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Local arc discharge mechanism and requirements of power supply in micro-arc oxidation of magnesium alloy

Ming CHEN, Yuezhou MA, Yuan HAO,

《机械工程前沿（英文）》 2010年第5卷第1期页码 98-105 doi: 10.1007/s11465-009-0088-8

摘要： To study the requirements of the power supply in micro-arc oxidation (MAO) of magnesium alloy, many experiments were performed under the DC, unipolar, and ambipolar pulse output modes. Based on the experimental results and electric arc theory, the separate local arc discharge mechanism was put forward. It is considered that magnesium MAO process consists of three stages including anodic oxidation, micro-arc oxidation, and large-arc discharge in turn with increasing source voltage. The MAO film is composed of metal oxides that resulted from numerous discrete local arc discharges, which accumulate the non-equilibrium structure after undergoing sudden heating and cooling cycles. Separate local arc discharge is caused by the process in which the oxygen-based gas is ionized in the conduct channel bearing electric field intensity, changed from insulator to conductor that presents sharp negative resistance effect, and produced partially high temperature to ignite locally metal oxidation. The local arc discharge model is described as four courses: gas created from electrolysis, arc discharge, metals oxidization, and cooling and shrinking of oxides. The purpose of pulse supply is to inhibit the large-arc discharge by intervening proper cooling time, which cannot be actualized by a unipolar pulse mode because of the strong capacitive load characteristics but can be reached by an ambipolar pulse supply because the negative pulse period acts as cooling time. Using a discharge loop to remove the influence of load capacitive, a new type of pulse power supply for MAO is developed, so that the large-arc problem is resolved effectively, the film-forming efficiency is improved, and the pollution of the film and electrolyte caused by negative voltage is avoided.

关键词： micro-arc oxidation local arc discharge pulse power supply magnesium alloy

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Will Germany move into a situation with unsecured power supply?

Harald SCHWARZ

《能源前沿（英文）》 2019年第13卷第3期页码 551-570 doi: 10.1007/s11708-019-0641-z

摘要： Together with a huge number of other countries, Germany signed the Paris Agreements in 2015 to prevent global temperature increase above 2°C. Within this agreement, all countries defined their own national contributions to CO reduction. Since that, it was visible that CO emissions in Germany decreased, but not so fast than proposed in this German nationally determined contribution to the Paris Agreement. Due to increasing traffic, CO emissions from this mobility sector increased and CO emission from German power generation is nearly constant for the past 20 years, even a renewable generation capacity of 112 GW was built up in 2017, which is much higher than the peak load of 84 GW in Germany. That is why the German National Government has implemented a commission (often called “The German Coal Commission”) to propose a time line: how Germany can move out of coal-fired power stations. This “Coal Commission” started its work in the late spring of 2018 and handed over its final report with 336 pages to the government on January 26th, 2019. Within this report the following proposals were made: ① Until 2022: Due to a former decision of the German Government, the actual remaining nuclear power generation capacity of about 10 GW has to be switched off in 2022. Besides, the “Coal Commission” proposed to switch off additionally in total 12.5 GW of both, hard coal and lignite-fired power plants, so that Germany should reduce its conventional generation capacity by 22.5 GW in 2022. ② Until 2030: Another 13 GW of German hard coal or lignite-fired power plants should be switched off. ③ Until 2038: The final 17 GW of German hard coal or lignite-fired power plants should be switched off until 2038 latest. Unfortunately the “Coal Commission” has not investigated the relevant technical parameter to ensure a secured electric power supply, based on German’s own national resources. Because German Energy Revolution mainly is based on wind energy and photovoltaic, this paper will describe the negligible contribution of these sources to the secured generation capacity, which will be needed for a reliable power supply. In addition, it will discuss several technical options to integrate wind energy and photovoltaic into a secured power supply system with an overall reduced CO emission.

关键词： CO₂ reduction mobility sector renewable generation coal commission secured power generation capacity reliable power supply power-to-gas power-to-heat

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High pressure air spray assistant power supply control strategies and their effects on diesel engine

HAN Yongqiang, LIU Zhongchang, WANG Zhongshu, ZHU Ruoqun

《能源前沿（英文）》 2007年第1卷第3期页码 295-299 doi: 10.1007/s11708-007-0042-6

摘要： In order to reduce smoke from direct-injection (DI) turbo-charged and after-cooled (TCA) diesel engines under transient operations, the real-time controlling and measuring system of a high pressure air spray assistant power supply (HPAS) was developed. Effects of HPAS on a DI TCA diesel engine under constant engine speed and increased torque (CSIT) transient operations were studied by using different control strategies. Pre-spray (PS) strategy, which means supplying highly pressurized air into the exhaust manifold two seconds before the accelerating-graph begins to rise and stopping spraying air when the accelerating-graph stops rising. Two other strategies—full-time-spray (FTS) and middle-time-spray (MTS)—were used to fully exploit HPAS potential. With the FTS and MTS strategies, the HPAS system can remarkably decrease smoke from DI TCA diesel engines under transient operations.

