PTD vs. PO effects in power and polarisation of PLANCK HFI 100 beams

收稿日期:2001-04-17基金项目:国家自然科学基金资助项目(59975050);清华大学“九八五”项目基金;中国博士后科学基金资助项目[2000]31号作者简介:赵冬斌(1972-),男,山东省掖县人,博士后。

文章编号:1004-2474(2001)06-0428-05机器人用PVDF 触觉传感器的国外研究现状赵冬斌,张文增,都　东,陈　强(清华大学机械工程系,北京100084) 摘　要:目前,国内外对具有人类功能的机器人操作器和灵巧手展开了广泛的研究,其中触觉传感是一个主要方面。

由于PV D F (聚偏二氟乙烯)压电薄膜具有压电能力高、柔韧、极薄、质轻等特点,其许多特性接近人类皮肤的特性,尤其受到研究人员的关注。

文章从PV D F 薄膜的原理和特性出发,展开介绍了国外机器人用PV D F 触觉传感器的研究现状。

关键词:触觉;PV DF ;机器人中图分类号:Q 811.21 文献标识码:AAbroad Research Status of PVDF Tactile Sensor for RobotZHAO Dong-bin ,ZHANG Wen -zen ,DU Dong ,C HEN Qiang (Dep t.of M ech anical Engineering ,Tsinghua University,Beijing 100084,China) Abstract :Recently ,ex tensiv e researches hav e been conducted o n r obot g rips a nd dex tero us hands ,one ma jo r aspect of which is tactile sensing.PV D F(Po lyv iny lidene fluo ride)pie zo electric film is cha racterized a s high piezo -elect ric,so ft,to ug h,super thin,ligh t,and so o n,are simila r to human skin,so it is specially co nce rned by r e-sea rchers .This paper fir st presents the principle and char acteristics of PV D F film and then intr oduces the a broad r esea rch sta tus o f PV D F tactile senso r fo r ro bo t .Key words :tactile;PV D F;ro bot 1　引言近年来,对机器人操作器和多指灵巧手的研究日渐深入,在机电结构和控制策略方面取得了一定的成绩。

现代电子技术Modern Electronics TechniqueApr. 2024Vol. 47 No. 82024年4月15日第47卷第8期0 引 言电网中高比例的新能源发电以及大量电力电子设备的应用，加之不平衡、非线性等种类繁多的负荷及储能设备的接入，使得电网中的谐波含量进一步增加。

未来电力系统中分布式新能源更易与大量的电动汽车储能等组成微电网，利用电动汽车充放电设备进行电网谐波补偿能够提高电网电能质量，减少传统治理设备的投入，降低配网的投资与运行成本。

但非理想电网条件下，性能优良且精准的谐波检测方法是补偿电网谐波的基础。

目前谐波检测算法主要有：基于瞬时无功功率理论的p ⁃q 法、i p -i q 法、FBD 法、离散傅里叶变换法以及自适应谐波检测法等[1]。

p ⁃q 法在电网电压波形发生畸变时，DOI ：10.16652/j.issn.1004⁃373x.2024.08.019引用格式：马玉立，原浩，陈良亮，等.基于DSOGI⁃PLL 与ANF⁃LPF 的i p -i q 三相谐波检测方法[J].现代电子技术，2024，47（8）：121⁃125.基于DSOGI⁃PLL 与ANF⁃LPF 的i p -i q三相谐波检测方法马玉立1，3， 原 浩1，2， 陈良亮1，2， 赵 阳3（1.国电南瑞南京控制系统有限公司， 江苏 南京 210000； 2.南瑞集团（国网电力科学研究院）有限公司， 江苏 南京 210000； 3.南京师范大学 电气与自动化工程学院， 江苏 南京 210000）摘 要： 随着分布式电源大规模接入电网，电力系统中频率波动、电压不平衡以及谐波畸变等问题日益严重。

