Sharif Digital Repository

Over the past decade, the power industry in many countries around the world has been undergoing massive changes to introduce competition. In power systems under transmission open access, an optimal schedule of generation of units to satisfy the demand at the minimum production and transmission costs with consideration of system operation constraints is an important issue. In this paper, a method for centralized economic dispatch in deregulated power systems is presented. The considered constraints are minimum and maximum power generation of units, capacity of transmission lines and ramp rate limits. Genetic algorithm is used to solve a nonlinear objective function. Simulations are performed... 

In this paper we discuss an improved method for the calculation of Available Transfer Capability (ATC) in a restructured power system. The ATC calculation is performed through an optimal power flow approach. The objective function is to maximize the sum of the receiving-end load in a specified area as well as to send generation to other control areas while a minimum cost of generation is continuously achieved. The constraints are ac power flow equations and system operation limits. It is assumed that the generation cost curve of each generator is available. A genetic algorithm is used for the optimization process. An IEEE 30 bus test system is used for testing the proposed algorithm and the... 

In many developing countries, restructuring is usually started by dividing vertically integrated power systems into regional companies. Analysis of the procedure of restructuring requires appropriate analytical tools for modeling interactive behavior of the regional companies in a competitive energy market. The problem of generation expansion planning in the competitive environment becomes more complex where the new generation units are constructed on the basis of decentralized decisions. Recent studies of long term expansion planning show that market equilibrium modeling is an effective technique to analyze the long-term optimum development of the generation systems. In the present paper, a... 

In this paper two novel search methods for solving optimal power flow (OPF) have been presented and compared. Electricity is undergoing a restructuring process, moving from integrated environment towards deregulation and reduced regulation all around the world. Electrical energy markets are going to be created as a consequence of this process. In order to meet technical issues, system operator would need to apply some ancillary services. Reactive power is one of the most important ancillary services, which should be injected to power network in order to decrease the total loss and control the voltage profile. The main goal of this study is to present a method based on a Locational Marginal... 

Procurement and pricing of electric power and ancillary services is one of the most important issues of electricity market manager under new restructured environment. Ancillary services are necessary to provide security and reliability constraints applied to the dispatching and scheduling problem while they are essential for commercial functions. In a market payments should be based on energy and ancillary services capacities. Spinning Reserve (SR) is an ancillary service that is coupled with energy capacity, should be procured and priced via a joint economic dispatch mechanism to provide a right signal for all electricity customers. This paper presents a new approach for joint economic... 

This paper presents a practical scheme that can be used for allocating the transmission loss to generators and loads. In this scheme first the share of a generator or load on the current through a branch is determined using Z-bus modified matrix. Then the current components are decomposed and the branch loss allocation is obtained. A motivation of proposed scheme is to improve the results of Z-bus method and to reach more fair allocation. The proposed scheme has been implemented and tested on several networks. To achieve practical and applicable results, the proposed scheme is simulated and compared on the transmission network (400kv) of Khorasan region in Iran and the 14-bus standard IEEE... 

In this paper, AC Optimal Power Flow combined with UPFC has been used to manage the congestion of transmission lines in a restructured power system with pool market model. The modeling of Unified Power Flow Controller (UPFC) has been adopted based on bipolar model and power injection method. To determine an appropriate location for UPFC as well as to set its parameters, an approach based on genetic algorithm has been suggested. The modified IEEE 14-bus system is used to determine the effectiveness and applicability of the proposed method and results are discussed. ©2006 IEEE  

Available transfer capability (ATC) provides important information for power marketers and planning sectors in restructured power systems. The stochastic nature of power system behaviour, however, made ATC determination a difficult and complicated task. A stochastic framework has been established for ATC calculation with implication of uncertainties in transmission failures, hourly peak loads and system cascading collapse. The proposed ATC calculation framework is based on parametric bootstrap technique which enables generating random samples of system operating condition with uncertainty at a predefined confidence interval. The IEEE RTS-96 network is employed to demonstrate the... 

This paper proposes a new technique to manage congestion in a short-run market model. The method consists of an iterative algorithm to search and apply a sequence of bilateral power exchanges among the generators that would optimally reduce and completely remove the congestions. A combination of fuzzy decision principle and sensitivity analysis is developed to choose the best exchange and AC load flow is used to apply it on the network in the iterations. The effectiveness of the proposed approach is illustrated in a case study on IEEE 118-bus system, and results are discussed in the paper in comparison with the mathematical and evolutionary-based optimization techniques  

Long-term electricity load and price forecasts have become critical inputs to energy service provider (ESP) decision makings in restructured environments. This paper presents a three-stage hierarchical approach for long-term electricity load forecasting. These stages are called yearly trend model (YTM), weekly trend model (WTM), and daily trend model (DTM). The first stage fits an appropriate function to data and extracts its yearly trend. The weekly and daily trends are then extracted using the Box-Jenkins method in WTM and DTM, respectively. For doing so, candidate trends are identified using auto correlation function (ACF) and partial auto correlation function (PACF) plots. Then, Akaike... 

This paper proposes a method for unit commitment in restructured power systems with high penetration of wind farms. As wind is an intermittent source of energy and can not be predicted with high accuracy, reliability of wind farms compare to conventional power plants is lower. By increasing penetration of wind farms in generation system, reliability of power system will decrease. Therefore, reliability constraint should be added to unit commitment (UC) formulation. On the other hand, wind is a green source of energy; additionally environmental crisis is very important issue in the 21st century. By adding emission constraint to UC, wind energy will be valued. Both reliability and emission...