Numerical Modeling of Conductive Particle Trajectories in Roll-Type Corona-Electrostatic Separators

Several attempts have already been made to simulate particle trajectories in roll-type electrostatic separators. However, the predictive value of the results is limited by an excessive number of simplifying assumptions regarding the electric field distribution, as well as particle charging and discharging mechanisms. The present work is aimed at improving the existing models by taking into account: (1) the non-uniformity of the electric field in the active zone of the separator and (2) the effect of spark discharges occurring between the electrodes. Based on previous observations, the conductive particles were assumed to lift-off when no longer exposed to corona discharge. The numerical simulations were performed for particles of various sizes. The electric field was computed in each point of the trajectory using a finite element program. It was found that: (1) some of the smaller particles impact the static electrode and are deviated to the middling compartment of the collector and (2) field annealing which accompanies spark discharges significantly affects the trajectories of conductive particles. The results of this study could guide the design of new electrostatic separation applications.     

不同电场中细颗粒物的荷电特性研究

为了研究细颗粒物在直流电晕放电和脉冲电晕放电条件下的不同荷电特性,采用静电低压撞击器分别测试直流电场和脉冲电场中不同电压条件下的单个颗粒平均荷电量,并与理论计算结果进行对比,结果表明:在直流电晕放电中细颗粒物直径小于0.2μm时主要以扩散荷电为主,大于0.2μm时主要以场致荷电为主;在脉冲电晕放电中细颗粒物主要通过自由电子和离子的迁移扩散进行荷电,最终小粒径段颗粒物荷正电且荷电量非常少,大粒径段颗粒物荷负电;在相同的线板式反应器中,脉冲电场可以比直流电场施加更高的峰值电压,加剧带电粒子与颗粒物之间的碰撞荷电,最终提高颗粒物的荷电量。     

窄脉冲放电粒子荷电过程分析

对脉冲流光放电粒子荷电过程进行了分析 ,脉冲流光放电状态不同于传统的直流电晕放电 ,窄脉冲流光放电电晕区可延伸到异性电极 ,区域内既有电子 ,也有正离子和负离子 ,电子能量远高于离子能量 ,正离子数量高于负离子数量。脉冲流光放电粒子荷电过程分两个阶段 ,在脉冲放电期内为电子荷电 ,脉冲期过后为离子荷电     

Numerical Modeling of Insulating Particles Trajectories in Roll-type Corona-Electrostatic Separators

The trajectories of the insulating particles in roll-type corona-electrostatic separators depend on the configuration of the electrode system, the applied high voltage, the roll speed, the size of the particles and the relative humidity of the ambient air. The aim of this work was to point out how numerical modeling can be of use in the study of the effects of these factors. Particle charging is modeled using the Pauthenier?s equation for spheres in uniform electric field. The equation of particle discharging was obtained after an experimental study of the surface potential decay of a granular layer of insulating material in contact with an electrode. The trajectories are computed based on the balance equation of the electrical and mechanical forces that act on such charged particles. The numerical results are in good agreement with the experimental findings.     

基于自适应变异粒子群算法的电动出租车充电引导

通过调研分析深圳市电动出租车的实际运营数据,提出充电站充电设备时间利用率的计算方法。针对区域内充电站之间设备时间利用率分布不均衡的问题,提出了基于充电站信息和车辆信息的电动出租车充电引导系统,建立了充电引导模型,并采用改进的自适应变异粒子群算法引导电动出租车的充电行为。根据深圳充电站的实际数据进行算例仿真,仿真结果表明,经过充电引导后的电动出租车能根据充电站内充电桩的规模均匀分布到相应的充电站,实现区域内充电站之间充电设备利用率的均衡分布,从而提高充电设备时间利用率。仿真结果验证了所提充电引导方法的可行性。     

可吸入颗粒物在不同温度差下的运动特性研究

应用CFD软件求解三维湍流N-S方程,对不同温差下竖直矩形管道内气固两相流场进行三维数值模拟计算。通过数值模拟,得到由于温度场的不同,使气固两相流的速度场发生改变。通过得到颗粒物的体积浓度的分布,分析在温度场中由于存在热泳力,从而对颗粒物浓度分布产生影响,并得到对不同粒径的颗粒物的浓度分布影响的规律。     

