UPS and downs

The latest annual report on distribution and transmission system performance from the Office of Electricity Regulation presents a reasonably cheerful picture to the electricity consumer in general. But it also throws into sharper focus the risks that businesses run if they fail to provide uninterruptible power support for their computer installations. The author describes how, nevertheless, many companies still run that risk. Many computer systems are more vulnerable to power-related problems now than ever before. If ever there was a time for companies to look at their power back-up strategy, it is now     

智能区域用电安全公共综合服务系统

随着电能的广泛应用,用电负荷越来越大。为保证用户安全用电,文中设计了一种基于分布式网络的综合服务系统。通过实时监测、分析和预测配电系统的运行状况,及时调度维护服务从而实现预知维护,进而缩短故障停电时间,提高用电安全性,同时也降低了配电系统的维护成本。     

Assimilating wind [wind energy contribution to UK energy needs]

The belief that wind energy can make only a marginal contribution to the UK's energy needs is based on fundamental misconceptions. The DTI suggests that up to half of the 2010 target for renewable electricity (10%) could be met by wind energy. The British Wind Energy Association argues that this is quite feasible and has carried out a detailed analysis, suggesting possible regional distributions. The industry struggles, however, to overcome misconceptions. 'What happens when the wind stops blowing?' is a frequent question, and even power engineers suggest-quite erroneously-that thermal plant must be held in readiness to pick up any reductions in output. It is also argued that electricity distribution systems, designed to cope with power flows from central power stations, cannot easily cope with power from wind farms flowing in the opposite direction. Although this may be true in some locations, wind is no different from any other form of generation-welcome in some locations, but more difficult to assimilate in others. Experience in Denmark suggests such problems can be overcome, with wind now accounting for more than a third of the generation capacity in Jutland. This paper discusses the issues and involved in overcoming the misconceptions. No matter how strong the engineering argument for wind energy, as with any other energy option, wind power will only be deployed on a significant scale if it can generate electricity at a cost comparable to alternative forms of generation technology. The latest figures suggest that wind is more than equal to this challenge     

Impact of Security on Power Systems Operation

This paper reviews the status of security analyses in vertically integrated utilities and discusses the impact of system security on the operation and the planning of restructured power systems. The paper is focused on the static security rather than the dynamic security of power systems. The paper also discusses assumptions, functions, and calculation tools that are considered for satisfying power systems security requirements. In addition, the security coordination among time-based scheduling models is presented. In particular, real-time security analysis, short-term operation,midterm operation planning, and long-term planning are analyzed. The paper highlights issues and challenges for implementing security options in electricity markets and concludes that global analyses of security options could provide additional opportunities for seeking optimal and feasible schedules in various time scales.     

Ultracompact pulsed power

Now more than ever, the pulsed power field is driven by size, weight, and volume constraints. In both the military and commercial arenas, there is an overwhelming need to provide more and more capability in ever smaller and lighter packages. The need for higher energy density, power density, reliability, and efficiency is driving progress in the field. This paper provides a review of the state of the art in various types of pulsed power components such as solid-state switches, capacitors, and power sources. In some cases, familiar components such as switch tubes are being replaced with whole new classes of devices. Batteries are being replaced by hydrocarbon or hydrogen-fueled mechanical systems that alter our paradigm for prime power sources. Trends over the past few years and future possibilities for ultracompact systems are discussed, including advanced techniques for heat removal and energy recovery. Finally, a few practical examples of ultracompact systems are given, emphasizing peak power and peak power density.     

Experience with solar home systems in developing countries: a review

Solar energy is widely perceived as a promising technology for electricity generation in remote locations in developing countries. It is estimated that 1.3 million solar home systems had been installed by early 2000. An estimated one‐third of installed systems were backed by foreign donor support in government programmes and two‐thirds supplied by commercial dealers. The estimated growth in the deployment of solar lanterns is less than for SHS. One out of every 100 households that gain access to electricity in developing countries uses solar power. In spite of these successes, doubts have arisen about the effectiveness and suitability of small PV systems for rural development. Many organisational, financial and technical problems appear to present difficulties. A literature survey has been conducted to make an inventory of experience with solar PV applications for households in developing countries. The main finding is that an adequate service infrastructure is required to make projects viable. Household choice in system sizes is often too restricted in donor‐funded projects. Smaller systems sold for cash can be a good alternative to credit systems by offering to increased affordability. Gaps in existing knowledge have been identified, which could be overcome by field monitoring programmes. Copyright © 2001 John Wiley & Sons, Ltd.     

