Charges and forces on conductive particles in roll-typecorona-electrostatic separators

Mathematical modelling is a powerful tool in the optimization of electroseparation technologies and equipment. This paper proposes the use of a numerical method of field analysis to evaluate more accurately the charges and forces on millimeter-size conductive particles of virtually any shape in contact with an electrode. A program based on the boundary-element method was tested for this purpose, and provided the input data to an algorithm for the computation of particle trajectories. The results were in good agreement with the observations made on a laboratory electroseparator. The effect of space charge on the behavior of conductive particles was studied with a three-electrode system (a grounded grid, between a corona electrode and a metallic plate, energized by two high-voltage supplies of opposite polarities). The accuracy of numerical simulations of electroseparation processes is expected to increase when a mathematical model of particle motion in DC corona fields will be incorporated in the existing computer programs     

Numerical computation of conducting particle trajectories in plate-type electrostatic separators

Development of new applications of plate-type electrostatic separators need increased controllability of particle trajectories. The aim of this paper is to model the particle behavior after lift-off from the plate electrode. A superficial charge simulation program was employed for the computation of the electric field in the active zone of the separator. This enabled the evaluation of the charge acquired by a conducting particle in contact with the plate electrode and the electric force exerted on it before and after detachment. Based on a previously derived mathematical model, the particle trajectories were calculated for various electrode configurations. The data of such numerical simulations can guide the experimental studies needed for the assessment of new industry applications of electrostatic sorting or classifying techniques.     

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.     

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.     

Halbach轴向永磁联轴器的分析与优化

为了提升Halbach轴向永磁联轴器永磁体利用率,采用转矩谐波分析与粒子群优化算法对Halbach轴向永磁联轴器进行分析与优化。建立Halbach轴向永磁联轴器的3D有限元模型,推导气隙磁密与转矩的傅里叶级数表达式。在有限元分析和计算的基础上,对气隙谐波次数和端部效应进行分析,发现特定的谐波分量可以有效产生稳定的转矩。为了定量比较和提升转矩性能,对Halbach阵列关键参数进行参数分析,对比多种基于粒子群算法的优化方法,采用数学模型与优化算法相结合的设计优化方法对Halbach轴向永磁联轴器进行优化。在转矩相同的约束下,优化后的Halbach轴向永磁联轴器转矩密度提升7.60%。通过有限元仿真结果验证了转矩谐波分析与粒子群优化方法的有效性。     

交流电压下绝缘子附近导电微粒运动特性

在施加交流电压条件下,对楔形布置的电极间聚四氟乙烯(PTFE)绝缘子附近自由导电微粒运动进行了实验观察.通过对微粒运动过程进行摄像和记录微粒起始运动电压,讨论球形导电微粒和线形导电微粒的运动特性.对不同外形绝缘子附近导电微粒运动规律进行了分析,认为绝缘子的存在能够降低微粒运动起始电压,并且能够吸引部分球形导电微粒沿电极表面滚动到达绝缘子表面;当绝缘子表面与接地电极夹角为锐角时绝缘子附近的微粒运动起始电压会显著降低.对绝缘子存在情况下的楔形电极间电场进行计算,并对微粒运动规律做出了合理的解释.     

Simulation of one-sided heating of boiler unit membrane-type water walls

This study describes the results of simulation of the temperature field and the stress-strain state of membrane-type gastight water walls of boiler units using the finite element method. The methods of analytical and standard calculation of one-sided heating of fin-tube water walls by a radiative heat flux are analyzed. The methods and software for input data calculation in the finite-element simulation, including thermoelastic moments in welded panels that result from their one-sided heating, are proposed. The method and software modules are used for water wall simulation using ANSYS. The results of simulation of the temperature field, stress field, deformations and displacement of the membrane-type panel for the boiler furnace water wall using the finite-element method, as well as the results of calculation of the panel tube temperature, stresses and deformations using the known methods, are presented. The comparison of the known experimental results on heating and bending by given moments of membrane-type water walls and numerical simulations is performed. It is demonstrated that numerical results agree with high accuracy with the experimental data. The relative temperature difference does not exceed 1%. The relative difference of the experimental fin mutual turning angle caused by one-sided heating by radiative heat flux and the results obtained in the finite element simulation does not exceed 8.5% for nondisplaced fins and 7% for fins with displacement. The same difference for the theoretical results and the simulation using the finite-element method does not exceed 3% and 7.1%, respectively. The proposed method and software modules for simulation of the temperature field and stress-strain state of the water walls are verified and the feasibility of their application in practical design is proven.     

