New models for design of distributed generation based expansion in electric networks

The demand for electrical energy is increasing due to technological developments, the increase in the world population, and electrification studies. Meeting the increasing demand without interruption is one of the main challenges faced by institutions responsible for electricity distribution. In order to cope with this challenge, it is necessary to regularly expand the current network with an appropriate investment plan and increase its capacity. Finding the most appropriate investment plan is a strategic design problem. The designed distribution networks are expected to be reliable, cost-effective, and clean energy-using networks in addition to meeting the increasing demand. In order to achieve these goals, planning the network in a distributed generation (DG) structure has become common in recent years. DG refers to a system that generates electricity at or near the place it will be used such as solar panels, wind turbines, hydroelectric power plants, geothermal energy, and combined heat and power systems. Within the scope of this thesis study, the expansion problem of electric distribution network containing distributed generation (DNEP_DG) is addressed. DNEP_DG basically involves strengthening the current network or adding new network components such as line, substation, and distributed generation source. Radial structures are often used in electric distribution networks. It is a widely used type of network, and it is also called a branched network since its shape resembles the branches of a tree. In this study, three models were proposed for the related fields defined below to make a multi-period expansion plan of the DNEP_DG problem: i) A new mixed-integer mathematical model was proposed for the best network design in which the total cost consisting of investment, maintenance, production, and emission costs is minimized. The necessary constraint that would form the radial structure in the model was developed based on the spanning tree subtour elimination constraints. As a result of the experimental calculation analysis, it was shown that the new model containing the radiality constraints proposed in this thesis instead of the existing constraint structure in the literature shortened the solution time of the related problem. ii) A new mathematical model was developed for DNEP_DG as an extension of this model, which considers the renewable energy source guarantee system (RES-G) and guarantees that the electricity used by consumers is generated from renewable sources. It was aimed to make the most appropriate expansion plan with this model that guarantees to meet the demands of customers who want to use renewable energy. iii) Lastly, the reliability of the designed network was focused on since the reliability of radial networks was low. Reliability in electric distribution networks is defined as the ability to provide uninterrupted service to the customer and is important for ensuring sustainable service. Considering the costs and impact of interruption, it is necessary to consider different levels of reliability for the consumer. For example, the reliability of a substation serving an area where hospitals are located is expected to be higher than that of a substation serving only a residential area. Therefore, the third model proposed in this thesis guarantees that each consumer receives services at a level of reliability in accordance with their needs. Therefore, a nonlinear mixed integer mathematical model that considers distributed generation and reliability was developed for the network expansion problem. The proposed mathematical models were applied for a sample 14-node test network, and the resulting network expansion design was given for three periods. In addition, the results of the computational analysis of the models were shown on 9, 14, 24, 30 and 40 node test problems. It was seen that the best result was achieved in reasonable times with the developed models. With the mathematical models developed within the scope of this thesis, it was aimed to create the best distribution network expansion design that considers the integration of renewable energy sources.