OPTIMUM CONTROL OF VIBRATION AND STRUCTURE－BORNE NOISE FOR MACHINERY ON FLEXIBLE FOUNDATION

Faced with the key problems of machinerv- induced vibration and structure-borne noise when dynamic machines are mounted on flexible foundations such as upper floors of facto- ry buildings, the vibration and noise transmission mechanism and optimal control for the flexible system are systematically studied by the novel approach of power flow. A more general system of machinery-isolators一flexible foundation is modelled. Based on substructure transfer matrix tech- nique the power flow input and transmitted are formulated in closed forms, and the effects that the flexibility of foundation and the asymmetricity of system have upon the power flow transmis- sion spectra are revealed, Also the inverse problems of isolation design are discussed by using an optimum method. Optimum design for a typical example about a force fan mounted on a con- crete building floor is successfully performed to show that the model is practical, the theory and the optimisation developed are reasonable and effective. Thereby, theoretical bases for accurate prediction of isolation effectiveness and an optimum method for practical design of a general flexi- ble isolation system are provided.

Fracture behavior and mechanism of highly fragmented steel cylindrical shell under explosive loading

An in-depth understanding of the fracture behavior and mechanism of metallic shells under internal explosive loading can help develop material designs for warheads and regulate the quantity and mass distribution of the fragments formed.This study investigated the fragmentation performance of a new high-carbon silicon-manganese(HCSiMn)steel cylindrical shell through fragment recovery experiments.Compared with the conventional 45Cr steel shell,the number of small mass fragments produced by the HCSi Mn steel shell was significantly increased with a scale parameter of 0.57 g fitted by the Weibull distribution model.The fragmentation process of the HCSi Mn shell exhibited more brittle tensile fracture characteristics,with the microcrack damage zone on the outer surface being the direct cause of its high fragmentation.On the one hand,the doping of alloy elements resulted in grain refinement by forming metallographic structure of tempered sorbite,so that microscopic intergranular fracture reduces the characteristic mass of the fragments;on the other hand,the distribution of alloy carbides can exert a"pinning"effect on the substrate grains,causing more initial cracks to form and propagate along the brittle carbides,further improving the shell fragmentation.Although the killing power radius for light armored vehicles was slightly reduced by about 6%,the dense killing radius of HCSiMn steel projectile against personnel can be significantly increased by about 26%based on theoretical assessment.These results provided an experimental basis for high fragmentation warhead design,and to some extent,revealed the correlation mechanism between metallographic structure and shell fragmentation.

Structural optimum design of bistable cylindrical shell for broadband energy harvesting application

The shallow cylindrical structure is suitable to develop broadband vibration energy harvesters due to the property of the inherent mechanical bistability. In this letter, the optimum design of the bistable cylindrical shell for broadband energy harvesting application is investigated from the structural point of view. The output power is evaluated by the concept of the harvestable power, which balances the frequency of snap through and the referred output energy associated with each snap through. The non- dimensional harvestable power is analytically expressed as the function of the non-dimensional curvature parameter and one constructed parameter. The universal dependence of the optimal curvature parameter and the associated optimal harvestable power on the constructed parameter is derived, which can be well aooroximated by the linear relation in double logarithmic coordinate.

Electrical characteristics of new three-phase traction power supply system for rail transit

A novel three-phase traction power supply system is proposed to eliminate the adverse effects caused by electric phase separation in catenary and accomplish a unifying manner of traction power supply for rail transit.With the application of two-stage three-phase continuous power supply structure,the electrical characteristics exhibit new features differing from the existing traction system.In this work,the principle for voltage levels determining two-stage network is dissected in accordance with the requirements of traction network and electric locomotive.The equivalent model of three-phase traction system is built for deducing the formula of current distribution and voltage losses.Based on the chain network model of the traction network,a simulation model is established to analyze the electrical characteristics such as traction current distribution,voltage losses,system equivalent impedance,voltage distribution,voltage unbalance and regenerative energy utilization.In a few words,quite a lot traction current of about 99%is undertaken by long-section cable network.The proportion of system voltage losses is small attributed to the two-stage three-phase power supply structure,and the voltage unbal-ance caused by impedance asymmetry of traction network is less than 1‰.In addition,the utilization rate of regenerative energy for locomotive achieves a significant promotion of over 97%.

