Showing papers on "Electricity generation published in 2000"

Determining the impact of distributed generation on power systems. I. Radial distribution systems

Abstract: Distributed generation (DG) has much potential to improve distribution system performance and it should be encouraged. However, distribution system designs and operating practices are normally based on radial power flows and this creates a special challenge to the successful introduction of distributed generation. This paper has described a few of the issues that must be considered to insure that DG will not degrade distribution system power quality, safety or reliability. This paper focused on radial systems, although some of the issues discussed are common to low voltage distribution networks.

Electrical energy storage device

Abstract: An electricity storage device and a portable electric-powered tool. The device comprises at least a battery; at least a super capacitor, which has lower internal impedance, when fully charged, than that of the battery and connects the battery in parallel; and an output end for supplying the electricity. The super capacitor is the major power supply for the pulse current output; the battery is used for generating electricity to the super capacitor and is the secondary power supply for the pulse current output. The connection of the battery and the super capacitor does not need any converters or current-limiting resistors.

Factoring the elasticity of demand in electricity prices

Abstract: As electricity markets are liberalized, consumers become exposed to more volatile electricity prices and may decide to modify the profile of their demand to reduce their electricity costs. This paper analyzes the effect that the market structure can have on the elasticity of the demand for electricity. It then describes how the consumers' behavior can be modeled using a matrix of self- and cross-elasticities. It is shown how these elasticities can be taken into consideration when scheduling generation and setting the price of electricity in a pool based electricity market. These concepts are illustrated using a 26-generator system.

Comparative study of maximum power point tracking algorithms using an experimental, programmable, maximum power point tracking test bed

Abstract: Maximum power point tracking (MPPT) is important in solar power systems because it reduces the solar array cost by decreasing the number of solar panels needed to obtain the desired output power. Several different MPPT methods have been proposed, but there has been no comprehensive experimental comparison between all the different algorithms and their overall maximum power point (MPP) tracking efficiencies under varying conditions (i.e. Illumination, temperature, and load). This paper such a comparison. Results are using a microprocessor controlled MPPT powered by a 250 W photovoltaic (PV) array and also a PV array simulator.

The Competitive Effects of Transmission Capacity in a Deregulated Electricity Industry

Abstract: In an unregulated electricity generation market, the capacity of transmission lines will determine the degree to which generators in different locations compete with one another. We show, however, that there may be no relationship between the effect of a transmission line in spurring competition and the actual electricity that flows on the line in equilibrium. We also demonstrate that limited transmission capacity can give a firm the incentive to restrict its output in order to congest transmission into its area of dominance. As a result, relatively small investments in transmission may yield surprisingly large payoffs in terms of increased competition. We demonstrate these effects in the context of the deregulated California electricity market.

The potential of distributed generation to provide ancillary services

Abstract: The growing concerns regarding electric power quality and availability have led to the installation of more and more distributed generation. In parallel and in the context of an accelerating trend towards deregulation of the electric industry, the unbundling of services, many grouped under ancillary services, should create a market for some of these services. This paper discusses the potential of distributed generation (DG) to provide some of these services. In particular, DG can serve locally as the equivalent of a spinning reserve and voltage support of the AC bus. The main types of distributed generation with emphasis on the power electronic interface and the configurations appropriate to provide ancillary services are reviewed. The flexibility and features provided by the power electronic interface are illustrated. In addition to control of the real power, other functions can be incorporated into the design of the interface to provide services, such as reactive power, and resources associated with power quality. These include voltage sag compensation and harmonic filtering. The implications on the design of the power converter interface are discussed.

Optimal energy management in series hybrid electric vehicles

Abstract: This paper deals with the optimization of the instantaneous electrical generation/electrical storage power split in series hybrid electric vehicles (SHEV). Optimal energy management is related to the optimization of the instantaneous generation/storage power split in SHEV. Previously, a power split type solution of the series hybrid energy management problem has been attempted using a rule-based approach. Our approach performs a dynamic programming solution of the problem of determining the optimal power split between both sources of energy, with realistic cost calculation for all considered power trajectories for the combined APU/generator, electric machines and battery efficiencies, and a penalty function formulation for the deviation of the ideal state-of-charge to be sustained over the length of time considered. The discrete state formulation of this dynamic programming approach makes the computation very efficient. Results are obtained for series hybrids for the FUDS drive cycle.

Life Cycle Assessment of a Natural Gas Combined-Cycle Power Generation System

Abstract: Natural gas is used for steam and heat production in industrial processes, residential and commercial heating, and electric power generation. Because of its importance in the power mix, a life cycle assessment on electricity generation via a natural gas combined cycle system has been performed.

