Showing papers on "Stand-alone power system published in 1999"

Dispersed generation impact on distribution networks

Abstract: The insertion of dispersed generation into existing electric power systems has a great impact on real-time operation and planning. Several uncertainties characterize the ability of the existing power system to integrate this form of generation, Hence, dispersed generation must be taken into consideration in power system performance so that operation and security are not disturbed. Dispersed generation increases the complexity of controlling, protecting and maintaining power distribution systems. This article focuses on some technical aspects, but not on the impact on the quality of supply and on tariff signals.

Development of vanadium redox flow battery for electricity storage

Abstract: There is serious demand today for superior technology for load levelling placed on power generation and transmission facilities. The vanadium battery, developed by Kashima-Kita, uses vanadium compounds as an electrolyte, recovered from boiler soot in Orimulsion-fired power stations to provide a solution to this problem. This battery is eminently suitable for load levelling, being operable at room temperature and normal pressure, easily convertible to a large scale and is environmentally friendly. In September 1997, Kashima-Kita built a 200 kW/spl times/4 hour-rate battery after having built both 2 kW and 10 kW prototype units. The battery is interconnected to the company's power plant grid system and has to date achieved 650 cycle continuous operation at the rated efficiency. This success has proved that a high-efficiency heat power station system equipped with such an electricity storage battery reusing byproducts of the power plant can be commercially viable.

Method and apparatus for a hybrid battery configuration for use in an electric or hybrid electric motive power system

Abstract: A power system for an electric motor drive such as may be used in an electrically propelled vehicle incorporates the combination of a high power density battery and a high energy density battery to provide an optimal combination of high energy and high power, i.e., a hybrid battery system. The hybrid battery system in one form includes components which prevent electrical recharge energy from being applied to the high energy density battery while capturing regenerative energy in the high power density battery so as to increase an electric vehicle's range for a given amount of stored energy. A dynamic retarding function for absorbing electrical regenerative energy is used during significant vehicle deceleration and while holding speed on down-hill grades, to minimize mechanical brake wear and limit excessive voltage on the battery and power electronic control devices. The high energy density battery coupled in circuit with a boost converter, a high power density battery, a dynamic retarder, and an AC motor drive circuit. The hybrid battery system is controlled by a hybrid power source controller which receives signals from a vehicle system controller using current and voltage sensors to provide feedback parameters for the closed-loop hybrid battery control functions.

Power exchange for frequency control (PXFC)

Abstract: This paper concerns markets for balancing power supply and demand in real-time Two qualitatively different market mechanisms are of interest: (1) primary electricity market(s) for supplying anticipated demand, and (2) a frequency control market for ensuring that system frequency remains within prespecified limits as demand deviates in real-time from its anticipated pattern We suggest that both types of markets are necessary for ensuring that frequency remains within its technically acceptable limits as power is provided competitively In particular, we develop one possible structure of a power exchange for frequency control (PXFC) that ensures frequency quality in a general primary electricity market comprising both bilateral and spot sub-markets

Power supply apparatus for charging and discharging battery with high energy efficiency

Abstract: A battery charge/discharge power supply apparatus for saving electric energy when performing charge/discharge operation of a storage battery. The power supply apparatus includes a direct current power source for switchably connected to the storage battery, an auxiliary battery switchably connected to the storage battery, and a converter provided between the storage battery and the auxiliary battery. The storage battery is charged by the power supplied from the auxiliary battery in the charge cycle of the storage battery. The auxiliary battery is charged by the discharge power from the storage battery in the discharge cycle of the storage battery. The direct current power source replenishes shortage of a power capacity in the auxiliary battery.

Power distribution systems for future homes

Abstract: With the advent of power electronics and the increasing demand for DC power, a new power distribution system for future homes is proposed. The system consists of a power-factor-corrected AC-DC pre-regulator, a battery charger, a bi-directional DC-DC converter, a DC-AC converter, a smart energy meter and an intelligent energy management system. Issues related to power quality, electricity pricing, enabling technologies, load requirements, design and compatibility are investigated. The advantages and feasibility of this system are also discussed.

Application of a power-controlled flywheel drive for wind power conditioning in a wind/diesel power system

Abstract: In isolated or autonomous power systems incorporating renewable power sources such as wind turbine generators, short-term energy storage devices are desirable for economic operation and transient load mitigation. The paper presents a 45 kW flywheel energy storage system with bi-directional power control capability along with its application into an autonomous wind/diesel power system. The technical aspects relating to system integration and those of the design and development of reliable active and reactive local power controllers are described. Practical results obtained from the application of the storage system for wind power conditioning are presented and supported by analysis.

System for controlling power flow in a power bus generally powered from reformer-based fuel cells

Abstract: A control system for controlling power flow in a power bus generally powered by a reformer-based fuel cell system (FCS) is provided. The control system comprises an energy storage device (ESD); a power interface unit coupled to selectively and bi-directionally pass power between the energy storage device and the power bus; and a controller coupled to the power bus to receive one or more signals indicative of the instantaneous power delivered by the fuel cell system. The controller may be configured so that the energy storage device may supply power to the power bus at least during transient conditions when the instantaneous power delivered by the fuel cell system drops below a (FCS) power command signal.

