Acceleration of Dielectric Charging in RF MEMS Capacitive Switches

To design and validate accelerated life tests of RF MEMS capacitive switches, acceleration factors of charging effects in switch dielectric were quantitatively characterized. From measured charging and discharging transient currents at different temperatures and control voltages, densities and time constants of dielectric traps were extracted. A charging model was constructed to predict the amount of charge injected into the dielectric and the corresponding shift in actuation voltage under different acceleration factors such as temperature, peak voltage, duty factor, and frequency of the control waveform. Agreement was obtained between the model prediction and experimental data. It was found that temperature, peak voltage, and duty factor were critical acceleration factors for dielectric-charging effects whereas frequency had little effect on charging     

Electrostatically Controlled,Pneumatically Actuated Microvalve with Low Pressure Loss

This paper describes a microvalve to control liquefied gas in a micro fuel reforming system. To realize both high pressure leak tolerance and low pressure loss, a main valve is pneumatically actuated by the pressure of the liquefied gas itself, and its pneumatic actuation is controlled by two electrostatic sub‐valves. The fabricated microvalve was tested in terms of pressure loss in the open state, leakage in the closed state, driving voltage, and response time. The pressure loss was close to the theoretical value, which was sufficiently low for the application. The apparent leakage was not detected until the input pressure reached 150 kPa (gage). The driving voltage of the sub‐valve was 30‐40 V. The response time from the closed to the open state is expected to be less than 200 ms. The experimental results suggest that all the required functions such as low pressure loss, electrostatic actuation and leak proof operation can be realized. © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Electrostatic Discharge and Cycling Effects on Ohmic and Capacitive RF-MEMS Switches

An extensive electrical characterization of radio frequency microelectromechanical systems (RF-MEMS) switches has been carried out to identify the dynamic response of both ohmic and capacitive devices, driven in different conditions of bias and actuation time. We have found that an optimum actuation voltage must be chosen as a tradeoff between good switch transmission and isolation properties and the need to avoid bouncing phenomena when the actuation voltage has been applied. Moreover, the degradation of shunt RF-MEMS strongly depends on the duty cycle of the actuation voltage waveform and, hence, on the time that the switch spends in the actuated state. We have also investigated the reliability to electrostatic discharge (ESD) events of the RF-MEMS switches. Using a transmission line pulser time domain reflectometer on wafer systems, we have stressed RF-MEMS switches in different conditions and found that the reliability of RF-MEMS devices could be heavily affected by ESD phenomena.     

国外对宇航用射频MEMS开关的研究

本文介绍了国外对宇航用射频MEMS开关的研究,包括其性能、结构、技术成熟度、生产制造、可靠性及环境应力。     

Mathematical Modeling and Analysis of MEMS Deformable Mirror Actuated by Electrostatic Piston Array

In this report, we constructed a simple mathematical analysis model for a new MEMS deformable mirror using an electrostatic piston array. The deformable mirror has been developed as a wavefront compensation device in adaptive optics for retinal observation. The device realizes a large convex deformation with a low operation voltage because of moving bottom electrodes on the pistons. The constructed model is based on the plate theory and simple superposition of the actuation components. The calculated deformation analyzed using this model agrees well with that analyzed using the finite element method not only in deformation shape but the peak‐valley deformations. In addition, the calculation time is much shorter, so the model can be used for design optimization of the device.     

地球同步轨道环境下外露介质深层带电仿真分析

空间高能带电粒子可导致航天器外露介质深层带电,从而对航天器的可靠运行带来潜在威胁。为了考察介质起电规律和最终评估深层带电危害,基于电荷守恒定律,建立了介质深层带电的数学模型,并通过数值求解,实现了对外露介质深层带电的时域3维仿真分析。该模型综合考虑了介质电导率受辐射剂量率、强电场和温度的影响。对典型的天线支撑介质结构进行仿真,结果表明:地球同步轨道环境下外露介质面临着严重的深层带电与介质击穿放电威胁,环境温度是影响外露介质内带电的关键因素。天线支撑结构的局部数10 MV/m以上强电场和10 KV以上高电压,很可能成为航天器表面放电或关键部位功能失常的诱导因素。     

