大面积VHF-PECVD用多点馈入平行板电极馈入点优化的数值研究

本文采用二维准平面电路模型,对大面积甚高频等离子体增强化学气相沉积（VHF-PECVD）用多点馈入平行板电极馈入点的优化进行了数值研究,讨论了不同的多点馈入模式对平行板电极间真空电势分布均匀性的影响。研究结果表明：对于给定激发频率和尺度的大面积平行板电极,功率馈入连接点位置分布和数量成为影响电极间电势分布均匀性的两个重要可控参量,通过优化功率馈入连接点数量和连接点位置分布,可以抑制电势驻波效应及功率馈入点对数奇点效应,很大程度上有效地改善了电极间电势分布的均匀性。本文数值计算结果在一定程度上为VHF-PECVD技术用平行板电极实现大面积薄膜均匀沉积的系统设计提供了理论指导。     

高压直流输电系统换相失败谐波分析研究

本文利用pscad分析了高压直流输电过程中发生换相失败后非特征谐波的变化以及谐波对保护算法影响,并提出了相关的解决措施来避免谐波的影响并探讨了不稳定谐波的控制措施,为今后直流输电工程的设计、调试和运行提供有用的参考和技术积累。     

反射率计超高真空动密封馈入系统的研制

结合在NSRL同步辐射光束线和实验站的实际工作,对新设计的超高真空高精度同轴旋转平移差分馈入系统的密封型式和结构进行了描述,本系统可以完成超高真空条件下的高精度旋转平移轴系的馈入,已在NSRL反射率计实验站上得到成功使用.     

大规模海上风电场输电方式的探讨

分析了大规模海上风电场的并网需求,比较了高压交流输电系统、基于电网换相换流器的高直流输电系统和电压源换流器的直流输电系统的技术特点,对系统损耗做了数值分析,从而得出各种输电系统的适用范围。     

非对称制动压力对汽车低频制动尖叫的影响

针对汽车制动尖叫问题,建立汽车制动器有限元模型并基于能量馈入法开展其非对称性和对称性制动压力下的复模态数值仿真.结果 表明,耦合子系统的相对馈入能量能直接反映出各子部件的振型情况,当整体系统相对馈入能量的值接近0时,对应频率的复模态就无法被激发.对称性压力能够有效地降低活塞-卡钳的相对馈入能量,使制动器的复模态振型以制...     

高压直流输电系统接地极周围地表电位分析

高压直流输电系统大地回路运行时地表电位分布的研究,是评估地下金属管道腐蚀、变压器直流偏磁、通信干扰等不良效应受地电流影响的重要依据。利用镜像法和电磁波的折射、反射规律,推导出多层垂直和水平复合分层的地表电位的计算公式,并通过对比不同模型的计算结果,建立华东地区的3层水平带海洋大地模型。最后,通过不同模型仿真计算华东地区高压直流输电系统大地回路单极运行时接地极地表电位的分布情况,得到华东地区理想的仿真计算模型。     

渝鄂柔性直流输电接入电网高频谐振与抑制分析

针对渝鄂柔性直流输电(voltage source converter based high voltage direct current transmission,VSC-HVDC)南通道渝侧接入交流电网产生的系统高频谐振,应用阻抗分析法对影响系统稳定的柔性直流输电换流器特性进行了分析。利用渝鄂柔性直流输电换流器和交流线路参数,建立了换流器和交流线路阻抗的数学模型。应用MATLAB进行了仿真计算,得到换流器和交流线路的阻抗幅频、相频特性。对渝鄂柔性直流输电南通道渝侧二次高频振荡进行了深入剖析,找到了引起高频振荡的原因。最后,提出了渝鄂柔性直流输电高频振荡抑制策略,通过PSCAD仿真计算验证了抑制策略的正确性。     

对一盘式制动器高频尖叫及抑制的分析

针对某制动器存在的13kHz高频尖叫、在制动片上安装了消声片及对摩擦片形状进行加槽和倒角后仍得不到抑制的问题,通过对其建模和应用该课题组研究确立的系统分析方法,包括复特征值分析、子结构模态构成分析、子结构模态参数灵敏度分析以及能量馈入分析方法等,进行了系统分析,找出了影响该阶高频尖叫的关键子结构的关键模态,指出了修改方向,通过优化设计方法给出了修改部件,并得到了模拟验证。     

接地极入地电流在地中电流场的模拟研究

在特高压直流输电工程中，接地的目的是利用地作为传导电流回路的一个元件，以保证人身和设备安全，维护系统和设施安全可靠运行。然而，接地极人地电流会在其周围的地中形成一定强度的电流场，从而引起对接地极附近输电线路杆塔接地体腐蚀的影响。由此，本文将从一个全新的角度，即利用三维电磁场仿真软件cS恻点电流源在地中电磁场的分布进行模拟研究，达到对接地极入地电流对附近输电线路杆塔接地体腐蚀影响的评估。     

微波电视站天馈系统的应用调试与维护

以多工器调频发射系统解决资源有限条件下微波电视站多频发射难题为背景,在总结微波电视站天馈系统的基础上,阐释天馈系统重要扩展部件多工器的分类及原理,重点探讨多工器调频发射系统的应用调试及维护方法。     

Application of the multi-level current reinjection concept to HVDC transmission

The self-commutating multilevel current reinjection (MLCR) reduces the converter current waveform to zero during the valves commutations and, thus, removes the converter dependence on line commutation. This property provides the conventional thyristor converter with the same flexibility as the self-commutating multi-level schemes in terms of reactive power control and harmonic elimination. This paper describes the structure and control of a current source HVDC transmission scheme using MLCR converters. Extensive EMTDC simulation is carried out to demonstrate the improved controllability of the proposed HVDC configuration     

Variable frequency SCR inverter with an auxiliary commutation circuit

With the recent development of static inverters using thyristors (silicon controlled rectifiers), many extensive attempts have been made to use them as adjustable frequency sources with the aim of realizing simple and accurate speed control systems of ac motors. For these applications, we have developed the improved inverter which has an auxiliary commutation circuit and a feedback current transformer. The auxiliary commutation circuit functions to improve the commutation characteristics and operation reliability, while the feedback current transformer improves the efficiency and stability. The distinguished characteristics of this new inverter have been proved by the experimental drives of induction motors and synchronous motors in wide frequency ranges.     

