Showing papers on "Stand-alone power system published in 2001"

Steady-State Performance of a Grid-Connected Rooftop Hybrid Wind-Photovoltaic Power System with Battery Storage

Abstract: This paper reports the performance of a 4 kW grid-connected residential wind-photovoltaic system (WPS) with battery storage located In Lowell, MA. The system was originally designed to meet a typical New England (TNE) load demand with a loss of power supply probability (LPSP) of one day in ten years, as recommended by the Utility Company. The data used in the calculation were wind speed and irradiance of Logan Airport Boston (LAB), obtained from the National Climate Center in North Carolina. The present performance study is based on two-year operation (May 1996 to April 1998) of the WPS. Unlike conventional generation, the wind and the sunrays are available at no cost and generate pollution-free electricity. At around noon the WPS satisfies its load and provides additional energy to the storage or to the grid. On-site energy production is undoubtedly accompanied with minimization of environmental pollution, reduction of losses in power systems transmission and distribution equipment, and supports the utility in demand side management (DSM). This paper includes discussions on system reliability, power quality, loss of supply, and effects of the randomness of the wind and the solar radiation on system design.

System and method for enabling the real time buying and selling of electricity generated by fuel cell powered vehicles

Abstract: The present invention relates to a network communication system and method to enable the real time buying and selling of electricity generated by fuel cell powered vehicles between a fuel cell powered vehicle and a consumer. The method comprises: providing connections to the vehicle for the supply of a fuel and for transfer of electricity; determining the current cost of fuel and price paid for generating electricity; based at least on the cost of fuel and price paid for generating electricity, determining whether to make the fuel cell powered vehicle available for generation of electricity; when fuel is consumed by the vehicle and electricity generated by the vehicle, collecting data on the quantity of fuel consumed and amount of electricity generated, calculating the cost of the fuel and the value of the electricity generated, providing a debit charge for the cost of fuel consumed and a credit charge for the value of electricity generated. A method to enable the real time buying and selling of electricity generated by fuel cell powered vehicles between an energy service provider and a consumer of electricity is also disclosed.

Understanding the potential benefits of distributed generation on power delivery systems

Abstract: Distributed generation offers the potential to offset traditional utility investments in distribution, transmission and generation facilities, and improve service to customers. Matching this potential to specific customer needs, and evolving technologies with current economics remains an ongoing challenge. Recent successes have involved strong customer needs, usually of commercial customers, matched to fossil fuel distributed generation systems that meet reliability and economic targets. Many utilities, through its subsidiaries, have been active participants in this marketplace. Distributed generation is starting to expand its reach to address electric utility power delivery needs as a means to offset the cost of system expansion. This paper provides an example method to analyze this potential. It also shows that while power delivery savings can be significant, these must also be matched with additional customer benefits to make distributed generation economical. Also, once the potential fit of the technology and economics is established, a wide range of local and operational issues surface that challenge field implementation.

Power quality issues in a hybrid power system

Abstract: We analyzed a power system network, which consisted of two types of power generation: wind turbine generation and diesel generation. The power quality and the interaction of diesel generation, the wind turbine, and the local load were the subjects of investigation. From an energy-production point of view, it is desirable to have as much wind energy production as possible in order to save fuel consumption of the diesel engines and to reduce the level of pollution. From the customer point of view, it is desirable to have good power quality at the receiving end. The purpose of this paper is to show the impact of wind power plant in the entire system. Also, we discuss how the startup of the wind turbine and the transient condition during load changes affects the voltage and frequency in the system.

Operating conflicts for distributed generation on distribution systems

Abstract: Distribution systems have been designed to optimize the delivery of power in one direction. The installation of distributed generation (DG) in significant capacity will result in some conflicts with the operation of the system. A selected set of conflicts is described. One conflict might result in changes to overcurrent device timing and reach that degrade reliability and power quality for other customers on the feeder. Interconnection requirements can increase the risk of equipment damage due to ferroresonant overvoltages. Transformer connections for DG involve a tradeoff between harmonic current injections, the risk of overvoltages, protective device coordination, and transformer life. The paper also addresses voltage regulation issues that often arise from the application of DG on distribution systems.

Power reserve in interconnected systems with high wind power production

Abstract: A capacity of installed wind power of 40 GW in Europe, control areas with a wind power production exceeding the maximum load-these are serious plans that may come true in several years. Due to the high fluctuations and the limited predictability of wind power, this development will cause a severe change in the demands on the power reserve. Therefore, this paper introduces an investigation that quantifies the technical consequences of the increasing wind power in Europe on the primary, secondary, and long-term reserve.