关键词： different after-cooled real-time controlling CSIT supply

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Modeling, evaluation, and optimization of gas-power and energy supply scenarios

Hossam A. GABBAR,Aboelsood ZIDAN

《能源前沿（英文）》 2016年第10卷第4期页码 393-408 doi: 10.1007/s11708-016-0422-x

摘要： Recently, renewable energy sources such as wind power and photovoltaic (PV) are receiving a wide acceptance because they are inexhaustible and nonpolluting. Renewable energy sources are intermittent ones because of climate changes in wind speed and solar irradiance. Due to the continuous demand growth and the necessity for efficient and reliable electricity supply, there is a real need to increase the penetration of gas technologies in power grids. The Canadian government and stakeholders are looking for ways to increase the reliability and sustainability of power grid, and gas-power technologies may provide a solution. This paper explores the integration of gas and renewable generation technologies to provide a qualified, reliable, and environmentally friendly power system while satisfying regional electricity demands and reducing generation cost. Scenarios are evaluated using four key performance indicators (KPIs), economic, power quality, reliability, and environmental friendliness. Various scenarios outcomes are compared based on the defined performance indices. The proposed scenario analysis tool has three components, the geographic information system (GIS) for recording transmission and distribution lines and generation sites, the energy semantic network (ESN) knowledgebase to store information, and an algorithm created in Matlab/Simulink for evaluating scenarios. To interact with the scenario analysis tool, a graphical user interface (GUI) is used where users can define the desired geographic area, desired generation percentage via gas technology, and system parameters. To evaluate the effectiveness of the proposed method, the regional zone of the province of Ontario and Toronto are used as case studies.

关键词： gas-power renewable key performance indicators (KPIs) reliability

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Constant temperature control of tundish induction heating power supply for metallurgical manufacturing

Yufei YUE, Qianming XU, Peng GUO, An LUO

《能源前沿（英文）》 2019年第13卷第1期页码 16-26 doi: 10.1007/s11708-018-0572-0

摘要： The tundish induction heating power supply (TIHPS) is one of the most important equipment in the continuous casting process for metallurgical manufacturing. Specially, the constant temperature control is greatly significant for metallurgical manufacturing. In terms of the relationship between TIH load temperature and output power of TIHPS, the constant temperature control can be realized by power control. In this paper, a TIHPS structure with three-phase PWM rectifiers and full-bridge cascaded inverter is proposed. Besides, an input harmonic current blocking strategy and a load voltage feedforward control are also proposed to realize constant temperature control. To meet the requirement of the system, controller parameters are designed properly. Experiments are conducted to validate the feasibility and effectiveness of the proposed TIHPS topology and the control methods.

关键词： tundish induction heating power supply (TIHPS) constant temperature control input harmonic current blocking load voltage feedforward

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上海港岸基船用供电系统研究与实践

包起帆

《中国工程科学》 2011年第13卷第9期页码 63-68

摘要：

描述的一种移动式岸基船用变频变压供电系统利用集装箱码头前沿为桥吊运行配备10 kV/50 Hz/2 000 kV ·A的高压电源，经过变压和变频为靠港船舶提供450 V/60 Hz电源。该方案灵活性强，节能减排效果明显，且无需对码头进行土木改造，为我国作业繁忙的集装箱码头实现岸基供电提供新方案。

关键词：岸基供电节能减排

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经济供电半径的Fuzzy几何规划模型与优选方法

曹炳元

《中国工程科学》 2001年第3卷第3期页码 52-55

摘要：

变电所供电半径的选择是一个复杂的问题。为了确定最佳供电半径，减少投资，降低损耗，建立了Fuzzy环境下的变电所供电半径选择的几何规划模型。它包括软约束问题和含Fuzzy系数的问题。通过数值实例的计算，验证所建立的模型，与静态和动态的优化数学模型如控制模型和经典几何规划模型相比较，包含更多的信息，且获得了更满意的结果。

