Dynamic Thermal Model and Temperature Control of Proton Exchange Membrane Fuel Cell Stack

A dynamic thermal transfer model of a proton exchange membrane fuel cell (PEMFC) stack is developed based on energy conservation in order to reach better temperature control of PEMFC stack. Considering its uncertain parameters and disturbance, we propose a robust adaptive controller based on backstepping algorithm of Lyaponov function. Numerical simulations indicate the validity of the proposed controller.

Efficient Power Conditioner for a Fuel Cell Stack-Ripple Current Reduction Using Multiphase Converter

Integration of fuel cell stack with an inverter is complex in nature. A number of factors have to be taken into account in designing the inverter as well as during the integration. One of these factors is ripple current which could affect the life of the fuel cell stack if there is fuel and/or oxidant starvation. In this paper an inverter topology is investigated which significantly reduces or even nullifies the ripple content in the fuel cell system. The investigations have been carried out using indigenously developed 1 KW PEMFC stack and a 4 kW PEMFC stack with single and multi phase inverter. The results are presented here.

New Approach of Multi-Cell Stacked Cell Inverter for Solar Photovoltaic System

In this paper, a new inverter topology dedicated to isolated or grid-connected PV systems is proposed. This inverter is based on the structures of a stacked multi-cell converter (SMC) and an H-bridge. This new topology has allowed the voltage stresses of the converter to be distributed among several switching cells. Secondly, divide the input voltage into several fractions to reduce the number of power semiconductors to be switched. In this contribution, the general topology of this micro-inverter has been described and the simulation tests developed to validate its operation have been presented. Finally, we discussed the simulation results, the efficiency of this topology and the feasibility of its use in a grid-connected photovoltaic production system.

Influence of PTFE on Electrode Structure for Performance of PEMFC and 10-Cells Stack

Water plays a critical role on the performance, stability and lifetime of proton exchange membrane fuel cells（PEMFCs）. The addition of poly tetrafluoroethylene（PTFE） to the gas diffusion layer, especially, the cathode side, would optimize the transportation of water, electron and gas and thus improve the performance of the fuel cell. But until now, the studies about directly applying the PTFE to the catalyst layer are rarely reported. In this paper, the membrane electrode is fabricated by using directly coating catalyst to the membrane method（CCM） and applying PTFE directly to the cathode electrode catalyst layer. The performance of the single cell is determined by polarization curves and durability tests. Electrochemical impedance spectroscopy（EIS） and scanning electron microscopy（SEM） techniques are used to characterize the electrochemical properties of PEMFC. Also the performance of a 10-cells stack is detected. Combining the performance and the physical-chemistry characterization of PEMFC shows that addition of appropriate content of PTFE to the electrode enhances the performance of the fuel cell, which may be due to the improved water management. Addition of appropriate content of PTFE enhances the interaction between the membrane and the catalyst layer, and bigger pores and highly textured structure form in the MEA, which favors the oxygen mass transfer and protons transfer in the fuel cell. While superfluous addition of PTFE covers the surface of catalysts and hindered the contact of catalyst with Nation, which leads to the reduction of electrochemical active area and the decay of the fuel cell performance. The proposed research would optimize the water management of the fuel cell and thus improve the performance of the fuel cell.

Study and performance test of 10 kW molten carbonate fuel cell power generation system

The use of high-temperature fuel cells as a power technology can improve the efficiency of electricity generation and achieve near-zero emissions of carbon dioxide.This work explores the performance of a 10 kW high-temperature molten carbonate fuel cell.The key materials of a single cell were characterized and analyzed using X-ray diffraction and scanning electron microscopy.The results show that the pore size of the key electrode material is 6.5 lm and the matrix material is a-LiAlO_(2).Experimentally,the open circuit voltage of the single cell was found to be 1.23 V.The current density was greater than 100 mA/cm^(2)at an operating voltage of 0.7 V.The 10 kW fuel cell stack comprised 80 single fuel cells with a total area of 2000 cm^(2)and achieved an open circuit voltage of greater than 85 V.The fuel cell stack power and current density could reach 11.7 kW and 104.5 mA/cm2 at an operating voltage of 56 V.The influence and long-term stable operation of the stack were also analyzed and discussed.The successful operation of a 10 kW high-temperature fuel cell promotes the large-scale use of fuel cells and provides a research basis for future investigations of fuel cell capacity enhancement and distributed generation in China.

