Electromagnetic transients in the control system of output parameters of a solar power plant in Tajikistan Central Asia region

At present, as the demand for electricity increases in all sectors, there is an urgent need to introduce alternative renewable energy sources into modern energy systems. Renewable energy sources, which consist of solar (photovoltaic, PV), wind and hydro power, are key alternative sources of “green energy’’ energies, but it can also be used to produce “green” hydrogen. Thanks to scientific and technological progress, the cost of photovoltaic solar radiation converters is constantly decreasing at a high rate, which makes it possible to build solar power plants of sufficiently large capacity. In the coming decades, solar energy will become an incentive for the economic development of countries that have the maximum “solar” resource. The Republic of Tajikistan is one of these countries with a high potential for solar energy.The article presents an analysis of the resources and potential of solar energy in the Republic of Tajikistan. The study of electromagnetic transients in networks with photovoltaic solar power plants is performed. The main equations, simulation model and calculations of transients are presented, taking into account changes in voltage on DC buses. An algorithm for controlling the system of automatic control of output parameters is proposed. The analysis of dynamic and static modes in parallel operation of a solar power plant with the grid is carried out. A block diagram and computer model is constructed in the MATLAB package together with Simulink and Power System Blockset.     

Small hydro power: technology and current status

Hydropower, large and small, remains by far the most important of the “renewables” for electrical power production worldwide, providing 19% of the planet’s electricity. Small-scale hydro is in most cases “run-of-river”, with no dam or water storage, and is one of the most cost-effective and environmentally benign energy technologies to be considered both for rural electrification in less developed countries and further hydro developments in Europe. The European Commission have a target to increase small hydro capacity by 4500MW (50%) by the year 2010. The UK has 100MW of existing small hydro capacity (under 5MW) operating from approximately 120 sites, and at least 400MW of unexploited potential. With positive environmental policies now being backed by favourable tariffs for ‘green’ electricity, the industry believes that small hydro will have a strong resurgence in Europe in the next 10 years, after 20 years of decline. This paper summarises the different small hydro technologies, new innovations being developed, and the barriers to further development.     

Determinant factors in site selection for photovoltaic projects: A systematic review

The choice of great places for installation of solar power plants has become a key issue in terms of project planning because of the increased number of investments in the photovoltaic sector. This study is a systematic review of the literature that seeks to identify the determining factors in choosing the best location for solar photovoltaic power plants, through previous research on the application of renewable energy technologies in great contexts of location. Among a total of 130 academic studies filtered by the keywords “photovoltaic energy,” “power plants,” “location,” and “factor” on the bases ScienceDirect, Scopus, Web of Science, and IEEE, a total of 27 studies were identified. These articles were carefully explored, including years of publication, countries of origin, and identification of factors that each author demonstrated. It has been extracted 28 factors, organized in six points of view: socioenvironmental, location, economic, political, climatic, and orographic. It was verified that the determining factors for choosing the best locations are solar irradiation, substation distance, slope, distance of roads, distance from urban areas, and land use. The results of this research may assist academic students and investors in identifying factors that they should consider in their decision making and may also assist in the efficient planning of renewable energy management to ensure the sustainable development of power generation through the photovoltaic source.     

可并网微型水力发电系统的控制研究

为提高偏远山区的用电质量、降低用电成本,依托山区微型水资源,在传统独立式微型水力发电系统基础上,提出了一种基于自励式不控异步发电机的可并网微型水力发电系统电路拓扑结构,采用带有输出电流反馈的电压闭环控制策略,以单位功率因数并网。利用补偿电容提供无功能量给异步电动机作微型水力系统发电部分,采用电力电子变换电路实现能量传输,减小并网能量损耗。通过搭建实验平台,验证了该系统的可行性。     

丝绸之路经济带能源合作现状及潜力分析

丝绸之路经济带内的中国与中亚五国的能源合作自上世纪90年代以来发展良好,在石油天然气勘探开发、炼油化工、管道运输、销售贸易和工程技术服务等方面有巨大的合作潜力以及良好的合作条件,但仍面临着地缘政治环境以及投资环境等多方面的挑战.     

