Relationship Between Noise Figure and Equivalent Input Noise Current Spectral Density for Optical Receiver Design

Based on the equivalent circuit model of a two-port optical receiver front-end,the relationship between the equivalent input noise current spectral density and the noise figure is analyzed. The derived relationship has universal validity for determining the equivalent input noise current spectral density for optical receiver designs, as verified by measuring a 155Mb/s high-impedance optical receiver front.end. Good agreement between calculated and simulated results has been achieved.

Improving the estimate of wind energy input into the Ekman layer within the Antarctic Circumpolar Current

Based on the data and method offered by Liu et al. （2009）, the direct wind and Stokes drift-induced energy inputs into the Ekman layer within the Antarctic Circumpolar Current （ACC） area are reestimated since the results of the former have been proved to be underestimated. And the result shows that the total rate of energy input into the Ekman-Stokes layer within the ACC area is 852.41 GW, including 649.75 GW of direct wind energy input （76%） and 202.66 GW of Stoke drift-induced energy input （24%）. Total increased energy input, due to wave-induced Coriolis-Stokes forcing added to the classical Ekman model, is 52.05 GW, accounting for 6.5% of the wind energy input into the classical Ekman layer. The long-term variability of direct wind and Stokes drift-induced energy inputs into the Ekman layer within the ACC is also investigated, and the result shows that the Stokes drift hinders the decadal increasing trend of direct wind energy input. Meanwhile, there is a period of 4-5 a in the energy spectrums, as same as the Antarctic circumpolar wave.

Input Admittance and Current Distribution of Infinitely Long Circular Cylindrical Antenna Driven at Center

In this paper, by change of integration path in complex spectrum domain and by defining input admittance as the ratio of complex radiated power to amplitude of square of voltage across the gap, new expressions of admittance (valid for all frequencies ) of infinitely long cylindrical antenna with and without conducting ground are obtained. Meanwhile corresponding formulas of current distribution are derived in detail. Some numerical computations are also given.

Effects of wind input and wave dissipation formulations on the steady Ekman current solution

The effects of different wind input and wave dissipation formulations on the steady Ekman current solution are described. Two formulations are considered: one from the wave modeling(WAM) program proposed by Hasselmann and Komen and the other provided by Tsagareli and Babanin. The solution adopted for our study was presented by Song for the wave-modifi ed Ekman current model that included the Stokes drift, wind input, and wave dissipation with eddy viscosity increasing linearly with depth. Using the Combi spectrum with tail effects, the solutions are calculated using two formulations for wind input and wave dissipation, and compared. Differences in the results are not negligible. Furthermore, the solution presented by Song and Xu for the eddy viscosity formulated using the K-Profi le Parameterization scheme under wind input and wave dissipation given by Tsagareli and Babanin is compared with that obtained for a depth-dependent eddy viscosity. The solutions are further compared with the available well-known observational data. The result indicates that the Tsagareli and Babanin scheme is more suitable for use in the model when capillary waves are included, and the solution calculated using the K-Profi le Parameterization scheme agrees best with observations.

Input-parallel output-parallel configuration of boost half bridge DC-DC converter with control strategy

The concept of connecting two boost half bridge DC-DC converter modules in input-paral- lel output-parallel configuration is presented. The input-parallel-output-parallel （IPOP） converter consists of multiple boost half bridge （BHB） DC-DC converter modules which are connected in par- allel at the input and output side. This kind of converter is an attractive solution for high power ap- plications. The correlation between input current sharing （ICS） and output current sharing （OCS） of the IPOP converter basic modules is described. Two loop control strategies, consisting of input cur- rent loop and output voltage loop, have been developed to achieve equal ICS and OCS in this present work. The control strategy for the IPOP configuration of boost haft bridge DC-DC converter has been verified for different load conditions （half load and full load）, The IPOP system proposed here is comprising of two modules but it can be extended to three or more. The performance of the pro- posed system along with the control strategy is verified by simulation in MATLAB using Simpower tool. Finally the satisfactory simulation results are obtained.

Input series out putparallel based multi-modular boost half bridge DC-DC converter with a dynamic control scheme

Multi-modular system plays an important role in power system architecture because low voltage and low power converters can be connected in any combination parallel or series at input/ output side in order to obtained any given power system specifications. Multi-modular boost haft bridge DC-DC converter in the configuration of input series output parallel has been investigated in this paper. The boost half bridge DC-DC converters are connected in input series output parallel con- figuration in order to achieve equal input voltage sharing and output current sharing between the con- verters. This can be achieved with the help of dynamic control scheme which consists of two loops, a voltage loop and a current loop, for each module. Dynamic behavior of multi-modular converter configuration has been observe by varying the load condition. Moreover, the results obtained through multi-modular converter describe that the system has good dynamic and steady state response. Al- though two converter modules are focused in this paper but it can be modified to any number of modules.

