JJB系列高频静电油烟净化机及高频高压开关电源的研制

本文介绍JJB系列高频静电油烟净化机的技术关键－静电油烟净化机用的高频高压开关电源。     

开关电源与环境问题

谋求开关电源高效化、小型化、轻量化是完全可能的。目前开关电源已开始用于民用机器,如在OA、FA等机器中及其很多的电子机器中已被广泛应用。另一方面,由于开关元件在开关时产生噪声,所以设计者必须认真研究消除噪声的实际对策。尤其是近来,高频电源的噪声已成为国际标准化规范化的方向。对于消除噪声的对策以及功率因数的改善应当加以详细地研究。本文对开关电源做     

基于单管准谐振逆变器的电磁炉端子骚扰电压测试、分析与抑制

家用电器中功率板设计最困难的是需满足相关电磁兼容法规要求。本文介绍了基于单管高频感应加热准谐振逆变器的工作原理、开关管反并联二极管实现零电压低损耗开关过程以及对谐振过程产生的谐振电流进行了理论推导;并按照GB 4824-2013标准要求对某款电磁炉进行了电源端子骚扰电压测试、不合格原因分析;并结合工程实践实施了改进抑制;最后通过复测验证了整改对策的有效性,以图为家电企业提供电磁兼容设计参考。     

便携式现场变压器局放感应耐压试验装置研究

目前变压器局放感应耐压试验装置多存在分散化现象,导致试验效率低,成本消耗较高,为此本文研究一种便携式现场变压器局放感应耐压试验装置,集各设备功能为一体,改善传统分立仪器测试模式。对新装置组成框架进行设计和分析,选择装置组成设备以及设计装置连接方案,完成对其运行程序进行设计,实现整个装置的安装与运行。结果表明:与常规变压器局放感应耐压试验装置相比,利用设计的新装置进行现场变压器局放感应耐压试验,所花费的时间仅为20 min 25 s,所用时间短,工作效率高,且产生的预算成本也更低为48万。由此说明新装置在局放感应耐压试验中更为有效,为变压器故障检测工作提供极大便利,保证了电力安全运行。     

基于GB/T 29309标准的HALT测试技术分析

本文以标准GB/T 29309-2012为基础,以某款开关电源为例,对HALT试验设备、工作极限与破坏极限、试验步骤及设备运行中注意点等方面展开介绍,为电子产品可靠性测试提供相关探讨。     

变压器发热试验自动测试平台的开发

研究开发了变压器认证标准GB19212．1（IEC 61558－1）中发热试验项目的自动测试平台,详细叙述了试验操作过程、自动测试平台的软硬件结构,继电器控制模块组成与硬件设计,以及虚拟仪器软件实现流程。该平台可显著减少检测人员的在线工作时间,并行测试可提高设备使用率,同时相比之前的手动测试,可明显降低人工测量部分的不确定度。     

隔吸声屏障在变压器噪声控制中的应用

针对城市电厂变压器的噪声污染,以北京太阳宫燃气热电冷联供工程中应用的变压器噪声控制为例,通过分析研究变压器声源不同的频谱特性,并根据厂界噪声控制目标计算声源的超标贡献量和设计降噪量,开发设计了变压器降噪隔吸声屏障,针对变压器的低频噪声,设计特殊的隔吸声结构,并成功应用于工程实践,取得了理想效果。     

开关电源模块可靠性的研究

本文分析了某军用开关电源模块的工作原理以及关键点波形,找出了开关电源模块中易于失效的关键元件,提出了目前开关电源发展所面临的可靠性寿命评价的关键问题。     

非耐短路变压器短路和过载保护试验的自动测试系统

针对变压器产品认证标准GB 19212.1(IEC 61558-1)中关于"短路和过载保护"的型式试验项目,研发了一套智能自动测试系统。对于两种类型的非耐短路变压器,即输入保护和输出保护类型,分别给出了系统软硬件配置和详细的测试操作流程。相比传统手动测试方式,该系统的应用可显著减少人员在线时间,同时降低人工测量环节的不确定度。     

