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Showing papers on "Electric power published in 1997"


Patent
18 Mar 1997
TL;DR: In this article, a power output apparatus consisting of a clutch motor (30) and an assist motor (40) is used to convert the energy output from an engine (50) driven at a high efficiency to energy expressed as the product of a revolving speed and a torque of a drive shaft (22) and to be output to the drive shaft.
Abstract: A power output apparatus of the invention includes a clutch motor (30) and an assist motor (40) that allow energy output from an engine (50) driven at a driving point of high efficiency to be converted to energy expressed as the product of a revolving speed and a torque of a drive shaft (22) and to be output to the drive shaft (22). In case that a large torque is required, for example, when the vehicle starts on a rising slope or runs at a low speed, the engine (50) is driven at a high-energy driving point having a large torque and a high efficiency. This structure causes large electric power to be generated by excess energy greater than the energy generally consumed and enables a battery (94) to be charged with the large electric power. The power output apparatus of the invention further has functions of predicting the process of charging the battery (94) with the large electric power based on a driving state of the vehicle and topographical information and lowering the remaining charge of the battery (94) in advance according to the requirements. This process effectively prevents the battery (94) from being damaged with excess charging.

470 citations


Patent
20 Mar 1997
TL;DR: In this article, a machine housing with a battery-driven electric motor and a jacketed vessel for inductive transmission of electric power from outside the machine housing into the batteries is described.
Abstract: The machine housing (1) contains a battery driven electric motor, whose output shaft is brought out from the housing. The batteries (6, 7) are located in a jacketed vessel (2) in the housing, whose walls (3, 4) a mirror-coated and the space (5) between the walls is evacuated (a Dewar vessel). The Dewar vessel opening can be closed by a stopper (10) of material with a low thermal conductivity. Pref. the Dewar vessel is fitted with an inductive coil (9), coupled to the batteries, for inductive transmission of electric power from outside the housing into the batteries.

377 citations


Patent
16 Jun 1997
TL;DR: In this article, an apparatus for supplying regulated voltage d.c. electrical power to an LED array (12) includes a rectifier (32) responsive to a.c power failure and a power factor correcting and voltage regulating buck/boost switchmode converter (38).
Abstract: An apparatus (10) for supplying regulated voltage d.c. electrical power to an LED array (12) includes a rectifier (32) responsive to a.c power for generating rectified d.c. power and a power factor correcting and voltage regulating buck/boost switchmode converter (38) responsive to the rectified d.c. power for generating regulated voltage d.c. power to illuminate the LED array (12). A battery backup system (62) receives the a.c. power applied to the rectifier (32) for charging a rechargeable battery (66) and sensing an a.c. power failure. A switch-over relay (82) is connected between the battery backup system (62) and the rectifier. Upon sensing a failure of the a.c. power, the battery backup system (62) controls the switch-over relay (82) to connect the battery backup system (62) to the rectifier (32) to provide d.c. power to the switchmode converter (38) to illuminate the LED array (12). A half wave power detector (88) causes the apparatus (10) to reduce regulated d.c. power to dim the LED array (12).

343 citations


Journal ArticleDOI
TL;DR: System dynamics has been used extensively to aid in resource planning in the electric power industry as discussed by the authors, which has proven useful to large and small power companies as well as to government agencies at the local, state and federal level.
Abstract: System dynamics has been used extensively to aid in resource planning in the electric power industry. The many applications constitute a major body of work that has proven useful to large and small power companies as well as to government agencies at the local, state and federal level. The work has been performed by utility analysts, government planners, consultants and academics. One of my recent publications on electric power was honored with the 1996 Jay Wright Forrester Award. This article documents the major points in my award address to the 1996 International System Dynamics Conference. It summarizes the impressive body of work that system dynamics practitioners have accumulated over the past several decades. It gives my interpretation of the important and unique features of the system dynamics approach. I argue also that we have contributed to useful change in the electric power industry. © 1997 by John Wiley & Sons, Ltd.