Control of variable speed wind turbines: Design task

Abstract: Owing to concern over the environment, there is much interest in renewable sources of electrical power generation, of which one of the most promising is wind power. There are essentially two types of wind turbines, namely constant speed and variable speed machines. In comparison to constant speed wind turbines, variable speed wind turbines are perceived to have several potential advantages which outweigh the considerable cost of the power electronics required to realize variable speed operation. The two frequently mentioned ones are: additional energy capture below rated wind speed and additional power-train compliance and associated load alleviation above rated wind speed. The purpose of this paper is to investigate the design of the control system (as opposed to the synthesis of the controller) for variable speed wind turbines. The choice of control strategy is investigated and appropriate realizations of the controller, to cater for the implementation issues of accommodation of variation in the plant d...

Control of variable speed wind turbines: Dynamic models

Abstract: Owing to concern over the environment, there is much interest in renewable sources of electrical power generation, of which one of the most promising is wind power. Wind turbines exploit this energy source to directly generate electrical power. There are essentially two types of windturbines, namely constant speed and variable speed machines. The purpose of this paper is to investigate the dynamics of variable speed wind turbines and determine suitable models to support the control design task. A basic but widely used dynamic representation of variable speed wind turbines and the corresponding models of the control plant dynamics are initially discussed. More detailed, yet still simple models, are derived separately for the rotor aerodynamics, the drive-train dynamics and the power generation unit dynamics before being combined to form the complete model of the wind turbine dynamics. The resulting combined model, in addition to supporting the control design task, enables the extent, to which the basic mod...

An approach to evaluate the general performance of stand-alone wind/photovoltaic generating systems

Abstract: This paper reports the development of a computer approach for evaluating the general performance of stand-alone wind/photovoltaic generating systems. Simple models for different system components are developed, integrated, and used to predict the behavior of generating systems based on available wind/solar and load data. The model is useful for evaluating the performance of stand-alone generating systems and gaining a better insight in the component sizes needed before they are built. Simulation results are presented for performance evaluation of a stand-alone generating system that has been previously designed to supply the average power demand of a typical residential house. An electric water heater model is used as a dump load, and the excess available wind/solar-generated power is used to heat the water. The heated water is used as the inlet water to the main house water heater, which is assumed to be nonelectric. It is shown that this strategy can be effective in reducing the amount of fuel used by the main residential water heater.

Full Load and Part-Load Performance Prediction for Integrated SOFC and Microturbine Systems

Abstract: During the last years, two new subjects among the others have risen interest in the field of small scale electric power generation: advanced microturbines and Solid Oxide Fuel Cells.This paper investigates the thermodynamic potential of the integration of the Solid Oxide Fuel Cell technology with microturbine systems, in order to obtain ultra-high efficiency small capacity plants, generating electric power in the range of 250 kW with 65% LHV net electrical efficiency and with the possibility of cogenerating heat. A detailed description of the calculation model is presented, capable of full and part-load performances analysis of the microturbine and of the integrated SOFC+microturbine system.Copyright © 1999 by ASME

Interconnection power converter and power generation apparatus using the same

Abstract: In a solar power generation apparatus using a solar battery having a relatively large ground capacitor and a power conditioner having a non-insulated input and output, a customer's ground fault interrupter may perform unwanted interruption due to a ground fault outside the customer's premises. To prevent this, when a ground fault is detected by a detector capable of detecting a ground fault within a shorter time than the customer's ground fault interrupter, the gate of inverter of the power conditioner is blocked, a switch is changed to an open state, and the input voltage of inverter is held at a voltage value higher than the peak value of the alternate current voltage of a power system until at least the switch changes to the open state.

An experimental study of the characteristics of a Darrieus turbine for tidal power generation

Abstract: The Darrieus turbine was initially developed for wind turbines. An example of its application to water turbines is found in the Darrieus turbine installed in a duct for low head power generation, but no example is known of its application in a natural water channel. The authors have developed a Darrieus turbine that is suitable for tidal current power generation with the aim of establishing tidal current power generation technology through demonstrations in test channels and oceans. The efficiency of tidal current power generation is influenced by the characteristics of the turbine. The characteristics of the Darrieus turbine are mainly affected by the solidity and the number of blades. The Darrieus turbine was tested in test channels to find the most suitable values for the rotor solidity and the number of blades. This paper describes and examines those test results. © 2000 Scripta Technica, Electr Eng Jpn, 132(3): 38–47, 2000

Maximum power point tracking control of photovoltaic generation system under non-uniform insolation by means of monitoring cells

Abstract: A photovoltaic power generation system (PV system) is operated under various insolation conditions. Sometimes the PV system is operated under nonuniform insolation, which may generate several maximum output power points on the V-I curve of the PV array and raises serious problem on maximum power point tracking (MPPT) control of the system. In order to solve this problem, the authors propose a novel practical MPPT method, which uses monitoring cells to get a proper starting point of operation as well as the incremental resistance method (dV/dI method).

