Interconnected Electric System Research Articles

Application of CFD to the design of the runner of a propeller turbine for small hydroelectric power plants

A procedure for the design of the runner of a pico hydraulic propeller turbine according to the specific conditions of water potential of the site of operation is presented based on a theoretical and technical analysis. For this purpose the main characteristics of the runner are determined and data such as the suction head, the rated flow, and the occurring forces are established during the design. Modern engineering tools such as Computational Fluid Dynamics (CFD) are utilized for predicting the flow and Computer Aided Engineering software (CAE) for the design verification. The Runner of the Propeller Turbines (RPT) designed can be a viable option for electricity generation innot interconnected zones (NIZ) of the national interconnected electric system in developing countries and can be manufacture locally.

Valorization of Irrigation Water in A Basin with Large Hydropower Production through Coupled Hydrological and Electric System Modelling

The problem of allocation of limited water resources for multiple and diverse activities with growing demand calls for the need to develop appropriate tools for water valorization. This work develops a methodology to estimate the economic value of water in a basin with large hydropower production and a growing demand for rice irrigation, based on a coupled hydrological and electric system modelling approach. Inflow deficits to the hydroelectric system induced by the irrigation reservoirs within the basin are simulated under different irrigation scenarios. The simulated inflow deficits are integrated to an existing model of the interconnected electric system to evaluate the associated increase in generation costs under different energy scenarios. The impact of inflow deficits in turbinated and spilled flow and generation costs are comprehensively explored. Both annual mean and interannual variability of overcosts increase with increasing irrigation demand. However, if normalized by yearly varying rice planted area, the distribution of additional costs does not change substantially. Moreover, the distribution of normalized overcosts per unit irrigated area is also invariant to energy scenarios, although the relative impact in total costs decreases as the proportion of hydroelectric generation diminishes.

Lost wax casting process of the runner of a propeller turbine for small hydroelectric power plants

The runner blade of a propeller turbine has a complex profile and an uneven thickness, which causes severe and unpredictable problems during the manufacture procedure. This paper describes the manufacture procedure which includes advance computer solidification simulation, lost wax casting process and machining processes of the runner of a pico hydraulic propeller turbine.The runner was manufactured in C99350 nickel bronze alloy. This alloy possesses high toughness along with excellent resistance to cavitation and erosion. The runner can be a viable option for electricity generation in not interconnected zones (NIZ) of the national interconnected electric system in developing countries and can be manufactured locally.

Role of network topology in the synchronization of power systems

We study synchronization dynamics in networks of coupled oscillators with bimodal distribution of natural frequencies. This setup can be interpreted as a simple model of frequency synchronization dynamics among generators and loads working in a power network. We derive the minimum coupling strength required to ensure global frequency synchronization. This threshold value can be efficiently found by solving a binary optimization problem, even for large networks. In order to validate our procedure, we compare its results with numerical simulations on a realistic network describing the European interconnected high-voltage electricity system, finding a very good agreement. Our synchronization threshold can be used to test the stability of frequency synchronization to link removals. As the threshold value changes only in very few cases when aplied to the European realistic network, we conclude that network is resilient in this regard. Since the threshold calculation depends on the local connectivity, it can also be used to identify critical network partitions acting as synchronization bottlenecks. In our stability experiments we observe that when a link removal triggers a change in the critical partition, its limits tend to converge to national borders. This phenomenon, which can have important consequences to synchronization dynamics in case of cascading failure, signals the influence of the uncomplete topological integration of national power grids at the European scale.

Optimal operation of smart grids including distributed generation units and plug in vehicles

The paper deals with the optimal operation of a Smart Grid (SG) including distributed resources based on dispersed generation (DG) units and plug-in vehicle fleets with the aim of furnishing some services both inside the SG and outside to the interconnected electrical system. The distributed resources are connected through power electronic interfaces and are coordinated by a centralized control system to provide the usual energy service as well as some ancillary services such as reactive power control and compensation for some continuous Power Quality (PQ) disturbances into the SG. In addition, plug- in vehicle fleets are coordinated to charge/discharge their storage systems with the aim to perform the Smart Charging service, so as to provide regulation service for the interconnected electrical system, as well as to compensate the variability of DG units powers based on uncertain primary sources. Computer time domain simulations were effected on a low voltage 30-bus SG including wind turbine, photovoltaic systems and plug-in vehicles.

