低压电网拓扑自动生成方法研究

为给低压电网规划和设计提供支持,提出基于分层布局的低压电网拓扑自动生成方法。首先,构建包含布局拓扑层、成图拓扑层在内的低压电网拓扑的分层布局结构,采用K-means聚类方法将低压电网划分为多个区域。在各区域引入引力-斥力模型,控制电网节点在引力、斥力以及合力的作用下的移动距离,以使节点受力达到平衡状态。然后,采用双层树连接方式,将低压电网的线路网络分为上层树和下层树。对应采用深度优先搜索和宽度优先搜索方法,连接低压电网主干线路和各分支线路,以自动生成低压电网上下层树的拓扑结构。最后,通过连接上下层树拓扑生成低压电网拓扑。试验结果表明:该方法生成的低压电网拓扑布线简洁清晰、结构完整。该方法搜索次数仅为305次。该方法可降低搜索设备和节点的次数、提高低压电网拓扑生成效率。该方法具有较好的聚类效果。

基于IEC 61850的低压配电物联网监控系统设计

低压配电线路缺少监控,随着分布式电源的大量接入,为保证电气安全、优化用电服务,需要建立低压配电线路监控系统。基于物联网技术构建的低压配电线路监控系统的终端种类繁多、数量巨大,亟需解决信息的互联互通、减少安装维护工作。在分析低压配电线路监控功能通信需求基础上,基于IEC 61850对各功能所需信息模型及终端设备进行了建模,并基于IEC 61850信息模型研发了低压配电线路监控终端、智能网关和智能管理模块。研发的低压配电线路监控系统已应用于广东江门某园区,实现了低压线路和分布式电源的监控,提高了低压配电线路的电气安全与用电服务。

New Identity,New Interests and New Diplomacy

At the end of 2003, two experts on Chinese affairs from the American Rand Corporation, Evan S. Medeiros and M. Taylor Fravel published an article, ＂ China＇s New Diplomacy,＂ demonstrating changes in China＇s international perspective, attitude toward international society, foreign policy, and the diplomatic policy-making system and process. ①This article initiated much research, both domestic and foreign, on China＇s new diplomacy. Most Chinese scholars depict China＇s new foreign policy in a comprehensive manner, describing its emphasis on common interests of bilateral diplomacy, developing multilateral diplomacy, strengthening public diplomacy, and expanding virtual and economic diplomacy and the good-neighbor policy. ② Foreign scholars, on the other hand, tend to analyze evidence of China＇s new foreign policy in a particular country or region. Examples of this are China＇s good-neighbor policy, the North Korean nuclear issue policy, the change of perspective on China＇s sovereignty and interference, and China＇s policy on Asean multilateralism. ③ Nevertheless, none of this research has touched on the deeper question of why China＇s diplomacy has transformed, none has expounded theoretically on these various behaviors. Of course, there are a few scholars who have made inroads. for us to explain the Su Changhe holds the view that it is impossible peaceful elements in China＇s development from the theory of realistic international relations. Many of China＇s new diplomacy can be explained by the liberal international relations theory. ④ The problem is why China＇s new diplomacy accords with liberal international relations theory. The authors think it is necessary to study China＇s new diplomacy theoretically in order to perceive reality more accurately and enhance our ability to predict the future. The constructivist theory not only enables us to think clearly about relationship among various phenomena in China＇s new diplomacy, but it also helps delve into underlying reasons.

高海拔下预喷策略对甲醇/柴油双燃料发动机燃烧与排放特性的影响

通过搭建甲醇/柴油双燃料发动机专用试验台架,对某4缸高压共轨柴油机进气歧管改造加装喷醇器,系统地研究了2000 m海拔70%负荷下M0、M10、M15、M20甲醇替代率的预喷策略对双燃料发动机燃烧与排放特性的影响.结果表明:大气压力减小会导致滞燃期延长和缸内燃烧压力下降,甲醇替代率增加会导致滞燃期延长和缸内燃烧压力增大.采用预喷策略结合甲醇喷射,可以提高燃烧压力,降低常规与非常规排放.在最大转矩转速(1800 r/min)中高负荷(70%,321.3 N·m)下,相比纯柴油模式,20%甲醇替代率滞燃期延长44.76%,NO_(x)排放降低16.64%,CO和HC排放增加,并出现了甲醇和甲醛非常规排放.滞燃期与预喷正时呈非线性关系,过早或过晚预喷都会使滞燃期延长.各替代率下NO_(x)排放分别增加了4.77%、4.56%、6.89%、7.05%.增大预喷油量到4 mg,各替代率下滞燃期缩短了55.84%、43.46%、35.58%、23.21%,缸内燃烧压力明显增加,NO_(x)排放增加了4.76%、5.11%、6.74%、12.51%,CO和HC略有降低.甲醇/柴油双燃料模式下,合理调节甲醇替代率和预喷策略可有效控制滞燃期与减少排放.在该工况下,滞燃期、最大峰值压力、NO_(x)和CO随预喷参数变化趋势与平原低负荷工况一致,但在高海拔、高负荷条件下受预喷油量影响更明显,变化幅度更大.HC、CH_(3)OH排放趋势与平原低负荷不同.预喷策略改善了2000 m海拔下的燃烧恶化,减少了NO_(x)、CO、CH_(3)OH和CH_(2)O排放.通过预喷策略与甲醇替代率的协调控制可以减少高海拔下的滞燃期延长并减少高海拔下燃烧压力的降低,进而改善DMDF发动机的高原性能,达到减排的效果.