More applications of superconductivity to electric power systems

The technology of superconducting bearings in flywheels and the possibility of an all-superconducting substation using such technology are discussed in this article. Some personal thoughts about the penetration of superconducting technologies into the power system of the future are also included     

Advanced electric power systems

An identification and preliminary evaluation was made of alternative advanced electric power systems which have been suggested for possible future use by the American electric utility industry. The motivation for interest in advanced power systems stems primarily from the rapidly rising costs of clean fossil fuels, especially conventional fuel oil, and uncertainties of fuel supply. Four basic energy sources have been identified for prospective future American utility applications; namely, coal, nuclear, solar and geothermal. Each source must generally be subjected to extensive preprocessing before thermal energy can be delivered in a form useful to an electric power conversion system. Numerous candidate advanced energy conversion systems can be matched to the various energy sources, including steam, open cycle gas turbines, combined cycles, closed cycle gas turbines, MHD, fuel cells, liquid metal topping, supercritical carbon dioxide topping and others. Each has advantages and disadvantages which can be ranked and weighted numerically, based on our present knowledge. A tentative selection of promising combinations of energy sources and conversion systems has been made to focus attention on those which satisfy the socio-political requirements and also offer potential profit opportunities for suppliers to the electric utility industry.     

From interconnections of local electric power systems to Global Energy Interconnection

The interconnections of electric power systems are developed for the economic benefits and in order to increase the overall power supply reliability and quality level. Development of power industry shows the positive effects in operation of the country-wide electric power systems and international interconnections. Creation of World Energy System or, by the other words, Global Energy Interconnection is objective trend on the way of expansion of international and intercontinental electric power interconnections. Several important aspects of above mentioned problems are discussed in this paper.     

Solar thermal electric power systems in Japan

The major subjects of this paper are to report the outline of the recent basic research and technical development for solar thermal electric power systems in Japan. Solar thermal electric power systems are presently being developed as one of the most important systems in Sunshine Projects which were initiated in 1974 to develop the utilization systems of new energy resources. Conceptional designs of solar thermal power systems were already done on the basis of the results of the supporting researches and two pilot plants of solar thermal electric power systems of a capacity of 1000 kWe are under construction on the basis of the conceptional and detailed designs and would be constructed by 1981. The present conditions of these pilot plants and the major researches which are thought to be most important subjects in the basic researches and technical developments for solar thermal electric power systems are described in this paper.     

Propagation of flicker in electric power networks due to windenergy conversions systems

Wind energy conversion systems (WECS) produce fluctuating output power, which may cause voltage fluctuations and flicker. Flicker assessment in networks may be difficult since its evaluation requires long computing time and special procedures to calculate the flicker severity index, Pst. In this paper, a frequency domain method to study flicker propagation is presented. This method is based on propagation of frequency components from WECS output currents throughout the grid. In this way, a fast flicker analysis in a network of any size can be performed. Also, an algorithm for flicker measurement in the frequency domain, which allows Pst calculation, is proposed. Several study cases have been performed, and results have been compared with time domain simulations, showing good agreement between them     

Incorporating stress in electric power systems reliability models

Electric power systems can be disrupted by a variety of circumstances impacting failure and recovery rates. However, conflict-induced stress, primary fuel supply disruptions, and impediments to repair have rarely been incorporated into a systematic analysis of power planning and dispatch. In this paper, we augment the traditional Monte-Carlo reliability modeling framework to also represent primary fuel delivery and distributed generation (DG) topologies. We characterize five failure modes for the integrated system and compare the performance of centralized to DG systems under various levels of stress including conflict-induced stress. Our findings show DG to be significantly more reliable than centralized systems and when whole-economy costs are considered they are also more economical. These findings are significant in power planning for areas concerned about conflict-induced stress or where other factors may impact reliability of supply to a far greater extent than has been the norm in OECD countries.     