Coupling PV and CAES power plants to transform intermittent PV electricity into a dispatchable electricity source

This study investigates the transformation of photovoltaic (PV) electricity production from an intermittent into a dispatchable source of electricity by coupling PV plants to compressed air energy storage (CAES) gas turbine power plants. Based on historical solar irradiation data for the United States' south western states and actual PV and CAES performance data, we show that the large‐scale adoption of coupled PV–CAES power plants will likely enable peak electricity generation in 2020 at costs equal to or lower than those from natural gas power plants with or without carbon capture and storage systems. Our findings also suggest that given the societal value of reducing carbon dioxide and the sensitivity of conventional generation to rising fossil fuel prices, this competitive crossover point may occur much sooner. Copyright © 2008 John Wiley & Sons, Ltd.     

A Power Plant for the Home

The use of energy in American homes is still being developed for better efficiency. The idea of having a power plant in your home's basement instead is a consideration. Combined heat and power (CHP) systems can utilize up to 90 percent of a fossil fuel's energy by simultaneously generating heat and electricity on-site, reducing energy consumption and slashing utility bills. Such systems already power several buildings and they are widely used for district heating in other countries. This paper discusses the idea of having your basement furnace generate electricity to the point that it can power and heat individual homes. This is achieved by the use of a micro-CHP unit     

压电直流无线能量传输系统研究

在很多工程应用中存在工作于密闭金属容器内的电子器件或系统,为对其进行电能供应并与之进行数据交互,传统的方法多是对容器做物理穿透。阐述了一种无线的方法,利用压电换能器产生和接收超声波,穿透金属进行能量传输,这样就保证了容器物理结构的完整性,从而较传统方法具有稳定性好、安全性高、维护成本低等优点。讨论了双端口阻抗匹配的方法,系统的硬件设计和构成,并给出了系统的实际性能测试结果。测试证明,穿透15 mm厚的钢板,系统可以稳定传输最大5 W的直流能量,最高传输效率约为16.6%,并仍有可提升的空间。     

Mini CHP systems-a small price to pay for bigger profits

The use of combined heat and power systems in the UK has traditionally lagged behind that in the United States and the rest of Europe-to some extent due to legislation and to the attitude of the gas and electricity authorities. The 1983 Energy Act created a measure of freedom in the UK so far as electricity was concerned, in that any generator of electricity can contract to sell power to the local network and indeed can use the local network to pass power from one part of the country to another. A company taking advantage of the new situation is Combined Power Systems Ltd. It has developed a neat packaged customer-friendly and yet very sophisticated combined heat and power (cogeneration) set which provides substantial energy savings for the user     

Power education at the crossroads

To meet the demands of designing and running far more complex and highly integrated electricity systems, a new kind of power engineer is needed. In this paper, the author describes how, though students tend to favor higher-tech and more lucrative fields than power engineering, reports of the discipline's demise are exaggerated     

Interaction between photovoltaic distributed generation and electricity networks

Electricity power systems worldwide have traditionally been designed to a vertically connected scheme characterised by centralised generation. Over the last few decades, several factors have dictated a gradual shift from the central‐control approach to a more distributed layout where distributed generation (DG) technologies are effectively integrated and not just connected (appended) to the networks; amongst others liberalisation of electricity markets, security and quality of supply and environmental issues. Photovoltaic powered distributed generation (PV‐DG), although still having a much lesser impact than other DG technologies, is increasingly being embedded into electricity distribution networks worldwide within the framework of successful regulatory state and marketing programmes. PV‐DG has added values (benefits) for the electricity systems that extend from peak power and load reduction (when deployed close to electricity consumption points) to participation in grid‐supporting or grid‐forming modes of operation. The question arises as to what the present situation of PV technology is for its optimal integration in distribution networks, whether there are still technical barriers to overcome as well as new opportunities for PV in future renewably supplied electricity systems. This paper presents the current state of knowledge concerning these topics from a European perspective with regard to different grid structures. It also discusses existing standards, new opportunities to provide grid services and research and development needs identified to fully exploit the added‐value—and still developing—benefits of PV‐DG. Copyright © 2008 John Wiley & Sons, Ltd.     

