Optimal placement of DGs using MINLP in deregulated electricity market

Distributed generators (DGs) are small generating units connected directly to the distribution networks. As distribution networks are interconnected with the transmission networks, the impact of these DGs to enhance the reliability of the whole system can be observed. System loadability, total power loss in the system and total cost of the system are some of the important aspects in planning the DGs throughout the network. In this work, optimal sites for placement of DGs have been identified by using mixed integer nonlinear programming (MINLP) approach. The optimal sites are the different distribution networks connected to the transmission system under consideration. Also, the sizing of the DGs is taken into consideration, while enhancing the reliability in terms of system loadability, total power loss in the system and total cost of the system. The approach includes three optimal power flow (OPF) problem formulations, in which the objectives are to maximize the system loadability, and minimize the total power loss in the system and total cost of the system subjected to the constraints of power balance equations, power flow limits in each transmission line, voltage limits at every bus. In these problem formulations one binary vector is introduced that indicates the site of the DG location at various load serving nodes. The results are illustrated on Standard 5-bus test system and IEEE 24-bus Reliability Test System (RTS).