微型平面6-cell组合再生式燃料电池电源的制作与性能

首次设计并制作了一种微型平面6-cell组合的质子交换膜再生式燃料电池(PEM-URFC)电源系统.该微型电源由一片含多个膜电极单元的质子交换膜做为电解和发电的双功能膜电极组件,一个装有储氢材料和电解用水的底盒做为氢气储放和给水装置,通过带有气流孔的底板、碳极板及顶板紧密压合而成.在电解模式时,该电源系统将水分解产生氢并通过储氢合金存储于底盒中;而在燃料电池模式时,氢再被释放出来与空气中的氧进行放电反应而产生电流.常温常压下,该微型电源的开路电压可达4.9 V,在3.0 V的工作电压下,能维持19 mA/cm2放电约40分钟左右.该电源系统具有良好的充放电循环能力,在10次充放电循环后,电池性能依然能保持稳定.

基于运行数据时空特征和Stacking集成学习的质子交换膜燃料电池故障诊断

为实现质子交换膜燃料电池(proton exchange membrane fuel cell,PEMFC)故障诊断的快速性和准确性,提出基于运行数据时空特征和Stacking集成学习的故障诊断方法。首先,采用客观赋权法为反映PEMFC运行状态的电压、电流、温度和压力等变量进行赋权,基于核主成分分析和长短时记忆神经网络提取其空间、时间特征,基于add思想融合空间、时间特征,构建时空特征集。然后,建立以卷积神经网络(convolutional neural network,CNN)、随机森林、K最近邻算法、极端梯度提升树(extreme gradient boosting,XGBoost)为基分类器,XGBoost为元分类器的Stacking集成学习框架,实现了对PEMFC系统正常、水淹、膜干和氢气泄漏四种运行状态的诊断。最后,算例结果表明,所构建的时空特征集在5种单一分类模型的平均诊断准确率为99.23%,相比空间特征集提升2.83%,在Stacking模型的诊断准确率为99.99%。同时,在满足相同损失函数的前提下,使CNN的运算时间减少28s。因此,所提方法能够实现对PEMFC系统故障的快速准确诊断。

一个新的MOS模拟单元电路版图的STACK生成方法

提出了一种新的 MOS模拟单元电路的 STACK版图自动生成方法 .该方法将电路网表映射为扩散图 ,基于扩散图进行电路划分、模板匹配和对称查找 .提出的对称查找算法适用于非全对称电路的最大匹配对称结构查找 .文中改进了 Atallah欧拉路径生成算法 ,通过增加哑元条保证欧拉路径的生成 .对生成的 STACK,采用分布式寄生电容模型计算各个节点的寄生电容 ,并计算 STACK的面积和形状 。

Nonlinear modeling based on RBF neural networks identification and adaptive fuzzy control of DMFC stack

The temperature models of anode and cathode of direct methanol fuel cell （DMFC） stack were established by using radial basis function （RBF） neural networks identification technique to deal with the modeling and control problem of DMFC stack. An adaptive fuzzy neural networks temperature controller was designed based on the identification models established, and parameters of the controller were regulated by novel back propagation （BP） algorithm. Simulation results show that the RBF neural networks identification modeling method is correct, effective and the models established have good accuracy. Moreover, performance of the adaptive fuzzy neural networks temperature controller designed is superior.

Organic photovoltaic cells with copper(Ⅱ) tetra-methyl substituted phthalocyanine

Efficient heterojunction organic photovoltaic （OPV） cells are fabricated based on copper tetra-methyl phthalocyanine （CuMePc） as donor and fullerene （C60） as acceptor. The power conversion efficiency of CuMePc/C60 OPV cell （2.52%） is increased by 88% compared with that of the non-peripheral substituted copper phthalocyanine （CuPc）/C60 OPV cell （1.34%）. The introduction of methyl substituent leads to stronger π–π interaction of CuMePc （～ 3.5 ？） than that of CuPc （～ 3.8 ？）. The efficiency improvement is attributed to the enhanced carrier mobility of CuMePc thin film （1.1×10-3 cm2/V·s） and better film morphology by introducing methyl groups into the periphery of CuPc molecule.

