EFFECTIVENESS OF THE DISTRIBUTION FACTOR APPROXIMATIONS USED IN CONGESTION MODELING

Congestion has widespread impacts on the availability and utilization of the existing transmission systems and consequently on the operation of competitive markets in electricity. The distribution factors play a key role in the modeling of congestion in various market appli- cations. These factors are linear approximations of sensi- tivities of variables with respect to various inputs and are computed for a specified network topology and parameter values. In practice, the factors are used over a wide range of system conditions. This paper investigates the analytical characteristics, the robustness and the quality of the ap- proximations provided by key distribution factors such as injection shift factors (ISFs) and power transfer distribu- tion factors (PTDFs). We examine the range of conditions over which these factors can provide a reliable approxima- tion for large power system networks. The numerical simu- lation results indicate that the errors of the approximations stay in an acceptable range under a broad spectrum of conditions including contingencies used to establish n-1 security.