On carrier-frequency gating systems for static switching circuits

Carrier-frequency gating systems for exciting static electronic switches such as thyristors are examined. The effect of the commutation in the output rectifiers during transmission of the carrier wave is to cause an instantaneous drop in the output voltage during commutation. A compensation for the commutation drop by an overlap technique is proposed, and comparative experimental observations presented on two types of systems.     

Research on DC Protection Strategy in Multi-Terminal Hybrid HVDC System

Multi-terminal hybrid high-voltage direct current (HVDC) systems have been developed quickly in recent years in power transmission area. However, for voltage-source converter (VSC) stations in hybrid HVDC systems, no direct current (DC) filters are required. In addition, the DC reactor is also not installed at the line end because the DC fault can be limited by the converter itself. This means that the boundary element at the line end is absent, and the single-ended protections used in line commutated converter (LCC) based HVDC (LCC-HVDC) systems or VSC-HVDC systems cannot distinguish the fault line in multi-terminal hybrid HVDC systems. This paper proposes a novel single-ended DC protection strategy suitable for the multi-terminal hybrid HVDC system, which mainly applies the transient information and active injection concept to detect and distinguish the fault line. Compared with the single-ended protections used in LCC-HVDC and VSC-HVDC systems, the proposed protection strategy is not dependent on the line boundary element and is thus suitable for the multi-terminal hybrid HVDC system. The corresponding simulation cases based on power systems computer aided design (PSCAD)/electromagnetic transients including DC (EMTDC) are carried out to verify the superiority of the proposed protection.     

Frequency domain model of an hvdc link with a line-commutated current-source converter. part I: fixed overlap

This study presents a frequency-domain model of an high voltage direct current (HVDC) transmission link with a line-commutated current-source converter. Using space-vector transfer functions between superimposed oscillations in the control signal and the AC and DC sides, expressions for voltages and currents have been derived. The dynamic properties of the HVDC link, taking the characteristics of the networks on both the AC and the DC sides into consideration, can be studied by applying classical Bode/Nyquist/Nichols control methods. The resulting model was validated by time-domain studies in PSCAD/EMTDC. The model is described in two papers. In this paper (Part I), it has been assumed that the overlap angle during commutation remains constant. It is shown in the validation that this assumption introduces resonances that cause severe errors at certain network conditions. In the second paper (Part II), the model is extended so as to cope with the varying overlap angle in order to bring the frequency-domain model into agreement with the results obtained from time-domain simulations.     

多电压等级直流电力系统发展与挑战

随着新能源发电规模越来越大,输送距离越来越远以及大规模分布式发电和直流负荷的接入,现有的交流电力系统越来越难以满足电力系统发展的需求。由于高压直流输电（high voltage direct current,HVDC）的技术优势,交流电力系统面临的这些挑战,却给直流电力系统的发展带来了新的契机。介绍了欧美各国和我国在高压直流输电系统、中压直流配电系统和低压直流供电系统等不同电压等级直流电力技术的发展现状,分别对高压直流输电技术、中压直流配电技术和低压直流供电技术的应用场景进行了说明,并针对现有交流输电技术的不足,分析了直流电力技术在新能源远距离输电和分布式电源接入等方面的优越性。最后介绍了现有技术水平下直流电力系统发展在关键设备研发、控制保护和标准制定等方面所面临的挑战。     

海外柔性直流输电工程项目质量管理体系及成熟度评价

海外柔性直流输电工程项目的质量管理与国内的工程质量管理存在一定差异。在管理过程中,需要根据国际相关标准的项目质量管理思路,树立正确的质量管理理念。结合ISO 9001：2015、ISO 21500：2012和PMBOK质量管理体系标准,从知识管理、变更管理、资源管理、利益相关者管理、风险管理、沟通管理6个方面改进项目质量管理流程,提出适用于海外柔性直流输电工程项目的质量管理体系。最后,提出了海外柔性直流输电工程项目质量管理成熟度综合评价方法,对该体系成熟度进行了分析验证,为海外柔性直流输电工程项目质量管理工作提供借鉴。     

A commutation strategy for IGBT-based CSI-fed parallel resonant circuit for induction heating application

A brief study on a commutation strategy for a current source inverter (CSI)-fed parallel resonant circuit, using switches formed by IGBTs with series diodes, is presented in this paper. The dynamic behaviour of the inverter and different strategies for its reliable operation are discussed here considering parasitic inductance and overlap time between CSI switching devices. The dynamic behaviour of the switches decides the upper frequency limit for the application. IGBTs with the series diodes behave as uni-directional current switches with bi-directional voltage blocking capability. This feature should be taken into account to decide on an appropriate switching strategy for this converter configuration.     

JEM 2100透射电镜照相系统故障分析

对JEM 2100透射电镜照相系统正常拍片程序进行了介绍,分析了卡片、传送机构不工作和传送中途失败等故障及其排除办法,可作为同类型电镜的照相系统故障维修时的参考。