SnGe Asymmetric Quantum Well Electroabsorption Modulators for Long-Wave Silicon Photonics

In recent years, SiGeSn alloys have been considered as promising materials for optoelectronic applications because they offer the possibility of a direct bandgap, and are compatible with Si-based technology; therefore, they have prospective applications such as in interband lasers and detectors, solar cells, etc. Here, we consider another possible application of nanostructures based on these materials: to extend the suite of Si-based optoelectronic devices for interband electroabsorption (EA) modulators. Using the 8-band $hbox{bf k.p}$ method, we have designed asymmetric double quantum wells that are optimized, by varying the well and barrier widths and material composition, to show large optical transmission sensitivity to the applied bias. Generally, these structures are useful for EA modulators in the midinfrared spectral range.      

High-Speed Miniaturized Photodiode and Parallel-Fed Traveling-Wave Photodetectors Based on InP

A periodic parallel-fed traveling-wave photodetector (TWPD) with monolithically integrated power splitter is presented. The device exhibits an impedance match to the 50-Omega environment as well as a velocity match between the optical and electrical signals and shows a 3-dB bandwidth up to 85 GHz. The electrical output power reaches +10 dBm at 10 GHz. The device is based on evanescently coupled low-capacitance waveguide-integrated p-i-n photodiodes (PDs) with optimized optical matching layer which reveal a bandwidth of 145 GHz when employed as a stand-alone photodetector     

Monolithic Wavelength Converters for High-Speed Packet-Switched Optical Networks

This paper describes the design and demonstration of advanced 40-Gb/s return-to-zero (RZ) tunable all-optical wavelength converter technologies for use in packet-switched optical networks. The device designs are based on monolithic integration of a delayed interference Mach-Zehnder interferometer (MZI) semiconductor optical amplifier (SOA) wavelength converter with a sampled-grating distributed Bragg reflector tunable laser and an on-chip waveguide delay. Experimental results are presented demonstrating error-free wavelength conversion with 1-dB power penalty at 40-Gb/s data rates. By incorporating label modulation functionality on-chip along with a fast tunable 40-Gb/s wavelength converter, fully monolithic packet-forwarding chips are realized that are capable of simultaneous error-free wavelength conversion of 40-Gb/s payloads, remodulation of 10-Gb/s packet headers, and data routing through fast wavelength switching     

Development and Investigation of a New High-Speed Directional Relay Using Field Data

In this paper, a new high-speed directional relay is proposed. The relay is based on the current and voltage signals before and after fault occurrence. The voltage signal is compensated and then used as a reference. The relay is used for the directional comparison protection of extremely high voltage transmission lines. An evaluation of the suggested directional relay is investigated using recorded fault data from the Alberta power transmission system. The real effects of the power system elements, which might have not been completely considered in the mathematical model of the power system, have been included in the recorded real fault data. In this case, the performance of the new directional relay can be verified in a more realistic environment than simulation.     

基于级联神经网络的电机转速和负载转矩辨识

合理选择电机容量具有重要意义,而电机容量可根据电机转速和负载转矩确定.此处提出利用级联BP神经网络估计电机转速和负载转矩的方法,将两个神经网络级联,第一级网络输入为电机定子电压,输出为定子电流和转速;第二级网络输入为第一级网络的输出,输出为负载转矩,形成了级联BP神经网络模型,实现了异步电机转速和负载转矩的同时估计.实...     

基于概率神经网络的凝汽器故障诊断研究

基于概率神经网络(PNN)提出了一种新的汽轮机组凝汽器故障诊断方法。PNN是一种可用于模式分类的神经网络,其实质是基于Bayes分类规则与Parzen窗的概率密度函数方法发展而来的一种并行算法。PNN可以克服反向传播神经网络(BPNN)学习收敛速度慢、易陷入局部极小值等问题,而且优于常见的凝汽器故障诊断方法:PNN学习规则简单,训练速度快,可以满足训练上实时处理的要求;训练不需要太多样本,模式分类能力强,而且具有很高的运算速度;抗干扰能力强,对传感器测量噪声具有较强的诊断鲁棒性;新的训练样本也很容易加入以前训练好的分类器中,很适用于在线检测。将该方法用于某汽轮机组凝汽器故障诊断中,仿真结果表明了该网络在分类应用中的快速性、准确性,而且易于工程实现。     

