A high-power-factor, three-phase isolated AC-DC converter using high-frequency current injection

A single-stage, three-phase AC-to-DC converter topology is proposed for high-frequency power supply applications. The principal features of the circuit include continuous current operation of the three AC input inductors, inherent shaping of the input currents, resulting in high power factor, a transformer isolated output, and only two active devices are required, both soft-switched. Resonant conversion techniques are used, and a high power factor is achieved by injecting high-frequency currents into the three-phase rectifier, producing a high frequency modulation of the rectifier input voltages. The current injection principle is explained and the system operation is confirmed by a combination of simulation and experimental results.     

A new high-power-factor three-phase AC-DC converter: analysis,design, and experimentation

This paper proposes a new high-power factor three-phase AC-DC power converter, which is composed of a line interphase transformer (LIT) and two three-phase diode rectifiers, followed by a pulsewidth modulation (PWM) DC-DC boost power converter. The active switch of the boost converter is gated at a constant frequency such that the AC input current is discontinuous. This procedure provides an input current shaping without the third, fifth and seventh harmonics. The currents that flow through the LIT and boost inductors have such a high-switching frequency that ferrite cores with a small size can be utilized. In addition, the output voltage is regulated by PWM to compensate for line voltage variations and load change. Theoretical analysis, design procedure and example, along with experimental results taken from a 6 kW laboratory prototype are given     

A new mathematical model and control of a three-phase AC-DC voltagesource converter

A new mathematical model of the power circuit of a three-phase voltage source converter (VSC) was developed in the stationary and synchronous reference frames. The mathematical model was then used to analyze and synthesize the voltage and current control loops for the VSC. Analytical expressions were derived for calculating the gains and time constants of the current and voltage regulators. The mathematical model was used to control a 140-kW regenerative VSC. The synchronous reference-frame model was used to define feedforward signals in the current regulators to eliminate the cross coupling between the d and q phases. It allowed the reduction of the current control loops to first-order plants and improved their tracking capability. The bandwidths of the current and voltage-control loops were found to be approximately 20 and 60 times (respectively) smaller than the sampling frequency. All control algorithms were implemented in a digital signal processor. All results of the analysis were experimentally verified     

多电飞机高压直流电力系统稳定性分析

大量使用的恒功率负载对飞机电网稳定性有至关重要的影响.分析了恒功率负载的特性,建立了多电飞机高压直流电力系统的等效电路模型,基于小信号分析法研究了恒功率负载变化对系统稳定性的影响.研究结果表明,恒功率负载增大会使系统的稳定性降低,而为其并联容性负载可以延缓稳定性降低的趋势.为保护系统,设计了参考电压控制器,重载时降低负...     

Extending the low-speed operation range of PM Generator in automotive applications using novel AC-DC converter control

This paper outlines a case study on an integrated starter-generator-torque-booster (ISGtB) for a hybrid propulsion system, with a particular focus on the generator operation in the low-speed range. The propulsion system consists of an internal combustion (IC) engine and a brushless dc machine and is intended to drive a street scooter. The complex functionality of the ISGtB, some outstanding characteristics of modern IC engines, stringent demands on the generated supply voltage, and operational principle of the selected electrical machine are the reasons for our research on the generator operation. An ac-dc converter and its control are proposed. By utilizing MOSFET transistor reverse conduction characteristics, the idea of synchronous rectification, and the principle of boost switching conversion, several improvements in the generator characteristics are accomplished. The proposed solution, enabling each of the three-phase converter legs to operate as an autonomous boost converter with synchronously driven upper transistors instead of using body diodes, extends the generator operation range below the nominal rotational speed and offers simple yet efficient energy flow control.     

多路输出正激变换器在雷达发射机中的应用

对普通多路输出正激变换器应用过程中存在的问题进行了探讨。对采用耦合滤波电感的多路输出正激变换器减小输出绕组间交叉调节的原理进行了介绍,并对耦合滤波电感的设计方法进行了探讨。设计了三路输出的正激变换器,通过设计实例,对采用耦合滤波电感的多路输出正激变换器设计步骤和设计方法进行了说明。文章最后给出了该变换器PSpice仿真结果及测试结果。     

LM331压频变换器在步进电机驱动器中的应用

本文介绍利用LM331压频变换器设计的一种实用的步进电机驱动器，着重介绍了芯片引脚功能驱动器系统电路及控制原理。     

Efficient application of power modules in energy converter with microprocessor control

At development of energy converters with application of pulse-duration modulation there are problems related to the concordance of levels and shape of pulses, generated by the microcontroller, with control signals at inputs of power transistors. The method this problem solution is considered in the paper.     

Performance evaluation of lead vapor heat-pipe as a stimulated Raman converter for XeCl lasers

High power (6.6 W at 43 pps) stimulated Raman scattering at 459 nm was obtained by down shifting the radiation of a XeCl excimer laser in a lead vapor heat-pipe. Experiments were conducted with different buffer gas species. Photon conversion efficiency as high as 66 percent and energy slope efficiency of 53 percent obtained with Xe as the buffer gas at 1300°C. The apparatus was in daily use for a period of six months without maintenance.     