TD-SCDMA/GSM/GPRS双模终端CELL CHANGE ORDER过程研究

随着TD-SCDMA系统的商用,同时需兼容已非常成熟运营的GSM系统,TD-SCDMA/GSM/GPRS双模终端已是市场的主流。本文针对双模单待终端(协议控制)CELL CHANGE ORDER过程进行研究,该过程是双模终端实现PS域切换的一种重要方式。首先,以TD-SCDMA/GSM/GPRS系统高层协议为基础介绍了双模单待自动切换终端的CELL CHANGE ORDER过程的各个阶段:系统间测量、网络判决及小区改变执行;然后详细地设计了小区改变执行的正常及异常处理流程,并对如何实现数据平面切换过程进行了重点描述;最后搭建板级测试环境,进行协议一致性测试,验证了CELL CHANGE ORDER过程的实现。

加长加宽的PEMFC电堆应力分布一致性仿真与优化

质子交换膜燃料电池可以通过扩大电堆的活性区域反应面积来获得更高的功率,但电堆反应面积扩大后,容易导致膜电极应力分布的不均匀性增加,从而引起燃料电池电化学性能的下降.为此,本研究设计了4种不同结构尺寸的燃料电池电堆,结合等效刚度模型法和有限元软件,分析了扩大反应面积的电堆结构对膜电极应力分布均匀性的影响,并进一步优化电堆内钢带的安装位置,以提升电堆内部接触压力分布均匀性.研究结果表明,膜电极接触压力分布的均匀性对反应区域宽度的变化较为敏感,当活性区域尺寸加宽,电堆内部活性区域的平均应力标准差增加了23.2%.而当活性区域加长,或同时加长和加宽时,相应增加一根捆扎钢带使电堆内部活性区域的平均应力标准差分别减小了8.6%和8.7%,表明适当增加捆扎钢带的数量可以提高电堆内部接触压力分布的均匀性.此外,钢带位置优化结果显示,电堆外侧钢带越靠近端板侧面时,电堆内部活性区域的应力分布越均匀.

基于龙伯格-滑模观测器的固体氧化物燃料电池温度估计模型

固体氧化物燃料电池(solid oxide fuel cell,SOFC)作为一种新型发电装置,因高效无污染、全金属固态结构、燃料来源广等优点,在未来各个领域具有广阔应用前景。电堆内部的温度分布对其安全稳定运行至关重要,针对其内部温度难以获取的问题,该文设计一种龙伯格-滑模观测器估计电堆内部温度分布。首先,观测器的输入考虑系统可观性和工程应用,并结合能观矩阵条件数筛选出最优组合;然后,基于龙伯格和滑模观测器理论构造观测器具体结构;其次,为提升观测器性能,将电堆误差系统进行解耦,通过极点配置重新构造反馈增益;最后,通过平滑非线性不连续项,抑制观测器抖振现象。结果表明,所设计观测器相较于龙伯格和滑模观测器在收敛速度和误差波动方面具有明显优越性。

浅析氢燃料电池发动机及其辅助系统状态监测与故障诊断

氢燃料电池发动机作为氢能车辆核心动力单元,其电堆运行状态健康监测和故障诊断直接影响车辆使用和电堆的寿命。当前采用的监测手段主要是对电堆电流和电堆单片电压的监控,通过判断电堆各个单体的电压一致性,以及是否有出现个别单体电压低的问题来判断电堆的健康状态。存在的问题是没有对先期机械故障即早期零部件失效进行监控,电堆能否正常工作也受制于提供空气和冷却的主要零件空压机和水泵的影响,当前仅通过电压巡检器对电堆单体电压的监测被动的报警,当报警时已经出现零件机械结构问题需要车辆进站维修更换零部件,影响车辆的正常出勤。所以有必要通过振动信号进行空压机、水泵等零部件故障的先期诊断评估,并在车辆保养或者闲时进行维修,可避免影响车辆正常营运,减少客户抱怨。

质子交换膜燃料电池在线监测方法研究进展

质子交换膜燃料电池作为一种高效、无污染的新一代发电技术在近年来得到广泛关注,但是其寿命问题依然严重制约其商业应用。通过对燃料电池状态进行在线监测来实现电池的快速故障诊断,是延长电池寿命的极有效的途径之一。本文对近年来质子交换膜燃料电池在线监测方向的文章进行了总结,并按照故障检测方法(包括极化曲线、循环伏安法、电化学阻抗谱等)进行分类讨论。同时,根据实际应用情况将单一检测方法和多种结合检测方法进行文献综述。另外,在总结现有的在线监测方法的基础上,本文提出了未来燃料电池在线监测需要解决的问题并进行展望。

