Bidirectional rotating direct-current triboelectric nanogenerator with self-adaptive mechanical switching for harvesting reciprocating motion

Amid the growing interest in triboelectric nanogenerators(TENGs)as novel energy-harvesting devices,several studies have focused on direct current(DC)TENGs to generate a stable DC output for operating electronic devices.However,owing to the working mechanisms of conventional DC TENGs,generating a stable DC output from reciprocating motion remains a challenge.Accordingly,we propose a bidirectional rotating DC TENG(BiR-TENG),which can generate DC outputs,regardless of the direction of rotation,from reciprocating motions.The distinct design of the BiR-TENG enables the mechanical rectification of the alternating current output into a rotational-direction-dependent DC output.Furthermore,it allows the conversion of the rotational-direction-dependent DC output into a unidirectional DC output by adapting the configurations depending on the rotational direction.Owing to these tailored design strategies and subsequent optimizations,the BiR-TENG could generate an effective unidirectional DC output.Applications of the BiR-TENG for the reciprocating motions of swinging doors and waves were demonstrated by harnessing this output.This study demonstrates the potential of the BiR-TENG design strategy as an effective and versatile solution for energy harvesting from reciprocating motions,highlighting the suitability of DC outputs as an energy source for electronic devices.

基于自适应移频分析法的Voltage-Behind-Reactance异步电机多时间尺度暂态建模与仿真

为满足对电力系统多时间尺度暂态过程准确、快速仿真的需要,提出了一种基于自适应移频分析法的voltage-behind-reactance(VBR)异步电机多时间尺度模型。首先,基于希尔伯特变换,将传统电气信号转换为相应的解析信号;进一步,引入灵活的移频变换,利用解析信号构建异步电机暂态仿真模型。这样,移动频率成为可调节的模型参数。所提出的电机模型通过设置不同的移动频率,能够同时实现准确的高频暂态过程仿真和高效的低频暂态过程仿真。当移动频率等于零时,该模型与传统电磁暂态电机模型等价,可刻画高频暂态过程。当移动频率等于系统基波频率时,该模型适用于大步长仿真,获得低频暂态包络曲线。仿真结果表明,所提出的模型可实现准确和高效的异步电机多时间尺度暂态仿真。

Constructions and Preliminary HV Conditioning of a Photocathode Direct-Current Electron Gun at IHEP

As one of the most important key technologies for future advanced light source based on the energy recovery linac, a photocathode dc electron gun is supported by Institute of High Energy Physics （IHEP） to address the technical challenges of producing very low ernittance beams at high average current. Construction of the dc gun is completed and a preliminary high voltage conditioning is carried out up to 440 k V. The design, construction and preliminary HV conditioning results for the dc gun are described.

CALCULATION OF SATURABLE LEAKAGE REACTANCES OF SQUIRREL CAGE ASYNCHRONOUS MOTORS

A general method of calculating the saturable leakage reactances of squirrelcage asynchronous motors is presented.The method synthesized the variety of effectswhich affect the saturation of leakage magnetic circuit.And the saturable reactances canbe precisely evaluated in any running condition.The computation results of Y-series mo-tors are in good agreement with the test ones.

Anomalous Direct-Current Josephson Effect in Semiconductor Nanowire Junctions

We investigate the dc Josephson effect in one-dimensional junctions where a ring conductor is sandwiched between two semiconductor nanowires with proximity-induced superconductivity. Peculiar features of the Josephson effect arise due to the interplay of spin-orbit interaction and external Zeenmn field. By tuning the Zeeman field orientation, the device can vary from 0 to π junction. Afore importantly, nonzero ,losephson current is possible at zero phase difference across the junction. Although this anomalous Josephson current is not relevant to the topological phase transition, its magnitude can be significantly enhanced whe, n the nanowire, s become topological superconductors where Majorana bound states emerge. Distinct modulation patterns are obtained for the semiconductor nanowires in the topologically trivial and non-trivial phases. These results are useful to probe the topological phase transition in semiconductor nanowire junctions via the dc Josephson effect.

Modeling of Pulsed Direct-Current Glow Discharge

A self-consistent model was adopted to study the time evolution of low-voltage pulsed DC glow discharge. The distributions of electric field, ion density and electron density in nitrogen were investigated in our simulation, and the temporal shape of the discharge current was also obtained. Our results show that the dynamic behaviors of the discharge depends strongly on the applied pulse voltage, and the use of higher pulse voltages results in a significantly increase of discharge current and a decrease of discharge delay time. The current-voltage characteristic cMculated by adjusting secondary electron emission coefficient for different applied pulse voltage under the gas pressure of 1 Torr is found in a reasonable agreement with the experimental results.

