with UPFC

Power flow computation is one of the most performed computations for a power system. Reviewing papers, one can note, that till now, sufficient attention has not been devoted to numerical aspect of the power flow computation for a power system with the embedded UPFC device. It can be noted, that in the case of the mentioned computation, utilization of the Newton-Raphson method in the polar coordinate system leads to numerical problems. After theoretical considerations, case study, which is devoted to different cases of realization of power flow computations, is presented. In the case study, conditioning and also convergence of the computation process are shown. At the end of the paper, special attention is paid to those cases in which the numerical problems are observed.