Dust Deposition in Electrostatically Enhanced Fibrous Filters

A theoretical model to predict the total bed collection efficiency of a fibrous filter across which a strong electric field is applied is proposed. The fluid flow, as well as the electrostatic fields considered in the model, take into account the geometric configuration of the fibers in the filter. To predict filter efficiencies, dust-particle trajectory calculations are carried out to include inertial, interceptional, and electrostatic effects. Both the theoretical and experimental results demonstrate the dramatic increase in filtration efficiency by applying external electric fields to the filter at low Stokes numbers (St < 0.1). Experimental data were obtained by passing through the filter different pollutants such as latex aerosols (1-μm in diameter), DOP smoke, and two different kinds of solid dust generated by a specially constructed disperser. The influence of gas humidity on the separation process in the filter is also studied. The reported experimental data show good agreement with theoretical predictions, demonstrating that the physics governing the process have been properly incorporated into the model.     

充电站内电动汽车有序充电策略

以充电站运营收益最大化为目标,以配电变压器容量及最大限度满足用户充电需求为约束条件,建立了充电站内电动汽车有序充电的数学模型。根据用户充电规律,采用蒙特卡洛模拟法模拟用户充电需求,对电动汽车在有序充电和无序充电2种情形下充电站运行的经济效益及配电变压器负载情况进行了仿真计算和分析。研究结果表明,通过动态响应电网分时电价,有序充电控制方法可显著提高电动汽车充电站的经济效益,并具备很高的计算效率。同时,由于相对便宜电价的激励,夜间采用有序充电方式也可能使大量的电动汽车集中充电而导致另外一个用电高峰的出现。     

电动汽车充换电站换电池的有序充电优化

大规模的电动汽车充电负荷具有大功率、波动性和不确定性的特点,将给电网带来峰值增高、电压波动等不利影响。为了降低电动汽车充电负荷对电网的不利影响,建立了电动汽车充换电站换电池的充电优化模型。通过对换电池在充电过程中充电时间、充电功率和电池电量的实测数据进行拟合,得到了电动汽车换电池的充电特性。以此为基础,建立了电动汽车充换电站的换电池有序充电模型,该模型在满足充电机数量、电动汽车对换电池的需求、充换电站容量和变电站容量约束的前提下,最小化所属变电站负荷曲线的离差平方和,并应用遗传算法实现了有序充电模型的快速求解。以山东省某电动汽车充换电站为算例,证明了该模型的快速性、正确性和有效性。     

电动汽车充电站有序充电调度的分散式优化

大量电动汽车无序充电会给电力系统尤其是配电系统的安全与经济运行带来影响甚至挑战。针对集中式优化与控制方法的不足和固定电价策略的缺陷,基于拉格朗日松弛法,将传统的电动汽车充电站有序充电调度集中式优化问题分解为N个子问题(N为需充电电动汽车数量),提出了有序充电调度的分散式优化策略。优化模型以充电站收益最大为目标函数,考虑了用户用电需求、充电时间、变压器容量等约束和充电站分时电价策略。为验证所提方法的有效性,采用蒙特卡洛法模拟电动汽车充电需求,对采用集中式优化和分散式优化策略的有序充电和无序充电情形,以及充电站售电固定电价和分时电价模式下的充电站收益、削峰填谷效果、计算效率等进行仿真计算和分析。结果表明,所提方法相比于无序充电及充电站固定电价策略,可显著提高收益;相比于集中式优化,计算效率更高;充电站采用售电分时电价虽有"填谷"效果,但平抑负荷波动效果并不十分理想。     

居民小区电动汽车充电负荷有序控制策略

针对当前居民小区电动汽车充电设施建设中遇到的配电变压器供电容量限制及物业管理方缺乏运营积极性等实际困难,研究了电动汽车充电负荷有序控制策略,主要目标包括预防配电变压器过载和实现充电收益最大化。首先提出了网格选取法,在保证变压器不过载运行的同时,灵活规划电动汽车的充电时段。进而基于峰谷分时电价构建了充电电费支出最小的目标函数,并基于遗传算法设计了求取最优网格选取结果的方法与步骤。最后,采用蒙特卡洛法进行算例仿真和分析验证。结果表明:网格选取法隐含了配电容量限制条件,简化了电动汽车的有序充电规划,更利于采用寻优算法进行求解。所求取的有序充电策略能有效实现负荷移峰填谷、降低电费支出,同时提高运营方的充电收益及参与积极性。     