功率分配方式对船用双堆燃料电池热管理效果分析

为研究船用双堆质子交换膜燃料电池(PEMFC)功率分配方式、热管理系统布置形式对热管理系统性能影响,基于AMESim软件建立了船用双堆PEMFC系统仿真模型,根据试验数据验证了仿真模型的可靠性。在此基础上,以串联式、并联式与旁通式热管理系统模型为研究对象,研究在变载工况下采用功率平均分配、逐级分配策略对电堆进出口冷却水温差的影响规律,最后比较在功率平均分配策略下3种热管理系统布置形式的性能。结果表明,3种热管理系统中电堆进出口冷却水温差均会在不同程度上受到功率分配策略的影响,在功率平均分配策略下,采用串联式热管理系统布置形式更有利于提高电堆内部温度一致性。

以掺氢天然气为燃料直接内重整固体氧化物电池堆的稳定性

本文研究了掺氢天然气直接内重整平管型固体氧化物电池短堆的长期稳定性和衰减机理。通过约3000小时的实测实验,结果显示,电堆的总体衰减率为2.3%·kh^(-1),电堆中三个金属连接板的面积比电阻分别增加了0.276Ω·cm^(2)、0.254Ω·cm^(2)和0.249Ω·cm^(2),但电堆中两个电池的电压反而分别增加了3.38 m V·kh^(-1)和3.78 m V·kh^(-1)。电堆衰减主要由金属连接件表层氧化及其与阴极集流层材料反应生成Sr CrO_(4)物质,两者共同作用增大了电池与金属连接体间的界面电阻所致。结果表明,以掺氢天然气为燃料直接内重整平管型固体氧化物燃料电池电堆具有良好的稳定性。本文工作为掺氢天然气在固体氧化物燃料电池堆中的直接内重整应用提供了理论参考与实验依据。

基于专利的固体氧化物燃料电池技术趋势分析

固体氧化物燃料电池(SOFC)作为一种在高温下将燃料中的化学能直接转化为电能的发电装置,具有能量转化效率高、燃料适应性强且来源广泛、对环境友好等优点。通过分析1990年以来国内外高温固体燃料电池专利情况,从专利申请趋势、专利申请人及专利地域布局等角度,研究了SOFC领域的技术关注重点、应用情况及技术发展趋势。现阶段高温固体燃料电池技术开发已进入快速发展期,国外固体氧化物燃料电池的研发方向主要聚焦于降低成本和提高稳定性,国内则主要集中在突破电堆关键技术、核心部件国产化及示范工程建设。

基于经验小波变换的SOFC泄漏故障诊断

固体氧化物燃料电池(SOFC)电堆通常在700℃以上的高温下工作。电堆所用密封剂在高温下易退化失效,导致泄漏故障,引发电堆的热失控和损坏,影响系统运行稳定性。提出一种基于电堆温度和电压信号的经验小波变换(EWT)诊断方法。通过EWT分解温度和电压信号,得到多分辨率分析(MRA),分析其中故障特征明显的MRA信号,求出时域特征,通过设定的阈值判断是否发生泄漏。通过千瓦级电堆实验平台数据,验证EWT诊断方法可较好地检测电堆泄漏故障,且相较于电压信号,温度信号的诊断更迅速。与集合经验模态分解诊断方法相比,EWT方法可更快地诊断出泄漏故障。

质子交换膜燃料电池电堆阳极饥饿反极的研究

目前,质子交换膜燃料电池(PEMFC)反极研究主要通过单电池完成,反极过程没有考虑相邻电池的影响,与电堆实际情况并不完全相同.本文通过控制加湿度和过量系数等测试条件分析了5片PEMFC电堆阳极在水淹和缺气情况下的饥饿反极情况.结果表明,在电堆阳极水淹情况下,反极单电池电压表现为缓慢下降到电解水平台然后迅速恢复的循环过程,性能恢复归因于水淹单电池阳极进出口压差上升使其液态水排出而氢气重新进入;在电堆阳极缺气情况下,反极单电池电压表现为迅速降低到碳腐蚀平台然后迅速恢复的循环过程,这是由于缺气单电池的阳极进出口压差下降使电堆内氢气重新分配.缺气反极电池电压会降低到碳腐蚀平台,因此会对电池性能造成不可逆的损害.