Analysis of basic conditions of the power grid interconnection among Xinjiang,Pakistan, and five Central Asian countries

Inter-regional and transnational grid interconnection is necessary for energy development. Xinjiang, which is rich in renewable energy resources, is adjacent to countries in Central Asia and has great potential for interconnection with its neighbors. This paper outlines China’s relevant policies for transnational power interconnection, and introduces the energy structure, load demand endowments, and power supply status of Xinjiang, Pakistan, and five Central Asian countries. Further, it analyzes the advantages of the multinational power interconnection from the aspects of power supply and load complementation. Finally, from the perspective of technical support and practical basis, the feasibility of interconnection between Xinjiang, Pakistan, and five Central Asian countries have been analyzed. This paper provides a theoretical basis for promoting and implementing China’s “Belt and Road” power transnational interconnected development strategy.     

Hydro energy potential of cooling water at the thermal power plant

The hydro energy of the gravity water flow from the coal-fired thermal power plant units to the river in an open cooling system of turbine condensers is determined. On the basis of statistical data for a long time period, the water net head duration curve due to the river annual level change, as well as the reduction of the hydro energy potential due to the thermal power plant overhauls periods, are evaluated in the case study of the Thermal Power Plant “Nikola Tesla B” in Serbia. A small hydro power plant is designed for the utilization of this hydro energy, and the economic benefits of the project are calculated. The internal rate of returns and pay back periods are calculated in dependence of the electricity price and total investment costs. The increase of profitability is assessed, bearing in mind that the plant might be realized as the Clean Development Mechanism project according to the Kyoto protocol. The obtained results show that the project is economically attractive, and it can be carried out with standard matured solutions of hydro turbines available at the market. Even for the relatively low electricity price from small hydro power plants in Serbia of 0.08 €/kW h the internal rate of return and the pay back period are 17.5% and 5.5 years.     

2006年中国水电建设全面提速

回顾我国2006年的水电发展态势,可以概括为水电建设全面提速,水电建设的春天已经到来。在中央关于“在保护生态的基础上有序发展水电”方针的指引下,由于我国经济持续高速增长对电力的旺盛需求,为减轻对煤炭的压力,减轻污染,减少温室气体的排放,增加清洁能源的需求促进了水电发展。同时,由于电力体制改革,通过市场竞争配置资源,由于水电的长期效益好,各大发电集团和水电公司、民营企业均加大水电开发力度,促进了水电发展。水电建设全面提速,各项指标达到世界领先水平。在大中型水电发展的同时,新农村建设促进了小水电发展,小水电占水电装机的1/3。水电建设全面提速促进机电设备国产化率提高;水电技术走向世界初具规模,水电科技达到世界先进水平。     

微型燃气轮机技术

高效微型燃气轮机发电机组可用于航空、航天等领域,还可用于分布式发电、军用车辆辅助动力装置、车用混合动力装置等,因此研究这种动力装置有重要的实用意义。首先介绍了微型燃气轮机的发展过程,简要说明了过去40年内微型燃气轮机在结构上发生的变化,随后给出了组成微燃气轮机的关键部件在设计过程中应注意一些问题。最后回顾了国内一些研究单位在这一领域所进行的研究工作,并指出今后的努力方向和工作重点。     

Flow acceleration by converging nozzles for power generation in existing canal system

Small-scale hydro or micro-hydro power has been increasingly used as an alternative energy source, especially in remote areas where other power sources are not viable. In the larger hydro projects potential energy of the water is converted to electrical power, whereas such small-scale hydro power systems utilize kinetic energy of the flow. These systems can be installed in small rivers or streams with little or no discernible environmental effects. Usually, these systems do not require a huge infrastructure like dam or major water diversions, rather use water wheels with least environmental impacts. This paper presents a report on how flow can be accelerated through convergent nozzles for run-of-river turbines in open flow channels. An existing canal in Pakistan has been used for the analysis based on its easily accessible data. The analytical and computational work presented here converts kinetic energy of water flow to electric power.     

