Stadium and quasi-stadium laser diodes

We present theoretical and experimental studies on two-dimensional microcavity laser diodes with stadium and quasi-stadium shapes. We report a demonstration of lasing for the first time in a fully chaotic microcavity-a stadium-shaped cavity which is rigorously known to be fully chaotic. We also present systematic studies on quasi-stadium laser diodes for three types of resonator conditions: stable, marginally stable, and unstable. Morphological dependence of lasing characteristics of quasi-stadium laser diodes is elucidated. We also show examples of the application of quasi-stadium laser diodes to beam switching operation and optical signal distribution by using patterned electrodes and the phase locking phenomenon between two resonator modes.     

基于虚拟同步发电机的微网运行模式无缝切换控制策略

对于采用对等控制策略的微网系统,如何实现孤岛/并网运行模式间的无缝切换是一项亟待克服的技术难点。文中首先介绍微网系统的基本结构与工作模式,针对微网孤岛与并网运行模式的特点,提出一种满足微网孤岛/并网切换的虚拟同步发电机(VSG)控制策略。其次,为了适应微网的并网运行特性,提出一种基于控制器状态跟随的并行切换方法,即PQ控制的电流源模式和VSG控制的电压源模式的相位和电流指令都实时跟踪,为PQ/VSG控制模式间的无缝切换奠定基础。最后,建立微网系统的仿真模型和实验平台,共同验证了所提控制策略和并行切换方法的有效性。     

Performance analysis and calculation of critical inductance and output voltage ripple of a simple non‐isolated multi‐input bidirectional DC‐DC converter

In this paper, a simple non‐isolated multiple input (MI) bidirectional DC‐DC topology is proposed which can operate in buck, boost, or buck‐boost modes. The proposed topology utilizes a battery pack to realize the bidirectional power flow operation especially when the input sources are non‐storable ones. The excess energy of input sources can be stored in the battery and be injected to the load, when required. Simultaneous or independent power transfer of input sources is also provided. For better evaluation, the proposed topology has been compared with several recently presented novel topologies, from view point of number of inductors, capacitors, switches, and diodes. Comparison results show that the proposed topology utilizes less number of components (switches, inductors, capacitors, and current sensors) which can reduce the size, cost, and complexity of converter. Different operational modes of the proposed topology (unidirectional buck, boost, buck‐boost modes, and bidirectional mode) have been presented. Also, boost mode of the proposed topology has been investigated in detail, from design point of view, and generalized relationships have been proposed for calculation of critical inductance (CI) and output voltage ripple (OVR) of proposed n‐input boost topology. To validate proposed theoretical concepts, the proposed topology has been modeled and simulated in PSCAD/EMTDC software, and the 3‐input boost version has been experimentally implemented. Simulation and experimental results confirm appropriate performance of the proposed topology.     

双降压式全桥逆变器

为避免桥臂功率管直通问题和提高输入直流电压利用率,在全桥逆变器和双降压式半桥逆变器的基础上,提出了双降压式全桥逆变器(dual buck full-bridge inverter,DBFBI),该逆变器具有无桥臂直通、输入直流电压利用率高、效率高、续流二极管可优化选取等优点。半周期调制方式减小了功率管的开关损耗及导通损耗,分析了半周期调制方式下电路的工作模态,给出了电感电流连续与断续时输入输出电压关系。设计了采用滞环电流控制的双降压式全桥逆变器系统,通过控制逻辑设计使之实现了半周期运行模式。仿真和实验结果证明该逆变器具有高质量的输出电压波形和良好的动态响应特性。     

Control of Electron-Beam Surfacing-Process Parameters Using Current Signals of the Wire and Article