提高有序用电避峰预案的科学合理和公平性的措施

最近几年,关于智能用电成为世界各地电网建设过程中重点研究的内容和领域,其是未来智能电网系统中的主要发展趋势,对提高电网供电效率和质量有着显著的促进作用。有序用电避峰预案是最近几年在供电企业中应用比较广泛的一种模式,但是其在实际的应用过程中还存在不少问题,需要管理人员及时采取措施将其解决。本文主要结合本人工作实际情况,就有序用电避峰预案执行过程中存在的问题进行分析,并提出了相应的解决对策,希望通过本次研究对更好的提供有序用电避峰预案的科学性和合理性有一定帮助。     

Power quality and the security of electricity supply

The high-tech and knowledge-oriented businesses of the 21st Century require high quality and ultra-reliable power in the quantities and time-frames which have not been experienced before. For mission-critical information systems, the availability of enhanced electric power is a far more important consideration than the commodity cost of electricity. This paper surveys such needs and highlights the electric utility and industry practices around the US to meet such demands for high quality power     

The timing of EV recharging and its effect on utilities

Electric vehicles (EV's) represent an important future load on the electric utility system which, if properly managed, could increase power plant utilization and reduce the average cost of generating electricity. A future EV population of 7.5 million is addressed, together with its characteristics, vehicle use, consequent recharging loads, and the impact of EV's on electric utilities in terms of the generation of electric power, fuel use, and costs. The impact on utilities will depend in part on when the vehicles are recharged. If the price of electricity is uniform throughout the day, recharging is likely to begin when vehicles are parked at home. Most of the recharging would then occur during late afternoon and early evening hours when other demands for electricity are high. In the year 2000, peak electricity demand would increase by 5700 MW, and oil- and gas-fired power plants would generate 39 percent of the recharge power. Marginal generating costs would average 7.6 cents/kWh in 1982 dollars. If electricity were priced by time of day, recharging could shift to late night hours when the other demands for electricity are low. The peak demand would increase by only 400 MW; 27 percent of the power would come from oil and gas, and marginal generating costs would average only 5.1 cents/kWh, some 25 percent less than the marginal cost of the system load without EV's. The fuels to recharge EV's were found to vary from one region of the country to the next. Utilities in the northeast would use the most oil and gas for recharging (more than 75 percent), while those in the central part of the country would use the least.     

基于区块链的智能电网监控

随着智能电网系统的广泛应用,电力公司可以通过网络获取实时用电数据以满足负荷预测以及电力营销等业务需求,电力用户也可及时得知当月电费,甚至了解何时用电量较大以及哪个电器耗电量最大等具体细节,但这也导致了数据泄露的风险。为此文中利用主权区块链技术和智能合约的实施,为电力公司和电力用户之间提供一个可信任系统,使得电力供需双方都能安全、透明地获取用电数据。     

校园公用建筑自动节能系统设计

为了解决校园公共建筑的用电安全和电能浪费问题,设计了一种自动节能系统,根据可见光强度和是否有人控制用电电源和照明电源的通断,避免白天或无人时仍然开灯,以及人走之后电器设备仍在使用而可能引发火灾的情况。考虑人性化因素,系统加入了手动开关,并配有时钟日历电路和上位机接口电路,便于学校的日常作息管理和远程监控。系统电路简单,控制灵活,适用于多种公用建筑供电系统的安全、节能管理。     

Tighter controls for busier systems [power systems]

A variety of new technologies are becoming available that will help utilities maintain power system reliability while handling the larger volume of transactions. For example, power electronic systems can provide unprecedented control over electricity flow on transmission networks, preventing or containing cascading disturbances. In addition, new sensor technology, faster communications between control centers, and advanced software tools can enable utilities to monitor system conditions in real time, letting them respond more quickly to disturbances and minimize their impact. Over the next decade, these technologies will facilitate increased power transfers through power delivery systems that are presently constrained, providing power at lower cost to a greater number of customers. It is a question of how to optimize power flow through an entire network by integrating multiple technologies and coordinating control over wide areas. Such integration and coordination will be necessary for deregulation to proceed smoothly toward its twin goals: reducing electricity costs to US consumers, while maintaining the high levels of reliability they have come to expect. The authors discuss the following technologies to help achieve these goals including: flexible AC transmission systems (FACTS), the next generation of FACTS controllers, hierarchical control of FACTS, on-line power systems analysis, control centre communications, and wide area measurement system     

Betriebsinformationssysteme für Energieerzeuger

The competition caused by the liberalization of the energy market forces the operators of transverse compound systems to use all technically possible and economically meaningful rationalization potentials more strongly than so far. Apart from the improvement of the technical processes in the production systems a special meaning comes to the optimal planning of the application of the power stations. Already at small power supply systems an EDP-supported editing of data and information from the enterprise process and the system inventory becomes inevitable due to the complexity and the ever growing information obligations to officials.     

光伏并网逆变器控制策略研究

随着光伏技术的日益发展,对太阳能的利用逐渐从无电地区发展到有电地区,许多国家都推出了光伏发电计划。在光伏并网发电系统中,逆变器实现把太阳能电池板产生直流电能转化为和电网同频同相的交流电能并且馈入电网,光伏并网逆变器是光伏并网发电系统的枢纽单元。