基于深度学习的航拍光伏板红外图像热斑检测方法研究

针对光伏电站光伏板热斑故障难以检测的问题,结合无人机巡检技术,提出一种基于深度卷积神经网络的光伏板热斑快速检测方法。首先设计了光伏板识别模型,将Yolov4主干特征提取网络替换成轻量级网络MobileNetV2,并将PAnet网络中标准3×3卷积替换为深度可分离卷积,实现了将光伏板快速从红外图像中识别出来。为快速识别热斑并解决光伏板反光噪声问题,将MobileNetV2网络引入DeeplabV3+模型中,改进由于下采样造成的目标缺失,并将交叉熵损失函数修改为Dice损失函数来进一步提高分割精度。试验结果表明,该方法能够准确识别光伏板热斑,光伏板识别准确率为99. 56%,检测速度为22. 1帧/秒。光伏板识别后的热斑分割准确度达到95. 99%,交并比mIou达到85. 58,检测速度为24. 5帧/秒,该方法能够满足光伏板故障检测的需要。     

天然酯绝缘油-纸界面的多分支流注放电仿真

油纸界面的局部放电是油浸式变压器中油纸绝缘失效的主要原因之一。本文在多分支流注放电数值模型基础上通过进一步考虑油纸界面的电荷输运特性,构建了油纸绝缘系统中的多分支流注放电模型,并利用有限元法分别对天然酯绝缘油/纸介电常数配比、针电极与纸板的间距影响下的沿面放电特性进行了研究。结果表明,针电极与纸板的间距及油/纸介电常数配比均会显著影响流注分支;针电极与纸板的间距越小,油纸界面处的流注分支间的抑制越明显,油纸界面的流注对z-轴流注的影响更显著;当绝缘油介电常数相比纸板大时,流注在油中的发展和分支更为显著,反之则流注更易沿纸板表面发展及在油纸界面聚集电荷。     

并联混合型有源电力滤波器的PSIM仿真研究

提出了一种利用仿真软件PSIM来研究和开发电力电子新装置的方法,并以韶冶谐波治理系统的设计过程为例, 说明了该方法与目前广泛使用的PSB仿真方法相比,具有更快的收敛速度和更友好的人机界面,使得研究电力电子系统更为简单。     

谐波条件下电容式电压互感器测量误差影响因素分析

电容式电压互感器(CVT)测量的准确度影响着电能计量的准确性和继电保护动作的可靠性。为了研究在谐波条件下CVT测量的准确性,为提高CVT的测量精度提供参考依据,文章基于CVT的等效电路模型,推导出了谐波条件下CVT变比的表达式,研究了谐波条件下CVT的励磁阻抗和电容分压比对测量精度的影响规律,并通过仿真分析对其进行了验证。     

基于粒子群优化算法的交流不对称故障下HVDC谐波计算

将基于调制理论的谐波分析计算方法与粒子群优化算法相结合,提出了一种基于粒子群优化算法的HVDC谐波计算方法.首先建立改进的换流器动态相量模型,解决了交直流系统的接口问题;然后,利用调制理论对频域下谐波相互作用进行分析,把交直流系统的谐波计算转化为对换流母线电压的优化;最后,应用粒子群优化算法,求解不对称故障情况下换流母线电压最优值,同时得到交直流系统的谐波分布.为验证算法,以CIGRE HVDC模型为例,采用该方法对交流系统各种不对称故障情况编制程序并计算,并与PSCAD/EMTDC软件得到的电磁暂态仿真结果相比较,证明了该算法准确有效.     

Numerical electric field analysis of capacitance and potential in space for estimation of permittivity distribution

We have been studying on measuring capacitance and potential using long‐distance electrode for estimating a permittivity distribution. The estimating method of permittivity distribution was proposed using finite element method (FEM) and genetic algorithm. However, the measurement accuracy was not reviewed. In this paper, we carried out numerical analysis using FEM in case of change of diameter, position, and permittivity of a rod of dielectric and discussed the measurement accuracy of capacitance and potential.     

并联型单开关管光伏组件优化器的研究与设计

在光伏发电系统中,因局部阴影遮挡造成的特性失配是引起输出功率降低的重要原因。传统方案大多针对组串及组件失配问题,将每个光伏组件的输出经过变换器独立的最大功率跟踪后再串联加以解决,改变了原有系统连接结构。针对小功率分布式光伏发电系统主要遭遇的组件内失配问题,研究了一种不改变原有光伏组件结构的优化方法,并采用单开关的拓扑实现。该方法在光伏组件遇到局部阴影等造成的组件内特性失配时,可以从光伏组件的输出抽取能量,对受遮挡部分进行补偿,使得各个光伏子串的工作状态可调,从而提高这种情况下的总输出功率。该方法属于部分功率变换,且电路拓扑仅采用单个开关管,控制算法简单,电路损耗和成本较低。仿真和样机实验结果表明,该方法能够显著提高局部阴影条件下光伏组件的输出功率。     