This paper presents a method of control of the metal-transfer mode during electron-beam surfacing with a filler-wire feed based on simultaneous recording of the potential of the wire and article connected with the apparatus frame through the resistors. The main metal-transfer modes are specified that are observed with a change of the energy-input rate. The importance of the solved problem for additive technologies is shown. A scheme of experimental investigations carried out at the ELA-15I apparatus is given, and the obtained oscillograms are presented. The relation of the characteristics of the registered signals with the operation modes of the equipment and transfer parameters is shown. It is noted that, with a change of only the filler-wire feed rate, a changeover from drop metal transfer to the scattering mode can be triggered. The possibility of detecting the mode of appearance of the shot metal, as well as emergency modes related with stopping the filler-wire feed or excessive increase of its feed rate, is substantiated. The influence of the plasma processes on the registered signals in the developed scheme is analyzed, and it is also shown that, to reduce the influence of these processes, it is necessary to decrease the resistance of the measuring circuit. Photographs of the process corresponding to the certain oscillogram intervals are given.     

独立模式串/并联输出并网逆变器的外特性

针对独立模式下串/并联输出并网逆变器的两种输出模式对输出电压外特性的影响,提出了一种新的控制策略。阐述了该逆变器的工作原理和串并联两种输出模式的控制策略,分析了两种输出模式的外特性及各参数对外特性的影响,并以一台1kVA串/并联输出双降压式半桥逆变器为例进行了仿真和实验验证。其结果表明,在新的控制策略下,串/并联输出模式均不影响输出电压的稳压精度。     

LLC谐振变换器PO模式增益公式与模式边界条件分析

电压增益-频率特性的求解是LLC谐振变换器设计的关键。变换器中整流电路存在的非线性使变换器具有多种工作模式,而电压增益-频率特性与工作模式密切相关。PO模式是一种有利于减少变换器开关损耗的断续工作模式,但在该模式下,变换器的增益频率特性计算烦琐,难以求解。文中基于子区间分析法,分析了PO模式下LLC谐振变换器的工作特性,推导了简洁易算且精度较高的电压增益计算公式;依据变换器整流电路的非线性特征,给出了解析且简洁的断续工作模式功率边界条件及PO工作模式功率边界条件的表达式。搭建了LLC谐振变换器的仿真模型和实验样机,仿真和实验结果证实了所提出的电压增益公式及工作模式边界条件的正确性。     

双母线直流微电网的级联稳定性分析

双母线直流微电网因具有供电可靠、负载匹配性高、接入中低压配电网系统灵活方便等特点,逐渐成为未来家庭和楼宇的主要供电架构之一,而级联稳定性分析是其设计中的重要问题.对双母线直流微电网在不同稳态运行模式下的级联小信号稳定性进行分析,利用广义状态空间建模法、传统状态空间平均建模法建立变换器的阻抗模型,根据系统各单元稳态运行模式的源荷属性提出4种模式,并利用阻抗比判据判定系统的小信号稳定性.仿真结果表明,在轻载模式下系统的稳定裕度最小,其中双有源桥、光伏变换器的阻抗特性不受功率交互的影响且一直具有负阻抗特性,而储能单元仅在作为负荷时具有负阻抗特性.对比3种无源阻抗方案以改善负载阻抗特性,提高系统的稳定裕度.实验结果表明:加入无源阻抗后轻载模式的负载电流纹波系数从14.3％下降至1.9％,可见无源阻抗可以改善负载阻抗特性,提高系统的稳定性和抗扰性能.     

Influence of representation model and voltage harmonics on metaloxide surge arrester diagnostics

Test results have been presented to demonstrate the hysteretic character of the volt-ampere relation of a metal oxide surge arrester (MOSA). Using a compensation technique described in the paper, it is shown that the use of single valued average volt-ampere characteristics does not introduce large errors in simulation studies. Results from computer simulation are presented to demonstrate the considerable influence of harmonics in the applied voltage on the magnitude of diagnostic indicators     

基于改进模态分解的中压地埋电缆载波通信信道特性分析

对中压电力线信道特性的研究是构建中压载波通信系统的重要基础。针对目前中压地埋电缆的多模传输特性尚未明确,屏蔽层与钢铠接地对信道特性的影响尚未被详细考虑的情况,将多导体传输线模型与回路分析相结合,通过改进模态分解确定了中压地埋电缆的4类传输模态及其传输特性,并通过比较该方法与高频结构仿真(HFSS)的计算结果验证了所提方法的有效性。之后,基于模态分解的结果计算了载波信号的衰减与相移特性,并通过实验测量验证了其可信性。最后,结合多模态传输特性讨论了屏蔽层与钢铠接地对中压地埋电缆信道特性的影响。结果表明:当信号通过芯线与屏蔽耦合时,其信道特性几乎不受屏蔽层与钢铠接地的影响;当信号通过屏蔽与地耦合时,信道特性与接地阻抗密切相关。     