Power interconnected system clustering with advanced fuzzy C-mean algorithm

An advanced fuzzy C-mean (FCM) algorithm was proposed for the efficient regional clustering of multi-nodes interconnected systems. Due to various locational prices and regional coherencies for each node and point, modified similarity measure was considered to gather nodes having similar characteristics. The similarity measure was needed to contain locational prices as well as regional coherency. In order to consider the two properties simultaneously, distance measure of fuzzy C-mean algorithm had to be modified. Regional clustering algorithm for interconnected power systems was designed based on the modified fuzzy C-mean algorithm. The proposed algorithm produces proper classification for the interconnected power system and the results are demonstrated in the example of IEEE 39-bus interconnected electricity system.

A New Flicker Contribution Tracing Method Based on Individual Reactive Current Components of Multiple EAFs at PCC

In this paper, a new flicker contribution tracing method has been proposed to determine the individual flicker contributions of multiple-electric-arc-furnace (EAF) loads to the flicker measured at the point of common coupling (PCC). The proposed method decouples the flicker contribution of the interconnected electricity system from the individual contributions of the loads connected to the measured PCC, using the individual current variations of the loads, and the estimated short-circuit system impedance. It has been shown that the individual flicker contributions of the loads are mainly caused by the variation of their reactive current components. Since the computational complexity of the proposed method is low, it is appropriate for online applications. The algorithm can easily be embedded on a power quality analyzer, which can be employed as a flicker contribution meter. Field data collected at a PCC supplying multi-EAF plants have been used to verify the validity of the proposed method in a successful manner.

A model for the development of a power production system in Greece, Part II: Where RES meet EU targets

This paper studies the electricity production system of the Greek Interconnected Electric System using a development model created with the software package WASP-IV. The period of study is from 2009 till 2030. It consists of three scenarios using three different criteria: energy, environmental, and economic. The three scenarios are the Renewable Energy Source (RES), the lignite–RES, and the natural gas–RES. Subsequently, a sensitivity analysis is carried out for annual growth rate of electricity consumption and load demand. It is considered that there are no other energy sources beyond those already in use (lignite, oil, natural gas, biomass, solar, wind, and hydropower), no CO 2 capture policies are implemented, and electricity production from RES meets targets of the European Union in 2020. The present paper completes the study started with the paper “A model for the development of a power production system in Greece, Part I: RES do not meet EU targets”. It is shown that with regard to fossil fuels, the use of natural gas is the best choice. The use of RES, though environmentally friendly, is an expensive solution.

Reliability Assessment of a Backup Gas Turbine Generation System for a Critical Industry Load Using a Monte Carlo Simulation Model

The Alberta Interconnected Electric System (AIES) forms a single integrated transmission network serving the Province of Alberta, Canada. A number of large critical industrial loads are served by the AIES. These loads operate 24 h a day and seven days a week. This paper deals with a critical industrial load which is normally supplied by the Alberta provincial grid through two 72-kV lines. This load also maintains a backup generation system consisting of a set of gas turbines to meet its operating demands in the case of Alberta grid failure. The basic objective of this paper is to derive the optimal number of gas turbines that this critical load should maintain in order to satisfy the plant's reliability criteria in the case of grid failure for continuity of its operation. A Monte Carlo simulation model is developed to assess the adequacy of the backup gas turbine system, and the results of a series of case studies performed using the developed model are presented in this paper.

Reliability Assessment of the Brazilian Power System Using Enumeration and Monte Carlo

Two methods have been largely studied and used in power systems reliability assessment: contingency enumeration and nonsequential Monte Carlo simulation. Both have their advantages and drawbacks. Contingency enumeration is conceptually simple and usually requires low computational effort. Conversely, Monte Carlo simulation is computationally harder, but much more versatile to model random aspects. This paper depicts some important practical aspects regarding the application of both methods, emphasizing how they can be used in a complementary way. The Brazilian interconnected electrical system is used to illustrate the risk assessment of an actual large scale power system, utilizing both techniques.