Efficient Supply Current Control Strategies for Bridgeless Interleaved AC-DC Converter

This paper presents an efficient supply current wave shaping technique for bridgeless interleaved Single Ended Primary Inductor Converter(SEPIC).The SEPIC converter converts an Alternating Current(AC)to Direct Current(DC)with the boost converter.Power Factor Correction(PFC)is progressively significant to achieve high energy efficiency.The overall system efficiency can be increased as the bridgeless topology has less conduction losses from rectifying bridges.Also,the bridgeless and interleaved techniques are incorporated in this study to achieve better performance.The performance of the system is analyzed on both current control and sensor-less techniques.Different controllers such as Proportional Integral(PI)control,peak current control,Non-Linear Carrier(NLC)control,and sensor-less current control are integrated.All the above controllers are implemented using MATrix LABoratory(MATLAB)/SIMULINK.The performance parameter,namely Power Factor(PF),Total Harmonic Distortion(THD),is computed for both open loop and closed loop condition.The sensor-less current control method is implemented using the DsPIC30F2010 controller.The circuit performance is also verified from the simulation and hardware results.The proposed controller has inbuilt Analog-to-Digital Converter(ADC),Digital-to-Analog Converter(DAC),Pulse Width Modulation(PWM)generator,and provides fast responses.

New Current Mode Lossy Integrator Employing CDDITA

This work presents a novel current-mode (CM) lossless integrator that uses one current differencing differential input transconductance amplifier (CDDITA) and one grounded capacitor. The configuration based on single active element has several advantages from the aspect of monolithic integration, few are: reduced power consumption, chip miniaturization. Employment of grounded capacitor is also beneficial for monolithic integration. Specifying some of the key features of integrator proposed are: 1) purely resistorless, 2) electronically tunable, 3) current output available at the port having high impedance, and 4) excellent performance under non-ideal conditions. So, a resister-less current mode lossy integrator with electronic control employing single CDDITA has been proposed in this paper. The verification of workability of the proposed current mode integrator is well explained by the help of SPICE simulations using TSMC CMOS 0.18 μm technology node.

Three Phase Dual Input Direct Matrix Converter for Integration of Two AC Sources from Wind Turbines

This project proposes a novel dual-input matrix converter (DIMC) which is used to integrate the output of the wind energy to a power grid. The proposed matrix converter is developed based on the traditional indirect matrix converter under reverse power flow operation mode, but with its six-switch voltage source converter replaced by a nine-switch configuration followed by the current source inverter (CSI). Matrix electric power conversion topologies and their switch functions are flexible and are used for specific applications. With the additional three switches, the proposed DIMC can provide six input terminals, which make it possible to integrate two independent AC sources from two independent wind turbines into a single grid tied power electronics interface. Commanded currents can be extracted from the two input sources to the grid. The proposed PI control and modulation schemes guaranteed sinusoidal input and output waveforms as well as reduced THD. The simulation results are provided to validate the effectiveness of the proposed control and modulation schemes for the proposed converter.

一种交叉倍压型高增益DC/DC变换器

针对光伏发电、燃料电池发电等领域对高增益直流变换器的需求,以两相交错并联升压变换器为研究对象,由2个含有电感的倍压单元组合设计出实现电压提升的交叉倍压结构,据此提出了一种新颖的交叉倍压型高增益DC/DC变换器。该变换器可实现(3n+4)/(1-d)倍的高电压增益(1∶n为耦合电感匝数比,d为变换器占空比),且具有电路器件的低电压应力特性。对于漏感引起的开关管电压尖峰问题,引入了钳位电容构成释放漏感能量通道,同时提升了输出电压。介绍了新型交叉倍压型高增益变换器的拓扑结构,分析了变换器各模态的工作过程,推导了电压增益、输入电流纹波及各器件电压应力等稳态特性,并搭建样机进行实验研究,验证了该直流变换技术方案的可行性和先进性。