Power control of a photovoltaic array in a hybrid electric generation system using sliding mode techniques

Abstract: A variable structure controller to regulate the output power of a standalone hybrid generation system is presented. The system comprises photovoltaic and wind generation, a storage battery bank and a variable monophasic load. The control law admits two modes of operation. The first takes place when the insolation regime is sufficient to satisfy the power demand. The second mode of operation takes place under insufficient insolation regimes. The latter leads the system operation at the maximum power operation point to save as much stored energy as possible. A new method based on the IncCond algorithm is developed. Sliding mode control techniques are used to design the control law. These techniques provide a simple control law design framework and contribute with their well known robustness properties. Finally, guidelines based on chattering considerations are given for the design of the practical system.

Power storage device and method of measuring voltage of storage battery

Abstract: A power storage device has a plurality of series-connected storage battery units, battery circuits associated with the storage battery units to control or monitor the storage battery units, respectively; a main circuit of a potential level different from that of the battery circuits; and a potential level changing circuits connecting the battery circuit to the main circuit. The power storage unit is small in construction and operates at a low power consumption in a high control accuracy.

Power system stabilization system and method employing a rechargeable battery system

Abstract: A power system stabilization system is provided between power generation equipment significantly fluctuating in output and a power system required to maintain a predetermined voltage. In the power system stabilization system, a voltage detection device and a current detection device detect voltage and current, respectively, of the power system and voltage and current thus detected are used to calculate a level of active power required and that of reactive power required which are referred to to provide charging and discharging from a rechargeable battery to the power system via an A-D converter.

Zero/low emission and co-production energy supply station

Abstract: The trend in personal and light commercial transportation vehicle choices is heading toward electric or fuel cell vehicles capable of zero emission. Their demand for electricity to re-charge batteries or hydrogen to operate fuel cells can best be met by variable onsite production of electricity and hydrogen from conventional transportation fuel by an on-site energy supply system employing a conversion device. This approach can result in minimum changes in the present day infrastructure of the automobile and truck service station industry and can avoid any disturbances to the normal operation of the electric power industry. The onsite hydrogen/electricity hybrid conversion device is a reformer and/or a fuel cell. The output of the system can be varied to either meet the demand of hydrogen fuel for fuel cell vehicles or to provide electricity for charging batteries used on the electrical vehicles. The onsite distributed energy supply system utilizing a high temperature solid oxide fuel cell system for electric generation and an integral steam reforming system for hydrogen production are the most desirable approaches. One such energy supply system allows the total CO 2 capture for sequestration or commercial uses, while concomitantly providing for high system efficiency and full system utilization. The CO 2 collection feature promotes the commercial realization of zero/low emission energy supply for onsite installations.

Novel inverter topologies for single-phase stand-alone or grid-connected photovoltaic systems

Abstract: Photovoltaic and battery systems often operate in small stand-alone or grid-connected applications, where the generator voltage is lower than the grid voltage. To boost the voltage up to the grid level a further element, either a DC/DC converter or 50 Hz transformer, is connected in series with a PWM inverter. To reduce the high cost of such low power systems, the costs of the power electronics should be minimized. In this paper, several new low-cost inverters with and without HF-transformers are presented. Simulation and experimental results of their operation and control for stand-alone as well for grid-connected applications are discussed.

Hydro-electric generating system

Abstract: A hydro-electric generating system for generating electrical energy and storing kinetic energy, in which, the process begins with the top reservoir filled with water directly from a river or local utility via a conduit. Then a multi megawatt wind turbine, such as the NEG micon 2-megawatt turbine, placed at heights, on the side of the structure that have never been reached with a man made mast or tower. The mega structure along with the extreme heights of this system will achieve increased wind shear on a high average. The wind turbine is secured to a cart for movement of the cart and the wind turbine. The wind turbine can move to locations along a track relative to wind direction. The wind turbine is the means to power the second pump. The second pump constantly replenishes the upper reservoir with water. The wind turbine produces more electricity than what the second pump requires. This surplus of electricity is sent, via electrical conductors to the regional power grid, which distributes power to cities and towns. The hydroelectric generator/pump, reversible, now has the kinetic energy above that is necessary to turn it's rotor blades and generate megawatts of electricity. This electricity is also sent to the electrical grid system via the electrical conductors. The hydro-electric generator/pump, which is reversible, is also used to replenish the upper reservoir. When back fed with electricity from the regional grid system or the wind turbine. The hydro-electric generator/pump, reverses and functions as a mega pump. This is efficient during off peak periods, when electricity is in less demand and, sold at a lower rate The water that is stored during off peak is released from the upper reservoir during peak periods. The water will flow down the conduit to the hydro-electric generator producing electricity in the greatly needed peak periods, this cycle is repeated as often as necessary.