Efficiency estimation for the grid-tie photovoltaic stations construction in some regions of Central Asia and Transcaucasia

An assessment of the economic expediency of the construction of network photovoltaic stations in some regions of Uzbekistan, Kyrgyzstan, Tajikistan, Turkmenistan, Kazakhstan, and Azerbaijan is presented, with an accounting for climate conditions and the electricity rates that were adopted to encourage the development of renewable power engineering. The analysis covers design variants of 5-MW model solar power plants on photovoltaic modules made according to various technologies with respective modern and advanced cost indicators. The performance indicators of PVPPs with multicrystalline photovoltaic modules and highly efficient HIT technology modules were made by the Hevel company in Russia.     

Prototype testing of the wave energy converter wave dragon

The Wave Dragon is an offshore wave energy converter of the overtopping type. It consists of two wave reflectors focusing the incoming waves towards a ramp, a reservoir for collecting the overtopping water and a number of hydro turbines for converting the pressure head into power.In the period from 1998 to 2001 extensive wave tank testing on a scale model was carried at Aalborg University. Then, a 57×27 m wide and 237 tonnes heavy (incl. ballast) prototype of the Wave Dragon, placed in Nissum Bredning, Denmark, was grid connected in May 2003 as the world's first offshore wave energy converter.The prototype is fully equipped with hydro turbines and automatic control systems, and is instrumented in order to monitor power production, wave climate, forces in mooring lines, stresses in the structure and movements of the Wave Dragon.In the period May 2003 to January 2005 an extensive measuring program has been carried out, establishing the background for optimal design of the structure and regulation of the power take off system. Planning for deployment of a 4 MW power production unit in the Atlantic by 2007 is in progress.     

A review on islanding operation and control for distribution network connected with small hydro power plant

Hydro power generation is the oldest generation and provides the largest contribution among the renewable energy types of generation. In distribution system, most of the distributed generation (DG) is small scale hydro generation of which utilizes the natural flowing water of the river. This generation requires governor and excitation control unit to control and sustain the power generation when subjected to any changes of load behavior. More advanced control strategy is critically expected when considering the recent interest in distribution system to perform islanding operation of DG. Many of the literature have clearly highlighted this issue, but only a few have discussed on the islanding operation of small hydro generation. This paper therefore reviews this topic and relates the discussion with the controller designed for other type of turbines interfaced with synchronous generator. To strengthen the knowledge on islanding operation, the background of islanding is also presented in this paper.     

Suboptimal design of hydroturbine governors

A state space method for the design of turbine governors in hydro power plants with Kaplan turbines is presented. The design is based on the suboptimal regulator problem solved by the use of projective controls. A design procedure that permits the design of multivariable static and low order dynamic hydroturbine governors is proposed. It provides an organized way of choosing the governor structure and the tuning of its parameters. A case study is presented to illustrate the proposed design method and to demonstrate the extensive applicability of the suboptimal solution and its merits as compared to conventional governors     

Using micro-hydropower in the Zairian village

This article presents the experiences learned using micro-hydro power at the village level. Site evaluation procedure, financing methods, turbine fabrication, and site construction are discussed. Micro-hydro power provides a decentralized energy source for several of the energy-intensive tasks of villagers. Low-head, small volume hydro potential is common in the Zairian countryside. Often a potential site also serves as the village water source, hence it is located near potential beneficiaries of the power. Over the past three decades, a religous NGO in the Ubangi and Mongala Subregions of northwest Zaire has been developing this small hydro potential as part of its technology transfer and village development program. Local materials and knowledge are used as much as possible in construction. Experiences gained constructing a 370 kW hydro-electric site, as well as building water wheels for water pumping has led to the construction of micro-hydro sites using locally made cross-flow turbines. Four water wheel sites and six micro-hydro sites have been built. The hydropower is used to mill flour and hull coffee. One site also generates 220 V electricity, and two others have 12 V generation planned.     