Effects of the sputtering power on the crystalline structure and optical properties of the silver oxide films deposited using direct-current reactive magnetron sputtering

This paper reports that a series of silver oxide （AgzO） films are deposited on glass substrates by direct-current reactive magnetron sputtering at a substrate temperature of 250 ℃ and an oxygen flux ratio of 15：18 by modifying the sputtering power （SP）. The AgxO films deposited apparently show a structural evolution from cubic biphased （AgO ＋ Ag20） to cubic single-phased （Ag20）, and to biphased （Ag20 ＋ AgO） structure. Notably, the cubic single-phased Ag20 fihn is deposited at the SP = 105 W and an AgO phase with （220） orientation discerned in the Ag^O films deposited using the SP 〉 105 W. The transmissivity and refiectivity of the AgxO films in transparent region decrease with the increase the SP, whereas the absorptivity inversely increases with the increase of the SP. These results may be due to the structural evolution and the increasing film thickness. A redshift of the films＇ absorption edges determined in terms of Tauc formula clearly occurs from 3.1 eV to 2.73 eV with the increase of the SP.

Research on corona discharge suppression of high-voltage direct-current transmission lines based on dielectric-film-covered conductor

Corona discharge suppression for high-voltage direct-current(HVDC)transmission lines at line terminals such as converter stations is a subject that requires attention.In this paper,a method based on a conductor covered with dielectric film is proposed and implemented through a bench-scale setup.Compared with the bare conductor,the corona discharge suppression effect of the dielectric-film-covered conductor under positive polarity is studied from the composite field strength and ion current density using a line-plate experimental device.The influences of film thickness and film material on the corona discharge suppression effect are investigated.The charge accumulation and dissipation characteristics of different film materials are also studied.The results show that the conductor covered with dielectric film has excellent ability to inhibit corona discharge.The ground-level composite field strength of the conductor covered with dielectric film is lower than its nominal field strength,and its ion current density is at the nA m^(−2) level.The corona threshold voltage can be promoted by increasing the film thickness,but the ability to inhibit corona discharge becomes weak.The larger the surface electric field strength,the more charge accumulated,but the faster the charge dissipation rate.Compared with polyvinyl chloride film,cross-linked polyethylene film has stronger charge accumulation ability and slower charge dissipation rate,which can better restrain the corona discharge of HVDC transmission lines.

Structural,Morphological and Electrical Properties of In-Doped Zinc Oxide Nanostructure Thin Films Grown on p-Type Gallium Nitride by Simultaneous Radio-Frequency Direct-Current Magnetron Co-Sputtering

Zinc oxide （ZnO） is one of the most promising and frequently used semiconductor materials. In-doped nanos- tructure ZnO thin films are grown on p-type gallium nitride substrates by employing the simultaneous rf and dc magnetron co-sputtering technique. The effect of In-doping on structural, morphological and electrical properties is studied. The different dopant concentrations are accomplished by varying the direct current power of the In target while keeping the fixed radio frequency power of the ZnO target through the co-sputtering deposition technique by using argon as the sputtering gas at ambient temperature. The structural analysis confirms that all the grown thin films preferentially orientate along the c-axis with the wurtzite hexagonal crystal structure without having any kind of In oxide phases. The presenting Zn, 0 and In elements＇ chemical compositions are identified with EDX mapping analysis of the deposited thin films and the calculated M ratio has been found to decrease with the increasing In power. The surface topographies of the grown thin films are examined with the atomic force microscope technique. The obtained results reveal that the grown film roughness increases with the In power. The Hall measurements ascertain that all the grown films have n-type conductivity and also the other electrical parameters such as resistivity,mobility and carrier concentration are analyzed.

Resistance and Reactance of Monopole Fields Induced by a Test Charge Drifting Off-Axis in a Cold and Collisional Cylindrical Plasma

We study the interaction of a uniform, cold and collisional plasma with a test charged particle moving off-axis at a constant speed down a cylindrical tube with a resistive thick metallic wall. Upon matching the electromagnetic field components at all interfaces, the induced monopole electromagnetic fields in the plasma are obtained in the frequency domain. An expression for the plasma electric resistance and reactance is derived and analyzed numerically for some representative parameters. Near the plasma resonant frequency, the plasma resistance evolves with frequency like a parallel RLC resonator with peak resistance at the plasma frequency pe, while the plasma reactance can be capacitive or inductive in nature depending on the frequency under consideration.