带辅助网络的倍流整流式全桥ZVS三电平变换器

针对传统全桥三电平零电压变换器存在的缺点,提出了一种新型的全桥三电平零电压变换器拓扑.在电路拓扑中,变压器一次侧加入了一个由耦合电感和电容组成的辅助网络,而在输出端采用了倍流整流电路.耦合电感和输出滤波电感中储存的能量使得变换器可在宽负载范围内实现每个开关管的零电压开关,而倍流整流电路可以使两个整流二极管在零电平的时候实现自然换流,从而克服变压器二次侧占空比丢失和电压过冲的问题.本文详细分析了此电路的工作模态以及其零电压、实现自然换流的条件,并通过一台24V/5A,50 kHz样机进行了实验,验证了理论分析的正确性.     

Room-temperature lasing operation of GaInNAs-GaAssingle-quantum-well laser diodes

We have succeeded in demonstrating continuous-wave (CW) operation of GaInNAs-GaAs single-quantum-well (SQW) laser diodes at room temperature (RT). The threshold current density was about 1.4 kA/cm², and the operating wavelength was approximately 1.18 μm for a broad-stripe geometry. Evenly spaced multiple longitudinal modes were clearly observed in the lasing spectrum. The full-angle-half-power far-field beam divergence measured parallel and perpendicular to the junction plane was 4.5° and 45°, respectively. A high characteristic temperature (T₀) of 126 K under CW operation and a small wavelength shift per ambient temperature change of 0.48 nm/°C under pulsed operation were obtained. These experimental results indicate the applicability of GaInNAs to long-wavelength laser diodes with excellent high-temperature performance     

Experimental and finite-element analysis of an electronic pole-change drive

The theory and modeling of an electronic pole-change drive for the purpose of extending the constant power speed range of a four-pole induction machine have been previously reported. This paper presents verification of the power capability characteristics of the proposed drive through experimental implementation. An indirect field-oriented controller is developed for the pole-change drive with the estimated rotor open-circuit time constant and d-axis-current commands dependent on the mode of operation. It is demonstrated that, for a constant power load, the drive can operate at 6340 r/min in two-pole mode without exceeding either the voltage or current limits at 3600 r/min in four-pole mode. A finite-element method is also utilized to examine the influence of magnetic saturation on the pole-change drive performance. The nature of the magnetic flux distribution and saturation progression is investigated in both four-pole and two-pole modes. The saturation-induced inductance variation is also studied and its influence on the dq inductance matrix is quantified.     

A Multi-Functional Single-Stage Power Electronic Interface for Plug-In Electric Vehicles Application

This paper proposes a Zeta-derived non-isolated single-stage power electronic interface for on-board application of plug-in electric vehicles, which provides all modes (plug-in charging, propulsion, and regenerative braking) of vehicle operation. In addition, the proposed converter can charge the battery through universal input voltage range, i.e., 90–260 V due to buck/boost operations in plug-in charging mode. In propulsion and regenerative braking modes, the proposed converter operates as conventional boost and buck DC/DC converter, respectively. Compared to existing single-stage converters, the proposed converter has least components to those converters which have buck/boost operation in plug-in charging mode. A voltage/current stresses and loss analysis of the converter have been investigated for each mode of converter operation. Detailed simulation and experimental results are given to show the effectiveness of the proposed converter.     