The Chivilingo plant [history

This article discusses the Chivilingo hydroelectric generating plant, the first hydroelectric plant in the Republic of Chile and only the second in all of South America. By demonstrating the benefits of hydroelectric power to a nation having abundant hydro resources, Chivilingo helped set Chile on a course that has resulted in today's modern and comprehensive interconnected electric system being hydroelectric power based. Chivilingo also represented the first instance of leadership by Chilean engineers and technicians in the electrification of South America. Over the years, Chile has remained a leader in the entire region in electrical development and the expansion of hydroelectric resources.

Post-Kyoto energy consumption strategies for the Greek interconnected electric system

Abstract The liberalization of the Greek electric market (Law 2773/99, updated with Laws 3175/2003 and 3426/2005 for incorporating Directive 2003/54 into the Greek legislation) is in its final structural transformation, which includes the fact that from 1.7.2007 each customer can select its electricity provider. This new status together with the procedure towards the formation of a post-Kyoto plan, raise the need of examining different energy saving strategies in the consumption side for evaluating their economic and environmental consequences. Such strategies may be useful for the decision makers or the electricity retail companies. This paper examines the influence of several post-Kyoto electricity consumption strategies in the Greek interconnected electric system for the period 2005–2025. The aim of the paper is to be used as a decision makers’ tool for investigating the potential of electricity consumption policies. The results show that policies related either to seasonal peak demand control, or targeting at the total electric consumption lead to significant gains and emission reduction. Moreover the influence of factors, such as the weather conditions, the discount rate of the energy investments, the fuel prices evolution and the consumers’ behavior linkage with oil prices are examined.

Real-Time Transient Simulation Based on a Robust Two-Layer Network Equivalent

Real-time digital simulation of large power systems requires not only significant computational power but also simpler and accurate models. This paper proposes a new approach for transient simulation of power systems using a robust two-layer network equivalent model and an advanced PC-cluster based parallel real-time simulator. Using a combination of well established fitting and optimization methods, the generated low-order model is of high accuracy compared to its full model over a wide frequency bandwidth. The merits of this method are its robustness in terms of stability and positive-realness, its accuracy at not only transient frequencies but also at dc and power frequency, and its optimal order determination feature. To validate the new method, a realistic large-scale power system - the Alberta interconnected electric system - is simulated in real-time. The real-time electromagnetic transient program is implemented in C++ language using object-oriented programming techniques on the PC-cluster. A time-step of 20 mus has been used for the real-time simulation. The captured oscilloscope results demonstrate excellent accuracy and efficiency of the proposed model in comparison to a full-scale off-line simulation of the original system in the ATP version of EMTP.

Use of system approaches for transmission open access pricing

The Latin American deregulated markets have based their open access schemes on a concept that considers a multilateral use of the transmission system, with all agents contributing to the financing of a common network based on physical and economic usage, irrespective of commercial arrangements. The paper describes the concept and the existing schemes and contributes with the formulation of alternative numerical approaches for open access pricing, taking into account energy and capacity use of the system by the participant agents. Distribution factors based on DC power flows are the basic elements of the formulation, which is built based on different physical and economic considerations. The approaches are numerically evaluated in the Chilean main interconnected electrical system, with a comparison of the resultant impacts on generators and consumers.

A Comparative Analysis of Various Optimization Models for Electricity Capacity Expansion

Abstract Several optimization models have been proposed in the literature to solve the project selection, timing and sequencing problem. Models based on dynamic programming (DP) such as embeded state DP, objective space DP, and others have been used to solve the capacity expansion problem. Also models based on mixed integer linear programming using Benders decomposition theory, and heuristic rules have been proposed to solve that problem. In this paper these models are analyzed and compared from the theoretical point of view. All the reviewed models are then compared using them to define the minimum cost expansion of the Colombian electric sector. The Colombian interconnected electric generation system has about 10,000 MW of installed capacity with a generation composition of 80% hydro-generation plants and 20% thermogeneration plants. The expansion planning of the system has been carried out at a national level using simulation and optimization techniques. All these techniques are reviewed and discussed in this paper. Some conclusions and recommendations are finally presented.