光伏发电系统中三种DC-DC转换电路的比较研究

为了提高光伏发电系统的转换效率,对降压式、升压式、升降压式这3种转换电路的电路结构和工作原理进行详细的分析。由这3种电路的等效电路图,在MATLAB/Simulink的环境下建立这3种电路的仿真模型,通过仿真的输出结果,计算比较它们的转换效率的高低,最终确定升压式转换电路作为光伏发电系统的DC-DC转换电路。     

浅谈GPS技术在未来林业中的应用

GPS这一先进的测量技术能够快速、高效、准确地提供点、线、面要素的精确三维坐标，广泛应用于造林绿化、森林防火、资源调查等林业工作中。     

未来移动通信的定位与应用

上世纪90年代以来,移动通信飞速发展.迄今全世界移动用户数已经超过17亿,并且越来越多的人使用移动电话接入互联网,仅日本就有6000万以上.目前,3G在全球已经进入规模发展的阶段.与此同时,业界已把目标瞄准容量更大、速率更高、功能更强的未来移动通信系统.那么,未来移动通信的定位是什么？能向我们提供哪些服务？对社会的影响如何？有什么功能要求和技术挑战？文中试图对上述问题作一些初浅的探讨.     

CS5522型A/D转换器及其在小角度测量中的应用

CS5522是24位高精度△-∑型串行A/D转换器.文中介绍了CS5522型A/D转换器的主要性能、引脚构成、内部寄存器及校准方法.结合CS5522型A/D转换器在小角度测量中的实际应用,给出了CS5522型A/D转换器与单片机的接口及系统电路图,最后给出了试验数据.     

基于故障树和神经网络的飞机电源系统故障诊断研究

介绍了基于故障树模型的故障诊断技术和基于神经网络的故障诊断技术，提出了基于故障树和神经网络的集成故障诊断思想。在此基础上，以交流发电机旋转整流器二极管开路故障为例进行了实例分析，说明了故障树和神经网络集成故障诊断技术对此故障的诊断，结果表明该方法用于解决此类问题是有效的。     

Comparative analysis of design concepts of mechatronics systems with a CAD tool for system architecting

In mechatronics systems design, designers need to deal with complexity derived from the integration of subsystems with various engineering disciplines. In particular, while developing product architecture for the next generation systematically, the present generation systems in the market should be reviewed in terms of their functional overview as well as module structure. This paper proposes a method for developing product architecture by a comparative analysis of the functional overview as well as physical decomposition of existing mechatronics systems. The method employs function–behaviour–state modelling and a computer-aided design (CAD) system for system architecting (SA-CAD) as a modelling scheme and modelling environment, respectively. The paper describes the application of the proposed method in the development of product architecture of autonomous vacuum cleaning robots.     

基于RBF神经网络在转炉炼钢终点预报中的应用研究

转炉炼钢控制目标是对终点温度和含碳量进行预测。由于我国转炉炼钢自动化控制水平的限制,特别是动态控制水平不够高,因此需要基于RBF神经网络建立终点预报模型。其基本思路为:基于RBF神经网络局部逼近网络的特性之上,采用k-均值聚类算法确定隐藏层的中心,权值调整采用递推最小二乘法,建立基于RBF神经网络在转炉炼钢终点预报的模型。最后结合实际数据进行模型的仿真研究。结果表明经RBF神经网络预测模型的实时训练,提高了终点预报的精度。     

The application of optical packet switching in future communicationnetworks

Telecommunication networks are experiencing a dramatic increase in demand for capacity, much of it related to the exponential takeup of the Internet and associated services. To support this demand economically, transport networks are evolving to provide a reconfigurable optical layer which, with optical cross-connects, will realize a high-bandwidth flexible core. As well as providing large capacity, this new layer will be required to support new services such as rapid provisioning of an end-to-end connection under customer control. The first phase of network evolution, therefore, will provide a circuit-switched optical layer characterized by high capacity and fast circuit provisioning. In the longer term, it is currently envisaged that the bandwidth efficiency associated with optical packet switching (a transport technology that matches the bursty nature of multimedia traffic) will be required to ensure economic use of network resources. This article considers possible network application scenarios for optical packet switching. In particular, it focuses on the concept of an optical packet router as an edge network device, functioning as an interface between the electronic and optical domains. In this application it can provide a scalable and efficient IP traffic aggregator that may provide greater flexibility and efficiency than an electronic terabit router with reduced cost. The discussion considers the main technical issues relating to the concept and its implementation     

MPLS在未来IP网络中的应用设想

分析了MPLS在未来IP网络中的可能的应用前景,认为信息骨干网络可能由光的MPLS和电的MPLS两层网络组成,并完成骨干网上的IP路由,边缘路由器完成边缘的IP路由交换,着重提出了光的MPLS的实现方法和基本原理及结构。     

The application of COTS technology in future modular avionicsystems

Current avionic systems make extensive use of military specifications and standards but are based on dedicated implementations for individual avionic functions. The result is a proliferation of military devices, software and support environments that are expensive to develop, procure and support. Future systems will be based on integrated modular avionic concepts in which all functions are implemented on a common processing platform constructed from a standard set of hardware and software modules. The paper describes the approach being taken to optimise the application to future modular systems: an architecture based on standardised interfaces will allow modules to be based on commercial components and standards to achieve affordability and exploit rapid advances in commercial technology. At the same time, approaches are being developed to deal with COTS (commercial off-the-shelf) application problems such as short commercial time-scales and loss of control over specifications and standards