基于粒子群遗传算法的电动汽车充电站的布局规划

电动汽车充电站属于电动汽车重要的配套设施,充电站的布局规划对电动汽车的推广有重要意义。提出了区域内车辆流量守恒原理,将区域内的电动汽车数量视为恒定,对电动汽车的总量以及分布进行预测。提出了电动汽车充电站的年最小年综合费用模型,以某城市小区为例,采用粒子群遗传算法对模型进行求解。计算结果表明,基于粒子群遗传算法的电动汽车充电站的布局划具有全局最优、适应性强、经济性好、简单实用等优点。     

交、直流电场作用下交联聚乙烯中的空间电荷习性

Polyethylene is one of the widely studied polymeric insulation materials,which have been used extensively for cable insulation.One of the major issues related to polymeric materials is its easy formation of space charge,a high chance to cause electric field distortions.This phenomenon is more significant under high voltage direct current(HVDC)stresses.Space charge can also be observed under high voltage alternative current(HVAC)stresses but with much less intensity due to the limited charge injection period and the effect of charge recombination caused by the constantly variance of the external fields.When considering the situation of an AC voltage combined with a DC offset,a possible scenario in HVDC technology,there was little research on charge dynamics in the insulation in terms of both experimental and simulation work.In this paper,a numerical simulation based a bipolar charge injection/transport model is used to obtain characteristics of space charge in polyethylene under the combined AC and DC high voltage at room temperature.The bipolar charge injection/transport model,which is widely used in HVDC space charge simulation,is applied in the combined conditions.The overall applied voltage,consisted of root mean square(RMS)values of the AC voltage and DC voltage,is kept the same,while the DC component’s voltage ratio and AC component’s frequency are changed respectively,to illustrate their effects on the space charge dynamics within the insulation under combined electric fields.The simulated charge distributions present notable differences when DC offset is increasingly added in,while relatively small differences when AC component’s frequency altering,especially for the cases whose frequency exceeding 0.5 Hz.     

基于组合预测模型的电动汽车充电站短期负荷预测研究

针对电动汽车充电站充电功率随机性大的难题,本文建立了ELMAN反馈式神经网络预测模型,然后采用粒子群算法对其进行优化,接着将优化之后的模型与模糊控制相结合,最终建立3种模型相结合的组合预测模型,并以青岛地区某一充电站的实际负荷数据为算例,验证了组合预测模型的有效性,提高了电动汽车充电站短期负荷预测的精度。     

Charging ahead

With the constant performance improvement and cost reduction of power electronics and motor drives, more efficient vehicles such as electric, hybrid electric, and plug-in hybrid electric vehicles (PHEVs) are becoming a reality. The commonality between all advanced vehicles is the presence of electric propulsion powered by an electric storage system. As a result, the development of adequate energy storage systems is now more important than ever. High energy density, modularity, and affordability have made batteries the technology of choice for vehicular applications. In recent years, battery technology has made great strides in improving the energy and power density. Still, a tradeoff between power and energy must be made to best meet space and weight constraints. In this article, we shed some light on this tradeoff. We also look at how batteries can be represented with equivalent circuits. Finally, we go into some detail on battery management requirements that ensure that the batteries perform as expected.     

基于自适应变异粒子群算法的电动汽车换电池站充电调度多目标优化

大规模电动汽车用户的无序充电行为会对电网造成“峰上加峰”等影响,因此电动汽车规模化应用迫切要求实现对充电行为的引导和调度.电动汽车换电站具有受可调度时间约束影响小等特点,与个体电动汽车相比较易实现充电调度.根据换电站的特点以换电站各时刻的充电功率为控制对象,建立多目标的调度策略数学模型,并采用自适应变异的粒子群算法求解以减小标准粒子群容易早熟对优化结果的影响,得到次日优化充电计划.基于某地区负荷曲线进行算例仿真,验证了算法的有效性,比较了单目标优化和多目标优化的调度策略对负荷曲线的影响.结果表明,换电站充电调度策略采用多目标优化时能够克服单目标优化填充“最低谷”效果差的问题,有效地降低电网峰谷差,达到平稳负荷波动的效果.     

