Showing papers on "Stand-alone power system published in 2003"

A novel high-performance utility-interactive photovoltaic inverter system

Abstract: This paper presents a novel photovoltaic inverter that cannot only synchronize a sinusoidal AC output current with a utility line voltage, but also control the power generation of each photovoltaic module in an array. The proposed inverter system is composed of a half-bridge inverter at the utility interface and a novel generation control circuit which compensates for reductions in the output power of the system that are attributable to variations in the generation conditions of respective photovoltaic modules. The generation control circuit allows each photovoltaic module to operate independently at peak capacity, simply by detecting the output power of the system. Furthermore, the generation control circuit attenuates low-frequency ripple voltage, which is caused by the half-bridge inverter, across the photovoltaic modules. Consequently, the output power of the system is increased due to the increase in average power generated by the photovoltaic modules. The effectiveness of the proposed inverter system is confirmed experimentally and by means of simulation.

Method and device for controlling photovoltaic inverter, and feed water device

Abstract: A photovoltaic inverter control method includes steps of monitoring a variation in output voltage of a solar battery by a power and voltage monitoring circuit (51) and, when the variation occurs, accelerating or decelerating an electric motor (3) to maximize the output voltage of the solar battery (1), whereby the electric motor for driving, for example, a pump and a fan by the solar battery as a power source can be driven by a photovoltaic inverter always at the maximum power point of the solar battery.

Power control interface between a wind farm and a power transmission system

Abstract: A power control interface between an unstable power source such as a wind farm and a power transmission line employs an Electrical Energy Storage, Control System, and Electronic Compensation Module which act together like an 'electronic shock absorber' for storing excess power during periods of increased power generation and releasing stored energy during periods of decreased power generation due to wind fluctuations. The Control System is provided with a 'look ahead' capability for predicting power output (wind speed conditions) and maintaining energy storage or release over a 'narrow-band' range despite short duration fluctuations. The Control System uses data derived from monitoring the wind farm power output and the power transmission line, and employs system-modeling algorithms to predict narrow-band wind speed conditions. The power control interface can also use its energy storage capacity to provide voltage support at the point of injection into the power transmission system, as well as fault clearance capability for 'riding out' transient fault conditions occurring on the power transmission line.

Reliability evaluation of small stand-alone wind energy conversion systems using a time series simulation model

Abstract: A time series simulation model for the reliability evaluation of small stand-alone wind energy conversion systems (SSWECS) containing battery storages is presented. The performance of such a system is quite different from one containing conventional generating units due to the dispersed nature of the wind at the specific site location. The reliability of a SSWECS depends on various factors such as the reserve margin, the battery size and charging (discharging) characteristics, the wind speed, the wind turbine generator's failure/repair characteristics and power ratings, the system load profile and the system operating philosophy. The results and discussions presented should prove useful in planning, designing, and operating small stand-alone wind energy conversion systems for electricity supply in remote areas.

Is the answer blowing in the wind

Abstract: Wind power is the most rapidly growing technology for renewable power generation. However, fundamental differences exist between conventional thermal, hydro, and nuclear generation and wind power. These differences are reflected in the specific interaction of wind turbines with the power system. Further, there are differences between the various wind turbine types, which also affect their system interaction. In this article, first the current status and the technology of wind power are briefly discussed. The general working principles are explained and the different wind turbine types are described. Then, the differences between wind power and conventional power generation are highlighted as well as their consequences for interaction with the power system, both locally and on a system level.

Voltage recovery of grid-connected wind turbines after a short-circuit fault

Abstract: A simulation model of a MW-level wind turbine with dynamic slip control and pitch control is developed in the simulation tool of PSCAD/EMTDC and stability investigations are carried out with respect to a short circuit fault in the external power system. After the fault has been cleared, the voltage at the wind turbine terminal has to be re-established, and the wind turbine should restore its normal operating condition. Controlling the generator slip and pitch angle can adjust the electromagnetic torque and the aerodynamic torque of wind turbine, which helps to rebuild the voltage at the wind turbine terminal. Simulation results prove that dynamic slip control and pitch control are effective methods to improve the voltage and maintain power system stability.

