微型太阳能光伏发电系统的两种直流升压电路

微型太阳能光伏发电系统直流升压电路主要采用反激变换器和交错反激变换器两种电路,首先分析了两种升压电路的工作原理,推导出两种电路的输出电压增益,然后通过理论推导与实验分析比较这两种升压电路的优缺点,进而得出以下结论:反激变换器与交错反激式变换器具有相同的电压增益;交错反激变换器采用两级反激变换器交错输出的方式,可减小输入大容量电解电容的纹波电流的有效值,从而延长电容的寿命,减少了输出电流的纹波,从而降低输出电流的总谐波失真。     

能馈式电子负载中交错并联直流模块的研究

针对能馈式电子负载中的直流模块特殊要求—低压大电流输入、高增益、高效率,在分析传统拓扑和手段的基础上,介绍了一种新颖输入并联、输出串联拓扑,利用耦合电感提高电路的增益,采用新颖有源箝位实现了软开关.在该电路的基础上设计了一个交错并联变换器以满足这些大功率等级,并进一步减小了输入电流纹波.阐述了在此应用下该变流器中死区时...     

交错并联技术在双向DC/DC变换器中纹波抑制分析与应用

为了使功率变换器输出电流纹波被抑制在一定范围内,设计了一种基于六路交错并联技术的双向DC/DC变换器。通过对低压侧电流理论波形进行叠加分析来验证交错并联技术具有减小输出电流纹波的特点,并得出低压侧电流纹波的大小与占空比和支路电感大小有关。最后通过MATLAB/simulink对六路并联的双向DC/DC变换器进行仿真验证,表明了多级交错并联技术对输出电流纹波具有明显地抑制效果。     

基于高频软开关技术的电镀电源设计

本文设计了一种基于高频软开关技术的电镀电源,单机满载输出功率为7.2kW(600A/12V).采用了移相控制和倍流整流技术,在变压器原边加入隔直电容和饱和电感,原边超前桥臂保持宽范围的零电压开通条件,滞后桥臂实现了无环流损耗的零电流关断:副边的倍流整流方式,两个二极管实现了自然换流,两个输出电感交错并联的方式,大大减小了系统电流纹波,减小了电感的尺寸,从而减小系统的体积和重量;运用均流控制芯片UC3907设计了电源模块的均流控制电路,实现了多模块并联组成大功率的电镀电源系统,提高了电源输出性能.     

串联优化器光伏系统中并网逆变器的控制策略研究

基于串联型优化器结构的光伏并网系统能够有效解决部分遮挡以及光伏组件不匹配导致的热斑效应,从而提高分布式光伏并网系统的输出功率。针对直流母线上100 Hz电压纹波影响并网电流质量的问题,对集中式逆变器的拓扑、控制策略、环路设计等方面进行了研究。设计了一种应用于集中式逆变器的双环控制器,电压外环稳定直流母线电压,电流内环控制并网电流。分析了直流母线电压100 Hz纹波对控制环路的影响,提出了一种电压环纹波补偿的控制策略,通过输入/输出功率、母线电容与电网相位的关系计算电压纹波的大小与相位,从而补偿电压外环的纹波干扰。研究结果表明,该方法可以有效减小直流母线电容,同时降低并网电流的总谐波失真(THD)。     

高压直流UPS电源的研究

针对传统通信基站UPS供电电源存在的系统结构复杂、电源效率低、可靠性差的问题,研究采用了一种两级结构的高压直流UPS电源。在电路结构方面,电源前级采用了T型三电平整流电路,改善了输入功率因数和输入电流THD;后级采用了输入串联输出并联型全桥电路,并采用交错并联技术,减小了输出电流纹波。在控制方面,引入了负载电流前馈控制,提高了电源的动态响应速度,保证电源在负载剧烈波动时输出电压纹波很小。研究结果表明,高压直流UPS电源的最高效率为96%;其负载突变时恢复时间小于200μs,电压波动小于5%,动态响应快,输出特性好。     

光伏发电系统交错并联BOOST的研究

BOOST电路在光伏最大功率点跟踪的DC-DC转换拓扑中被广泛应用,系统的动态性能受到电路参数的影响.为设计高性能的最大功率跟踪系统,提高系统的动态响应速度,给出了带耦合电感的交错并联BOOST变流器拓扑.并在此基础上详细分析了其稳态和动态特性,最后以60 W光伏发电蓄电池充电DC-DC变流器的仿真渡形验证了设计的合理性.     

车载充电机功率因数校正电路分析与对比

针对电动汽车车载充电机的应用,选取了传统Boost PFC电路与交错并联Boost PFC电路进行设计与实验。实验结果表明:交错并联Boost PFC电路比传统Boost PFC电路功率因数高,纹波电流小,对器件要求低,更加适合大功率车载充电机的应用。     

基于双环控制的光伏制氢变流器设计与仿真

变流器是实现光伏发电适用于制氢系统的重要器件,因此,研究变流器相关技术具有十分重要的使用价值和理论意义。该文研究了光伏制氢变流器及双环控制方法。首先,根据光伏制氢系统要求分别计算Boost电路和Buck-Boost电路的元件参数。然后,设计了光伏发电模块的控制回路,通过控制Boost电路中IGBT的导通和关断来升高光伏阵列的输出电压,使其能够达到最大功率点。设计基于电流环和电压环相结合的双环控制策略,控制电路中开关的导通和关断,保证系统输出电压和功率的稳定。储能模块的控制回路通过控制Buck-Boost电路中IGBT的导通和关断,实现蓄电池的充电和放电使得母线电压保持稳定。蓄电池的控制回路采用双环控制,使得光伏制氢系统的控制精度更高。完成设计后搭建光伏制氢系统仿真模型,观察系统在不同情况下的输出波形,验证设计的可行性。     

全桥直流变换器在MPPT中的应用

由于光伏硅电池的独特输出特性,为能够将光伏阵列转换的能量以最大功率输出,就需要对光伏阵列的输出电流、电压进行实时控制,以实现最大功率点跟踪;另外,随着具有MPPT功能的DC/DC变换器的引入,对光伏发电系统的效率也产生了很大的影响.为提高光伏发电系统的效率,采用了移相全桥ZVS DC/DC 变换器作为光伏发电系统 MPPT 变换电路,并对应该具备 MPPT 功能的 DC/DC 变换器进行了设计.最后,采用了1 kW实验样机进行了一系列的实验.实验结果验证了该理论分析和设计的正确性.     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.