Security-Constrained unit commitment using PTDF and LODF sensibility factors

Abstract

The unit commitment (UC) problem consists in optimally determining which generation units must supply power to the system in a typical time horizon of 24 hours. The security- constrained unit commitment (SCUC) is a problem of high computational cost due to the quantity and nature of the variables involved. This paper presents an alternative formulation of the SCUC to reduce its computational cost, by using the PTDF and LODF sensitivity factors. In contrast to classic formulations, the use of these factors allows calculating power flows without using nodal angles, reducing the number of variables and constraints of the model. In addition, an N-1 active contingency filter methodology is implemented that further reduces the computational burden through user cuts. Results are presented for the IEEE-RTS96 system that demonstrates the robustness and applicability of the proposed approach. It was found that the use of PTDF and LODF sensitivity factors, in conjunction with the contingency filter methodology, reduces the computational cost by up to 86% with respect to its conventional formulation. Additionally, the proposed methodology identifies which lines are more vulnerable due to overloads, and which lines cause the greatest impacts to the system when they fail.