单/三相混合微电网中虚拟组合式三相变流器功率协调控制

针对单/三相混合微电网系统孤岛运行时单相电源和负载引起的三相电压不平衡问题,提出了虚拟组合式三相变流器及其功率协调控制。详细阐述了基于虚拟三相瞬时功率的下垂控制和虚拟阻抗控制,实现同相并联单元的功率分配。针对组合式三相变流器相间同步控制难点,提出了新型120°鉴相器和基于锁相环原理的相间同步控制,提高三相电压平衡度。在此基础上,给出了电压补偿控制,进一步改善供电质量。同相及相间功率协调控制无需附加任何同步芯片或通信线,原理简单,控制灵活,可靠性高。最后,仿真和实验结果表明所提控制策略可以实现动稳态工况下同相并联单元间功率按照设定比例分配以及不同相间相位和幅值的同步控制,100%不平衡负载下电压不平衡度为0.1%,供电质量较高。     

An investigation of the relation between the temperature dependences of the initial unbalance and the output signal of resistance strain sensor bridge circuits

The relation between the initial unbalance and the output signal of bridge circuits when acted upon simultaneously by the physical factor being measured and the temperature of the surroundings when the bridge is supplied from a voltage or current source is investigated. Analytic relations are obtained which explain the temperature dependence of the useful output voltage under external physical action. __________ Translated from Izmeritel’naya Tekhnika, No. 1, pp. 48–49, 2007.     

总降有载调压变压器直阻不平衡的分析与处理

分析有载调压变压器不平衡的原因,找出可行的处理方法,使变压器直阻达到平衡。     

A heuristic based on multi-stage programming approach for machine-loading problem in a flexible manufacturing system

Manufacturing industries are rapidly changing from economies of scale to economies of scope, characterized by short product life cycles and increased product varieties. This implies a need to improve the efficiency of job shops while still maintaining their flexibility. These objectives are achieved by Flexible manufacturing systems (FMS). The basic aim of FMS is to bring together the productivity of flow lines and the flexibility of job shops. This duality of objectives makes the management of an FMS complex. In this article, the loading problem in random type FMS, which is viewed as selecting a subset of jobs from the job pool and allocating them among available machines, is considered. A heuristic based on multi-stage programming approach is proposed to solve this problem. The objective considered is to minimize the system unbalance while satisfying the technological constraints such as availability of machining time and tool slots. The performance of the proposed heuristic is tested on 10 sample problems available in FMS literature and compared with existing solution methods. It has been found that the proposed heuristic gives good results.     

交流滤波器保护配置和实现

分析了超高压直流输电系统中交流滤波器运行的各种工况，介绍了其保护配置，针对性地提出了自动跟踪补偿由于环境等参数影响产生的不平衡电流的电容器不平衡保护和基于综合谐波特性的电抗器过负荷等原理，并给出了这些保护原理的数字仿真、动模试验和现场运行结果。     

高压电容器不平衡保护的相关问题

电容器不平衡保护直接反应电容器内部元件的损坏情况，是高压电容器保护中最重要的保护功能之一。文中结合南方电网平果／河池／百色串补及天广／高肇直流工程实际，分析了电容器不平衡保护中的电流互感器的配置、选型及匹配问题，总结、比较了目前普遍使用的高压电容器不平衡检测原理以及不平衡保护定值计算中需要注意的问题。     

通信电缆线对电容不平衡测试方法的研究

分析了传统的通信电缆线对电容不平衡测试方法的不足,提出简便和新颖的多线对电容耦合测试方法,并给予了证明。同时介绍了线对电容不平衡测试方法的实现过程。     

高利润率环境下的房地产投资目标失衡分析

随着我国房地产市场的不断发展,房地产企业的数量和规模也都在急剧扩大,房地产企业的投资目标也日趋多元化,对其投资目标的正确认识也显得尤为重要。文中主要针对当前高额利润诱惑下的房地产企业的投资目标的缺失现象进行分析,探讨了这种缺失将产生的严重后果,给出了房地产企业应如何正确认识投资目标的次序,以求能对房地产企业制定可持续发展战略有所裨益。     

振动分析在电机制造厂的成功实践

简要介绍了振动分析技术在电机故障(包括电机滑动轴承间隙不当、电机转子不平衡和电机转子动态气隙偏心)诊断中的成功应用。振动分析和诊断过程对电机的故障诊断具有一定的参考价值。     

电压互感器二次侧三相电压不平衡现象的分析

从中性点不接地的电力系统中的绝缘监测功能单元及铁磁谐振角度出发,对安装消谐电阻器后引起电磁式电压互感器星三角接线二次侧三相电压不平衡现象进行了详细的分析和计算,得出了不平衡的一些原因及误差范围,并提出了改进措施,在实际使用中取得了较好的效果.