Shape of the microgrid

Abstract: Shape of the Microgrid Chris Marnay, F Javier Rubio, and Afzal S Siddiqui Ernest Orlando Lawrence Berkeley National Laboratory C_Marnay@lbl.gov * tel: +1.510.486.7028 preliminary summary of presentation to be given in the panel Role of Distributed Generation in Reinforcing the Critical Electric Power Infrastructure at the IEEE Winter Meeting, Columbus, OH, 31 January 2001 Restrictions on expansion of traditional centralized generating and delivery systems may be becoming so tight in the industrialized countries that they cannot reasonably be expected meet future electricity demand growth at acceptable cost. Meanwhile, technological advances, notably improved power electronics that permit grid interconnection of asynchronous generation sources, is tilting the economics of power generation back towards smaller scales, thereby reversing a century long trend towards the central control paradigm. Special power quality requirements or opportunities for combined heat and power applications make on-site generation an even more attractive option for customers. The existence of a significant amount of electricity sources dispersed throughout the low voltage distribution system could create a power system quite different to the one we are familiar with and creating it offers significant research and engineering challenges. Moreover, the electrical and economic relationships between customers and the distribution utility and among customers may take forms quite distinct from those we know today. For example, rather than devices being individually interconnected in parallel with the grid, they may be grouped with loads in a semi-autonomous neighborhood that could be termed a microgrid. A microgrid is a cluster of small (by the standards of current power systems, e.g. < 500 kW) sources, storage systems, and loads which presents itself to the grid as a legitimate single entity. The heart of the microgrid concept is the notion of a flexible, yet controllable electronic interface between the microgrid and the familiar wider power system, or macrogrid. This interface essentially isolates the two sides electrically; and yet connects them economically by allowing delivery and receipt of electrical energy and ancillary services (EE&AS) at the interface. From the customer side of the interface, the microgrid should appear as an autonomous power system meeting the power quality and reliability requirements of the customer. Such issues as local voltage, reliability, losses and quality of power should be those that support the customers' objectives. From the macrogrid side, however, the microgrid should appear as a legitimate entity akin to current interconnected generators or loads. A key distinction between microgrids and our familiar arrangements is the expanded role of electricity endusers in determining the pattern of development of the overall power system, which must not only accommodate purchases and sales of EE&AS to and from established markets but also contractual agreements between microgrids. Fundamentally, the characteristics and capabilities of the microgrid will be determined by its internal requirements together with the technical, economic, and regulatory opportunities and constraints it faces, and not by established objectives for capacity expansion and reliability of the macrogrid. The goal of Consortium for Electric Reliability Technology Solutions (CERTS) work underway at the Berkeley Lab is to anticipate possible patterns of microgrid development that can help focus research efforts on the key technical problems that must be solved to enable microgrid deployment. C:\WINNT\Profiles\jose\Desktop\LBNL-47451.doc

Neural network modelling of the emissions and performance of a heavy-duty diesel engine

Abstract: Internal combustion engines are being required to comply with increasingly stringent government exhaust emissions regulations. Compression ignition (CI) piston engines will continue to be used in cost-sensitive fuel applications such as in heavy-duty buses and trucks, power generation, locomotives and off-highway applications, and will find application in hybrid electric vehicles. Close control of combustion in these engines will be essential to achieve ever-increasing efficiency improvements while meeting increasingly stringent emissions standards. The engines of the future will require significantly more complex control than existing map-based control strategies, having many more degrees of freedom than those of today. Neural network (NN)-based engine modelling offers the potential for a multidimensional, adaptive, learning control system that does not require knowledge of the governing equations for engine performance or the combustion kinetics of emissions formation that a conventional map-based engine model requires. The application of a neural network to model the output torque and exhaust emissions from a modern heavy-duty diesel engine (Navistar T444E) is shown to be able to predict the continuous torque and exhaust emissions from a heavy-duty diesel engine for the Federal heavy-duty engine transient test procedure (FTP) cycle and two random cycles to within 5 per cent of their measured values after only 100 min of transient dynamometer training. Applications of such a neural net model include emissions virtual sensing, on-board diagnostics (OBD) and engine control strategy optimization. (A)