基于可控串联电抗的新能源送出线路故障性质识别方法

针对不带并联电抗器的新能源送出线,能否正确区分故障性质是确保新能源系统安全可靠运行的重中之重。为降低新能源送出线故障对电力设备和系统的冲击,提高重合闸成功率,减少新能源发电系统脱网的发生,提出基于可控串联电抗限流信息的新能源送出线路故障性质识别方法。在送出线路上设计串联可控限流电抗器,在线路故障相跳闸时基于等值阻抗的预判投入可控电抗,在串联电抗限流特性下分析瞬时性故障和永久性故障时的线路电流差异,建立电流突变量比较判据,并能够确定故障电弧熄灭时刻,进而构建新能源场站送出线路基于故障性质识别的自适应重合闸策略。仿真结果表明,所提方法能快速、可靠地识别结果,应用在新能源场站送出线路工程上能有效提高线路的重合率。

基于四电极多频率扫描的生物阻抗法人体成分测试仪设计

生物阻抗包含丰富的人体病理和生理电信号,可以作为医务人员准确判断病人症状和治疗疾病的主要依据。基于此,提出一种基于Cole-Cole理论的人体多种参数测量系统。构建人体阻抗模型,通过碳纳米材料电极对人体阻抗进行采集分析,得到人体的各种成分参数。通过信号发生电路产生注入人体的低频信号,利用幅度检测电路检测流经人体电流产生的电压,采用分段检测法测得人体不同分段的阻抗信息;信号经放大电路输入RT1052微处理器,对数据和人体成分参数相关性进行分析,得到人体各种成分参数并显示测量结果。通过对系统进行测试分析,得出所设计系统能够准确地对人体蛋白质、脂肪等参数进行测量,误差范围可以控制在5%以内,具有很好的应用前景。

特高压直流换流站短路电流超标机理及抑制措施研究

随着电网规模的不断扩大,短路电流不断上升,成为制约电网发展的关键问题。针对特高压直流送端换流站单相与三相短路电流均超标,并且单相短路电流甚至大于三相短路电流的问题,分析了其产生的原因及机理,并从短路电流抑制效果、经济性以及电网运行可靠性等多个维度比较了不同短路电流限制措施,研究表明:串联电抗器与变压器中性点小电抗的组合方案最适合解决此类短路电流超标问题。兼顾方案经济性以及降低对电网运行的影响,提出了串联电抗器与变压器中性点小电抗组合方案的参数实用设计方法,简易方便,可为解决特高压直流换流站短路电流超标问题提供参考。

电机学中的一些“反常”现象及其成因分析

描述了电机学中的一些“反常”现象,分析了这些现象的成因,并用简明的语言进行归纳,为相关领域的研究人员提供一定参考。

远一点真的没有关系吗?空间距离对消费者朋友圈分享奖励计划的影响研究——抗拒体验的调节作用

虽然互联网的出现突破了空间距离的限制,但移动互联网环境下空间距离能否对顾客在线分享意愿产生影响及如何影响仍需进一步探讨。本文通过两个实验考察了空间距离和消费者抗拒体验对消费者朋友圈分享奖励计划的影响。实验一主要考察在不同空间距离下的朋友圈分享奖励计划对消费者的影响,结果发现远空间距离比近空间距离带来更低的消费者心理所有权、更高的感知社会成本和更低的分享意愿,同时心理所有权和感知社会成本是空间距离对分享意愿影响的中介变量。在此基础上,实验二主要考察消费者抗拒体验在空间距离与消费者反应关系中的调节作用。研究再次证实了远空间距离和近空间距离对消费者的差异影响,并证实了抗拒体验在空间距离与消费者反应关系间具有调节作用:抗拒体验强的消费者比抗拒体验弱的消费者在空间距离对心理所有权、感知社会成本和分享意愿的影响上差值更大。

Intelligent algorithm-based maximum power point tracker for an off-grid photovoltaic-powered direct-current irrigation system

This research aims to enhance the performance of photovoltaic(PV)systems on a 2-fold basis.Firstly,it introduces an advanced deep artificial neural network algorithm for accurate and fast maximum power point tracking,ensuring optimal extraction of electrical power from PV arrays.Secondly,it proposes the use of 96-V,2.98-kW direct-current(DC)water pumps for farm irrigation,aiming to improve efficiency,reduce cost and complexity,and overcome challenges associated with connecting faraway farm irrigation systems to the utility grid.In this study,it has been demonstrated that the use of DC pumps greatly improves system performance and efficiency by eliminating the need for isolation transformers,power passive filters and inverters,therefore simplifying the architecture of the system.The efficacy of the proposed methodology is confirmed by MATLAB®/Simulink®simulation results,whereby the proposed algorithm attains a mean squared error of 6.5705×10^(-5)and a system efficiency approaching 99.8%,ensuring a steady voltage under varying load conditions.