Power quality issues-a distribution company perspective

Abstract: Scottish Power supplies electricity to a customer base of three million in the south of Scotland and Manweb. A high proportion of the manufacturing and process industries in Scotland are involved in semiconductor production, requiring a consistent and high quality power supply. The quality of supply is therefore important to both customers and Scottish Power in terms of attracting and keeping new industry and business. This paper discusses why power quality is such an important issue and then discusses Scottish Power's company strategy to improve power quality. The strategy is chiefly based on the classification of voltage dips as a quality of supply indicator. The voltage dips are detected by digital fault recorders (DFRs) installed across the Scottish Power distribution system. This strategy enables Scottish Power to provide industrial and commercial customers with tangible system performance reporting and feedback. This method of network assessment also promotes practical dialogue between Scottish Power and the customer during the specification of new customer loads to ensure that the subsequent load characteristics do not degrade the performance of the load or the network. Two case studies are examined.

System-interconnected power system

Abstract: PROBLEM TO BE SOLVED: To sell superfluous part of photovoltaically generated power, and to try not to sell power stored in a power storage system, in a combined system of photovoltaic power generation and power storage, and to suppress system power peak with high precision by discharge from the power storage system, even when it is combined with the photovoltaic power generation. SOLUTION: This system-interconnected power system has a means for inputting power generated by a solar battery, a power storage means for storing the power of a power system or the generated power of the solar battery, a means for storing power in this power storage means by charging, a means for discharging power from the power storage means, a means for converting the power of the solar battery or power storage means into AC power and outputting it to the power system, or a means for inputting the AC power from the power system, and a means for detecting power system side power. In the power system, the generated power of the solar battery is supplied to a load, or is stored in the power storage means through charging. When the load power is smaller than the power by the photovoltaic power generation, generated power is sold to a power system, and power stored in the power storage means is discharged, so that the power of the power system will not exceed a specified value.

A method for determining the introduction limit of distributed generation system in distribution system

Abstract: This paper describes a new method for determining the introduction limit of DGS (distributed generation system) when DGS is introduced into distribution system of which the voltage is generally controlled by LCT (load-tap changing transformer) and LDC (line drop compensator). Nowadays, small scale DGS is being introduced into power distribution systems. But in that case, it is difficult to properly maintain the terminal voltage of low voltage customers within a permissible range. This paper reveals some correlations between the traditional voltage regulation method by LCT and LDC and the output of DGS, and also presents a method for determining the permissible introduction limit of DGS under proper voltage regulation of the power distribution system. This proposed method is applied to a 22.9 kV class power distribution system, and its validity is proofed through the simulation results.

Nodal probabilistic congestion and reliability evaluations of a transmission system under the deregulated electricity market

Abstract: This paper presents a method for evaluating nodal probabilistic congestion and reliability indices of transmission systems. Quantitative evaluation of transmission system reliability is very important because successful operation of an electric power system in the deregulated electricity market depends on transmission system reliability management. The key point is that the reliability level of the transmission system is equal to the reliability level difference between the composite power system (HLH) and the generation system (HLI). Risk indices of a composite power systems are larger than those of the generation system as the composite power systems include uncertainties and capacity limits of the transmission lines. The characteristics and effectiveness of this methodology are illustrated by the case study using a small test system.

Solar power generation system having storage battery

Abstract: PROBLEM TO BE SOLVED: To provide an optimum system which can reduce peak power demand, using a small storage battery. SOLUTION: A solar power generation system, which is linked to a power system, supplies the power generated at a solar cell device to an inverter device for conversion to alternating current, and feeds it to a power consumption part, comprises a storage battery to charge power from the solar cell device, and a changeover control means to output the power from the solar cell device to the storage battery or to the inverter device upon changing over; and supplies the power to the inverter device in addition to generated energy from the solar cell device, by controlling to charge the storage battery with one or more of power selected from the generated power by the solar cell device during off-peak time of power demand after sun rising or power from the power system during night time, and by controlling discharge of energy stored in the storage battery corresponding to a fluctuation curve of the power demand in a particular time zone the power demand is high.