Optimum Energy Harvesting for Series-Connected Power Sources with Uniform Voltage Distribution

This paper presents a power system architecture where SIPO （series-input parallel-output） converters are controlled to achieve uniform inpt voltages across their respective series-connected power sources while also tracking the system optimum power point; the system optimum power point is the maximum power drawn from the series-connected power sources while their voltages are kept uniformly distributed. With proper uniform input voltage distribution control, near maximum use of the power sources is achieved by employing only one MPT （maximum power tracking） controller instead of multiple MPT controllers dedicated for their respective power sources. Provided that the maximum power point voltages of the input power sources are similar, the resulting system architecture offers near-maximum power transfer with a lower parts count. A feasibility study using computer simulation has successfully validated two SIPO power architectures and their control concepts for optimum power transfer.

Wind Power Potential in Interior Alaska from a Micrometeorological Perspective

The wind power potential in Interior Alaska is evaluated from a micrometeorological perspective. Based on the local balance equation of momentum and the equation of continuity we derive the local balance equation of kinetic energy for macroscopic and turbulent systems, and in a further step, Bernoulli’s equation and integral equations that customarily serve as the key equations in momentum theory and blade-element analysis, where the Lanchester-Betz-Joukowsky limit, Glauert’s optimum actuator disk, and the results of the blade-element analysis by Okulov and Sorensen are exemplarily illustrated. The wind power potential at three different sites in Interior Alaska (Delta Junction, Eva Creek, and Poker Flat) is assessed by considering the results of wind field predictions for the winter period from October 1, 2008, to April 1, 2009 provided by the Weather Research and Forecasting (WRF) model to avoid time-consuming and expensive tall-tower observations in Interior Alaska which is characterized by a relatively low degree of infrastructure outside of the city of Fairbanks. To predict the average power output we use the Weibull distributions derived from the predicted wind fields for these three different sites and the power curves of five different propeller-type wind turbines with rated powers ranging from 2 MW to 2.5 MW. These power curves are represented by general logistic functions. The predicted power capacity for the Eva Creek site is compared with that of the Eva Creek wind farm established in 2012. The results of our predictions for the winter period 2008/2009 are nearly 20 percent lower than those of the Eva Creek wind farm for the period from January to September 2013.

城市中压配电网雪花格式网架结构初探

为适应新型电力系统建设需求,提出一种适合国情的雪花格式网架结构。首先,总结国内外典型城市中压配电网结构的特征与优缺点;然后,结合天津已有网架结构,提出雪花格式网架结构及其构建方法;其次,分析测算雪花网结构的负荷转移能力、可靠性与效率效益水平;最后,从结构形式、适合场景等方面给出雪花网结构与花瓣结构等的综合对比情况。结果表明,雪花格式网架结构具有一定综合比较优势,可为中压配电网远景目标网架规划提供指导。

核电工程异形水箱流固耦合分布式参数模型与效用研究

在流固耦合动力分析领域,传统的Housner模型在工程设计中发挥重要作用。但其理论推导仅适用于规则水箱,采用集中质量总体模型描述液体晃动的整体效应,难以有效模拟异形水箱储液结构的局部精细响应,亟须建立适用于不规则水体晃荡的分布式附加质量模型。基于势流理论推导了一种模态综合法模型,实现了分布质量与储液器壁激振加速度的解耦。该模型能够有效剥离分布式的脉冲质量与对流质量;同时,实体网格的振型分析适用于任意形状水体的动力分析。通过算例的形式将该模型与精细声学-结构耦合(Acoustic-Structural coupling,CAS)模拟法进行了比较,验证了模型的精确性与可靠性。最后,基于本文的模型研究了核电异形的安全水箱在不同水位和减晃格栅分布下的动力响应规律,并检验了其在工程中的适用性。

基于改进ADMM的含分布式光伏的配电网电压无功优化方法

由于所建立含分布式光伏(PV)的有源配电网电压无功优化模型是一个典型的非凸混合整数非线性优化模型,提出一种改进交替方向乘子法(ADMM)来求解含分布式光伏的配电网电压无功优化问题。首先以有载调压变压器和投切电容器组为例,建立一种新的广义可分解有源配电网电压无功优化模型,然后根据ADMM算法将有源配电网电压无功优化模型分解为2个子问题求解,并设计惩罚参数的自适应调节机制以加速收敛。在3个不同规模有源配电网算例上进行仿真测试,结果表明,所提出改进ADMM方法具有较好的收敛性和最优解。

