一种光伏逆变器的多输出辅助开关电源设计

本文设计了一种光伏逆变器的辅助开关电源。由于光伏逆变器需要的辅助电源路数很多,且要考虑高、低压的隔离,所以设计了两个反激式开关电源。文中介绍了这两个开关电源的计算和设计过程,重点论述了变压器磁芯及绕组的设计、反馈及稳压电路的设计。设计的辅助电源已经用于光伏逆变器上,运行稳定可靠。良好的实验结果证明了设计方法的正确性。     

一种应用于多重化逆变的变压器研究

传统的多重化变压器中,所采用的叠加变压器中铁心结构体积复杂、重量过大。因此本文基于多重叠加的基本原理,提出了一种新型的叠加变压器的铁心结构,逆变器方波电压输入后,高次谐波磁动势在叠加过程中被削弱,从而输出三相正弦波电流。对其建立数学模型并进行仿真分析,仿真结果验证了该方法的有效性。     

An integrated modelling approach for the bicriterion vehicle routing and scheduling problem with environmental considerations

The consideration of pollution in routing decisions gives rise to a new routing framework where measures of the environmental implications are traded off with business performance measures. To address this type of routing decisions, we formulate and solve a bi-objective time, load and path-dependent vehicle routing problem with time windows (BTL-VRPTW). The proposed formulation incorporates a travel time model representing realistically time varying traffic conditions. A key feature of the problem under consideration is the need to address simultaneously routing and path finding decisions. To cope with the computational burden arising from this property of the problem we propose a network reduction approach. Computational tests on the effect of the network reduction approach on determining non-dominated solutions are reported. A generic solution framework is proposed to address the BTL-VRPTW. The proposed framework combines any technique that creates capacity-feasible routes with a routing and scheduling method that aims to convert the identified routes to problem solutions. We show that transforming a set of routes to BTL-VRPTW solutions is equivalent to solving a bi-objective time dependent shortest path problem on a specially structured graph. We propose a backward label setting technique to solve the emerging problem that takes advantage of the special structure of the graph. The proposed generic solution framework is implemented by integrating the routing and scheduling method into an Ant Colony System algorithm. The accuracy of the proposed algorithm was assessed on the basis of its capability to determine minimum travel time and fuel consumption solutions. Although the computational results are encouraging, there is ample room for future research in algorithmic advances on addressing the proposed problem.     

高速铁路牵引变压器冲击合闸保护误动作分析

分析了牵引变压器合闸时保护装置误动作案例,重点阐述了励磁涌流的产生、特点和影响因素,并提出几种减小励磁涌流影响的技术措施。     

特种变压器变比及连接方式的测试方法初探

分析了基于单项电源的变比测试仪在特种变压器变比测试中存在的问题和误差,提出了基于三相标准电压源输出的测试方法,并给出了实测结果.试验表明,基于三相标准电压源的变比测试仪可以较好地满足特种变压器的变比及连接方式测试.     

220kV变电所电气系统设计分析

为满足提高电力网容量、电压等级和综合自动化水平的需求,对具有220kV侧有8回出线、110kV侧有10回出线的变电所进行电气设计。通过对3种方案的技术分析和比较,选择双母线接线技术,同时确定主变压器容量、主变压器台数、主变压器型式和结构,最终选择变电所变压器的型号。     

630连续挤压机腔体内阻加热系统的电源功率

为确定内阻加热系统中电源的功率参数,掌握系统工况条件对电源设备要求,利用电、热学理论,并结合能量守恒定律对630连续挤压机腔体的加热系统进行分析,从而确定电源最大功率为500 kW,进而选定所使用的变压器为500 kVA,最终给整个加热系统提供必要的设备依据.     

Benthic assemblages of a temperate estuarine system in South America: Transition from a freshwater to an estuarine zone

The objectives of the present study were to describe the species composition, diversity and distribution of the zoobenthic assemblages, to estimate the abundance and biomass of the dominant species, and to identify the main environmental factors determining the distribution patterns of the invertebrates from a freshwater to an estuarine zone in a temperate estuary of South America. The Río de la Plata estuary is a microtidal system characterized by a high concentration of suspended solids. Fifty-three taxa of meso- and macro-invertebrates were identified in the samples collected during November and December 2001. Molluscs, annelids, crustaceans and nematodes were found at 90% of the sampling sites. Molluscs comprised up to about 90% of the total zoobenthos biomass: the remaining percentage corresponded mainly to annelids and less to nematodes and crustaceans. An ecocline along the salinity gradient could be observed for the benthic assemblages from the freshwater to the estuarine zone in Rio de la Plata. A Canonical Correspondence Analysis shows that results from sampling sites in the outer zone were strongly related to salinity, depth and pH and less to oxygen and percentage of clay. The results from stations in the inner zone, and part of the middle zone, were mainly related to the occurrence of sand and contents of NH₄⁺–N, NO₃⁻–N, and PO₄³⁻–P.     

Distributed and Redundant Design of Ship Monitoring and Control Network

The world trend in ship automation is to integrate the monitoring, intelligent control and systematic management of the instruments and equipments both on bridge and in engine room. The paper presents a design scheme of the ship integrated monitoring and operating system based on two layers distributed and redundant computer network. The lower layer network is the field bus network connected mainly by CAN bus; the upper one is the PC local network in TCP/IP protocol, which consisted of a database server, monitoring and operating computers, industrial computers and a set of switches. Distributed schemes are fully applied to both software and hardware. This paper specifically describes the composition, software distribution and redundant technology of the upper local network and gives some important sample codes for the implement of the redundant and distributed design. The technologies here have been proved in the many applications and it may be applied to other industrial fields.     

电力机车主变压器防寒橡胶的选择与应用

详细分析了防寒对电力机车主变压器密封橡胶件的要求,并比较了几种常用耐低温橡胶性能,从而选择合理的电力机车主变压器防寒密封橡胶。