Operation and Optimization of Silicon-Diode-Based Optical Modulators

An optical modulator in silicon based on a diode structure has been operated in both forward and reverse bias. This modulator achieves near state-of-the-art performance in both modes, thereby making this device ideal for comparing the two modes of operation. In reverse bias, the device has a V $_pi$L of 4.0 V·cm and a bandwidth of 26 GHz. In forward bias, the device is very sensitive, a V$_{pi}$ L as low as 0.0025 V·cm has been achieved, but the bandwidth is only 100 MHz. A new geometry for a reverse-bias device is proposed, and it is predicted to achieve a $V_{pi}L$ of 0.5 V·cm.      

Using Neural Networks in Controlling Low- and Medium-Capacity Gas-Turbine Plants

The possibilities of using neural network technologies for synthesizing new and improving existent gas-turbine plant (GTP) control systems are considered. Modern gas-turbine plant control systems are often developed on the basis of aviation automatic control systems, without taking into account the peculiarities of load changes in electricity generation. As a result, frequency-related quality indicators of electricity, such as maximum deviation and recovery time, do not always meet requirements that have been set out. This study is aimed at improving the quality of generated electricity. A list of different disturbances that can arise in an electric power system is provided, as well as the results of using the neural network model of a GTP to optimize the parameters of the gas-turbine unit adjuster.     

Off-Road Path and Obstacle Detection Using Decision Networks and Stereo Vision

Autonomous driving in off-road environments requires an exceptionally capable sensor system, particularly given that the unstructured environment does not provide many of the cues available in on-road environments. This paper presents a complex vision system, which is able to provide the two basic sensorial capabilities needed by autonomous vehicle navigation in extreme environments: obstacle detection and path detection. A variable-width-baseline (up to 1.5 m) single-frame stereo system is used for pitch estimation and obstacle detection, whereas a decision-network approach is used to detect the drivable path by a monocular vision system. The system has been field tested on the TerraMax vehicle, which is one of the only five vehicles to complete the 2005 Defense Advanced Research Projects Agency (DARPA) Grand Challenge course.     

Performance of a High-Speed Motor Drive System Using a Novel Multilevel Inverter Topology

The performance of a novel multilevel six-switch (SS) three-phase inverter drive is examined for low-voltage high-speed motor applications. The switching losses of hard-switched voltage-source-inverter topologies place limits on the maximum feasible switching frequency. When operating at higher fundamental frequencies, this results in low-frequency modulation ratios and either high load harmonic currents that cause excessive rotor heating or larger than desired output reactors with a large fundamental voltage drop. The multilevel inverter structure examined offers an increased number of output pulsewidth-modulated (PWM) voltage levels, higher frequency PWM output waveforms, reduced dead-time effects, and a significant reduction in harmonic content. These features reduce the total losses in the motor load when compared to the standard SS three-phase inverter. The harmonic reduction provided by the multilevel topology relative to the standard inverter is experimentally demonstrated with a 15-hp 18 000-r/min induction machine.     

EDITORIAL - Power Modulators and Repetitive Pulsed Power

Plasma breakdown at dielectric windows in the output of high power microwave systems has become an important challenge with the advent of GW power level sources. The modeling and simulations have played a crucial role in understanding the physics of plasma breakdown. In this work, we report a number of recent advances which have significantly improved understanding of the physics of vacuum multipactors, gaseous discharges driven by microwaves, and the transition from one regime to the other by varying the gas pressure.     

BP网络在无刷直流电机参数辨识与控制中的应用

在无刷直流电机控制系统中，采用基于熵类误并准则学习算法的BP网络，克服了传统BP算法收敛速度慢，易收敛于局部极小值的缺点，避免了“过学习”的现象，实现了控制系统中电机参数的实时辨识，从而提高了控制系统的性能。     

High bit-rate OTDM transmission over standard fiber using mid-spanspectral inversion and its limitations

An accurate modeling of very high bit-rate transmission systems over standard-fiber using mid-span spectral inversion (MSSI) is reported. As for the pulsewidth, comparison of simulations with experimental data in an 80-Gb/s transmission system over 106 km shows that second-order group velocity dispersion (GVD) is the limiting factor in this transmission scheme. Additionally, it is shown that even though first-order GVD can be compensated easily second-order GVD, is still remaining. It is pointed out that the performance of the system is very sensitive to the length of the different fiber spans     