A comparative analysis of various optimization models for electricity capacity expansion

Several optimization models have been proposed in the literature to solve the project selection, timing and sequencing problem. Models based on dynamic programming (DP) such as embeded state DP, objective space DP, and others have been used to solve the capacity expansion problem. Also models based on mixed integer linear programming using Benders decomposition theory, and heuristic rules have been proposed to solve that problem. In this paper these models are analyzed and compared from the theoretical point of view. All the reviewed models are then compared using them to define the minimum cost expansion of the Colombian electric sector. The Colombian interconnected electric generation system has about 10,000 MW of installed capacity with a generation composition of 80% hydro-generation plants and 20% thermogeneration plants. The expansion planning of the system has been carried out at a national level using simulation and optimization techniques. All these techniques are reviewed and discussed in this paper. Some conclusions and recommendations are finally presented.

Interchange scheduling: discipline or disorder?

Electric power transmission access is being opened and many interested parties want to get in on the act. The world of interchange scheduling is now a mixture of both old and new players, with changing rules, and uncertain risks to electric system reliability. Reliable electric system operation requires rigorous discipline in executing interchange schedules. Here, the author examines: whether disorder can be avoided in this rapidly changing environment; and how the reliability of the interconnected electric systems in the United States will be impacted by these changes.

Optimal operation of reservoirs for electric generation

Several tests have been performed with a simple test system under special conditions in order to highlight the influence of several factors including water head, discount rate, inflow seasonality, and system design. According to the results, reservoirs should operate at the highest possible storage level in order to maximize the generation efficiency of their associated power plants. This conservative behavior is shown to be the most economic for generation purposes. On the other hand, in a cascade system, the water head factor has the effect of specializing the behavior of the reservoirs. Reservoirs in the upper part of the cascade should play a regulation role while in the lower part of the cascade they should operate as run-of-river plants. These results have been verified on an actual large-scale hydroelectric system, the Brazilian South-Southeast Interconnected Electric System, composed of 51 hydro plants and 31 reservoirs. >

Electromagnetic compatibility, essential for fusion experiments

Electromagnetic compatibility has been of crucial importance to fusion experiments, long before ot was known by its present name, EMC. The huge amounts of pulsed power required to create and heat a plasma, and the stray fields produced in large volumes made it difficult, in earlier and in present experiments, to reach the ideal EMC-state where interference does not hinder (or impede) operation, measurements and data acquisition. The pressure to obtain results from the experiments has led to many ingenious solutions, but left usually little time for a more fundamental study. A basic problem is that the complex three-dimensional (and often toroidal) circuitry of a fusion experiment cannot be correctly represented by network theory models. In particular extended leads no longer “transport” potentials or voltages, but of course continue to transport currents. We therefore concentrate on currents and on all closed current loops rather than on worrisome (but meaningless) “jumping potentials”. With concepts developed along these lines we can design grounding systems which protect large interconnected electrical systems against interference. Such a grounding system may use wide strips, conduits or tubes to carry all interconnecting cables from subsystem to subsystem. Alternative descriptions of this grounding system may help to clarify its operation: a screen room reduced to its essential current-carrying elements, a minimization of transfer impedances or a structure to keep the common mode circuits closely under control. In this context ground loops can be quite useful, and we abandon the concept of single-point grounding. Next to the protection by grounding and shielding, additional measures can be taken to carry signals safely into subsystems. Larger amplitude or differentiated signals are advantageous, provided the first attenuator or integrator section in the “receiver” uses only passive, linear components. EMC is essential for fusion experiments, as stated in the title. Techniques borrowed from fusion can however also be quite useful in other fields. Examples in power engineering measurements and in lightning studies are briefly mentioned.

Modernization of a Burner Control System in a Thermoelectric Power Plant using Logic Programmable Controllers

The increasing need of maintenance, the lack of spare parts and the extra requirements of a very complex interconnected electrical system demands a new strategy which can support the reliability of a particular power plant. The present maturity of microprocessor technology makes feasible the development of a Burner Management System based on programmable controllers (PLC's). This paper reviews the retrofit of such system utilizing local PLC's developed by the Institute of Electrical Research (IIE). The problem is described in detail including its main constraints. The general characteristics (hardware and software) of the new system are also mentioned.