DAS开关自动化模式的应用实践

介绍了DAS开关的自动化模式；分析了其实现原理；总结了DAS开关的应用实践经验，对DAS自动化模式进行了探讨。     

Particle Charging in Combined Corona-Electrostatic Fields

The association of several ionizing and nonionizing electrodes generates combined corona-electrostatic fields, characterized by space charge zones of well-defined extensions. In a previous paper, the authors presented an effective numerical method for the computation of such fields. The aim of this present work is to show how these results can be employed for estimating the charge acquired by insulating and conducting particles when passing through the space charge zones generated by various corona-electrostatic electrode geometries. The study is done under several assumptions that authorize the use of Pauthenier's formula. Diffusion charging can be neglected, the applied electric field is quasi-uniform in the vicinity of particles, and particle speed is low compared with that of air ions. The charging model takes into account the computed spatial distribution of the electric field and charge density. The computations were performed for various values of the geometrical parameters of the electrode system and of the particle transit time through the corona discharge zone. The results can be used for the design of the electrode system of any electrostatic process employing corona discharge fields.      

Tuning in to RF MEMS

RF MEMS technology was initially developed as a replacement for GaAs HEMT switches and p-i-n diodes for low-loss switching networks and X-band to mm-wave phase shifters. However, we have found that its very low loss properties (high device Q), its simple microwave circuit model and zero power consumption, its high power (voltage/current) handling capabilities, and its very low distortion properties, all make it the ideal tuning device for reconfigurable filters, antennas and impedance matching networks. In fact, reconfigurable networks are currently being funded at the same level-if not higher-than RF MEMS phase shifters, and in our opinion, are much more challenging for high-Q designs.     

漏电开关常见故障分析与处理

漏电开关是一种新型的安全保护装置,可以作为接地或接零保护的补充,能有效地防止触电伤亡、电气火灾与爆炸,迅速切断漏电设备的电源。     

开关电器的神经网络设计与算法

根据神经网络的基本理论 ,研究了神经网络在电器设备中的应用 ,提出了神经网络的分块构造方法和神经网络分块学习算法 ,并通过实验模拟达到实际要求。     

变电站母线接地开关配置的探讨

对于屋外配电装置，为保证电气设备和母线的检修安全，应恰当地配置母线接地开关。停电母线上电磁感应电压，取决于平行带电母线的电流和它们的相对间距。通过实例分析，介绍了确定母线接地开关的安装数量和间距的计算方法。     

开关电源电磁兼容测试现状

祥细讨论了开关电源电磁兼容测试的测量仪器设备、测试场地；环境电平、30MHz～l000MHz的辐射和电源端传导干扰电压/电流等物理量的直接测试方法；还讨论了开关电源电磁兼容的替代的测试方法。最后阐述了我国电磁兼容试验技术的发展动态。     

配电网线路分段开关的优化规划

以分段开关加入后配电系统的可靠性成本和可靠性效益为目标函数,计及分段开关的年投资、年维护费用、系统停电损失等综合费用和相关技术约束,建立了配电网线路分段开关的优化规划模型,提出用改进遗传模拟退火算法来求解的研究思路,把遗传算法全局搜索能力强与模拟退火算法局部搜索能力强的特点结合起来,提高了算法的局部寻优能力,有效地解决了早熟现象,具有很好的全局收敛性。通过对IEEE RBTS BUSS局部网络分段开关的优化规划证明了该思路的有效性和科学性。     

智能变电站网络交换机在线监测设计与实现

文中根据当前智能变电站中交换机使用和管理现状,分析了变电站交换机实现在线监测的对象和采集数据及数据处理方法,提出了兼容不同厂家、不同类型交换机私有变量、端口数量跨网络的多设备防阻塞并行采集设计方案,并以此开发了交换机在线监测网络管理程序,实现了变电站交换机的在线监测应用。