在这样不平衡和失真的电网条件下，传统i p -i q 谐波检测法已不能满足工程需要。

为解决这一问题，文中提出一种基于DSOGI⁃PLL 与ANF⁃LPF 的i p -i q 三相谐波检测方法。

一方面，采用DSOGI⁃PLL 提高复杂电网下提取基波相位的能力；另一方面，采用一种具有选择性谐波滤波能力的改进结构LPF ，来提高谐波检测的抗干扰能力。

普林斯顿输力强电化学普林斯顿输力强电化学是指在普林斯顿大学进行的一项关于电化学的研究工作。

电化学是研究电与化学之间相互转化关系的学科，它涉及到电解、电极反应、电化学反应动力学等内容。

而在普林斯顿大学的研究中，强电化学的概念被引入，旨在探究在高电场下材料的电化学行为。

普林斯顿大学以其卓越的研究实力和先进的科研设备而闻名于世，强电化学的研究也是其研究领域之一。

强电化学是电化学领域的一个新兴分支，它通过施加高电场来改变材料的电化学特性，进而探索电化学反应的机理和性质。

普林斯顿大学的研究人员在强电场下对材料进行电化学测试和分析，通过观察材料在高电场下的行为，揭示了电化学反应的新规律。

通过普林斯顿输力强电化学的研究，人们对电化学反应的理解得到了进一步的拓展。

普林斯顿大学的研究人员发现，在强电场下，电化学反应的速率和机理可能会发生变化，这与传统的电化学理论存在差异。

强电场下的电化学反应可能受到电场力的影响，电子和离子的运动方式也可能发生改变，从而导致反应速率的变化。

这些发现对于电化学反应的控制和应用具有重要的意义。

强电化学在许多领域都有着广泛的应用前景。

例如，在电池领域，强电化学研究可以帮助人们更好地理解电池的充放电机制，进而提高电池的性能和循环寿命。

在催化剂领域，强电化学研究可以揭示催化反应的机理和活性位点，从而设计出更高效的催化剂。

此外，强电化学还可以应用于电化学传感器、电解水制氢等领域。

普林斯顿输力强电化学的研究为电化学领域的发展带来了新的思路和方法。

通过施加高电场，可以改变材料的电化学特性，揭示电化学反应的新规律，为电化学反应的控制和应用提供了新的思路。

强电化学在电池、催化剂等领域的应用前景广阔，有望为相关领域的发展提供有力支持。

随着普林斯顿输力强电化学的不断深入研究，相信电化学领域将迎来更多的突破和进展。

第27卷㊀第12期2023年12月㊀电㊀机㊀与㊀控㊀制㊀学㊀报Electri c ㊀Machines ㊀and ㊀Control㊀Vol.27No.12Dec.2023㊀㊀㊀㊀㊀㊀DAB 级联单相逆变器系统的阻抗特性及稳定性分析刘欣,㊀袁静,㊀高鑫波(华北电力大学电气与电子工程学院,河北保定071003)摘㊀要:针对双有源桥(DAB )直流变换器级联单相并网逆变器系统因阻抗失配而造成系统发生振荡失稳的问题,通过建立DAB 和单相逆变器的输出和输入阻抗模型,基于阻抗分析法对级联系统的交互稳定性进行了分析㊂首先,推导采用双环控制策略的前级DAB 输出阻抗模型和考虑锁相环影响的后级逆变器直流侧输入阻抗模型,并通过扫频法验证其准确性㊂在此基础上,建立二者阻抗交互模型,详细分析了DAB 反馈控制器的PI 参数对其输出阻抗频率特性和级联系统稳定性的影响,并据此提出一种DAB 控制参数的优化设计方法,在兼顾动态性能的同时提升了级联系统的稳定性㊂最后,通过仿真算例验证了阻抗模型的准确性,分析了结论的正确性以及稳定性改善方法的有效性㊂关键词:级联系统;稳定性;阻抗重塑;双有源桥;单相并网逆变器;阻抗模型DOI :10.15938/j.emc.2023.12.001中图分类号:TM46文献标志码:A文章编号:1007-449X(2023)12-0001-11㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀收稿日期:2023-03-17作者简介:刘㊀欣(1980 ),男,博士,副教授,研究方向为新能源发电系统建模与控制㊁电力电子系统电磁兼容和瞬态特性;袁㊀静(1997 ),女,硕士研究生,研究方向为电力电子变流器建模与控制;高鑫波(1999 ),男,硕士研究生,研究方向为电力电子变流器建模与控制㊂通信作者:袁㊀静Impedance characteristics and stability analysis of DAB cascadesingle-phase inverter systemLIU Xin,㊀YUAN Jing,㊀GAO Xinbo(School of Electrical and Electronic Engineering,North China Electric Power University,Baoding 071003,China)Abstract :Aiming at the problem of oscillation instability of the dual active bridge (DAB)DC-DC con-verter cascaded single-phase grid-connected inverter systems due to its impedance mismatching,the out-put and input impedance