偏斜转子槽形感应电机正反转性能差异的研究

转子槽形沿径向偏斜后的电机电磁性能受电机转向影响。为减小偏斜转子槽形电机正反转时的性能差异,提出一种槽身偏斜槽形,保证槽形的槽口区域轴对称。基于转子槽漏磁模型,对比径向偏斜与槽身偏斜槽形,探讨槽形偏斜后的等效磁路变化,以及转子槽漏抗与主电抗参数随偏斜距离的变化规律。利用冻结磁导率法隔断主磁通的气隙路径,假设由槽内导体电流产生的转子漏磁场仅包括槽漏磁场,计算电机正反转下不同槽形偏斜距离时的槽漏抗值,并根据等效电路模型计算相应的主电抗值。最后,仿真计算两类偏斜转子槽电机的输出转矩与功率因数,结果表明转子槽身偏斜电机正反转时的性能接近,而且受槽形偏斜距离的影响较小。偏斜转子槽形的不对称槽口区域是引起电机正反转性能差异的主要原因。

基于阻抗判据的变电站并联电容器组串抗率选择方法

为保证谐波不超标,实际应用中一般先投入高串抗率电容器,高、低串抗率电容器动作次数存在着差异性和不均衡性,而高串抗率电容器的配置和使用带来更大的有功损耗,经济性较差。针对这一问题,本文提出一种基于阻抗判据的变电站并联电容器组串抗率选择方法。首先,获取公共连接点谐波数据,建立状态空间表达式,采用卡尔曼滤波算法和标准差最小原则估计系统谐波阻抗;然后,依据电能质量标准得出限值谐波阻抗,分析并联电容器组限值谐波阻抗、等值谐波阻抗与谐波放大倍数的关系,确定串抗率选择的阻抗判据;最后,通过仿真算例验证本文方法的有效性和合理性。结果表明,所提方法能降低并联电容器组配置时优先使用高串抗率电容器带来的有功损耗,提高经济性。

基于动态虚拟电抗的虚拟同步机系统有功环电压动态补偿策略

为解决新型电力系统中的虚拟同步机(Virtual synchronous generator,VSG)在电网电压跌落时出现的功角暂态失稳和过电流问题,对采用VSG控制的并网换流器暂态控制策略进行了改进。为降低故障期间有功功率的参考值进而实现VSG的功角暂态稳定控制,根据VSG的功角特性、有功功率参考值与功角稳定性之间的关系,引入电压动态补偿,并利用相图曲线理论分析了控制策略参数选取对暂态稳定的影响。为限制故障发生瞬间和故障切除瞬间的冲击电流、保证故障期间VSG系统的暂态功角稳定、实现故障限流,提出了一种以指数形式变化的虚拟电抗模型,确定了虚拟电抗的投切参数。仿真实验结果验证了改进策略的有效性。

基于高阻接地距离继电器的零序电流保护选择性提升方案

交流线路零序电流保护最末一段均采用300 A定值,存在无序跳闸风险。因此,文中提出了基于零序电抗线和非故障相极化的高阻接地距离继电器原理。继电器采用先选相、后测量的技术路线,选相元件将零序电抗线与非故障相极化方法相结合,构成多种组合判据,以分工完成选相。由于保护安装处零序电流与故障点零序电流存在相位差异,单相接地故障的故障相和相间接地故障的超前相的零序电抗线在故障点位于整定点附近时存在混叠区。区内近端、低阻单相接地故障时非故障相工作电压大幅变化,不利于区分混叠区的两类故障,故将选相元件分为低阻模块和高阻模块。低阻模块采用下偏的零序电抗线,用于识别近端、低阻故障;经低阻模块辅助后,高阻模块只需针对性处置故障点位于整定点附近的故障,可有效区分两类故障。选相完成后,通过非故障相极化的方法获得故障前工作电压,从而确定继电器的动作特性。高阻距离继电器的耐过渡电阻能力远超规程要求,提高了接地后备保护对高阻接地故障的选择性。