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- Type of Document: M.Sc. Thesis
- Language: English
- Document No: 41541 (05)
- University: Sharif University of Technology
- Department: Electrical Engineering
- Advisor(s): Abbaspour Tehrani Fard, Ali; Saadate, Shahrokh
- Abstract:
- In the recent years, there is a worldwide wave of considerable changes in power industries, including the operation of distribution networks. Deregulation, open market, alternative and local energy sources, new energy conversion technologies and other future development of electrical power systems must pursue different goals. Also growth in the demand and change in load patterns may create major bottlenecks in the delivery of electric energy. This would cause distribution system stress.Furthermore, in competitive electricity markets, operators determine the electricity price for specific intervals during a day, taking into account various economical and operational factors. Traditionally, a Distribution System Company (DISCO) purchased energy other electrical identities such as Transmission Companies (TRANSCOs) connected to DISCO distribution system, at a high voltage level, and then transfers this energy to final customers. Nevertheless, the restructuring process of the energy sector has stimulated the introduction of new agents and products, and the unbundling of traditional DISCO into technical and commercial tasks, including the provision of ancillary services.In this condition, DISCOs should provide a least-cost plan and should not damage the environment. The DISCOs planner attempts to find the best strategy from a large number of possible alternatives. Thus, the complexity of the problems related to distribution systems planning is mainly caused by multiple objectives. It is predicted that Distributed Generation (DG) will play an increasing role in the electrical power system of the future, not only for the cost savings but also for the additional power quality.Careful coordination and placement of DGs is mandatory. Improper placement can reduce DGs benefits and even jeopardize the system operation and condition. This thesis discusses the effects of DG implementation under different distribution system conditions and states not only to decrease system costs and losses but also to improve power quality, system voltage and line congestion.This thesis introduces three methodologies included mathematical model to obtain the optimal DG capacity sizing and sitting investments with capability to solve large distribution system planning problem.The first proposed optimization model allows minimizing total system planning costs for DG investment, DG operation and maintenance, purchase of power by the DISCOs from TRANSCOs and system power losses. The proposed model provides not only the DG size and site but also the new market price as well. Three different cases depending on system conditions and three different scenarios depending on different planning alternatives and electrical market structures have been considered. This model is valid as both single-period model and multi-period model.In the second framework, it is presented a mathematical distribution system planning model considering three planning options to system expansion and to meet the load growth requirements with a reasonable price as well as the system power quality problems. DG is introduced as an attractive planning option with competition of voltage regulator devices such as Synchronous Condenser (SC) and Interruptible load. In mathematical model, the object function includes investment costs, which are evaluated as annualized total cost, plus total running cost as well as cost of curtailed loads and losses. This model identifies the optimal type, size and location of the planning options. This methodology is also studied fluctuation of load and electricity market price versus time period and the effect of DG placement on system improvement.In the third framework, it is presented a new two-stage methodology (integrated electric-market investment model) for optimal placement, size and investment payback time of DG in competition with voltage regulator devices such as SC. In first stage, the object is the minimization of the total costs to find the optimal sizing and siting versus investment payback times. In the second stage, the goal consists in the maximization of the Total System Benefit (TSB) to find the optimal payback time. A total costs object function is proposed as an approach to identify optimal DG placement and sizing and candidate payback time. In this framework, the object function includes investment costs, which are evaluated as annualized total cost, plus total running cost as well as cost of Energy Not Supply (ENS) and losses. To provide some scenarios of variety of DGs available in the market, several DG types with different cost characteristics are considered. For each DG type, an optimal placement, size and investment payback time is identified. With so much to consider, it is often difficult for the planners to determine which technology is the best suited one to meet their specific energy needs. In this framework, it is compared five types of DG technologies to give choices for decision makers in a given case study and under different system conditions. This framework creates an electric market price forecasting model to predict the electricity market price. TSB is incorporated with the proposed optimization model (first or second framework) to provide a modified integrated electric-market investment model.
These frameworks have allowed validating the economical and electrical benefits of introducing DG by solving the distribution system planning problem and by improving power quality of distribution system. DG installation increases the feeders’ lifetime by reducing their loading and adds the benefit of using the existing distribution system for further load growth without the need for feeders upgrading. More, by investing in DG, the DISCO can minimize its total planning cost and reduce its customers’ bills.To solve the proposed mathematical planning model a new software package interfacing MATLAB and GAMS is developed. This package is enabling to solve large extent distribution system planning program visually and very fast. The proposed methodology is tested in the modified IEEE 30-bus test system. Different system conditions are considered to study their effect on planning decisions. It is also studied the effect of DG placement on system conditions improvement.
- Keywords:
- Dispersed Generation ; Distribution System ; Planning ; Multi Objective Programming ; GAMS-MATLAB Interface
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