Interconnection of a photovoltaic panels array to a single-phase utility line from a static conversion system

Abstract: This paper presents the analysis of a static conversion system for treatment of the solar energy from photovoltaic panels. This system is interconnected with the mains power supply, contributing to the generation of the electrical energy. The power structure is composed of a current-fed push-pull converter, a buck converter, and a current inverter. The main features of the system are: simple control strategy, robustness, lower harmonic distortion of the current and natural isolation. The principle of operation, design procedure and experimental results are presented.

Distributed electrical power management system for selecting remote or local power generators

Abstract: Computer based energy service provider (ESP) information service has been developed for providing operational and management services for distributed local power generation units. The ESP is a subscription service for customers that purchase power from utilities and generate their own power on site from a local power generation unit. The ESP service enables those customers to decide when to purchase power from the utility or generate their own power, and may provide control of the customer's power generation unit. Using the ESP, a customer may select whether to exclusively purchase power from a utility, exclusively generate its own power or allow the ESP service to determine whether power should be purchased or self-generated. The ESP service stores the customer's selections and remotely controls and operates the local power generation unit and a switch which connects the customer site alternatively to a utility power source or the power generation service.

Modeling Utility-Scale Wind Power Plants Part 2: Capacity Credit

Abstract: As the worldwide use of wind turbine generators in utility-scale applications continues to increase, it will become increasingly important to assess the economic and reliability impact of these intermittent resources. Although the utility industry appears to be moving towards a restructured environment, basic economic and reliability issues will continue to be relevant to companies involved with electricity generation. This article is the second in a two-part series that addresses modelling approaches and results that were obtained in several case studies and research projects at the National Renewable Energy Laboratory (NREL). This second article focuses on wind plant capacity credit as measured with power system reliability indices. Reliability-based methods of measuring capacity credit are compared with wind plant capacity factor. The relationship between capacity credit and accurate wind forecasting is also explored. Published in 2000 by John Wiley & Sons, Ltd.

Short-current pulse based adaptive maximum-power-point tracking for photovoltaic power generation system

Abstract: This paper proposes a novel maximum-power-point tracking (MPPT) method with a simple algorithm for photovoltaic (PV) power generation systems The method is based on the use of a short-current pulse of the PV array to determine an optimum operating current for the maximum output power and completely differs from conventional hill-climbing based methods In the proposed system, the optimum operating current is instantaneously determined by taking a product of the short-current pulse amplitude and a parameter k because the optimum operating current is exactly proportional to the short current under various conditions of illuminance and temperature Also, the system offers an identification function of k by means of fast power-vs-current curve scanning, which makes the short-current pulse based MPPT adaptive to disturbances such as shades partially covering the PV panels The above adaptive MPPT algorithm has been adopted to a current-controlled boost chopper and a multiple power converter system composed by PV-chopper modules Various operating characteristics have been examined, and excellent MPPT performance has been confirmed through the experimental tests

A method for determining the generators' share in a consumer load

Abstract: In the paper, a new method for determining the generators' contribution to a particular load is presented, The method uses the nodal generation distribution factors (NGDF-s). It features a search algorithm, capable of handling the active and reactive powers. The method has been tested on the IEEE 118 and on the Slovenian 275 bus systems. The results demonstrate that electrical energy flows from a producer to a customer based on physical rather than on economical rules. By means of the new method, it can be shown that in general, the customer does not obtain the full power from the selected power plant according to the contract but also from other power plants. The method of the NGDF-s can be used for transmission service pricing, for congestion management and for reactive power management.

Infrared signal transmission by a laser-micromachined, vibration-induced power generator

Abstract: Presents the development of a vibration-induced power generator with total volume of /spl sim/1cm/sup 3/ that uses laser-micromachined springs to convert mechanical energy into useful electrical power. The goal of this project is to create a minimally sized electric power generator capable of producing enough voltage to drive low-power ICs and/or micro sensors for applications where mechanical vibrations are present. Thus far, we have developed a generator capable of producing 2V DC with 64Hz to 120Hz input frequency at /spl sim/250/spl mu/m vibration amplitude. We have also demonstrated that this generator has enough power to drive an IR transmitter to send 140ms pulse trains with /spl sim/60sec power generation time.