247 citations


Journal Article
TL;DR: Weiner et al. as discussed by the authors predict five ways in which the electric utility industry will be affected by virtual value networks: prices, contracts, new products and services, information intensity, de-regulation, and global scope.
Abstract: Electric utility companies will have to reinvent themselves to change from 'vertical to virtual' integration based on value networks segmented into six areas: generation, transmission, distribution, energy services, power markets, and IT products and services." Several forces are creating challenges and opportunities in the electric power business. Customers and legislators are pushing for greater competition, while utilities are trying to preserve the status quo. Power companies are increasingly competing against each other, much like airlines and trucking and telecommunication companies. Changes in generation, transmission, and distribution are changing every segment of the value chain. Weiner et al. predict five ways in which the electric utility industry will be affected: 1. Prices. Competition and consolidation will result in reduced prices. 2. Contracts. The number of short-term contracts will increase, as customers buy on the spot market. 3. New products and services. De-regulation means that electric utilities will be able to offer such items as on-line billing, remote appliance scheduling and control, energy-use monitoring, home-security systems, and electrical appliance maintenance contracts. 4. Global scope. Faced with little domestic growth, utilities will have to go abroad to develop new markets. 5. Information intensity. The amount of information and computer technology to develop efficient markets will grow exponentially. To reduce costs, increase revenue, and expand globally, utilities will have to focus on six segments of the value chain: generation companies, intelligent transmission networks, distribution companies or "WireCos," energy services or "EsCos," power markets, and IT products and services. As the industry breaks apart, new entrants focused on high-profit, high-growth niches will not own all or even most of the assets in the value chain. They will configure only those activities that add value and that customers want. The authors foresee the evolution of three value network models: 1. Regulated value networks. States will mandate the initial form of value network in a transition to competition. 2. Virtual value networks. Each company will manage its own assets and competencies and expand its product scope to include energy and energy services, telecommunications, computing, and facility services. 3. Customer-designed value networks. With technology and direct market access, customers will manage their own networks.

245 citations


Journal ArticleDOI
TL;DR: In this paper, a polynomial approximation with respect to time is applied to the waveform of the transients in estimating the inertia constant, and a simple model based on the idea of average system frequency is assumed to estimate the capacity of the generators.
Abstract: A procedure for estimating the inertia constant M(=2H) of a power system and total on-line capacity of spinning-reserve support generators, using transients of the frequency measured at an event such as a generator load rejection test, is presented. A polynomial approximation with respect to time is applied to the waveform of the transients in estimating the inertia constant, and a simple model based on the idea of average system frequency is assumed in estimating the capacity of the generators. Results of the estimation using the transients at 10 events show that the inertia constant of the 60 Hz power system of Japan is around 14 to 18 seconds in the system load base, and the capacity of the spinning-reserve support generators is 20 to 40% of the system load. The proposed procedure is expected to be tested by Kansai Electric Power Company with increased number of events. This effort will contribute to estimate and evaluate the dynamic behavior of the system frequency in loss of generation or load.

224 citations


Patent
09 Dec 1997
TL;DR: In this article, a method and apparatus for generating electrical power from multiple vehicles powered by fuel cells while the vehicles are parked in a parking lot is presented, where a plurality of spaced-apart electrical receptacles (25) are provided for receiving an electric cable (22) for connection to a parked vehicle for electrically connecting the fuel cell in each of the parked vehicles.
Abstract: The present invention provides a method and apparatus for generating electrical power from multiple vehicles (10) powered by fuel cells while the vehicles are parked in a parking lot. A plurality of spaced-apart electrical receptacles (25) are provided for receiving an electric cable (22) for connection to a parked vehicle for electrically connecting the fuel cell in each of the parked vehicles to the plurality of electrical receptacles. An electric power grid (12) is electrically connected to the plurality of electrical receptacles for transferring D.C. electrical power from the fuel cells in the parked vehicles to the electric power grid. At least one electric power collection station is electrically connected to the electric power grid for collecting at a common point the D.C. electric power in the electric power grid. In addition, at least one inverter is electrically connected to the electric power collection station for converting the D.C. electric power to A.C. electric power. Apparatus is provided for supplying the A.C. electric power to a load or a utility grid.