Power storing system

Abstract: PROBLEM TO BE SOLVED: To provide a power storing system which enables a user to use economical nighttime power without waste. SOLUTION: A power storing system is provided with a battery 5 and a bidirectional inverter 4, which converts the AC power of commercial power supply into a direct current and the DC output of the battery 5 into an alternating current, stores the AC power of the commercial power supply in the battery 5, and supplies the power stored to electrical equipment. The system is also provided with a control section 33, which stores several types of one-day discharge patterns of the battery 5 in advance so that the user of the system can select the patterns and controls the one-day discharge pattern of the battery 5. When the power storing system is constituted in this way, the user can effectively use economical nighttime power charged in the battery 5 without waste, because the using pattern of the nighttime power can be set in accordance with the daily living pattern of the user. Consequently, the electricity charges to the user can be reduced, and power loads can be leveled.

Modelling of frequency control in an island system

Abstract: The day to day operation of an island power system differs considerably in many ways from that of large interconnected networks. In particular, the control of system frequency in isolated systems poses technical problems that are an order of magnitude greater than those experienced by large interconnected networks. The control of system frequency also has to be achieved in relatively short timescales. The Electricity Supply Board of Ireland is such a system and some of its operational issues are highlighted in this paper. In particular, frequency regulation and primary frequency control are addressed. The modelling of system incidents is examined and in the light of new market structures a discussion of important considerations is presented.

Results from the investigations on leaking electricity in the USA

Abstract: The rapid proliferation of electronic devices, which are consuming electricity in the standby mode or when they are switched “off’ , has created a new category of electricity consumption. There are several names for this category, including “standby use”, “minimum use” , and “leaking electricity” . While “standby use” is technically more accurate, the expression “leaking electricity” is rapidly gaining popularity because it is easy to understand. Leaking electricity is a global phenomenon because the largest “leakers” are internationally-traded appliances, such as televisions, audio equipment and cordless telephones.

Application of a permanent magnet machine in the novel Hygen adjustable-speed load-adaptive electricity generating system

Abstract: Hygen is an adjustable-speed load-adaptive electricity generating system comprising one or more energy sources, e.g. an engine-generator unit, an energy storage means and a power electronic converter system with microprocessor control. A medium frequency permanent magnet alternator is integrated into a diesel engine to form a compact generator unit. A variable-ratio boost rectifier converts the variable voltage/frequency of the generator unit and regulates the output as required by the converter system. This combination provides a compact and efficient energy delivery sub-system with many benefits.

Testing battery power source of uninterruptible power supply

Abstract: A method of testing the battery of an uninterruptible power system by changing the priority of the battery to make it a primary, rather than secondary, power source. This allows the battery to be tested in a fail-safe mode such that a battery failure during the test will not cause any interruption of power to the inverter and thus the load.

Off-grid electricity for developing countries

Abstract: Access to electricity is a key element in determining quality of life. In this paper, the author describes some of the approaches to supplying electricity to poor rural communities beyond the reach of a conventional electricity grid connection.

Technical and economic assessment of utility interactive PV systems for domestic applications in South East Queensland

Abstract: Electric utilities in Australia have been developing policies to stimulate interest and permit the purchase of electricity generated by renewable energy sources such as photovoltaic systems (PV). Studies show that, under current conditions, it is technically feasible to introduce small-scale, grid connected, roof-top photovoltaic generation systems with or without battery storage. Economic analysis show that the electricity tariff structure for PV and other renewables requires a major change to allow a reasonable and an acceptable pay-back period if PV is to become an attractive economic investment to private owners. The technical policy developed by the utility should be reviewed to better match the operational characteristics of PV and inverter systems.

Power storage system and plug socket unit

Abstract: PROBLEM TO BE SOLVED: To provide a power storage system which can cope with a long time of power failure by supplying power from a storage battery to indispensable minimum load apparatuses when a commercial power gives out, and also can cope with it, even if the user changes the installation place of the load apparatus due to pattern change or the like of the room. SOLUTION: In a power storage system where a system switching device 2 is connected in the system for supplying a commercial power source 1 to load apparatuses 15-19 and the system switching device switches the system into a charge system leading to a storage battery 4 via a bidirectional inverter 3 from the commercial power source 1 or a power supply system leading to the load apparatuses 15-19 via the bidirectional inverter 3 from the storage battery 4, the system switching device 2 is provided with a power failure detector 27 which detects the power failure of the commercial power source 1, and it is switched to supply the power of the storage battery 4 only to an emergency plug socket by the command of the power failure detector 27 at the failure of the commercial power.

Electricity storing system and electric power feeding system

Abstract: PROBLEM TO BE SOLVED: To make it possible to easily install an electricity storing system in a solar cell power generating system at low cost later on. SOLUTION: This electricity storing system is connected to a solar cell power generating system provided with a solar cell power converter 2 having an inverter 3 and a control circuit 4 and solar cells 1. This system receives and stores DC electric power from a converter 19 that converts AC electric power at night of a commercial power source 10 into DC electric power. Provided with a secondary battery 13 that feeds the stored electric power to the inverter 3, it also controls the supply of electric power from the secondary battery 13 to the inverter 3 by a control circuit 32.

