Power flow tracing for transmission open access

In this paper, graph theory is used to analyze real power transfer between individual generators and loads, which is important to transmission open access. Related lemmas are proved first to present necessary conditions required by the method. Based on an AC load flow solution a novel method is suggested which can determine downstream and upstream power flow tracing paths and calculate the contribution factors of generations and loads to the line flows efficiently in the system without circulating power. When the existence of circulating power in the system is detected, by revealing the reasons which cause circulating power, the optimal power flow (OPF) approach is suggested to eliminate it and a new feasible AC load flow solution will be obtained for tracing. The computer tests yield satisfactory results. The suggested method is suitable for both active and reactive power flow tracings of real power systems.