Centralized and decentralized optimal decision support for congestion management Brijesh Singh, R. Mahanty, S.P. Singh ⇑ Department of Electrical Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005, India article info Article history: Received 24 July 2013 Received in revised form 18 June 2014 Accepted 6 July 2014 Keywords: AC optimal power flow Decentralization Open access Optimal pricing Power market Security constrained optimal power flow abstract This paper presents a framework to carry out optimal power flow in a coordinated multi-transaction/util- ities decentralized system. An AC power flow model has been used in this work for independent optimal dispatch of each utility. The global economic optimal solution of the whole electric energy system with congestion management has also been done in this work using the interior point (IP) optimization pro- cedure. In this approach, each participant tries to maximize its own profit with the help of information announced by the operator which are information related to system security constraints and public issues. The developed algorithm can be run in parallel, either to carry out numerical simulations or to obtain an optimal generation schedule in an actual multi-utility electric system. The study has been con- ducted on a three utility modified IEEE-30 bus system with two market models and six utility modified IEEE-118 bus system. The results clearly show the effectiveness of the suggested IP optimization based optimal generation schedule in decentralized scenario. It has been demonstrated that the suggested decentralized approach produces improved optimal dispatch solution with enhanced market benefits and can effectively manage the congestion in the system as compared to the centralized approach. Ó 2014 Elsevier Ltd. All rights reserved. Introduction The congestion management is one of the most challenging operational problems with open access transmission. The power system is said to be congested if the transmission network is oper- ated at or beyond one or more transfer limits [1]. Because of the present trends of bilateral and multilateral contracts in the elec- tricity market, the role of independent system operator (ISO) is increasing. Under this new scenario, the role of ISO is to create a set of rules that ensure sufficient control over producers and con- sumers to maintain an acceptable level of power system security and reliability [2]. As such, in a tight pool market, ISO has con- straints to operate the system without the violation of operational constraints. Due to this, all the market participants are bound by some rules of coordination. For a better competition in the market, it is essential that all the participants are free to optimize their own profits. Hence, a decentralized decision making based methodology can play a vital role in market competition [3]. As the electric power industry is undergoing restructuring, it results into higher degree of decentralized decision making in the power system. This change has been affecting long term expansion planning of independent investors with less centralized coordination. After the restructuring of the electric power industry, profit generating companies have been developed to deliver electric energy in a competitive market. In such a case, independent regulated trans- mission system operators (TSOs) manage the operation of the transmission system. The congestion management is one of the central issues of centralized optimal power flow (COPF) [4,5]. The recent trends in electricity market are towards large multinational electricity markets, such as, the internal electricity market (IEM) in Europe. However, there are technical and economic challenges in the operation of a single joint market by combining different regio- nal electricity markets. If an individual market optimizes its own electricity market without coordinating with its neighbouring markets, seam issues arise among regional electricity markets. In multiple market environments, seam issues lead to market ineffi- ciency in the operation of the combined markets. Hence, a decen- tralized approach is needed to facilitate economically efficient and viable energy trading among regional electricity markets [6]. A decentralized model partitioned by tie-line between individ- ual markets has been proposed for coordinating trading between regional electricity markets [7]. The tie-line information is exchanged at the end of each iteration, until the final convergence is achieved. Different decomposition methods for dividing the interconnected electricity markets into individual markets have also been introduced [8]. After decomposition the single joint http://dx.doi.org/10.1016/j.ijepes.2014.07.026 0142-0615/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +91 9415336705. E-mail addresses: singhb1981@gmail.com (B. Singh), mahantyr@yahoo.co.in (R. Mahanty), spsingh.eee@itbhu.ac.in (S.P. Singh). Electrical Power and Energy Systems 64 (2015) 250–259 Contents lists available at ScienceDirect Electrical Power and Energy Systems journal homepage: www.elsevier.com/locate/ijepes