212 citations



Book
01 Oct 1997
TL;DR: The second edition of a bestseller as mentioned in this paper covers all aspects of testing and maintenance of the equipment found in electrical power systems serving industrial, commercial, utility substations, and generating plants.
Abstract: The second edition of a bestseller, this definitive text covers all aspects of testing and maintenance of the equipment found in electrical power systems serving industrial, commercial, utility substations, and generating plants. It addresses practical aspects of routing testing and maintenance and presents both the methodologies and engineering basics needed to carry out these tasks. It is an essential reference for engineers and technicians responsible for the operation, maintenance, and testing of power system equipment. Comprehensive coverage includes dielectric theory, dissolved gas analysis, cable fault locating, ground resistance measurements, and power factor, dissipation factor, DC, breaker, and relay testing methods.

150 citations


Journal ArticleDOI
TL;DR: The internal structure of the Earth together with the heat transfer mechanisms inside the mantle and crust are described in this article. But the location of geothermal fields on specific areas of the earth is not discussed.
Abstract: Geothermal energy is the energy contained as heat in the Earth's interior. The paper describes the internal structure of the Earth together with the heat transfer mechanisms inside the mantle and crust. It also shows the location of geothermal fields on specific areas of the Earth. The Earth's heat flow and geothermal gradient are defined, as well as the types of geothermal fields, the geologic environment of geothermal energy, and the methods for geothermal exploration Geothermal energy, as natural steam and hot water, has been exploited for decades to generate electricity, both in space heating and industrial processes. The geothermal electrical installed capacity in the world is 7173.5 MWe (December 1996), and the electrical energy generated is 38 billion kW h/year, representing 0.4% of the world total electrical energy which was 13,267 billion kWh in 1995. The thermal capacity in non-electrical uses (greenhouses, aquaculture, district heating, industrial processes) is 8664 MW1 (end of 1994). Electricity is produced with an efficiency of 10–17%, and the geothermal kWh is generally cost-competitive with conventional sources of energy, in the range 3–12 US cents/kWh. The geothermal electrical capacity installed in the world is probably comparable with that from biomass. but almost twice that from solar or wind sources summed together. In developing countries, where total installed electrical power is still low, geothermal energy can play a significant role: in El Salvador 15% of electricity comes from geothermal steam, 15% in Nicaragua. 21% in the Philippines, and 6% in Kenya and Costa Rica. Financial investments in geothermal electrical and non-electrical uses worldwide are summarised. Present technology makes it possible to control the environmental impact of geothermal exploitation. The future use of the geothermal energy from advanced technologies such as the exploitation of geopressured reservoirs, hot dry rock systems and magma bodies is briefly discussed. While the viability of hot dry rock technology has been proved., research and development are still necessary for the other two sources. Finally, a brief discussion follows on training of specialists, geothermal literature, on-line information, and geothermal associations. © 1997 Published by Elsevier Science Ltd

146 citations


Proceedings ArticleDOI
16 Jun 1997-Sensors
TL;DR: In this article, the first power MEMS-based gas turbine generator is presented, which can produce 10-20 W of electric power while consuming 10 grams/hr of H/sub 2.
Abstract: MIT is developing a MEMS-based gas turbine generator. Based on high speed rotating machinery, this 1 cm diameter by 3 mm thick SiC heat engine is designed to produce 10-20 W of electric power while consuming 10 grams/hr of H/sub 2/. Later versions may produce up to 100 W using hydrocarbon fuels. The combustor is now operating and an 80 W micro-turbine has been fabricated and is being tested. This engine can be considered the first of a new class of MEMS device, power MEMS, which are heat engines operating at power densities similar to those of the best large scale devices made today.

Journal ArticleDOI
TL;DR: The main changes are deregulation and privatisation in the electric utility environment in North America and Europe, the forces creating them and the possible reliability issues associated with them are described in this paper.
Abstract: Considerable change is occurring in the structure and operation of electric power systems throughout the world. This paper describes some of these changes in North America and Europe, the forces creating them and the possible reliability issues associated with them. The main changes are deregulation and privatisation in the electric utility environment.