关键词： Fuzzy几何规划经济供电半径优选变电所容(数)量

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Analysis and design of pulse frequency modulation dielectric barrier discharge for low power applications

Tang-tang GUO,Xing-liang LIU,Shi-qiang HAO,Chi ZHANG,Xiang-ning HE

《信息与电子工程前沿（英文）》 2015年第16卷第3期页码 249-258 doi: 10.1631/FITEE.1400185

摘要： For low power dielectric barrier discharge (DBD) used in small-size material treatment or portable devices, highstep transformer parasitic capacitance greatly influences the performance of the resonant converter as it is of the same order of magnitude as the equivalent capacitance of DBD load. In this paper, steady-state analysis of the low power DBD is presented, considering the inevitable parasitic capacitance of the high-step transformer. The rectifier-compensated first harmonic approximation (RCFHA) is applied to linearize the equivalent load circuit of DBD at low frequency and the derived expressions are accurate and convenient for the analysis and design of the power supply. Based on the proposed linear equivalent load circuit, the influence of transformer parasitic capacitance on the key parameters, including the frequency range and the applied electrode voltage, is discussed when the power is regulated with pulse frequency modulation (PFM). Also, a design procedure is presented based on the derived expressions. A prototype is constructed according to the design results and the accuracy of the design is verified by experimental results.

关键词： Dielectric barrier discharge Rectifier-compensated first harmonic approximation Parasitic capacitance Power converter design

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Simulation of grid connection and maximum power point tracking control of brushless doubly-fed generatorin wind power system

Hicham SERHOUD, Djilani BENATTOUS

《能源前沿（英文）》 2013年第7卷第3期页码 380-387 doi: 10.1007/s11708-013-0252-z

摘要： In this paper, based on the analysis of the mathematical model in a common synchronous reference frame of the brushless doubly-fed generator (BDFG), the grid connection strategy and maximum energy extraction control were both analyzed. Besides, the transient simulation of no-load model and generation model of the BDFG have been developed on the MATLAB/Simulink platform. The test results during cutting-in grid confirmed the good dynamic performance of grid synchronization and effective power control approach for the BDFG-based variable speed wind turbines.

关键词： brushless doubly-fed generator (BDFG) modeling grid connection control back-to-back pulse-width modulation (PWM) converter wind power generation

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Esophageal pulse oximetry is more accurate and detects hypoxemia earlier than conventional pulse oximetry

null

《医学前沿（英文）》 2012年第6卷第4期页码 406-410 doi: 10.1007/s11684-012-0217-3

摘要：

The esophagus is perfused directly by prominent arteries and may provide a more consistent tissue source for pulse oximetry. The goal of this study was to evaluate the sensitivity and accuracy of an esophageal pulse oximetry probe on patients during controlled hypoxemia in comparison to measurements obtained with conventional pulse oximetry (SpulseO₂). Forty-five ASA I–II adult patients were included in this prospective observational study. Nellcor digital oximetric probes were placed on finger tips for SpulseO₂ before anesthesia. After tracheal intubation, an esophageal probe was placed in the lower segment of the esophagus for esophageal oximetric monitoring (SoesO₂). All patients were disconnected from the breathing circuit to establish a controlled hypoxemia, and were re-connected to the breathing circuit and ventilated with 100% oxygen immediately when SoesO₂ dropped to 90%. Matched SoesO₂ and SpulseO₂ readings were recorded when SoesO₂measurements were at 100%, 95%, 90% and the lowest reading. The time for SoesO₂ and SpulseO₂ to drop from 100% to 95%, 90% and return to 100% was recorded. Oxygen saturation from arterial blood samples (SartO₂) was also measured at each time point respectively. The linear correlation coefficient of the regression analysis between SartO₂ and SoesO₂ was 0.954. The mean±2SD of the difference was 0.3%±4.3% for SoesO₂vs. SartO₂ and 6.8%±5.6% for SpulseO₂vs. SartO₂ (P<0.001). The 95% confidence interval for the absolute difference between SoesO₂ and SartO₂ was 0.3% to 0.7% and 6.2% to 7.4% between SpulseO₂ and SartO₂. The time to reach 90% saturation measured with SoesO₂ was approximately 94 seconds earlier than the SpulseO₂ (P<0.001). In conclusion, SoesO₂ is more accurate and enables earlier detection of hypoxemia when compared to conventional pulse oximetry during hypoxemia for patients undergoing general anesthesia.

