Sharif Digital Repository

In this paper, a simple and efficient method for fast dynamic stability assessment of power systems is presented. The proposed approach determines the dynamic stability of a power system without the full dynamic formulation and eigenvalue analysis. This method could be applied as a valuable aid for monitoring dynamic stability in a new system control centers. Application of the singularity of standard load-flow Jacobian has already been presented for evaluation of dynamic stability under certain conditions, but the result is optimistic for any type of dynamic analysis. This deviation is misleading for system control operators and is not recommended. The modification proposed here can... 

To study the dynamic stability of a power system, suitable models of the network and dynamic devices, with different levels of accuracy, are needed. In this paper, a modular method is introduced for modelling power systems. The method is perfectly suited for systems containing FACTS devices. Due to the modularity of the method, which is based on augmentation of state equations of the network and dynamic devices, the introduction of new devices is straightforward. The method presented here can cover both high and low frequency ranges of dynamic phenomena in power systems  

In this paper, a novel fast straightforward method for thermal generating units scheduling is presented. The new method decomposes the solution of the unit commitment (UC) problem into three subproblems. In the first subproblem, the quadratic cost functions of units are linearized and hourly optimum solution of UC is obtained considering all constraints except the minimum up/down time constraints. In the second subproblem, the minimum up/down times are enforced through a novel optimization process by modifying the schedule obtained in the first step. Finally, in the third subproblem, the extra reserve is minimized using a new decommitment algorithm. For testing the proposed method, the... 

Waves encountering can cause significant ship motions and affect the photovoltaic power generation capacity in All-Electric Ships (AES) during extreme conditions. In this paper, a comprehensive strategy is proposed to examine the impact of modern vessels' movements on the PV system output and the ship power quality during various operating scenarios. The proposed theoretical model-based technique determines ship angles in a wave collision and assesses sun-related angles concerning the vessel motions. Based on the panel angles, the solar irradiance and the PV system power variations can be derived. The developed method can simultaneously evaluate the effect of ship motions on the photovoltaic... 

Load management and cost optimization are among the important factors in trigeneration systems and combined cooling, heating and power (CCHP) systems. In this study, an innovative CCHP system uses a gas turbine as the prime mover and has a heat recovery steam generator (HRSG) in addition to an auxiliary boiler, electric and absorption chillers. The system is tied with the bulk electric grid; to export and sell excess power or import power when necessary. This study analyzes load management and cost optimization of CCHP systems. A heuristic strategy to optimize the total energy cost is then presented. The optimal size of CCHP is determined from the study results. This paper proposes a model... 

Over recent years, the concept of waste heat recovery from the generators of wind turbines for driving a thermal-driven desalination system was introduced, and its advantages were highlighted. However, any selection of a bottoming thermal-driven desalination system among different existing technologies should be taken under consideration before making an ultimate recommendation. Unfortunately, no comprehensive comparison is available in the literature to compare the performance as well as the cost aspects of using the waste thermal energy of the generator of a wind turbine for desalinating seawater, comparing them with those of a layout where the power of the wind turbine is directly... 

Today, the flow of gas-solid, solid-liquid and liquid-liquid mixtures is broadly used in many industries such as slurry transportation, propulsion, dredging and power generation equipment. In this paper, single solid particle motion through free and forced vortices is analytically studied. The equations are solved for cases in which the drag, pressure gradient, added mass, buoyancy and weight forces are considered individually and simultaneously. Verification has been done for the value of ReP , which confirms the solution for the first t = 0.1 s. The results show that the most important force governing particle motion is the pressure gradient force  

This paper mainly focuses on operational reliability studies of modern power systems taking into consideration the effects of energy storage systems (ESSs). The aim is to develop a new evaluation tool to assess the effects of different factors such as penetration rate, operational strategies and capacities of the ESSs in determining the role of these systems as an operating reserve resource. In this regard, at first, some modifications are made to the PJM method aimed to precisely model the short-term variability in output generation of wind farms in reliability studies. Then, this algorithm is employed to examine the effects of ESSs operating strategies in operational reliability level of... 

Uncertainty and variability in the supply sector of renewable-penetrated power systems is becoming a new challenge for secure operation of these systems which if not responded properly may cause large amounts of load and supply curtailments. To meet this challenge, some ISOs recently have employed a new product named Flexible Ramping Product (FRP) into their markets which enhances the capability of the system to overcome such uncertainties by reserving additional ramp rates. In this regard, a new framework for implementing FRP in real-time market is proposed here. The proposed framework provides a proper opportunity for participation of thermal generating units in procuring FRP requirements.... 