球形二自由度超声波电机的运行机理和特性

球形二自由度超声波电机可以实现二个自由度的运动,从二自由度行波型超声波电机的基本结构与驱动原理出发,建立了定转子的位置关系式,从而得到电机的驱动力方程,进而求出定子的驱动力矩方程,然后分别对转子在静止和转动情况下的驱动力方程做了讨论,最后求出球形二自由度超声波电机的驱动力矩数学模型.随之通过电机的结构参数对电机的驱动力矩进行了仿真计算,然后通过实验对驱动力矩做了初步验证,实验结果证明了数学模型的有效性,对二自由度行波型超声波电机的优化设计和性能提高奠定了理论基础.     

基于模糊神经网络的超声电机的位置控制

超声电机的优良特性使其得到越来越广泛的应用,但由于其时变和非线性特性,使电机的速度和位置控制成为研究热点。文中将模糊神经网络用于电机的位置控制中,模糊逻辑部分获得专家知识,神经网络部分调整参数,通过改变超声电机的驱动频率来实现精确的位置控制,并通过实验和仿真来验证这种方法的有效性。     

基于双DSP和FPGA的行波超声波电动机测控系统

根据对行波超声波电动机(TUSM)测试和高精度控制的要求,设计了基于双DSP和FPGA的超声波电动机高性能测试控制平台.其中控制核心采用了双DSP结构,可以在对行波超声波电动机进行控制的同时,将必要的参数读取出来进行分析和研究;采用现场可编程门阵列(FPGA)的直接数字频率合成(DDS)电路来产生控制开关管导通关断的两相四路高精度PWM波,减轻了DSP的负担.驱动部分采用全桥电路对信号进行功率放大.该系统的优点在于实时性好、精度高、功能完备.最后以直径为60 mm的行波超声波电动机为例,测试分析了驱动频率、电压以及相位差等调节量对电机输出的影响,验证了该系统的性能.     

应用无线传感网络的分布式电力系统接地状态监测

为提高检修工作的可靠性,针对变电站线路检修时倒闸操作和挂接地线的情况,研发了一套接地检测与管理系统,系统基于非接触传感和ZigBee无线局域网络技术,采用双钳口法测量激励、检回信号,节点可以移动技术,最大限度减少了系统线路的铺设与维护;在建立了应用于接地状态检测中的无线传感器网路结构模型后,给出了无线传感网络接地检测系统的硬件设计与软件实现方法,该系统实现了状态检测、分析、管理、集中显示各点接地状态等功能。理论分析和仿真结果表明,系统数据采集链路的传输可靠性,系统数据会聚时延,接地电阻测量精度,网络节点的维护等指标均达到较高水平,系统满足电力系统对接地状态实时监控的要求。     

使用辅助槽减小高速永磁电动机的转子涡流损耗

在高速永磁电动机中,转子涡流损耗会使转子温度升高,影响电机效率等性能,甚至导致永磁体过热退磁。针对高速永磁电动机中的转子涡流损耗问题,提出使用辅助槽来减小转子涡流损耗,研究了不同宽度、深度、槽型、数目和槽角的辅助槽对转子涡流损耗的影响,分析了其减小转子涡流损耗的原因以及开辅助槽对电机性能的影响。得出通过选取合适的辅助槽可以减小转子涡流损耗,同时不会明显降低电机的反电势。对高速永磁电动机的设计和分析具有重要的理论研究和工程应用价值。     

Protection of large partitioned MTDC Networks Using DC-DC converters and circuit breakers

This paper proposes a DC fault protection strategy for large multi-terminal HVDC (MTDC) network where MMC based DC-DC converter is configured at strategic locations to allow the large MTDC network to be operated interconnected but partitioned into islanded DC network zones following faults. Each DC network zone is protected using either AC circuit breakers coordinated with DC switches or slow mechanical type DC circuit breakers to minimize the capital cost. In case of a DC fault event, DC-DC converters which have inherent DC fault isolation capability provide ‘firewall’ between the faulty and healthy zones such that the faulty DC network zone can be quickly isolated from the remaining of the MTDC network to allow the healthy DC network zones to remain operational. The validity of the proposed protection arrangement is confirmed using MATLAB/SIMULINK simulations.