Journal ArticleDOI
TL;DR: In this article, a Newton-Raphson load flow program has been developed which includes comprehensive control facilities and yet exhibits very strong convergence characteristics, and a generalized nodal admittance model is presented for series compensators, phase shifters, interphase power controllers and unified power flow controllers.
Abstract: This paper addresses the issue of controllable branch models suitable for assessing the steady state response of FACTS devices on a network wide basis. Generalised nodal admittance models are presented for series compensators, phase shifters, interphase power controllers and unified power flow controllers. A Newton-Raphson load flow program has been developed which includes comprehensive control facilities and yet exhibits very strong convergence characteristics. Test results are presented which demonstrate the effectiveness of the proposed models.

Patent
16 Sep 1997
TL;DR: In this article, a power supply system for enhancing the economic viability of different modes of transportation that incorporate fuel cells to generate electricity is presented, where off-board stations are provided for delivery of fuel to the vehicle and/or for receiving the electrical power generated by the fuel cell.
Abstract: A power supply system for enhancing the economic viability of different modes of transportation that incorporate fuel cells to generate electricity. For example, the power supply system of the present invention provides for the off-board use of the electric power generated by an on-board power plant, such as a fuel cell, of a mobile vehicle power system, such as an electric car. Off-board use, or use remote from the vehicle, of the electrical power includes the delivery of power to a remote site. Off-board stations are provided for delivery of fuel to the vehicle and/or for receiving the electrical power generated by the fuel cell. The off-board station and the vehicle are appropriately equipped for quick and easy interconnection such that electrical power is drawn from the fuel cell for off-board use.

Patent
Samer Takriti1, Lillian Wu1
21 Jul 1997
TL;DR: In this paper, a computer implemented tool is used to forecast the spot price of electric power in a deregulated market and the amount of power that may be traded in this market.
Abstract: A computer implemented tool forecasts the spot price of electric power in a deregulated market and the amounts of power that may be traded in this market. Using generating capacities of multiple utilities, price functions, weather forecasts, and transmission variables, the computer implemented tool makes these forecasts at different delivery points, providing the decision maker with probabilistic distributions for spot prices and trading.

Patent
04 Feb 1997
TL;DR: In this paper, an aircraft mounted gas turbine engine system consisting of three shaft propulsive gas turbine engines having three electrical generators is described. And two of the generators are additionally configured to function as electric motors so as to facilitate power transfer between the engine shafts.
Abstract: An aircraft mounted gas turbine engine system comprises a three shaft propulsive gas turbine engine having three electrical generators; each one respectively associated with one shaft of the engine. Two of the electrical generators are additionally configured so as to function as electric motors so as to facilitate power transfer between the engine shafts. One of the electric generators provides the primary source of electrical power for the aircraft, while the remaining electrical generators provide electrical power for the engine and back-up power for the aircraft.

Journal ArticleDOI
TL;DR: In this article, the authors present a summary of guidelines for modeling power electronics in various power engineering applications, which are designed for use by power engineers who need to simulate power electronic devices and sub-systems with digital computer programs.
Abstract: This paper presents a summary of guidelines for modeling power electronics in various power engineering applications. This document is designed for use by power engineers who need to simulate power electronic devices and sub-systems with digital computer programs. The guideline emphasizes the basic issues that are critical for successfully modeling power electronics devices and the interface between power electronics and the utility or industrial system. The modeling considerations addressed in this guideline are generic for all power electronics modeling independent of the computational tool. However, for the purposes of illustration, the simulation examples presented are based on the EMTP or EMTP type of programs. The procedures used to implement power electronics models in these examples are valuable for using other digital simulation tools.

Patent
10 Sep 1997
TL;DR: In this article, a plurality of electric apparatuses are connected to a power line having a predetermined maximum consumable power, and a power consumption of the power line is measured as a first power consumption.
Abstract: In supplying power to a plurality of electric apparatuses connected to a power line having a predetermined maximum consumable power, a power consumption of the power line is measured as a first power consumption. When a second power consumption predetermined in each of the electric apparatuses is told, a sum of the second power consumption and the first power consumption of the power line is compared with the predetermined maximum consumable power of the power line, and it is determined whether the second power consumption by the electric apparatus is permissible. A result of the determination is told to the electric apparatuses.