变压器式可控电抗器的控制特性和谐波特性

控制特性和谐波特性是变压器式可控电抗器(controllable reactor of transformer type,CRT)的2个重要特性。文中首先给出CRT绕组电流计算模型;其次,对顺次单支路工作模式和解耦工作模式这2种典型工作模式的特点进行了分析;最后,结合具体算例,基于绕组电流计算模型,分别在顺次单支路工作模式和解耦工作模式下对CRT的控制特性和谐波特性进行了计算和对比。计算分析结果表明:顺次单支路工作模式下谐波系数总能满足要求,但各控制绕组的额定值设计较困难且绕组材料浪费严重;解耦工作模式下绕组材料利用率大大提高,但却有谐波系数较大而且不可控的缺点。上述结果揭示了CRT的控制特性和谐波特性与工作模式之间的关系,为不同工作模式下CRT的控制特性和谐波特性的分析计算,以及工作模式的选择和改进提供了参考。     

Novel laser structures based on MQW interdiffusion using rapidthermal annealing technique

In this paper, experimental results for GaAlAs-GaAs multiple-quantum-well (MQW) interdiffusion using rapid thermal annealing (RTA) technique under different processing conditions are presented and discussed. Two kinds of novel laser structures based on such technique are also proposed and fabricated. First, a laser diode with window region for high-power operation is designed and fabricated. The maximum output power of such a device shows an increase by 18% over laser diodes without interdiffused window region. Then a transverse mode controlled laser structure taking advantages of the refractive index change induced by MQW interdiffusion is realized using RTA technique. Single-mode operation up to four times the threshold current has been demonstrated for this RTA treated laser diode     

双馈风电场接入交流或交直流混合系统低频振荡 模态对比分析

目前,风电并入交直流混合系统低频振荡模态研究未见文献报道。在PSASP中搭建了CEPRI36节点系统中含双馈风电场的纯交流系统和交直流混合系统的小信号稳定性分析的详细模型。对计及了风力机传动链、双馈发电机、变换器和直流输电动态模型及其控制策略,且直流系统运行在双极两端中性点接地、单极大地回线、单极金属回线、单极双导线并联大地回线四种不同接线方式下的小信号稳定性进行了仿真。从双馈风电场接入交流或交直流混合系统并参与有功或无功调度两种运行方式角度,采用模态分析法进行了电网区间和局部区域低频振荡模态对比分析。结果表明：双馈风电场接入交直流混合系统的低频振荡特性不仅与直流线路运行接线方式存在关联,而且受接入的风电场运行方式影响。与接入交流系统比较,接入交直流混合系统区间振荡的恶化程度变大、稳定裕度更差。     

LCC?HVDC逆变侧换流站近区交流线路高阻接地故障保护

基于电网换相换流器的高压直流(LCC-HVDC)换流站近区交流线路高阻接地故障切除不及时易引发连续或后续换相失败,造成换流站单双极闭锁,威胁着系统运行安全性.文中分析了影响零序差动保护动作特性的关键因素,指出高阻接地故障保护需从传统的阈值整定模式调整为对被保护线路故障支路特性变化的定性描述和甄别.基于弧光高阻接地故障支路的非线性伏安特性辨识以及同塔并架相邻线路广域方向信息的配合,提出了适用于LCC-HVDC换流站近区交流线路的高阻接地故障启动元件、方向元件及保护方案.最后,通过仿真验证了保护方案的有效性.     

The Performance of a Single-Phase Current-Fed Inverter with Counter EMF?Inductive Load

Current-fed inverters that have series diodes to trap the charge on a commutating capacitor can supply ac loads of any power factor. A single-phase circuit with counter emf-inductance load, such as a motor, has been analyzed by digital computer simulation, valid for all modes of operation. The magnitude and phase of the ac load current are graphically related to the direct current and thyristor firing angle with respect to the counter emf. The ratio of the operating frequency to the natural ringing frequency of the commutating capacitance and the load inductance is a parameter of the circuit that significantly affects its behavior. Problems associated with high-frequency operation in a drive system are discussed.     

泵站用同步电动机反向发电运行方式的研究

本文阐述了利用现有泵站进行反向发电的意义和应用价值,分析了泵站反向发电时同步电动机可采用的运行方式,论述了泵站反向发电运行方式选择的依据,并以江苏某泵站为例,说明了运行方式选择的方法.