宽输入电压范围的软开关四路均流LED驱动器

为了应对LED的不同输入电压等级应用场合,提出了一种具有宽输入电压范围的四路LED驱动器。该驱动器将Buck-Boost结构集成到全桥网络中,通过不同的开关组合工作在不同的模式,从而获得宽增益。采用无源均流方式实现了四路LED输出均流。由于驱动器的工作特性,开关管无需添加无损缓冲电路即可在全范围内实现零电压开通。详细分析了该驱动器的调制策略、工作原理和性能。最后,搭建了一个69 W的实验样机,实验结果表明该驱动器的输入电压范围为17 V~216 V,均流误差低于3.7%,最大效率可达97.8%。

2种典型森林凋落物动态变化及其分解特征研究

森林凋落物是土壤有机碳和植物养分循环的主要来源,为揭示辽宁冰砬山森林生态系统碳循环及能量转换规律,该文以蒙古栎次生林和长白落叶松人工林为研究对象,采用地表凋落物样地调查、凋落物收集、尼龙袋分解等,开展凋落物现存量、输入量及其分解动态特征研究。结果表明:蒙古栎林地表凋落物现存量(7.73 t·hm^(-2))小于长白落叶松林(25.82 t·hm^(-2)),年凋落物输入量(3.59 t·hm^(-2)).大于长白落叶松林(3.22 t·hm^(-2))。两种林型各龄组凋落物月输入量均为单峰动态模式,10月为凋落物输入量最高,凋落叶为主要来源。两种林型凋落叶分解过程符合Olson指数衰减模型,表达式分别为y_(蒙)=0.98704e^(-0.214x),y_(落)=1.02.61e^(-0.213x),得出蒙古栎凋落叶分解系数(0.214)大于长白落叶松(0.213),分解达到95%时,蒙古栎需要时间(13.94年)小于长白落叶松(14.19年)。

一种低输入电流总谐波畸变率的三相Buck整流器不对称调制策略

传统空间矢量脉宽调制(SVPWM)三相Buck整流器没有考虑直流链电流纹波对输入电流的影响,且在扇区切换点处输入电流存在严重畸变,导致输入电流总谐波畸变率(THD)升高。该文分析直流链电流纹波对三相Buck整流器输入电流的影响,分析输入电流扇区切换点畸变产生的原因,提出一种新型不对称SVPWM策略,显著降低了三相Buck整流器的输入电流THD。最后,通过仿真和1 kW的实验样机验证了理论分析的正确性以及所提调制策略的有效性。

基于谐波状态空间的高压直流输电系统SISO阻抗建模及稳定性分析

近年来,电网换相换流器型高压直流输电(line commutated converter based on high voltage direct current,LCC-HVDC)系统的稳定性问题得到广泛关注,多位专家学者建议采用谐波状态空间(harmonic state space,HSS)等线性周期时变建模方法对其分析。然而,HSS不可避免地提高了建模的复杂度与维数,在面对大规模交直流系统时具有局限性。同时,LCC-HVDC包含多类型谐波耦合,各部分耦合对稳定性的影响大小尚未得到充分论证。为此,文中以HSS为底层理论建立LCC-HVDC的耦合阻抗矩阵,揭示高压直流输电系统内部的谐波耦合机理。进一步,通过多频电路等效思想,提出三相系统多维阻抗的降维方法,将耦合阻抗矩阵无损降维成单入单出阻抗,以此分析不同次数的谐波耦合对阻抗特性与稳定性的影响。结果表明,考虑到13次谐波截断可以有效提升高压直流输电系统阻抗模型精度,但对稳定性分析结果的影响小于忽略工况变化、简化逆变侧带来的误差。

基于偏流补偿的低失调运算放大器的设计

基于双极型工艺,设计了一种具有低输入失调电压、低输入偏置电流的运算放大器。电路结构包含偏置电路、差分输入级电路、中间级电路和输出级电路。差分输入级电路采用共射-共基耦合对,能够降低失调电压,并且采用基极电流补偿结构抵消输入偏置电流在外围电路上所产生的影响,提高电路精度。中间级为整个电路提供增益,并且将双端输入信号转换为单端输出信号。输出级电路为AB类输出级,具有低静态功耗,能够提高电路效率,增大电路带负载能力并为负载提供更多功率。电路采用齐纳修调技术,在封装后对芯片进行修调,避免封装后引入的二次失调。流片后测试结果表明:在±15 V电源电压条件下,输入失调电压≤10μV,输入偏置电流≤3 nA,输入失调电流≤1.5 nA,大信号电压增益≥110 dB。