Isolation type DC-DC power conversion unit and electrical system for an electric vehicle

Abstract: A switch circuit comprising a semiconductor switch and an inverse-parallel diode is connected between a main electricity storage unit 4 and a primary winding 142P of an insulating transformer 142 and a switch circuit including a semiconductor switch and a diode is connected in inverse-parallel between a secondary winding 142S of the insulating transformer 142 and an auxiliary electricity storage unit 10. The switch circuits are controlled on/off, whereby power is supplied from the main electricity storage unit 4 to the auxiliary electricity storage unit 10 or from the auxiliary electricity storage unit 10 to the main electricity storage unit 4 for charging the electricity storage unit 10 or 4.

Reliability-based impact analysis of independent power producers for power system operations under deregulation

Abstract: In this paper, the authors present an evaluation procedure of independent power producers' impact on reliability and associated costs of existing power systems under deregulation. Independent power producers (IPPs) with competitive electricity prices can contribute to the cost reduction of electricity supply under the open access power systems. However, there is a concern that the high standard of power system reliability may not be maintained because of possible failures of such new generators. IPPs' effects on supply reliability are closely related to generation and transmission operation of existing power systems. In the proposed approach, the reliability is measured by expected unserved power (EUP) and the additional cost of reliability maintenance is calculated by the cost of generation adjustment. The optimal redispatch problem is solved with the reliability index as a constraint. Also, a transmission system congestion is considered in the redispatch. Numerical simulations have been conducted on a model system with six nodes and seven branches.

Keeping the lights on [power system reliability]

Abstract: Of all the energy conversion processes in existence, the US electric power system is the largest and most complex. Unlike industries such as communications and transportation, where a demand in excess of supply produces a "busy signal" or temporary grid lock, the nature of the electric power system is one of instantaneously matching supply and demand. Failure to sustain this balancing act can result in partial or complete breakdown of the grid system. In this paper, the authors describe how maintaining reliable electricity grids in a deregulated power industry will become harder, as temptations to cut corners multiply.

Optimal power flow formulation in market of retail wheeling

Abstract: Power system deregulation along with retail wheeling was proposed in legislation for the future power system operation. Retail wheeling implies customers have more choices. One important option is the power supplier providing cheaper power. In this paper, the authors introduce new concepts of generation sets and load sets to model the behavior of power supply and load distribution in the new retail wheeling market. Formation of the optimal power flow (OPF) problem, in which public interests are maximized, is demonstrated. The IEEE-14 bus system is used as an example.

Electricity generation system for use with cryogenic liquid fuels

Abstract: An electricity generation system comprising electrical generation means (34, 35) that generates electricity from cryogenic fuels stored in tank (33). Power electronics system (32) conditions the electrical output of generation means (34, 35) to provide an output having a fixed voltage and frequency. Heat-exchanging means (37, 38) is arranged to cool electrical generator (35) and/or electronics system (32) by absorbing waste heat resulting from the electricity generating process and using this waste heat is to change the phase of the stored fuel to produce a gaseous fuel for use in turbine (34). The efficiency of electronics system (32) is increased by operating at the cryogenic temperatures present during the phase change of the fuel. Electrical generation means (34, 35) may comprise a fuel cell.

Multimode battery energy storage system for custom power applications

Abstract: EPRI and Salt River Project (SRP) have installed a multi-mode transportable battery energy storage system (TBESS) manufactured by Omnion Power Engineering Corporation, as part of a joint tailored collaboration project. The TBESS is capable of operating in both power quality and power management modes. In power quality (PQ) mode, it is capable of protecting the loads up to 2 MW/2 MVA for up to 15 seconds against voltage disturbances including complete outages. In power management (PM) mode, it can deliver 200 kW for 45 minutes, i.e., 150 kWh. The power management modes are, peak shaving, block load discharge, load following, voltage regulation and spinning reserve. TBESS has been under test at an SRP site since August 1997. In addition to the disturbances in the utility distribution system against which TBESS protected the loads during this period, TBESS performance was tested for more than 150 simulated and real outages lasting several seconds. This paper presents mainly the power quality performance results during this test period.

Voltage control in radial systems with dispersed generation

Abstract: After the introduction of the competitive electricity market in many countries, the number of small-size generators connected to the distribution systems is rapidly increasing. This paper analyses the interactions among the voltage control operated in the HV/MV substation and the possible voltage control operated by the dispersed generators connected to the MV nodes of the distribution system. A novel controller of voltage and reactive power of the dispersed generator is proposed. With this controller, when the voltage at the network side remains in an acceptable range, the reactive power generation of the dispersed generator is null with minimum losses for the generator and its transformer; otherwise, the dispersed generator gives an additional contribution to control the voltage of the system. Results showing the effectiveness of the proposed controller are presented for an actual distribution system.