含多微源的微网并网控制运行特性研究

文章以永磁同步风力发电机、光伏发电系统、蓄电池储能系统建立了混合微网结构模型。为了充分发挥各微源的优势并保证微网的供电质量,对各微源控制器采用不同控制策略进行。对风力发电系统采用改进PQ控制、光伏发电DC/DC变换器进行最大功率跟踪法控制以及蓄电池采用定直流电压控制来维持直流母线电压。文章基于PSCAD/EMTDC软件对系统不同运行工况进行仿真,结果表明控制策略具有正确性及可行性。     

循环流化床锅炉燃烧系统的控制研究

针对CFBB(循环流化床锅炉)燃烧系统分别选择了分散、集中多变量及部分分散3种控制方案。首先基于模型预测控制的PID方法,在分析分散控制结构的基础上设计了分散控制器,并与集中多变量控制器进行比较。结果表明CFBB燃烧系统具有较强耦合性,分散控制不能取得较好的效果。为了克服集中控制器结构复杂,参数不宜整定的问题,采用部分分散控制结构对该系统进行调整。在采用Gramian方法对模型进行部分分散控制分析基础上,对可选的两种部分分散控制结构进行了控制器设计,并与集中多变量控制进行了比较。结果表明:部分分散控制方法能够取得比分散控制更好的性能,可以达到与集中多变量控制相近的控制性能,而且结构更简单,便于工程实践,具有较好的应用价值。     

基于根轨迹法的高压直流输电附加控制器设计

针对高压直流输电系统受扰动故障出现振荡的问题,提出一种基于根轨迹校正方法的附加阻尼控制器设计方法。首先通过采用最小二乘—旋转不变算法辨识出系统的低阶线性化模型,再根据根轨迹校正方案设计直流附加控制器。为进一步提高控制效果,基于该方法设计发电机励磁附加控制器,进行机网协调控制。在PSCAD/EMTDC中搭建四机两区域仿真模型,并分别对比传统控制器和根轨迹控制器在系统发生扰动故障时的振荡控制效果,结果表明轨迹控制器可有效控制系统振荡,具有较强的鲁棒性,提高了系统稳定性。研究成果可应用于工程实际。     

基于虚拟仪器的柴油机模糊-PID调速控制研究

采用NI PCI6221多功能数据采集卡建立了基于虚拟仪器的柴油机速度控制系统,设计了增量式模糊-PID控制器。针对模糊-PID切换控制中出现的系统响应动态特性和稳定性不佳的问题,对切换控制器进行了优化;采用偏差及偏差变化率作为切换依据及双阈值判断方法,有效改善了系统动态特性,提高了控制器切换稳定性。试验结果表明:优化后的柴油机模糊-PID调速控制系统在动态特性、稳定性上都取得了更好的控制效果。     

自适应模糊控制在热力系统容错控制中的应用

在热力系统中采用容错控制技术,可以提高控制系统的可靠性,同时降低运行成本。研究采用自适应模糊控制实现非失效的被动容错控制。提出一种新的自适应模糊控制器;采用基于动态神经元网络的辨识模型学习被控对象的动态特性,设计了评价模糊控制器性能的FITAE指标;采用遗传算法优化模糊控制器参数,同时优化比例因子和控制规则表。为了提高模糊控制器的自适应调整速度,采用二阶段优化策略。仿真研究表明:自适应模糊控制器的热力系统被动容错控制方法是可行的。图3参7     

考虑发电机励磁的AC/DC系统模型与控制器设计

针对高压直流输电系统(HVDC)与发电机励磁协调控制问题,建立了HVDC和发电机励磁综合控制模型,采用微分几何变换法进行部分线性化获得了与原系统相同定性行为的线性系统.基于该线性化模型设计了控制方案并对控制器进行仿真.仿真结果表明,验证了控制器的有效性、可靠性,易于实际应用.     

基于电力线通信技术的城市路灯节能监控系统

针对传统城市路灯控制方案能源消耗大、维护成本高等问题,基于电力线通信技术,利用监控中心计算机、区域控制器、单灯控制器构建了路灯节能监控系统,系统中的单灯控制器通过基于DSP技术的PLT-22电力线收发器和自动中继技术实现了系统在电力线信号上的相互通信,无需重新布线,路灯镇流器采用开关控制和节电率调节相结合的方式节省电能消耗.     