Boosting immunity to blackouts

Abstract: There have been several key developments that make it conceivable that it would soon be possible to reduce the frequency and intensity of interconnected power system failures. System protection is one of the technologies undergoing radical changes that holds a strong promise that cascading system outages can be mitigated or even eliminated. The increasing use of digital relays that will allow the implementation of exciting new concepts has made this a strong possibility. In this article, we report on future concepts in power system protection, communication, wide area measurement systems (WAMS), system control, and electricity market considerations, Adding a summary of our own research in associated studies and our assessment of future investigations, our aim is to provide a blueprint for a secure power system infrastructure.

Steady as she blows [wind power, energy storage]

Abstract: Power electronics and exotic energy storage devices are making wind power steady enough to compete with conventional electricity sources. Systems based on advanced power electronics and energy storage devices are massaging and managing power flows from wind turbines, enabling them to contribute to electricity grids without putting those grids at risk. Not only are the technologies making wind power more palatable to grid operators, they are even making it possible for engineers to finally harness wind energy's tremendous potential in wind-swept, remote locales. This article discusses the power electronic and energy storage technologies used in wind power.

Excess electricity diagrams and the integration of renewable energy

Abstract: This article presents a methodology of showing the rate of integration of specific renewable energy sources (RESs) into the electricity supply system. The methodology is used on large-scale integration of wind, photo voltaic and wave power into a future Danish reference energy system. The possibility of integrating RES into the electricity supply is expressed in terms of the ability to avoid excess electricity production. The different sources are analysed in the range of an electricity production from 0 to 100% of the electricity demand. The excess production is found from detailed energy system analyses on the computer model EnergyPLAN. The analyses have taken into account that certain ancillary services are needed in order to secure the electricity supply system. The conclusion is that different patterns of each of the RES can be shown in terms of excess electricity diagrams. Such diagrams do not differ from one year to another, but do differ from one RES to another.

Hybrid power system with a controlled energy storage

Abstract: We investigated a small isolated hybrid power system that used two types of power generation; wind turbine and diesel generation. The interaction of diesel generation, the wind turbine, and the local load is complicated because both the load and the wind turbine fluctuate during the day. These fluctuations create imbalances in power distribution (energy sources are not equal to energy sinks) that can affect the frequency and the voltage in the power system. The addition of energy storage will help balance the distribution of power in the power network. For this paper, we studied the interaction among hybrid power system components and the relative size of the components. We also show how the contribution of wind energy affects the entire power system and distribution and the role of energy storage under the transient conditions caused by load changes and wind turbine start ups.

B#: a battery emulator and power profiling instrument

Abstract: This paper describes B# (B-sharp), a programmable power supply that emulates the behavior of a battery. It measures the current load, calls a battery simulation program to compute the voltage in real time, and controls a linear regulator to mimic the voltage output of a battery. This instrument enables validation of battery-aware power-optimization techniques with accurate, controllable, reproducible results. This instrument also supports training mode with actual batteries, and it can even be used for recording and playback of a solar power source. This design has been prototyped and tested on hand-held devices with high accuracy and fast response time.

Frequency control on an island power system with increasing proportions of combined cycle gas turbines

Abstract: As combined cycle gas turbines (CCGT) comprise an ever-increasing proportion of generating capacity on an island electricity system, the importance of understanding the effects of their characteristic behaviour on the system, particularly on frequency control, becomes crucial. A suitable mathematical model of a CCGT is developed to study its response following a frequency disturbance. This model is then integrated into a larger model, representative of the Irish electricity system, and the effects of increasing proportions of CCGT generation are examined. The results of this study are then considered in conjunction with the impact of increased amounts of wind power and of interconnection via HVDC to a larger system.

Stand-alone photovoltaic energy storage system with maximum power point tracking

Abstract: This digests deals with the study of a stand-alone photovoltaic system, which is able to extract the maximum power from photovoltaic array for all solar intensity conditions and to provide output voltage regulation. The proposed system consists of a DC-DC converter in combination with battery energy storage in a simple structure. Operating principle and control strategy are described. Digital simulation is included, supporting the validity of the concept.