Exhaust hood for steam turbines-single-flow arrangement

In the past, increased attention was given to the development of an optimal shape for the inlet part of LP turbine casings in SKODA POWER. A double-flow design is typically used for high power output turbines. An optimized shape for the internal diffuser has been found, which transforms the kinetic energy of steam into increased pressure, thus effectively increasing the thermodynamic efficiency of the stage. Some conclusions have been drawn from laboratory experiments, others derived directly from on-site measurements at power plants. The conclusions from the development of double-flow turbines form the basis for the design of the single-flow turbine arrangement. Single-flow design is typically used for lower output turbines. There are still some limitations in applying this arrangement. The designer needs to resolve the bearing position and how to ensure access to them. Reinforcing the ribs and supports are used, therefore, to ensure the rigidity of the entire casing. The optimization of the single-flow diffuser shape is therefore the subject of the study presented below.     

The representation of variable hydro potential in long-range electricity planning models

The long-range planning of electricity supply in countries for which hydro power constitutes a sizeable proportion of total capacity should take into account the effects of variable hydro inflow. Fluctuations occur in the water intake to storage lakes from year to year; reserve generating capacity is required to ensure that demand can still be met in years of low water intake. The least cost choice for reserve capacity must take into account not only the capital costs of generating capacity but also the extra fuel and operating costs, the latter costs being incurred only when water intake is low.This paper describes an LP model of the long-range planning problem in which the effects of both low water inflows and high water inflows are included. The formulation used to represent these variable elements in the model was designed to minimise the number of additional constraints required.     

Autonomous WPP/HPP power system operating modes study

Today, there are centralized and decentralized energy supply areas world-wide. Centralized energy supply is provided by united energy grids which cover most habitable areas; they incorporate several types of power sources with centralized control system. Decentralized energy supply areas cover territories disconnected from power grid, and they incorporate only one type of power source.Autonomous diesel power plants (DPP) are nowadays used mainly to power decentralized consumers and consumer groups. DPP basic disadvantages are power production high cost, diesel fuel nonregenerability, greenhouse gas emission and environmental pollution. The possibility of power supply by autonomous power systems combining wind power plants (WPP) and hydro power plants (HPP) as alternative to diesel generation due to hydraulic energy storage advantages has been considered.Autonomous WPP/HPP power system is a combination of WPP, HPP with water-storage reservoir, automatic control system and switchgear, combined by power, infrastructural and data connections. Hydrogen energy storage is considered to be the second energy storage.HPP water-storage reservoir parametrization procedure considering operating specificity of HPP and WPP as a part of power system with hydraulic and hydrogen energy storage has been suggested. Mathematical models for operating modes of WPP, HPP and storage reservoir have been developed, which consider resources, technical and technological features of their performance in decentralized power supply system. Technique for determining storage reservoir backup volume with allowance for wind conditions parameters, WPP features and storage reservoir configuration have been suggested. Method of day-ahead WPP power calculation in solving problem of operational planning of power system operating modes has been suggested. Simulation of WPP/HPP power system operating modes with seasonal-storage reservoir and hydrogen energy storage have been carried out.The suggested techniques could be used for solving design problems to substantiate decentralized power supply system parameters in remote and isolated areas, as well as for evaluating energy efficiency of replacing the existent decentralized power supply systems on the basis of DPP using imported diesel fuel by environmentally safe systems on the basis of local energy resource – wind energy and hydraulic energy. The suggested techniques are also focused on solving problem of power system operating modes for operational planning.     

Optimum sizing of wind-pumped-storage hybrid power stations in island systems

Pumped storage is generally viewed as the most promising technology to increase renewable energy source (RES) penetration levels in power systems and particularly in small autonomous island grids. Combined wind and pumped-storage “virtual power plants”, called hybrid power stations (HPS), constitute a realistic and feasible option to achieve high penetrations, provided that their components are properly sized. In this paper, the optimum sizing is investigated for a pumped storage HPS operating in an island system. The analysis addresses the sizing of the main HPS components (hydro turbines, pumps, wind farm, reservoirs), adopting either the investor’s perspective, where the objective is to maximize the return on the HPS investment, or a system perspective, where the optimization target is the maximization of RES penetration, along with maintaining the lowest possible generation cost in the system. Genetic Algorithms (GAs) are applied for the optimization and a real isolated island power system is used as a study case. The adopted operating policy and pricing principles, which critically affect the optimal sizing of an HPS project, are based on the existing regulatory framework for storage stations in Greek islands.