太阳能路灯控制器的设计与实现

控制器是整个太阳能路灯系统的核心。文中采用一种基于Atmega48单片机的控制器,其采用PWM脉冲调制控制技术通过对蓄电池电压、充电电流等参数进行检测,控制开关管的关断,来实现充放电控制和保护功能。经测试,其使用安全可靠。     

单元机组协调控制系统模糊自适应控制研究

单元机组协调控制系统的负荷控制对象存在耦合性和时变性,常规PID控制方案在负荷大范围变化时控制效果变差.为了提高协调控制系统的调节性能,采用了一种模糊自适应控制方案.基于300MW直流锅炉单元机组不同工况下采集的数据,建立了机组在210MW和270MW工况下的负荷控制对象动态数学模型,并进行了动态特性分析;基于常规PID协调控制方案,设计了一种模糊自适应PID控制器,可以自动调整控制器参数以适应工况的变化.锅炉控制器和汽轮机控制器均采用模糊自适应PID控制器.仿真结果表明,单元机组协调控制系统模糊自适应控制与常规PID控制相比,超调量降低,调节时间缩短,抗干扰能力和负荷适应能力增强.     

IGCC气化炉控制方案的仿真研究

针对ALSTOM气化炉的非线性、多变量动态特性,提出了两种基于常规PID控制器的气化炉多变量控制方案,这两种方案采用不同的操纵变量-被控变量配对并设计了相应的前反馈控制器。对两种控制方案进行了详细的多工况仿真测试,测试结果表明:方案一只要在适当放宽煤量改变速率限制的情况下,不仅可以满足ALSTOM气化炉的基准测试要求,而且各项控制指标均优于方案二;方案二能严格满足各项基准测试要求,但系统总的动态控制品质逊于方案一。与许多复杂控制算法(例如模型预测控制)不同,所研究的控制方案基于常规PID控制,便于工程实现,对工业应用具有更好的指导意义。     

Performance assessment of some ice TES systems

In this paper, a performance assessment of four main types of ice storage techniques for space cooling purposes, namely ice slurry systems, ice-on-coil systems (both internal and external melt), and encapsulated ice systems is conducted. A detailed analysis, coupled with a case study based on the literature data, follows. The ice making techniques are compared on the basis of energy and exergy performance criteria including charging, discharging and storage efficiencies, which make up the ice storage and retrieval process. Losses due to heat leakage and irreversibilities from entropy generation are included. A vapor-compression refrigeration cycle with R134a as the working fluid provides the cooling load, while the analysis is performed in both a full storage and partial storage process, with comparisons between these two. In the case of full storage, the energy efficiencies associated with the charging and discharging processes are well over 98% in all cases, while the exergy efficiencies ranged from 46% to 76% for the charging cycle and 18% to 24% for the discharging cycle. For the partial storage systems, all energy and exergy efficiencies were slightly less than that for full storage, due to the increasing effect wall heat leakage has on the decreased storage volume and load. The results show that energy analyses alone do not provide much useful insight into system behavior, since the vast majority of losses in all processes are a result of entropy generation which results from system irreversibilities.     

Effect of co-cultivation of Chlamydomonas reinhardtii with Azotobacter chroococcum on hydrogen production

Chlamydomonas reinhardtii cc124 and Azotobacter chroococcum bacteria were co-cultured with a series of volume ratios and under a variety of light densities to determine the optimal culture conditions and to investigate the mechanism by which co-cultivation improves H₂ yield. The results demonstrated that the optimal culture conditions for the highest H₂ production of the combined system were a 1:40 vol ratio of bacterial cultures to algal cultures under 200 μE m^?2 s^?1. Under these conditions, the maximal H₂ yield was 255 μmol mg^?1 Chl, which was approximately 15.9-fold of the control. The reasons for the improvement in H₂ yield included decreased O₂ content, enhanced algal growth, and increased H₂ase activity and starch content of the combined system.     

Exergetic evaluation of 5 biowastes-to-biofuels routes via gasification

This paper presents the exergy analysis results for the production of several biofuels, i.e., SNG (synthetic natural gas), methanol, Fischer–Tropsch fuels, hydrogen, as well as heat and electricity, from several biowastes generated in the Dutch province of Friesland, selected as one of the typical European regions. Biowastes have been classified in 5 virtual streams according to their ultimate and proximate analysis. All production chains have been modeled in Aspen Plus in order to analyze their technical performance. The common steps for all the production chains are: pre-treatment, gasification, gas cleaning, water–gas-shift reactions, catalytic reactors, final gas separation and upgrading. Optionally a gas turbine and steam turbines are used to produce heat and electricity from unconverted gas and heat removal, respectively. The results show that, in terms of mass conversion, methanol production seems to be the most efficient process for all the biowastes. SNG synthesis is preferred when exergetic efficiency is the objective parameter, but hydrogen process is more efficient when the performance is analyzed by means of the 1st Law of Thermodynamics. The main exergy losses account for the gasification section, except in the electricity and heat production chain, where the combined cycle is less efficient.     