Patent
22 Jan 1997
TL;DR: In this paper, a method and apparatus for charging batteries of a plurality of vehicles includes a power source converter connectable to a Power source to receive electrical power and for converting the electrical power to a selected voltage potential that is distributed on a distribution bus.
Abstract: A method and apparatus for charging batteries of a plurality of vehicles includes a power source converter connectable to a power source to receive electrical power and for converting the electrical power to a selected voltage potential that is distributed on a distribution bus. A plurality of vehicle connecting stations are connected to the distribution bus. Each vehicle connecting station includes a station power converter for receiving electrical power from the power source converter for charging the battery and a station controller to control electrical power flow to the vehicle battery.

Patent
19 Aug 1997
TL;DR: In this article, an electric power conversion unit for driving a pump run by electric power generated by a solar panel, a storage battery connected to the solar panel via the switch 6, and a controller 7 for controlling the EPC unit and switch 6 are provided.
Abstract: An electric power conversion unit 2 for driving a pump 3 run by electric power generated by a solar panel 1 , a storage battery 5 connected to the solar panel 1 via the switch 6 , and a controller 7 for controlling the electric power conversion unit 2 and the switch 6 are provided. The controller 7 closes the switch 6 during any period when the amount of insolation is large and performs the maximum power point tracking control of the solar panel 1 , and otherwise, controls the electric power conversion unit 2 to drive at one of plural fixed frequencies in dependence upon an output voltage from the solar panel 1 by closing the switch 6 . Accordingly, it is possible to utilize output from an unstable electric power supply efficiently, such as a solar cell, thereby providing a reliable electric motor driving apparatus having a simple configuration and a control method therefor.

Patent
30 Oct 1997
TL;DR: In this paper, a battery controller for controlling at least two batteries of different kinds, including a kind-of-battery detection unit for detecting a kind of battery, and a battery switching unit in which a switching voltage, a suspended mode shift voltage and a termination voltage having different values in accordance with the kind of the battery detected by the kind detector are previously set to compare an output voltage of a battery being discharged with the previously set switching voltage.
Abstract: A battery controller for controlling at least two batteries of different kinds, includes a kind-of-battery detection unit for detecting a kind of battery, and a battery switching unit in which a switching voltage, a suspended mode shift voltage and a termination voltage having different values in accordance with the kind of the battery detected by the kind-of-battery detector are previously set to compare an output voltage of a battery being discharged with the previously set switching voltage, suspended mode shift voltage and termination voltage so that switching of the battery being discharged, stopping of operation of an apparatus being supplied with electric power by the battery being discharged or stopping of supply of electric power by the battery being discharged is performed.

Journal ArticleDOI
TL;DR: In this article, the authors describe the planning concerns, the study objectives, and the UPFC function in resolving voltage and thermal loading concerns in parts of its Kentucky/West Virginia service areas.
Abstract: In 1995, American Electric Power (AEP), an investor owned electric utility company, completed detailed planning studies to resolve voltage and thermal loading concerns in parts of its Kentucky/West Virginia service areas. These studies led to the initiation of a project including a unified power flow controller (UPFC), which is currently being developed through a tailored collaboration by AEP, Electric Power Research Institute (EPRI), and Westinghouse Electric Corporation (Westinghouse). This paper describes the planning concerns, the study objectives, and the UPFC function in resolving these concerns. It also provides information on the UPFC modeling for system studies and its technical parameters that would be of interest to transmission system planners and other prospective users of this new technology.


Journal ArticleDOI
Michael Hsu1
TL;DR: In this paper, the fundamental theory of transmission pricing is presented and three alternative market/pricing structures, contract network, financial replication and property rights, are discussed, with the focus on short-run operations and long-term capital investments.

Patent
25 Jul 1997
TL;DR: In this article, a power supply system with a stack of fuel cells and a storage battery includes a remaining charge monitor 42 for measuring the remaining charge of the storage battery 30 at the time of starting the system.
Abstract: A power supply system 10 with a stack of fuel cells 20 and a storage battery 30 includes a remaining charge monitor 42 for measuring the remaining charge of the storage battery 30. At the time of starting the power supply system 10, the remaining charge monitor 42 detects the remaining charge of the storage battery 30. The power supply system 10 estimates output electric current of the fuel cells 20 based on the observed remaining charge of the storage battery 30 and an amount of electric power required for auxiliary machinery 34, and supplies required amounts of gases to the fuel cells 20 based on the estimated output electric current.