柔性直流输电启动充电过电流分析及改进

本文首先对厦门柔性直流工程鹭岛站出现的充电电阻过流问题进行了深入研究,研究结果表明充电电阻过流是由于变压器剩磁导致充电过程中变压器渐进饱和引起的。为了复现过流现象,在电磁暂态仿真程序PSCAD/EMTDC中搭建了详细的厦门柔性直流模型,针对仿真软件中变压器模型不能模拟初始剩磁的问题,提出了变压器初始剩磁模拟方法,仿真复现了启动充电过流现象,并根据实际工程应用需求提出了针对启动充电过程的改进措施。     

Optimization of contactless transformer coupling transmission system by Taguchi method

A contactless transformer coupling (CTC) transmission system transmits electric energy via an alternating magnetic field through an air-gap. The transmitted power can be enhanced by the application of resonant effects. Transmitting and receiving coils are usually single layer solenoids with series capacitors, which, in combination, allow the receiving element to be tuned to the required transmitter frequency. An input DC source is used to obtain high-frequency AC signal through the standardized half-bridge DC/AC switching circuit. Further, the high-frequency signal passes through matching transformer and contactless coupling induction coil, which can be considered as an isolated input and output stage. Coupling must be tight to achieve high efficiency. This paper then applies the methods of Taguchi parameter design forthe contactless transformer coupling transmission system, which enhances the output voltage, loss factor, and output efficiency of the transmission system. The results of measurement verify the feasibility of this structure in the experiment.     

医用电气设备电源变压器的过载试验

采用电阻法测量医用电气设备电源变压器过载试验时的绕组温升,试验电流和试验时间的选取与熔断器、过流释放器、热断路器等保护装置有关。     

电源变压器温升试验中（绕组法）的影响因素及不确定度的评估

本文中探讨的是根据绕组法计算电源变压器绕组温升的试验方法,以及对整个试验过程中环境、仪器设备、仪表、人为因素所引起的误差等对最终试验结果的影响,并对其测量不确定度进行评估。     

基于LabVIEW的变压器绕组发热试验自动测试软件

遵照变压器认证标准GB19212．1（IEC 61558－1）中型式试验的关键项目一发热试验的一般要求,针对试验中最广泛使用的热阻法,并使用常见的离线测试方式和经验公式代入计算法,编写了一套基于LabVIEW开发环境的自动测试软件,构建以图形化软件为核心的下一代自动化测试系统。     

Relating soil phosphorus to dissolved phosphorus in runoff: a single extraction coefficient for water quality modeling

Phosphorus transport from agricultural soils contributes to eutrophication of fresh waters. Computer modeling can help identify agricultural areas with high potential P transport. Most models use a constant extraction coefficient (i.e., the slope of the linear regression between filterable reactive phosphorus [FRP] in runoff and soil P) to predict dissolved P release from soil to runoff, yet it is unclear how variations in soil properties, management practices, or hydrology affect extraction coefficients. We investigated published data from 17 studies that determined extraction coefficients using Mehlich-3 or Bray-1 soil P (mg kg(-1)), water-extractable soil P (mg kg(-1)), or soil P sorption saturation (%) as determined by ammonium oxalate extraction. Studies represented 31 soils with a variety of management conditions. Extraction coefficients from Mehlich-3 or Bray-1 soil P were not significantly different for 26 of 31 soils, with values ranging from 1.2 to 3.0. Extraction coefficients from water-extractable soil P were not significantly different for 17 of 20 soils, with values ranging from 6.0 to 18.3. The relationship between soil P sorption saturation and runoff FRP (microg L(-1)) was the same for all 10 soils investigated, exhibiting a split-line relationship where runoff FRP rapidly increased at P sorption saturation values greater than 12.5%. Overall, a single extraction coefficient (2.0 for Mehlich-3 P data, 11.2 for water-extractable P data, and a split-line relationship for P sorption saturation data) could be used in water quality models to approximate dissolved P release from soil to runoff for the majority of soil, hydrologic, or management conditions. A test for soil P sorption saturation may provide the most universal approximation, but only for noncalcareous soils.     