A two-stage stochastic optimization planning framework to decarbonize deeply electric power systems

In 2015, 195 countries signed the Paris Agreement under the United Nations Framework Convention on Climate Change. To achieve the ambitious greenhouse gas-reduction targets therein, the electric power sector must be transformed fundamentally. To this end, we develop a two-stage stochastic optimization model. The proposed model determines the optimal mix of generation and transmission capacity to build to serve future demands at least cost, while respecting technical constraints and climate-related considerations. The model uses a mix of AC and high-voltage DC transmission lines, conventional and renewable generation, and different types of energy-storage units to meet these objectives. Short- and long-term uncertainties are modeled using operating conditions and scenarios, respectively.We demonstrate the model using a case study that is based on the Texas power system, with 2050 as the target year of the analysis. We include explicit carbon-emissions constraints. Doing so allows us to examine the effect of carbon-reduction targets and deep decarbonization of electricity production on investment decisions. As expected, we find that thermal-dominated power systems must transition toward having a renewable-dominated generation mix.     

Medium-term scheduling of operating states in electric power systems

This article presents a mathematical model for the medium-term scheduling of the operating states of electric power systems. The scheduling period is divided into several time intervals. The model can be used to determine the equilibrium state in which each supplier earns maximum profit from supplying electricity to the wholesale market. We estimated the maximum value of public welfare, which indicates the total financial gains of suppliers and consumers, to determine the prices at the nodes of the power system. This was done by considering the balance constraints at the nodes of the power system and constraints on the allowable values of generation, power flows, and volumes of energy resources consumed over several time intervals. This problem belongs to the class of bi-level Stackelberg game-theoretic models with several leaders. The market equilibrium is modeled simultaneously in several intervals, given the multiplicity and duration of interactions. We considered two approaches for solving the multi-interval equilibrium state problem. The first approach involved directly solving a system of joint optimality conditions for electricity suppliers and consumers. The second approach involved iterative searches until the equilibrium state was reached. This article presents the results of medium-term scheduling using a case study of a simplified real-world power system.     

Design of electric power generation systems using waste heat energy

The recent energy crisis forces engineers to take into account reduction of electricity consumption as well as heat energy consumption in industry. As it is very difficult to save the amount of electricity, they have tried to recover electric power using waste heat energies. In this paper, the possibilities of electric power recovery from waste heat energies are discussed based on the relationship between supply heat sources and demand heat sources in chemical process systems. In solving such problems, the following difficulties appear: calculation of maximum quantity of generated electric power, determination of a suitable working fluid and its temperatures in the Rankine cycle, and so on. The proposed method can solve them using the temperature-enthalpy diagram and, furthermore, has the advantage of being able to design a final heat exchanger network with heat exchangers in a power plant by means of a synthesis method using the same diagram.     

Conceptual design of compressed air energy storage electric power systems

Conceptual design studies have been conducted to identify Compressed Air Energy Storage (CAES) systems which are technically feasible and potentially attractive for future electric utility load-levelling applications. The CAES concept consists of compressing air during off-peak periods and storing it in underground facilities for later use. During peak-load periods the air would be withdrawn, heated by recuperation and combustion and expanded through turbines to generate power. By using off-peak electricity for compression and stored air for peak-load generation, the resulting oil consumption would be about 40 per cent of that consumed by conventional gas-turbine peaking plants. The turbomachinery requirements for this type of system could be met using existing equipment with relatively modest modifications. Although the study discussed herein focused on the storage of air in hydraulically compensated, mined, hard-rock caverns, the compressed air could also be stored in underground aquifers or leached-out salt cavities. Conventional underground excavation technology could be used to construct these storage caverns. A geological survey of the north-central and north-east regions of the United States indicated that sufficient siting opportunities exist such that a prudently designed CAES plant should have little long-term adverse impact on the environment. The competitive position of CAES relative to conventional generation alternatives is highly dependent on utility-specific factors. The cost of electric energy from CAES is generally competitive with costs from conventional peak-shaving systems such as gas turbines and will improve as low-cost off-peak energy from nuclear plants becomes available.     