Patent
10 Oct 1997
TL;DR: In this article, a plurality of power converters (18, 20, 114, 116, 118, 158A, 158B, 158C, 158D) are connected to separate power couplers (160B, 160C, 160D) in order to charge vehicles.
Abstract: A method and an apparatus for charging one or more electric vehicles includes a plurality of power converters (18, 20, 114, 116, 118, 158A, 158B, 158C, 158D) connectable to a source of electric power (14) to receive electric power therefrom. A switch (23) selectively connects the power converters (18, 20, 114, 116, 118, 158A, 158B, 158C, 158D) together to provide combined power to a first power coupler (22, 160A) in order to charge one electric vehicle, or connects the power converters (18, 20, 114, 116, 118, 158A, 158B, 158C, 158D) to separate power couplers (160B, 160C, 160D) in order to charge a plurality of vehicles.

Patent
Louis Roland1
28 Feb 1997
TL;DR: In this article, an electric power generator driven by a fluid circulating under pressure in a pipe (9) includes an internal moving contact (1) placed inside a non-magnetic section (10) of the pipe, and a stator (4) placed around the pipe.
Abstract: An electric power generator driven by a fluid circulating under pressure in a pipe (9) includes an internal moving contact (1) placed inside a non-magnetic section (10) of the pipe (9), and a stator (4) placed around the pipe (9). The internal moving contact (1) includes permanent magnets (2), a rotational drive means (3), and means (7 and 8) of support. The electric power generator does not require any sealed joints for the passage of mechanical shafts or electric cables and is particularly adapted for the production of electricity from dangerous fluids which circulate in pipes under high pressure. The electric power generator has application in gas and liquid transport networks, particularly at isolated hydrocarbon production sites.

Patent
19 Sep 1997
TL;DR: In this article, a membrane separation step was used to remove a portion of the nitrogen from the gas, which was used as fuel for a turbine or other driver, which provided mechanical power to drive an electric power generator.
Abstract: A method for generating electric power from natural gas or the like that has a low Btu value and a high nitrogen content. The method involves a membrane separation step to remove a portion of the nitrogen from the gas. The upgraded gas is used as fuel for a turbine or other driver, which provides mechanical power to drive an electric power generator.

Patent
14 May 1997
TL;DR: In this article, a customer side power management system including at least one auxiliary fuel cell(s) source is provided, and when the power derived from the electric utility reaches a predetermined threshold level, all remaining power needed to supply the customer's loads is obtained from the at least hydrocarbon powered fuel cell which is/are located within the facility.
Abstract: A customer side power management system including at least one auxiliary fuel cell(s) source is provided. When the power derived from the electric utility reaches a predetermined threshold level, all remaining power needed to supply the customer's loads is obtained from the at least one hydrocarbon powered fuel cell which is/are located within the customer's facility. In such a manner, high peak demand utility charges are avoided by the customer, and the simple cost effective power generation from the fuel cell is provided.

Patent
Kenji Esaki1, Nozaki Ko1
30 Apr 1997
TL;DR: In this paper, the regenerative power density of the first battery is high, and the regeneration current from the motor 32 is mainly stored by the second battery 14, which has a high output power density.
Abstract: To obtain an electric vehicle power supply 10 having a high output power density and regenerative power density, and which is compact and lightweight wherein a first battery 12 whose regenerative power density increases with decrease of the SOC and a second battery 14 whose output power density increases with increase of the SOC are used as an electrical storage device, and control is performed so that the SOC of the first battery 12 is maintained low while the SOC of the second battery 14 is maintained high. The regenerative power density of the first battery 12 is therefore high, the regeneration current from the motor 32 is mainly stored by the first battery 12, and the force used to drive the motor 32 is mainly output by the second battery 14 which has a high output power density.