液压系统常见的故障诊断及处理

任何工程机械式液压设备使用时出现故障是不可避免的。但是怎样确定故障的原因及找到好的解决方法，这是使用者最关心的问题。讲述了液压系统常见的故障及其排除方法。     

Economie d'énergie en trigénération

Trigeneration is defined as the production of three useful forms of energy—heat, cold and power—from a primary source of energy such as natural gas or oil. For instance, trigeneration systems typically produce electrical power via a reciprocating engine or gas turbine and recover a large percentage of the heat energy retained in the lubricating oil, exhaust gas and coolant water systems to maximize the utilization of the primary fuel. The heat produced can be totally or partially used to fuel absorption refrigerators. Therefore, trigeneration systems enjoy an inherently high efficiency and have the potential to significantly reduce the energy-related operation costs of facilities. In this paper, we describe a model of characterization of trigeneration systems trough the condition of primary energy saving and the quality index, compared to the separate production of heat, cold and power. The study highlights the importance of the choice of the separate production reference system on the level of primary energy saving and emissions reduction.     

Mineralogical characterization of the intraseam layers of Lofoi lignite deposits in Florina basin (western Makedonia,northwest Greece)

The mineralogical composition of intraseam layers from Lofoi lignite deposits (northwest Greece) is the subject of the present study. The samples were examined by means of X-ray diffraction (XRD), thermo-gravimetric (TG/DTG) and differential thermal analysis (DTA), and Fourier transform infrared (FT-IR) spectrometry. The clay minerals prevail in most samples, with illite-muscovite being the dominant phase, and kaolinite and chlorite being the other major clay components. No smectite was found. Quartz and feldspars, dominate in two cases. The studied materials are characterized as clays to clayey sands, showing significant similarities with the intraseam layers of the adjacent Achlada lignite deposits.     

Innovative methodologies in renewable energy: A review

This paper is concerned with innovative approaches to renewable energy sources computation methodologies, which provide more refined results than the classical alternatives. Such refinements provide additional improvements especially for replacement of fossil energy usages that emit greenhouse gas (GHG) into the atmosphere leading to climate change impact. Current knowledge gap among each renewable energy source calculation is rather missing fundamentals of plausible, rational, and logical explanations for the interpretation of results. In the literature, there are rather complicated and mechanically applicable methodologies, which require input and output measurement data match with missing physical explanations. The view taken in this review paper is to concentrate on quite plausible, logical, rational, and effectively applicable innovative energy calculation methodologies with simplistic fundamentals. For this purpose, a set of renewable energy methodological approaches is revisited with their innovative structures concerning solar, wind, hydro, current, and geothermal energy resources. With the increase in the renewable energy utilizations to combat the undesirable impacts of global warming and climate change, there is a need for better models that will include physical environmental conditions and data properties in the probabilistic, statistical, stochastic, logical, and rational senses leading to refined and more reliable estimations with application examples in the text. Finally, new research directions are also recommended for more refined innovative energy system calculations.     

Constrained Optimization of Heat Transfer from an Extended Surface

Two different zero‐order optimization techniques are used to maximize the rates of heat transfer from a fin assembly of a specified cost and in the shape of several annular fins that are mounted on a central stem. The problem is formulated to account for two‐dimensional steady‐state heat transfer that is limited by several inequality constraints. The dimensionless governing equations are used to identify the relevant decision variables. The number of fins making up the assembly is treated as an input parameter. A digital computer is used to determine the required temperature distributions and to implement the optimization search algorithms. Three different fin materials are assessed—aluminum, copper and carbon steel. Design optimizations of the extended surface assembly were made over a range of operating conditions, encompassing several different convection heat transfer coefficients that are representative of free and forced convection in air, and several different overall temperature differences between the substrate surface and air. A few recommendations based on trends in the predicted results are given. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res, 43(6): 504–521, 2014; Published online 3 October 2013 in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21093     

CY6D78Ti型柴油机的开发研制

本文介绍了CY6D78Ti型柴油机的开发研制过程及现状,CY6D78Ti型柴油机能满足国内中、重型卡车和豪华客车市场对柴油机动力性、经济性、可靠性的需求。由于该机型的高档配置,保证了其排放达到欧Ⅱ标准,同时为进一步提高性能、降低排放,采用电控及高压共轨等技术手段搭建了平台。     

我国车用柴油机的技术现状及发展趋势

本文根据国内外信息和资料，分析了我国目前车用柴油机制造技术方面与国际水平所存在的差距，预测今后若千年内车用柴油机要向节能降耗、应用增压技术、提高可靠性、降低排放、采用电控技术方面发展，以尽快接近和赶上国际先进水平．