关键词： esophageal pulse oximetry conventional pulse oximetry hypoxemia

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三峡漂浮物分布式供能系统研究

李年君

《中国工程科学》 2010年第12卷第6期页码 99-103

摘要：

长江漂浮物是威胁三峡电站运行安全的重要问题。在对三峡漂浮物数量和特点的调查和分析基础上，提出了以漂浮物能源化利用为主线，污染物治理和资源回收为两翼的三峡漂浮物生态能源系统路线，通过利用分布式能源技术系统可以为用户侧提供更可靠、清洁的高品质能源服务。研究结果表明，充分利用三峡漂浮物进行冷热电联供，可以在实现三峡库区污染治理的同时，对三峡漂浮物进行资源化利用，分布式供能系统年处理漂浮物4.7×10⁴～9.5×10⁴ t，节能1.3×10⁴～3.6×10⁴ t标煤，投资回收期4.5～8年，具有良好的技术经济性能。

关键词：三峡漂浮物污染分布式供能

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我国中长期发电供应能力研究

白建华, 辛颂旭

《中国工程科学》 2011年第13卷第6期页码 65-74

摘要：

结合我国能源资源储量、禀赋特点和能源发展相关政策，对我国中长期发电供应能力进行了全面的分析，包括燃煤发电、水电、核能发电、风力发电、太阳能发电、生物质能发电和天然气发电的供应能力。在此基础上，以社会总体成本最小为原则，对我国中长期电源结构调整进行了研究，同时研判了我国中长期电源发展布局。

关键词：发电供应能力中长期电源结构电源布局

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海上风电开发与多能源协同供电规模化制氢（氧）产业基地建设研究

金春鹏

《中国工程科学》 2015年第17卷第3期页码 56-59

摘要：

中国风能资源丰富，沿海尤其是近海海域风能资源更为丰富，为大规模、超大规模海上风电发展创造了巨大空间。大规模非并网风电的应用，更是开辟了一条中国特色风电多元化发展之路。本文分析了海上风能资源布局及沿海风电开发现状；在风电非并网理论指导下，以规模化制氢产业为例，探讨非并网风电与高载能产业间的链合路径，并构建相应产业链；依据产业链合机制，探讨多能源协同供电规模化制氢（氧）产业基地建设的实施目标与战略规划。

关键词：海上风电；多能源协同供电；规模化制氢（氧）；产业基地

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中国高速铁路牵引供电关键技术

钱清泉,高仕斌,何正友,陈奇志,吴积钦

《中国工程科学》 2015年第17卷第4期页码 9-20

摘要：

本文结合中国高铁建设和运营的经验，从高速铁路牵引供电不同层面，系统地介绍了高铁牵引供电系统的一系列关键技术。同时，就目前牵引供电系统的发展现状，展望了新型供电技术、主动运营维护、节能与效能提升、检测监测等新技术，可为中国高铁牵引供电技术的发展与应用提供指导。

关键词：高速铁路；牵引供电系统；关键技术

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Regional GIS-based evaluation of the potential and supply costs of forest biomass in Sweden

Dimitris ATHANASSIADIS, Tomas NORDFJELL

《农业科学与工程前沿（英文）》 2017年第4卷第4期页码 493-501 doi: 10.15302/J-FASE-2017179

摘要： The potential for harvestable forest fuel (logging residues and stumps from regeneration fellings and small diameter trees from early thinnings) in Sweden, divided in five regions, is provided. Marginal cost curves for logging residues and stumps are calculated through a GIS-based method based on forest inventory plots and locations of selected terminals, and heat and combined heat and power facilities. Four supply chains for logging residues and two for stumpwood were compared. Fixed and variable costs of harvesting equipment and transport vehicles were used for determining the costs of each of the supply systems under consideration. A list with the GPS coordinates of all facilities and terminals was made based on their geographical location. The distance from the center of each forest inventory plot to the nearest receiving point within the region, either facility or terminal, was estimated. There were large differences in the estimated potential of harvestable forest fuel between the regions. The overall annual potential for each of the five regions ranged from 0.97 to 2.73 million oven dry tonnes and the total potential amounted to 9.39 Mt (oven dry). One of the northernmost regions (R1) had the steepest slope in its marginal cost curve. For the other regions, the slope of their cost curves was less dramatic. Information on the economic availability of logging residues and stumps in each region is important for forest fuel suppliers and receiving facilities.

关键词： GIS logging residues heat and-power faci-lities stumpwood