Auxiliary battery for portable devices

Abstract: An auxiliary battery for portable devices that can be used for a variety of applications with high power capacity The auxiliary battery includes a power input section for receiving electric power from an external power source, a power storage section having a secondary battery for receiving a charge current from the power input section, a power output section having one or more output terminals for producing electric power at output terminals, and an power switch circuit for selectively inputting electric power to the power output section either from the power input section or from the power storage section

Role of distributed generation in reinforcing the critical electric power infrastructure

Abstract: Distributed generation has the potential to improve the security of the electric power infkwtructure in many ways, includ~ the possibility of deliberate operation of the powel grid in small islands centered around critical installations. Once the effects of disturbances (random or intentional) are isolated to an island or two, existing technology could then be used to track down and eliminate the source of the disturbance. Such a scenario will require the development of a control and command infkstructure around critical installations to sense the presence of a disturbancedattack in any fo~ initiate the iskmding process, and start distributed generators as needed to maintain acceptable operational levels.

Power wheeling pricing using power tracing and MVA-KM method

Abstract: This paper introduces a new wheeling pricing technique called the MVA-KM method, which applies AC power flow and considers apparent power. A technique of buses sorting with ordering is incorporated with the proportional sharing principle and the upstream looking algorithm to trace the flow of electricity. An application example is illustrated. Computational results obtained by applying the proposed MVA-KM method are compared with that applying the MW-MILE method.

Implementation of nonuniform reliability in a deregulated power market

Abstract: Power system deregulation has introduced some fundamental problems regarding system security and customer reliability. This paper presents some reliability models for different market players in an arbitrary power market. A generation system is represented by an equivalent multi-state generation provider and a transmission system is represented by an equivalent multistate transmission provider. The parameters of the equivalent service providers are determined using reliability network equivalent techniques. The determination and implementation of nonuniform reliability are illustrated. A test system is used to illustrate the application of these techniques.

Uninterruptible power supply system having an NiMH or Li-ion battery

Abstract: An uniterruptible power supply (UPS) system that includes one or more NiMH or Li-ion batteries is provided. In one general aspect, the invention features a power supply system including a power input to receive input power from a power source, a power output to provide output power to a load, at least one NiMH or Li-ion battery having a battery output that provides battery power, at least one power module coupled to the power input to receive the input power, coupled to the battery output to receive the battery power and coupled to the power output to provide the output power, a controller, coupled to the at least one power module, constructed and arranged to monitor and control the output power from the at least one power module. A UPS system using a NiMH or Li-ion battery typically uses less space and weigh less than a UPS having a lead acid battery. Additionally, NiMH and Li-ion batteries perform better at temperature extremes than do comparable lead acid batteries.

Compressed air power supply/rechargeable battery pack

Abstract: A self-charging continuous EOT power supply/battery pack operates from excess air pressure available in a train's air system. An electric generator is driven by compressed air from the locomotive that is transmitted through the air brake system of the train. The generated electricity is input to a circuit card assembly that regulates the output voltage and generator speed. The regulated voltage is supplied to the EOT electronics and also to a storage battery to recharge the storage battery, which provides peak operating power as well as back-up power if the generating system is inoperable.

The scope for energy saving in the EU through the use of energy-efficient electricity distribution transformers

Abstract: The scope for saving energy in the EU through the use of energy-efficient distribution transformers, has been estimated at 22 TWh/year, worth 942 million Euros at 1999 prices. Despite the efficiency of individual units, up to 2% of total electricity generated is estimated to be lost in distribution transformers, nearly one-third of the overall losses from the transmission and distribution system. This is comparable in scope with the energy savings potential estimated for electric motors and classes of domestic appliances. It is equivalent to the annual energy consumption of 6 million homes, or the electricity produced by three nuclear power stations in Europe. Because of the long life span of distribution transformers, ultimate market penetration will only be achieved gradually. Despite this, the authors estimate that energy-efficient units could contribute 7 TWh of savings by 2010, representing 1% of the European commitment to reducing carbon emissions.

Potable charging system unit for electric vehicle

Abstract: PROBLEM TO BE SOLVED: To provide a potable charging system unit for an electric vehicle which is capable of charging electricity to the electric vehicle, using electricity obtained by solar power and wind power and is capable of being moved easily SOLUTION: The potable charging system unit for an electric vehicle is equipped with a structure 4 comprises a floor 1, a roof 3 supported by a support 2 standing on the floor 1, solar power cell modules 5 installed on the roof 3, a wind power generator 7 installed on a pole 6 provided in a protruding position upward from the structure 4, a battery charges power generated by the solar power cell modules 5 and the wind power generator, and a charging stand 8 which supplies the electric vehicle with electricity for charging