Seismic monitoring and modelling of supercritical CO2 injection into a water-saturated sandstone: Interpretation of P-wave velocity data

This paper reports on an integrated laboratory and numerical simulation study of ultrasonic P-wave velocity response to supercritical CO₂ displacement of pore water in Tako sandstone. The analysis of dynamic velocity data recorded using an array of piezoelectric transducers mounted on a core sample showed that the P-wave velocities at different positions displayed a similar trend in time, i.e., an initial sharp fall followed by a more gradual decline. Considerable variations observed in the measured P-wave velocity reductions across the sandstone core could largely be attributed to the final state of saturation (e.g. uniform, patchy or in-between) attained by the two-phase fluids. Numerical simulation of the injection test using a simple 1D model was carried out to provide an estimation of the phase saturation changes underlying the measured P-wave velocity reductions. A second order polynomial correlation between the measured ultrasonic P-wave velocity reductions and the estimated CO₂ saturation was established. Comparison with the Gassmann velocities showed that the empirically established relationship marks a clear deviation from both the patchy and uniform saturation velocity curves.     

Accurate power-sharing,voltage regulation,and SOC regulation for LVDC microgrid with hybrid energy storage system using artificial neural network

ABSTRACT

In this paper, an artificial neural network-based control strategy is proposed for low voltage DC microgrid (LVDC microgrid) with a hybrid energy storage system (HESS) to improve power-sharing between battery and supercapacitor (SC) to suit the demand-generation imbalance, maintain state-of-charge (SOC) within boundaries and thereby to regulate the dc bus voltage. The conventional controller cannot track the SCs current rapidly with the high-frequency component that will place dynamic stress on the battery, further resulting in shorter battery life. The significant advantage is that in the proposed control strategy, redirections of unwaged battery currents to SCs for fast compensations enhance battery life span. The proposed control strategy effectiveness was investigated by simulations, including a comparison of overshoot/undershoot and settling time in dc bus voltage with a conventional control strategy. The results have been experimentally verified by hardware-in-loop (HIL) on a field-programmable gate array (FPGA)-based real-time simulator.     

Measurements of non-wetting phase trapping applied to carbon dioxide storage

We measure the trapped non-wetting phase saturation as a function of the initial saturation in sand packs. The application of the work is for CO₂ storage in aquifers where capillary trapping is a rapid and effective mechanism to render injected CO₂ immobile. The CO₂ is injected into the formation followed by chase brine injection, or natural groundwater flow, which displaces and traps CO₂ on the pore scale as a residual immobile phase. Current models to predict the amount of trapping are based on experiments in consolidated media, while CO₂ may be stored in relatively shallow, poorly consolidated systems. We use analogue fluids at ambient conditions. The trapped saturation initially rises linearly with initial saturation to a value of approximately 0.13 for oil/water systems and 0.14 for gas/water systems. There then follows a region where the residual saturation is constant with further increases in initial saturation. This behaviour is not predicted by the traditional literature trapping models, but is physically consistent with unconsolidated media where most of the larger pores can easily be invaded at relatively low saturation and there is, overall, relatively little trapping. A good match to our experimental data was achieved with the trapping model proposed by Aissaoui.     

Prediction of dissolved gases content in power transformer oil using BASA-based mixed kernel RVR model

In this paper, beetle antennae search algorithm-based mixed kernel relevance vector regression (BASA-MkRVR) model is presented and applied to predict the dissolved gases content in power transformer, and beetle antennae search algorithm (BASA) is used to select the appropriate kernel parameters and controlled parameter. The RVR model with RBF kernel (RBFRVR) and the RVR model with Sigmoid kernel (SigmoidRVR) are, respectively, used to compare with the proposed BASA-MkRVR model in order to testify the superiority of BASA-MkRVR compared with RBFRVR and SigmoidRVR. The experimental results indicate that BASA-MkRVR has more excellent prediction ability for the dissolved gases content in power transformer oil than RBFRVR and SigmoidRVR.