工频电压下片状自由金属微粒带电特性与运动规律研究

GIS/GIL因安装、运输等环节会不可避免地产生多样性的金属微粒,而片状金属微粒因其"潜伏性"较难检出,从而威胁GIS/GIL的绝缘性能。采用数值计算结合实验方式开展了工频电压下片状金属微粒起跳与运动规律研究。片状金属微粒采用旋转椭球体模型进行等效,并通过理论推导获得片状金属微粒的带电量与临界起跳场强。搭建工频电压下片状金属微粒运动观测平台。采用高速相机观测其起跳和运动行为,并与数值计算结果进行对比分析。结果表明:片状金属微粒起跳场强与厚度的1/2次方近似呈正比关系,而随微粒半径增大呈现出微弱的上升趋势。密度较大的片状金属钢微粒竖起后,存在原地旋转与沿地电极表面来回滚动两种运动模式,并在微粒底部与电极间隙伴有微弱的局部放电;密度较小的片状金属铝微粒竖立后,在电极间隙内发生剧烈地上下跳动。     

基于远程操作的通用变频器研究与开发

通用变频器功能齐全，根据不同应用场合，需进行指令参数设定。介绍了基于远程操作的通用变频器及其操作面板的设计方法。变频器与操作面板的连接采用SPI接口；SPI接口为同步串行I／O口属于短距离通信，经信号转换后可实现距离传输。介绍了转换RS-485的实现原理系统的硬件设计、软件设计及实验结果。实验结果证明，所构建的变频系统实用新颖、功能齐全、可靠性高，成功地解决了生产实际中的问题。     

Numerical investigation of powder trajectories and deposition intribocharge powder coating

An iterative numerical algorithm for simulating particle trajectories in the tribocharge powder-coating process is presented in this paper. The electric field distribution is determined by means of the finite-element method. The particle trajectories are predicted by integrating the differential equation of motion, resulting from the Newton equation. The density of the space charge in the powder cloud is estimated using the particle-in-cell algorithm. All problems are solved iteratively until a self-consistent solution is found for all the involved parameters. The algorithm has been applied to a few different models of the problem assuming mono- and polydispersed powders. The effect of powder parameters on the wrap-round and Faraday-cage effects has been investigated     

An analysis of EMG electrode configuration for targeted muscle reinnervation based neural machine interface.

Targeted muscle reinnervation (TMR) is a novel neural machine interface for improved myoelectric prosthesis control. Previous high-density (HD) surface electromyography (EMG) studies have indicated that tremendous neural control information can be extracted from the reinnervated muscles by EMG pattern recognition (PR). However, using a large number of EMG electrodes hinders clinical application of the TMR technique. This study investigated a reduced number of electrodes and the placement required to extract sufficient neural control information for accurate identification of user movement intents. An electrode selection algorithm was applied to the HD EMG recordings from each of four TMR amputee subjects. The results show that when using only 12 selected bipolar electrodes the average accuracy over subjects for classifying 16 movement intents was 93.0 (+/-3.3)%, just 1.2% lower than when using the entire HD electrode complement. The locations of selected electrodes were consistent with the anatomical reinnervation sites. Additionally, a practical protocol for clinical electrode placement was developed, which does not rely on complex HD EMG experiment and analysis while maintaining a classification accuracy of 88.7+/-4.5%. These outcomes provide important guidelines for practical electrode placement that can promote future clinical application of TMR and EMG PR in the control of multifunctional prostheses.     

Dependence of dc output of a rectenna array on the method of interconnection of its array elements

In 1994 and 1995, a ground-to-ground microwave power transmission (MPT) experiment was carried out by a group including participants from Kyoto University, Kobe University, and Kansai Electric Power Company. Among the MPT technologies, which are one of the most important key issues for the realization of the Solar Power Satellite, the “rectenna” (rectifying antenna) has been studied to achieve higher efficiency of conversion from microwave to dc We had developed a new rectenna panel which can effectively rectify a microwave power of 2.5 W at 2.45 GHz, prior to the ground-to-ground MPT field experiment. We examine the sum of the outputs of two or three rectenna panels which are connected either in parallel or in series or in a hybrid manner under the same microwave circumstances. The experiments lead us to conclude: (1) The sum of the dc outputs from two rectenna panels connected in parallel is larger than that from those connected in series. (2) The sum of the dc outputs of two rectenna panels is generally smaller than the sum of the dc output of the individual panels unless their outputs are equal. (3) Better total output dc power of a rectenna array is achieved when we take careful account of the array element balance. Based on the experiments, we propose an optimum method for connection of individual rectenna elements to form a high-efficiency rectenna array. © 1998 Scripta Technica, Electr Eng Jpn, 125(1): 9–17, 1998     

1 000 MW汽轮发电机端部磁-热耦合分析

基于有限元方法，对1 000 MW汽轮发电机端部行波电磁场和三维温度场进行了时谐耦合场分析。在发电机额定短路运行工况下，端部结构件的耦合场数值分析计算结果和相应温度实测数据间的误差满足工程分析精度要求，表明构造的时谐耦合场计算模型和分析方法的正确、有效性；并给出了空载、额定负载和进相0.95等运行工况下结构件的涡流损耗及其温度分布。该文采用的方法可用来指导电机的稳定安全运行，并为预测汽轮发电机的进相运行能力提供了可靠的理论分析基础。