基于不同购电模式相结合的电动汽车充换电站运营模式研究

电动汽车达到一定规模后可能带来大量充电负荷,为使收益最大,提出充换电站应采用充电与换电相结合的工作方式,充電模式采用直接从电厂购电,而换电模式通过电网购电。以充换电站的运营收益最大为目标,结合了合同电价与市场电价之间的联动模型对该工作模式下的充换电站运营进行了经济效益分析,确定了最佳充换电比例。最后针对某地区充换电站运营进行了算例分析,证明了此方法的可行性。     

不确定充电习惯对电动汽车充电负荷需求及充电负荷调节的影响

采用二项分布描述电动汽车用户充电习惯的不确定性,本文建立了含有不确定性因素的充电负荷需求计算模型。基于此计算模型,分析了不确定性充电习惯、充电起始时间延时和充电功率对电动汽车充电负荷需求的影响;然后以配电网负荷方差最小为目标函数,以充电起始时间和充电功率为控制变量,考虑电动汽车充电功率约束和电动汽车用户充电能量需求约束,建立了基于不确定充电习惯的充电负荷优化调节模型。以北京市汽车行驶数据和典型配电网负荷数据为例,验证了本文所提充电负荷优化调节方法的优越性。     

变负载无线充电系统的恒流充电技术

基于磁耦合共振原理,设计了一套采用平板磁心结构的变负载恒流充电无线电能传输系统。利用等效电路模型分析影响传输功率、系统效率和充电电流的主要因素。根据超级电容恒流充电过程中等效负载电阻动态变化规律,采用不同阻值的功率电阻模拟其充电特性。首先,分析二次侧Buck变换器对充电电流的调节作用,得到占空比与充电电流的关系,采用PI控制算法实现变负载的恒流充电;其次,通过理论分析和仿真实现磁耦合机构参数优化设计;最后,搭建系统实验平台对系统设计方法进行验证。在传输距离为15cm且负载电阻为0.5~5?时,实现29A的恒流充电。当负载电阻为3.2?时,系统效率和传输功率分别为87.7%和2.58k W。     

基于变权Voronoi图和混合粒子群算法的电动汽车充电站规划

针对城市电动汽车充电站规划布局及服务范围划分的问题,提出一种基于变权Voronoi图和混合离散粒子群算法的优化算法。为解决离散粒子群算法在达到最优解时容易发生变异的问题,改进了离散粒子群算法中的概率映射函数,提高算法迭代中后期的全局搜索能力;引入加权Voronoi图生成过程中可随充电站的服务能力和最大服务半径约束动态调整的变权重系数,使充电站服务范围的划分可控且更为合理;利用最短路径法求得用户充电行驶过程中的交通路径距离来取代传统的欧式距离,提高算法的准确性。运用改进后的混合离散粒子群-变权Voronoi图算法求解算例模型,通过算例结果验证了所提算法用于电动汽车充电站规划的有效性。     

电动公共汽车充电站充电管理系统设计

设计了一种电动公共汽车充电站充电管理系统。系统主要对充电设备管理、充电交易管理、充电桩监控、BMS数据分析以及充电数据发布进行功能分析及设计。结合网络技术、视频技术和通信技术设计实现充电站的智能化、无人化管理。     

基于动态分时电价的电动汽车充电站有序充电策略

提出基于动态分时电价的电动汽车充电站有序充电控制方法。该方法在综合考虑用户的充电需求和电网负荷水平的基础上,以削峰填谷为目标,采用启发式算法动态求解接入充电站电动汽车的分时电价时段,由用户自主响应,以实现充电站内电动汽车有序充电。为验证所提方法的有效性,采用蒙特卡洛方法模拟用户充电需求,对电动汽车充电站在有序充电和无序充电两种情形下的配电变压器负荷、充电站运营经济效益和用户充电成本进行仿真计算和分析。结果表明:相较无序充电方法,用户通过自主响应充电站制定的动态分时电价激励,可显著降低充电站的运营成本和电动汽车用户的充电成本,并有效实现充电负荷削峰填谷。     

中压充气柜

所谓充气柜是将高压元件如母线、断路器、隔离开关、互感器等密封在充有较低压力(0.01～0.05Mpa)SF6或其他气体的壳体内。充气柜带来许多优势,其最大优势是不受外界环境的影响,如凝露、污秽、小动物及化学物质等。另一个优势是因为使用压缩气体绝缘(如SF6、N2或空气),有利于向小型化方向发展。充气柜有性能良好的无油开关特别是免维护或少维护的真空开关,大大减少了维护和检修工作量。从世界看,充气柜发展很快,使用量剧增。以德国为例,前几年对工业电网使用的中压开关设备做过调查,当时充气柜在12kV占5%,在24kV占9%,在36kV占19%;但据200…