基于等价输入干扰的分布式光伏电源出力控制策略

分布式电源能够改善配电网潮流分布,使得电力系统具有更高的能源利用率以及灵活性,然而分布式电源的不合理出力则难以充分发挥自身优势,并且死区效应、电网电压畸变及系统参数不确定性等不确定性扰动也会对电力系统的可靠性构成严重威胁。针对此问题,提出了基于改进的等价输入干扰方法(improvedequivalentinputdisturbance,IEID)的分布式电源出力控制方法。其中上层优化结构以配电网网损最小为目标,建立配电网优化降损模型并求解得到分布式电源出力值;下层控制结构基于所提IEID设计分布式电源控制策略,把模型耦合项、死区效应、网压畸变及系统参数不确定性等干扰对系统输出的影响等价到输入通道上,并对其进行估计和补偿,能够有效地抑制未知扰动并高精度跟踪上层输出的出力值,极大地改善并网电能质量。以某21节点真实居民配电网为算例,仿真结果表明所提方法具有较好的扰动抑制能力,能够自主平稳出力,降低配电网网损。

“权力—权利”结构视角下中国地权的历史谱系演进与现代启示

研究目的:探讨传统社会权力干预对土地收益分配的影响,梳理中国地权的历史谱系演进并为现代地权制度中的增值收益合理分配提供启示。研究方法:理想型建构法,分析性叙述法。研究结果:(1)以中央权力与地方权力对私权利不同程度的干预,建构了哑铃型与纺锤型两种理想的地权形态;(2)不同地权形态下的“权力—权利”互动模式可以总结为均田薄赋、经界并税与隐占兼并;(3)地权的历史谱系演进呈现为在王朝治乱周期下,形态由哑铃型向纺锤型的转换,这不仅呈现出中央权力与地方权力干预强弱转换下的表层循环特征,也潜藏着权力干预弱化与权利演化的深层特征。研究结论:建国以来的“权力—权利”结构体现为“中央—地方—农民”的关系,面对结构失衡产生的城乡差距扩大,中央应通过将横向社会反馈纳入纵向政府问责来约束地方政府的权力干预,并通过推动城郊区集体建设用地入市及差异化征税、远郊区农地国有化向农民还权赋能,走向“权力—权利”结构的制衡。

配电自动化技术在智能电网中的应用

阐述配电自动化技术在智能电网系统中的作用、应用优势、应用策略,它具有先进、高效率、安全和兼容的优势,可以确保供电系统运行安全、改善系统结构、构建一体化系统。

农村配电网的规划策略分析

阐述农村配电网规划建设的特征、问题及原因,提出改进建议,包括合理规划农村电网结构、加快健全农村配电网规划制度与技术导则、加强实地勘测、根据用电需求进行规划设计。

新型电力系统下配电网网络结构研究

随着风电和光伏等分布式电源、储能系统、电动汽车、综合能源等装置的接入,配电网逐渐成为满足各类电力用户复杂化、互动化服务需求的服务平台,保障配电网可靠供电、安全稳定和经济运行意义愈加重大。针对新型电力系统下配电网的发展需求,提出一种分层分级式并列环网平台型的高中压配电网结构。首先,提出“212”型双侧电源和“323”型三侧电源链式结构以构建110 kV高压配电网,该结构采用闭环设计、环网运行方式,能够提高供电安全性并降低线路投资;其次,采用220 kV变电站作为新型电力系统配电网的上级电源点,将提出的两种配电网结构应用于110 kV变电站;最后,采用“212”型双侧电源环式结构构建10 kV中压配电网。所提高中压配电网结构对打造更加坚强、更高弹性的配电网具有重要意义。

