两级式光伏并网发电控制系统仿真分析

阐述了两级式光伏并网发电控制系统的结构及其控制过程,建立了光伏阵列模型和光伏并网发电系统模型,利用光伏阵列模型模拟了光照条件变化时光伏并网系统的输出情况进行仿真分析。实验表明,此两级式光伏并网发电系统能迅速有效地跟踪到光伏阵列的最大功率点,而且能够控制并网电流的波形,使逆变器的输出电流与电网电压同频同相,保证电流输出波形为正弦波。     

非电专业PLC实验中的编程技巧教学

根据高校教学改革的宗旨：一条主线与两个结合的教改思想．即教学以提高学生综合应用能力和素质为主线,理论与工程实际相结合,教学内容与新技术相结合的教育思想。针对非电专业“电工学”课程具有内容多学时少,尤其实验学时更少的特点,笔者总结自己在非电专业PLC实验教学中的经验,摸索出了一些行之有效的PLC编程方法与技巧,教学效果良好。本文以两台电动机循环控制为例进行了介绍。     

Comparison of in-situ measurement techniques of solder joint reliability under thermo-mechanical stresses

Thermo Mechanical Cycle Lifetime (TMCL) test is a widely used test methodology for evaluating the reliability of solder joints in the microelectronics industry. The commonly used measurement techniques to monitor solder joint failures during the TMCL test are either event detector or data logger. In this study, TMCL test has been carried out on the same devices in parallel with both measurement techniques. The pros and cons of both techniques are compared. It is observed that the solder joint reliability results on the investigated samples by both techniques are comparable. The event detector can catch short intermittent events, while the data logger is able to capture the details of the solder joint degradation process. In applications for which performance is dependent on the transmission of signals with a frequency of several hundred megahertz or more, the event detector technique shall be used. In such cases the data logger technique may overestimate product lifetime. On the other hand, for some applications where the performance is less susceptible to intermittent solder joint interconnect interruption but more to the increase of the solder joint resistance, the data logger shall be used. In such cases the event detector technique may underestimate product lifetime. In conclusion depending on the end application of the device, the most suitable technique can be selected.     

蒸汽压缩式制冷循环教学实验台的研制

为改进机械式实验仪器,即蒸汽压缩式制冷循环实验台的性能缺陷,设计了基于STM32F103的数据采集板卡,提高数据采集的精度和稳定性;采用基于C#语言的实验软件并结合ASP.NET技术实现实验过程自动化和远程实验教学功能。在此对上述功能的实现过程进行必要的阐述并对实验台的重要性能指标不确定度进行了详细的分析。结果表明实验台能满足现有教学实验要求,并对同类实验装置的研发具有一定的参考价值。     

时隙式随机争用多址系统分析方法研究

本文给出一种新的平均周期分析方法,并对时隙式随机争用多址系统进行了分析,得到了系统的信息分组发送成功的平均长度公式、信息分组发生碰撞的平均长度公式和空闲时隙的平均长度公式,并在讨论了系统的冲突分解特性后,给出了系统的吞吐量。     

平板显示基板玻璃窑炉烟气脱硝技术探究

随着生态环境意识的加强和环保治理力度的提升,平板玻璃窑炉烟气氮氧化物治理已经全面落实.而由于平板显示基板玻璃窑炉烟气性质的独特性,其脱硝技术路线的选择也取决于不同地区氮氧化物排放浓度的限值差异.详细介绍了选择性催化还原法(SCR)、选择性非催化还原法(SNCR)和逆向流选择性催化还原法(CSCR)三种脱硝技术并对比了三...     

脉动微波循环注热开采煤层气数值模拟

为获取脉动微波循环加热条件下低渗透储层煤层气运移采出规律,文中综合运用多孔介质传热学、电磁学、渗流力学、岩石力学等相关理论,建立低渗透储层煤层气微波注热开采过程渗流电磁-热-流-固多物理场耦合数学模型,结合COMSOL Multiphysics有限元分析软件进行了脉动微波循环加热过程煤层气运移采出规律的数值模拟,获取了...     

基于信息生命周期的政府信息服务安全保护模型研究

我国政府信息服务正逐渐从简单的信息提供向信息公开、数据开放和与互联网深度整合方向发展,在此发展过程中,如何实现政府信息服务与信息安全的平衡是政府服务信息服务提供者需要面对的问题.基于生命周期理论提出了以政府信息(数据)生命周期为核心,围绕人、地、事、物等要素,开展政府信息服务全生命周期安全运营的政府信息服务安全保护框架...     

Energy payback and life‐cycle CO2 emissions of the BOS in an optimized 3·5 MW PV installation

This study is a life‐cycle analysis of the balance of system (BOS) components of the 3·5 MW_p multi‐crystalline PV installation at Tucson Electric Power's (TEP) Springerville, AZ field PV plant. TEP instituted an innovative PV installation program guided by design optimization and cost minimization. The advanced design of the PV structure incorporated the weight of the PV modules as an element of support design, thereby eliminating the need for concrete foundations. The estimate of the life‐cycle energy requirements embodied in the BOS is 542 MJ/m², a 71% reduction from those of an older central plant; the corresponding life‐cycle greenhouse gas emissions are 29 kg CO₂ eq./m². From field measurements, the energy payback time (EPT) of the BOS is 0·21 years for the actual location of this plant, and 0·37 years for average US insolation/temperature conditions. This is a great improvement from the EPT of about 1·3 years, estimated for an older central plant. The total cost of the balance of system components was $940 US per kW_p of installed PV, another milestone in improvement. These results were verified with data from different databases and further tested with sensitivity‐ and data‐uncertainty analyses. Copyright © 2005 John Wiley & Sons, Ltd.     

Modeling Energy Recovery Using Thermoelectric Conversion Integrated with an Organic Rankine Bottoming Cycle

Engine and industrial waste heat are sources of high-grade thermal energy that can potentially be utilized. This paper describes a model system that employs thermoelectric conversion as a topping cycle integrated with an organic Rankine bottoming cycle. The model has many parameters that define combined system quantities such as overall output power and conversion efficiency. The model can identify the optimal performance points for both the thermoelectric and organic Rankine bottoming cycle. Key analysis results are presented showing the impact of critical design parameters on power output and system performance.