An OPF sensitivity based approach for handling discrete variables

This paper presents an approach for handling discrete variables, i.e. transformer taps and shunt capacitors, in Optimal Power Flow (OPF). It requires sensitivities of the objective function with respect to these discrete variables, obtained from the Hessian of the Primal-Dual Interior Point method (PDIPM). The difference in using OPF based sensitivities and the conventional power flow (PF) based sensitivities, for the same, has also been brought out. These differ especially under stringent operating conditions. The proposed method has been tested on a 5 bus system and two IEEE test systems. Results show that the proposed method provides superior solution in terms of objective and is almost as efficient as the one based on PF sensitivities.