Optimized Hydrogen and Electricity Generation from Wind

Abstract: Several optimizations can be employed to create hydrogen or hydrogen and electricity from a wind energy source. The key element in hydrogen production from any electrical source is an electrolyzer to convert water and electricity into hydrogen and oxygen. Modern wind turbines employ a control system used in conjunction with power electronics in order to connect to the grid. It may be possible to use the turbine's controller and power electronics system to operate the electrolyzer as well, thereby eliminating component duplication. Such a coupled system would reduce the overall cost of independent stand-alone systems. Electrical power provided to the electrolyzer in such a system would be controllable with excess power provided to the grid. Thus, a combined system would have more dispatchability than a wind-electric turbine alone. Such dispatchability might be used to provide the utility with a measure of control over the wind farm's total output that does not exist in current wind farms. Produced hydrogen needs to be stored, transported, and/or regenerated into electricity offering additional synergies. This paper examines several coupled systems that offer enhanced capability, efficiency, and cost reduction opportunities over stand-alone component systems.

System for the co-production of electricity and hydrogen

Abstract: Described herein is a system for the co-generation of hydrogen gas and electricity, wherein the proportion of hydrogen to electricity can be adjusted from 0% to 100%. The system integrates fuel cell technology for power generation with fuel-assisted steam-electrolysis. A hydrocarbon fuel, a reformed hydrocarbon fuel, or a partially reformed hydrocarbon fuel can be fed into the system.

DER Benefits Analysis Studies: Final Report

Abstract: The electric power industry in the United States is undergoing dramatic change. Once totally controlled by utilities that had monopolistic holds on the supply, transmission and distribution of electricity in their service areas, the electric power system is being deregulated, introducing competition among electricity providers who can distinguish themselves by price, services and other factors. The new electric power system will feature advanced technologies and services that can be used on-site or located in close proximity to the load, instead of depending solely upon large, central station generation and transmission. Using a variety of advanced modular generating technologies (including small-scale renewables), distributed energy resource (DER) plants supply base-load power, peaking power, backup power, remote power and/or heating and cooling, and in some cases supply higher and more reliable quality power. Currently, DER represent a minor part of the electric supply system. If the potential of DER is to be realized in the new electric power market, a full understanding of the value and benefits these technologies provide to the electric system is necessary. This report includes 30 key quantitative studies reporting on the values and benefits of distributed energy generation technologies (including renewables) in various applications, as well as amore » matrix that permits key comparisons.« less

Backup method for inverter dc power supply in elevator, and device for the method

Abstract: PROBLEM TO BE SOLVED: To provide an emergency power device that feeds power to an inverter only at a power failure and performs battery charging, when receiving commercial power for surely conducting long-time operation at power failure, and to provide a control method for the device. SOLUTION: There is provided a device for operating power at a power failure that estimates and operates inverter power consumption at the time of the power failure from an electrolytic capacitor capacity and an hourly descending amount of a DC bus bar voltage; and a discharging current initial value is calculated from the estimated power value and a battery voltage and used as an initial current command value at the start of discharge control, thus making a battery constantly charged, when an inverter power supply is in normal state, so that the battery is maintained in a full charged state. COPYRIGHT: (C)2005,JPO&NCIPI

Operation of Hybrid Wind-Turbine Compressed-Air System for Connection to Electric Grid Networks and Cogeneration

Abstract: This paper describes a storage system that uses wind energy to compress air in a series of high-pressure storage tanks. When needed, the compressed air is expanded through a turbo-expander to generate electricity. The system is designed for the storage of wind energy and utilises above-ground compressed-air storage with 8,278 kPa (1,200-psia) tanks. It is applicable in the operational power region between (1) electrical storage batteries for relatively small peak power and (2) large pressurized underground salt caverns for large peak power. Therefore, it is most economic for between 0.5 and 100 Megawatt electric power systems. The key advantages over these other storage methods are that there is no need to either purchase, maintain and dispose of waste chemicals, or locate large underground caverns. In addition to supplying electrical power, the by-product heat may be utilised as cogeneration. For instance, the multi-stage compressor coolant may heat domestic water and the cooled exhaust air from the turb...

Evaluating Influence of Power Output Fluctuation of Photovoltaic Power Generation Systems on LFC based on Multiple Observation of Insolation

Abstract: A large-scale installation of a photovoltaic power generation system (PV system) may cause some diculties in the operation of electric power systems. Taking into account a smoothing effect of power outputs of PV systems by dispersed installation, this paper discusses the LFC (Load Frequency Control) capacity for power output fluctuation of PV systems based on the insolation data simultaneously observed at 5 points around Nagoya, Japan. The main results are (1) the frequency deviation might not exceed the tolerance (0.05Hz)when the installed PV system is 2% of system capacity, which is Japan’s target value toward 2010, (2) when the larger capacity of PV system is installed, the frequency deviation would be larger than 0.05Hz, and the capacity of LFC generator must be increased, (3) the frequency deviation due to the installation of PV system might be larger in holiday with smaller electricity demand than in weekday.