This paper proposes a robust investment and operation model to attend the power and heat needs of a microgrid (MG) connected to the distribution system. The optimization algorithm decides on the best investment and operation of combined heat and power (CHP), boilers, PV power generation and battery energy storage systems (BESS). For the BESS, the algorithm estimates the optimal energy storage capacity (MWh) as well as the maximum hourly delivery capacity (MW). The non-linear and non-concave heat rate chart is recast by a mix-integer linear model to have a tractable and precise model. The model considers the uncertain in some parameters using probability density function (pdf) to portrait its... 

This paper examines the strategies of a local supplier of high technology capital goods (or complex product systems, CoPS) in a middle-income developing economy, Iran, in its efforts to acquire technology and catch up with market leaders. The study draws upon both the development and business strategy literatures to develop a novel conceptual framework of latecomer strategy which is then applied to the Iranian firm engaged in the design, production and implementation of electricity generation systems. Although exploratory, the study shows that the firm was able to exploit its linkages with local clients, favorable government policies and a growing domestic demand to overcome barriers to... 

In recent decades, many countries have shown a growing interest in the use of renewable energies for power generation. Geothermal energy is a clean and environmentally friendly source of renewable energy that can be used to produce electricity and heat for industrial and domestic applications. While Afghanistan has undeniably good geothermal potential that can be utilised to alleviate the country’s current energy limitations, so far this potential has remained completely untapped. In this study, the suitability of 21 provinces for geothermal project implementation in Afghanistan was evaluated using multiple multi-criteria decision-making (MCDM) methods. The stepwise weight assessment ratio... 

The role of gas turbine power plants in electrical energy production has been considerably increased in the last two to three decades. Various methods have been proposed to improve the performance of gas turbine cycles. In this research, two methods, a reheat cycle and a cycle with a reheat and a recuperator, were investigated and compared with a simple cycle. The main objective of this paper is to study the performance of an simple cycle and reheat cycle under actual conditions. In this regard, all processes are treated as actual, and in particular a relatively simple and reliable approach is used to predict the amount of cooling air. The results obtained on the basis of a model developed... 

In recent years, the development of distributed power generation has resulted in significant reduction in network losses and transmission costs while it has increased reliability. Microturbine is one of these power generators that has the ability of relatively high power generation in spite of its small volume [1], [2]. In this paper, different layouts for advanced microturbine cycles are analyzed. In order to modify cycle characteristics such as power and efficiency, and reduce exergy destruction, different configurations including intercooler, aftercooler, and heat recovery boiler are separately and synthetically analyzed and compared. The effects of various parameters, such as compressor... 

On pool market structure, the generating units are typically dispatched in order of lowest to highest bid as needed to meet demand requirement as well as considering network constraints. Generally, no account is taken of generating unit's reliability when scheduling them. This paper proposes a new structure for electricity market to consider generating unit's reliability in the scheduling problem. GAMS (General Algebraic Modeling System) language has been used to solve the social welfare maximization problem using CPLEX optimization software with mixed integer programming. ©2006 IEEE  

This paper discusses the application of unified power quality conditioner (UPQC) for improving power quality of a system supplying an electric arc furnace (EAF). The UPQC comprises a combined series and shunt active filters sharing a common DC link. It is used to mitigate voltage disturbances and compensate for reactive power, harmonics and interharmonics. A novel control strategy of the UPQC is presented. Since voltages at the point of common coupling (PCC) contain low frequency interharmonics, conventional methods can not be used for extracting voltage reference signals. In the proposed method, voltage references are extracted using active power processing to generate sinusoidal waveforms.... 

This paper presents a dynamic programming methodology for finding the optimum preventive maintenance schedule of generating units of a GENCO in open power systems. The objective function for the GENCO is to sell electricity as much as possible, according to the market price forecast. Various constraints such as generation capacity, duration of maintenance and maintenance crew are taken into account. In a case study, introducing a GENCO with six generating units, and implementing dynamic programming, we obtain the optimal maintenance schedule over the planning period. © 2002 IEEE  

The major source of energy is fossil fuels, known as hydrocarbon containing C and H as the main elements. The heat generated from combustion of these fuels is used in power generation cycles to generate electricity. Main products of a hydrocarbon combustion reaction are water and carbon dioxide, but due to some reasons such as excessive temperature and inappropriate air-fuel mixing, always some pollutants are formed. One of the major concerns of recent years are NOx pollutants, which is mostly generated in the high temperature combustions. According to the geographical and economic issues, most countries are using coal as fuel and many researches have been conducted about pollutant formation...