贫困地区分布式光伏电站并网发电系统应用研究

为充分利用贫困地区空置屋顶及土地资源优势,发展光伏发电产业,降低碳排放,保护环境并改善居民经济状况,本文以某贫困地区安装总容量约为650kWp的分布式光伏电站设计为案例,根据当地太阳能资源和气候条件等情况,选取合适的光伏电池组件和逆变器型号,通过PVsyst软件模拟仿真计算得出光伏阵列最佳安装倾角,由此计算确定光伏阵列的布置间距,最后推算出本案例25年内的发电量,并对环境效益进行评估,为光伏扶贫工作提供借鉴和经验。

VSG控制型分布式光伏聚合模型和稳定控制方法

在新型配电系统中,众多分布式光伏系统通过直接并联或间接互联配置呈现。虚拟同步发电机(virtual synchronous generator,VSG)作为一种典型的并网分布式光伏逆变器,在电网故障时,不同的控制参数和电路参数组合产生不同的动态响应。现有研究多关注于单个VSG的稳定性上,但对多VSG并网系统的综合分析和控制策略的研究相对较少。因此,提出了一种辨识同调VSGs并网系统的方法,并建立了同调VSGs并网系统的等效单VSG模型,该模型不仅具有明确的物理意义,而且能够准确描述原系统的动态特性。基于这一模型,本文进一步提出了一种策略,旨在提升同调VSGs并网系统的暂态性能。仿真实验结果验证了所提方法的有效性,为多VSG并网系统的稳定性和性能优化提供了新的视角和解决方案。

数字正义视角下弱势群体的权利实现

随着智能化、数据化时代的到来,数字治理得到广泛应用。这不仅带来了极大便利,也提升了社会整体效率。与此同时,数字弱势群体正遭受横向与纵向层面的数字正义困境。究其原因,主要在于数字资源的分配不均与社会权力结构的异化。而实现数字弱势群体的权利,帮助其融入数字社会,不仅符合宪法的正义精神,更顺应了数字时代的实践需求。因此,应着眼于平衡社会各方主体之力量,实现数字资源的合理分配、数字权利的合理配置与权力的有效制约,弥合数字鸿沟,修复数字正义。

新能源高比例接入电网的配网管理与技术措施

在高比例新能源接入电网之后通过智能电网分析,以人工智能和大数据基础系统为核心,完成智能电网技术变革,这是关于配电网模式,以及电网调配控制的关键技术。该研究通过对电网配置以及目前电网结构体系进行分析,明确高比例新能源接入电网之后对部分地区的影响,并且对电网电压补偿、智能变电站等关键技术作出同步应用研究。进一步提高电网配置的有效性,也实现基于新电网配置及功能效率内容的调整。

基于耦合负压原理的10kV直流负荷开关设计

为满足柔性直流配电系统负荷电流频繁投切对开关操作寿命的高要求,解决直接采用直流断路器方案成本高、体积大的难题,文中研究了一种基于耦合负压原理的直流负荷开关方案。首先对其拓扑和工作原理进行了介绍,然后设计了基于双动结构和电磁斥力机构的主支路快速机械开关、基于耦合负压装置的换流单元和采用反串联拓扑的电力电子开关阀单元,最后,根据苏州某换流站工程需求,研制出10 kV耦合负压型直流负荷开关样机并进行试验验证。结果表明:所研制的10 kV直流负荷开关可在3 ms内开断额定电流和最大开断电流,且能连续动作,体积为目前国内同等参数最小,并具有低损耗、高机械寿命和高可靠性的优点,完全满足工程要求,同时为后续直流负荷开关产品的开发提供了参考。

混凝土屋面分布式光伏发电系统的结构设计浅析

结合混凝土屋面分布式光伏发电系统的工程实例,从增设光伏发电系统后既有建筑的承载力复核,光伏组件的压块设计,光伏支架的檩条、斜梁、立柱及基础的设计,电气设备支架及其基础设计,电缆桥架及其基础设计几个方面,对混凝土屋面分布式光伏发电系统结构设计的具体内容及设计过程中需要注意的细节问题进行了讨论分析。研究结果表明:混凝土屋面分布式光伏发电系统的结构设计方案并非仅局限于结构的本体设计,还需要综合考虑与其相关的周边事物(例如:屋面新增荷载计算、光伏组件安装倾角设计、屋面的防水处理、检修通道设计、安全护栏设计、楼板开洞设计)及周边环境的影响,从而选择最优的混凝土屋面光伏发电系统整体设计方案,以保证整体设计的安全性及合理性。