Comparison of unified power flow controller models for power flow studies

The unified power flow controller (UPFC) is an advanced member of flexible AC transmission systems (FACTS) group. This paper is focused on three techniques for inclusion of the steady state models of the UPFC in power flow programs. Three models are selected of many available models for the UPFC and incorporated in a MATLAB power flow program. based on the Newton-Raphson algorithm. They are: decoupled UPFC model, injection UPFC model and comprehensive NR UPFC model. A comparison among the load flow results using those models has been held to illustrate the validity, merits and demerits of those UPFC models at different operation modes. Each of them has advantages over the other for certain conditions.