Maximising distributed generation capacity in deregulated markets

Abstract: The capacity of distributed generation (DG) is set to increase significantly with much of the plant connecting to distribution networks. This paper briefly reviews the technical problems associated with the connection of DG plant at distribution-level and the mitigation strategies currently available. Further it examines the shortcomings of current connection practice in terms of the potential for inadvertently limiting network capability in absorbing new DG. Finally, it demonstrates the use of optimal power flow with a technique that could facilitate maximisation of renewable generation capacity in the deregulated electricity market.

Stand-alone hybrid power supply system composed of wind turbines and photovoltaic modules for powering radio relay stations

Abstract: In this paper, we describe a simulation method and the fundamental construction of a stand-alone hybrid power supply system composed of wind turbines and photovoltaic modules. The system has been developed to supply power for telecommunications equipment in areas with no commercial power source. We also report on a comparison of simulation results with actual measured ones. We found that the developed hybrid system is effective as a power supply for telecommunications equipment.

Flexible energy systems: integration of electricity production from CHP and fluctuating renewable energy

Abstract: Renewable energy sources and distributed generation play a crucial role in supporting the European Union's key policy objectives of combating the greenhouse effect. In order to bring about a substantial long-term penetration of distributed energy resources in Europe, one of the most important future challenges seems to be the management of the integration of fluctuations in electricity production from renewable energy sources and CHP. In Denmark approximately 15%; of electricity demand is produced by wind power, and approximately 50%; by CHP, and both technologies are intended for further expansion in the coming decades. Even now the high percentage of wind and CHP causes problems, and based on the existing energy system with large steam-turbine plants, it has been estimated that Denmark, in the year 2030, will be forced to produce approximately 45%; more electricity than needed simply because of regulation problems, i.e. problems of producing electricity in accordance with fluctuations in demand. This paper discusses and analyses different national strategies for solving this problem and points out key changes in the energy system in order to achieve a system which can benefit from a high percentage of wind and CHP without having surplus production problems, introduced here as a flexible energy system.

Power supply method

Abstract: PROBLEM TO BE SOLVED: To eliminate the use of a terminal in each house at the time of photovoltaic power generation and wind power generation, and enable the accurate prediction of a power generation amount based on climate information for each region for predicting the power generation amount for each region by means of the photovoltaic power generation and the wind power generation at a previous day and real time, by collecting climate information regarding sunshine and a wind force, and calculating an over-and-short power supply amount for each region at the previous day and the real time to indicate over-and-short electric energy for a power supply method for supplying power generated by using natural energy. SOLUTION: This method has a step for predicting natural energy for each region based on the climate information, a step for predicting a power generation amount by the power generation facility by taking a power generation facility in the region out of a prepared table based on the predicted natural energy, and a step for indicating a power generation amount predicted for each region. COPYRIGHT: (C)2005,JPO&NCIPI

The Generation of Electricity

Abstract: This chapter contains sections titled: The Development of Water Power, The French Turbine, American Experiments, The Centrifugal Pump, The Steam Turbine, The Parsons Steam Turbine, The Turbine and Electric Power, Developments in Lighting, Ferranti and High Pressure Current, The Sophistication of the Steam Turbine, The Liberator of New Materials, The Revolution in Transport, The Slow Adoption of Electrical Power in England

Application of emergency and standby generation for distributed generation. I. Concepts and hypotheses

Abstract: Experience has shown that the demand for electricity imposes excessive peaks for short periods of time. On a yearly basis, these "needle peaks" exist for less than 200 h cumulatively. However, meeting them has produced excessively high costs of electric energy or rolling blackouts when the additional energy was not available. A viable alternative to this excessive cost or blackout is the use of installed emergency and standby capacity for these short intervals of time. To meet the challenges of orchestrating a safe and acceptable interface of the varied power sources, utility companies and state regulators are struggling with the development of suitable interconnect requirements. While there are different strategies for bringing this installed base into service during such periods, this discussion centers on those issues concerned with the parallel operation and interconnection of emergency and standby synchronous generation resources with the electric power system.