Solar thermal electric power systems: Comparison of line-focus collectors

Three types of line-focusing collectors: parabolic though, fixed slats with movable absorber and movable slats with fixed absorber, are evaluated to find those systems that are capable of producing the lowest costs of electrical energy. Minimum costs per kW-hr are found using sequential optimization techniques that consider variations in rim angle, reflectance, aperture width, length, orientation, tracking, contour error, slat width, slat curvature, tangent slat angle, slope, installation methods, materials, fabrication methods, absorptance, emittance, cover transmittance, field shape, layout, pipe sizes, insulation thicknesses and turbine-generator-cooling lower efficiencies and designs. This approach provides a uniform treatment of both cost and performance for a solar thermal electric power system. This uniform treatment of solar thermal electric power systems for all collector types insures that valid comparisons are made.     

A neuro-fuzzy program approach for evaluating electric power generation systems

This paper uses neuro-fuzzy programming to perform a comparison between the different electricity power generation options for Jordan. Different systems are considered: in addition to fossil fuel power plants, nuclear, solar, wind, and hydropower systems are evaluated. Based on cost-to-benefit ratios, results show that solar, wind, and hydropower are considered to be the best systems for electricity power generation. On the other hand, nuclear electricity turns out to be the worst choice, followed by fossil fuel electric power.     

Health risks of high-Btu gas pipeline and electric power transmission systems

The Institute of Gas Technology (IGT) has determined the health risks associated with transmission systems for electric power and high-Btu gas. These preliminary estimates were made in an independently-funded R&D study in which the gas system was found to have one-third the health risk of the electric system.¹ Most of these risks are associated with construction of the systems and transportation of the required construction materials. The systems have a capacity of 650 billion Btu/day, are 500 miles long, operate at 80% capacity factors, and have a 30-yr lifetime.     

Impact of plug-in hybrid electric vehicles on power systems with demand response and wind power

This paper uses a new unit commitment model which can simulate the interactions among plug-in hybrid electric vehicles (PHEVs), wind power, and demand response (DR). Four PHEV charging scenarios are simulated for the Illinois power system: (1) unconstrained charging, (2) 3-hour delayed constrained charging, (3) smart charging, and (4) smart charging with DR. The PHEV charging is assumed to be optimally controlled by the system operator in the latter two scenarios, along with load shifting and shaving enabled by DR programs. The simulation results show that optimally dispatching the PHEV charging load can significantly reduce the total operating cost of the system. With DR programs in place, the operating cost can be further reduced.     

Development of a methodology for assessing the adequacy of electric power systems

This study presents the results of a research into the developing a methodology for assessing the adequacy of advanced electric power systems characterized by the integration of various innovative technologies, which complicates their analysis. The methodology development is aimed at solving two main problems: 1) increase the adequacy of modeling the processes that occur in the electric power system and 2) enhance the computational efficiency of the adequacy assessment methodology. This study proposes a new mathematical model to minimize the power shortage and enhance the adequacy of modeling the processes. The model considers quadratic power transmission losses and network coefficients. The computational efficiency of the adequacy assessment methodology is enhanced using efficient random- number generators to form the calculated states of electric power systems and machine learning methods to assess power shortages and other reliability characteristics in the calculated states.     

Market-based congestion management in electric power systems with increased share of natural gas dependent power plants

The paper addresses market-based congestion management (MBCM) in electric power systems taking into account the constraints of the electric power system (EPS) and the natural gas system (NGS). The proposed method is based on the countertrade methodology, where the system operator performs minimum-cost redispatching according to bids from generators and loads. The EPS is presented by the DC model for power flow calculation, which uses power transfer distribution factors (PTDFs) to describe the relation between generators/loads and line-power flows. The proposed solution applies the Benders decomposition method to decouple the problem into a master problem and subproblem. The master problem includes the bid-based redispatching for congestion relief and the EPS feasibility check. The subproblem checks the NGS operation feasibility when gas-fired generating units are redispatched in the master problem. Any NGS violations from the subproblem are incorporated into the master problem as power constraints for the next iteration of congestion management. The master problem is solved by linear programming. The NGS is presented in a nonlinear model and its feasibility check is performed using successive linear programming. Case studies illustrate the applicability of the proposed congestion management method on simple test models of the EPS and the NGS.     

洁净燃煤发电系统综合性能的赋权相关分析

采用层次分析法确定权系数,将模糊关系处理数据的多指标相关分析法应用于洁净燃煤发电系统综合的评价。该结果与其它文献综合评判结果完全一致。