基于调峰裕度分析的榆林电网风电接纳能力

研究电网对风电的接纳能力可以为合理编制风电发展规划、合理制定开发时序和电网规划方案提供参考。以2010年陕西电网夏小方式调峰裕度分析为基础,研究了陕西电网2010年风电接纳能力。以风资源丰富的榆林电网为例,在陕西省网接纳风电能力研究的基础上,结合相关电气计算结果,给出了2010年榆林电网风电接纳规模。给出了提高电网接纳风电能力的措施。     

双馈电机风电场等裕度无功分配策略

双馈式异步发电机可实现P-Q解耦控制,能够为电网提供无功支持,但其输出功率受变流器容量限制。为充分发挥双馈机无功调节能力,提出等裕度无功分配策略:根据各台风机无功极限的大小,以各机组具有相同的无功裕度作为无功分配的标准。该策略能够使风电厂在满足电网功率因数要求的同时,有效防止有功出力较大的双馈机由于变流器电流越限而发生跳机的现象,提高风电场运行可靠性。采用PSCAD/EMTDC软件进行仿真研究,通过与等功率因数无功分配策略进行比较,验证了等裕度无功分配策略的有效性。     

纳米石蜡乳液的制备及分析

采用反相乳化(EIP)法,以Span-20、Tween-20为复合乳化剂,其HLB值为10.5、浓度为8%,选择HMHEC/锂皂石为助乳化剂,制得稳定的水包油纳米石蜡乳液.所得纳米石蜡乳液滴为负电性,平均粒径在96～126nm之间,乳液粒径在5个月内无显著变化,具有好的长期稳定性,无机盐对其长期稳定性无影响.     

Improvement of transient stability of power systems with STATCOM-controller using trajectory sensitivity

This paper discusses the use of trajectory sensitivity analysis (TSA) in determining the transient stability margin of a power system compensated by a shunt FACTS device. The shunt device used is static synchronous compensator (STATCOM). It is shown that TSA can be used for the design of controller for the STATCOM. The preferable locations for the placement of the STATCOM for different fault conditions are also identified. The effects of STATCOM in maintaining different bus voltages in the post-fault condition are studied. The STATCOM is modeled by a voltage source connected to the system through a transformer. The systems used for the study are the WSCC 3-machine 9-bus system and the IEEE 16-machine 68-bus system.     

基于双向二维最大间距准则的局部放电灰度图像特征提取

针对高压交联聚乙烯电力电缆中间接头绝缘缺陷的辨识问题,提出一种局部放电灰度图像特征提取的双向二维最大间距准则方法,对获取的局部放电灰度图像从水平和垂直2个方向进行投影,得到了不同类别灰度图的鉴别矢量,选用最近邻分类器进行局部放电分类,以辨识电缆中间接头出现的不同绝缘缺陷。该方法解决了局部放电灰度图像特征提取维数大、识别样本少的难题。在对实验室4种典型电缆接头绝缘缺陷产生的PD信号进行对比辨识表明,其局部放电特征提取的速度和绝缘缺陷的识别率优于常用的主成分分析或Fisher鉴别分析方法。     

风电系统距离Ⅲ段保护动作特性分析

研究了异步发电机对输电线路距离Ⅲ段保护动作特性的影响.基于设定的定子电压,给出异步发电机理论阻抗.建立区分定、转子回路的风电系统潮流算法,计算异步发电机实际阻抗.根据风电系统节点电压对输入机械功率的灵敏度,以及保护动作裕度对节点电压的灵敏度,建立保护动作裕度对输入功率的线性关系.计算结果表明:异步发电机呈现负电阻、正电抗特性,使得线路远风电场节点测量阻抗类似反向故障;输入机械功率增加和定子电压降低,将减小异步发电机阻抗模值,降低保护动作裕度;风电场附近负荷增长,可能大幅降低线路远风电场节点距离Ⅲ段保护动作裕度.     

砌体防倒塌钢桁架加固方法研究

上世纪后30年,我国建造了大量砌体结构,而现用中小学校舍占有其中相当的比例.对于砌体结构的改造与加固在现时代仍具有十分重要的意义.本文提出了一种利用钢桁架对砌体结构进行防倒塌加固的方法,包括计算假定以及设计理论,并且给出了该加固方法的设计流程.分析表明,防倒塌钢桁架加固方法,在提高结构系统的安全储备方面可以发挥重要作用...     

13级静叶可调高炉鼓风机气动设计

本文采用S1和S2流面计算与三维CFD计算相结合的方法对出口巴西的一台高炉鼓风机进行气动设计和校核,设计结果不仅具有较高的效率,并且具有较宽的工况性能和较大的喘振裕度。     

Stability and leakage characteristics of novel conducting PMOS based 8T SRAM cell

The stability and leakage power of SRAMs have become an important issue with scaling of CMOS technology. This article reports a novel 8-transistor (8T) SRAM cell improving the read and write stability of data storage elements and reducing the leakage current in idle mode. In read operation, the bit-cell keeps the noise-vulnerable data ‘low’ node voltage close to the ground level and thus producing near-ideal voltage transfer characteristics essential for robust read functionality. In write operation, a negative bias on the cell facilitates to change contents of the bit. Unlike the conventional 6T cell, there is no conflicting read and write requirement on sizing the transistors. In standby mode, the built-in stacked device in the 8T cell reduces the leakage current significantly. The 8T SRAM cell implemented in a 130 nm CMOS technology demonstrates 2× higher read stability while bearing 20% better write-ability at 1.2 V typical condition and a reduction by 45% in leakage power consumption compared to the standard 6T cell. Results of the bit-cell architecture were also compared to the dual-port 8T SRAM cell. The stability enhancement and leakage power reduction provided with the proposed cell are confirmed under process, voltage and temperature variations.     

Wang Jiahua: China's Rigid Demand For Mineral Resources Will Continue to Grow For 15~20Years

正"Currently China’s mining industry is at the stage of downturn deep adjustment period,and the key factor affecting the recovery is the downward margin and adjustment duration.The only way out is to deepen reform,speed up structural adjustment,kick off a new round of technological innovation,improve labor