基于虚拟阻抗的三相Buck整流器输入不平衡控制策略

三相输入电压不平衡时,传统双环控制三相Buck整流器的输出电压存在二倍频脉动,输入电流发生明显畸变,严重影响整流器的性能和可靠性。为抑制输出电压脉动和输入电流畸变,该文通过建立三相Buck整流器在两相静止坐标系下的等效电路模型及功率传输数学模型,分析输出电压二倍频脉动及输入电流畸变产生的机理,在此基础上提出一种基于虚拟阻抗的输入不平衡控制策略,最后通过仿真和1 kW的实验样机验证了理论分析的正确性和所提控制策略的有效性。

一种高共模电压集成差分放大器的设计

针对差分放大器芯片国产化的需求,基于兼容金属薄膜电阻40 V双极工艺,设计一款高共模抑制比(Common Mode Rejection Ratio,CMRR)、±120 V共模输入电压的集成差分放大器。文章介绍了高共模电压差分放大器的基本原理和结构组成,分析了差分放大器的设计难点,分别为共模抑制比、输入失调电流以及增益误差,采用片内集成金属薄膜电阻结合激光在线修调技术实现高共模抑制比、通过改进型的基极电流补偿结构降低了输入失调电流,减少输入失调电流对电路采样精度的影响,采用改进型达林顿管提高放大器的开环增益,降低放大器的增益误差。整体芯片尺寸为2.82 mm×2.02 mm,采用±15 V双电源供电,静态电流为1.36 mA。流片后的测试结果表明:差分放大器在正常供电时,共模抑制比达到85 dB,输入失调电流仅为84 pA,失调电流的补偿精度达到98.1%,增益误差为0.02%。

MMMC两侧电流基于Lyapunov函数的控制策略

分频传输系统(fractional frequency transmission system,FFTS)是一种海上风电电能传输方案,FFTS中最为关键的装置为大功率AC/AC变换器,而模块化多电平矩阵变换器(modular multilevel matrix converter,MMMC)是一种高电压、大功率AC/AC变换器。针对MMMC输入输出两侧的电流控制,目前一般都采用传统PI控制,其控制参数多且控制效果不理想,而基于Lyapunov函数的控制策略的控制器数量、控制复杂程度和效果都优于PI控制,因此提出了MMMC输入输出两侧电流的Lyapunov函数控制策略。根据MMMC的拓扑结构,推导出MMMC输入输出两侧电流解耦模型,再结合Lyapunov函数控制理论,推导出MMMC输入输出两侧电流的Lyapunov函数控制的数学模型,证明了所提控制具有全局渐进稳定性,讨论了Lyapunov函数控制的不精确以及参数选择问题。最后在MATLAB仿真平台上针对MMMC输入输出两侧电流控制采用所提控制策略和传统控制策略分别在不同工况下进行实验比较,仿真结果验证了所提控制策的正确性与优越性。

基于k值调制三电平Boost PFC变换器的变占空比控制

随着国家大力发展城市轨道交通,不间断电源(uninterruptible power supply,UPS)系统作为关键供电装置,具有重要的研究意义和价值。为了满足相关电能质量法规的要求,集成功率因数校正(power factor correction,PFC)输入级是保证轨道交通基础设施设备供电的UPS系统的重要要求。三电平Boost PFC在采用传统载波调制时,在一定的输入电压范围内输入电流始终为零,导致变换器功率因数校正效果较差。因此,提出一种基于k值调制的变占空比控制的方法,不仅可以解决高输入电压下传统载波调制存在的问题,且可进一步抑制输入电流的畸变从而提高输入电流波形质量。首先介绍了这种k值调制方法,分析了其原理以及k值对变换器功率因数和电感电流有效值的影响。在此基础上,结合电压平衡策略对k值进行优化,解决直流侧输出电容电压上下不均衡问题。最后,针对高输入电压下输入电流仍然严重畸变的问题,提出一种基于k值调制的可变占空比控制方法,分析了变占空比控制对变换器功率因数、输出功率、电压纹波以及电感电流峰值的影响。最后通过仿真和搭建小功率实验平台,验证了所提控制方法的正确性和有效性。

衣物干燥机的浅析

简单介绍了衣物干燥机的工作原理及分类,从电气安全方面浅析了衣物干燥机的常见质量问题,主要涉及的不合格项目有标志和说明、输入功率和电流、耐潮湿、内部布线。并对消费者如何选购合格的衣物干燥机产品以及生产企业如何降低产品不合格率提出了建议。