models of DAB and single-phase inverter were established,and the interaction stability of the cascade system was analyzed based on impedance analysis method.Firstly,the output im-pedance model of the front-stage DAB using the double-loop control strategy and the DC-side input im-pedance model of the back-stage inverter considering the influence of the phase-locked loop were derived,and the accuracy of the models were verified by frequency sweep method.Based on this,the impedance interaction model between the two was established.Additionally,the effects of PI parameters of DAB feedback controller on its output impedance frequency characteristics and cascade system stability wereanalyzed in detail,and the optimal design method of DAB control parameters was proposed accordingly,which improves the stability of the cascade system while taking into account the dynamic performance.Fi-nally,the simulation examples verify accuracy of the impedance model,correctness of the analytical con-clusions and effectiveness of the stability improvement method.Keywords :cascaded system;stability;impedance reshaping;dual active bridges;single-phase grid-con-nected inverters;impedance model0㊀引㊀言在光伏系统㊁蓄电池㊁超级电容,车网互联(ve-hicle to grid,V2G)等交流并网型储能系统中,通常需要使用两级式DC /AC 变换器实现并入交流电网和双向功率控制的功能[1]㊂其中,双有源桥变换器由于具有高功率密度㊁电流隔离㊁能量双向传输和易实现零电压开关等优点[2-4],很好地适应了交流并网型储能系统的需求,是第一级DC /DC 变换器的理想选择,而单相逆变器用于与电网连接㊂基于双有源桥(dual active bridge,DAB)变换器的两级式DC /AC 变换器的典型电路拓扑如图1所示㊂该拓扑整体结构简单,易于实现,控制方法较为成熟,被大量应用于电动汽车充电桩领域[5-8]㊂然而,由于变换器复杂的输入输出特性以及级联结构的存在,尽管两级变换器在单独运行时能保持稳定,但子系统之间的相互作用可能会使系统性能下降,导致直流母线产生电压振荡,以至于系统崩溃[9]㊂因此,通过稳定性分析㊁合理参数调整㊁控制优化等方法改善级联系统的稳定性和可靠性是当今研究的一个热点与难点问题[10-12]㊂图1㊀两级式DC /AC 变换器主电路拓扑及控制框图Fig.1㊀Main circuit topology and control block diagram of two-stage DC /AC converter㊀㊀基于阻抗的Nyquist 阻抗匹配原则[13]已经被广泛应用于各类级联系统的交互稳定性的研究中㊂准确的阻抗模型对于级联系统稳定性分析是必要的㊂目前,常用的逆变器阻抗建模方法包括谐波线性化法[14-16]和dq 坐标系下的阻抗建模法[17-18]㊂谐波线性化将系统视为2个单输入单输出系统,主要用于分析三相系统的谐波稳定性;而dq 阻抗建模法通常将电气量转变为d 轴和q 轴分量,以便单独控制有功和无功功率,有利于在稳态工作点处进行小信号分析㊂文献[19]在dq 坐标系下推导了使用不同控制策略的三相并网逆变器的直流侧输入阻抗模型,此方法适用性较强,但并未应用到单相逆变器系统中㊂文献[20]提出一种基于二阶广义积分器(second order generalized integrator,SOGI)的dq 坐标系下单相整流器的阻抗建模方法,但此方法并未推广到单相并网逆变器的阻抗建模中㊂由于阻抗相互作用是造成两级式DC /AC 级联系统失去稳定的根本原因,可以通过重塑源变换器或者负载变换器的总线端口阻抗来提高系统的稳定性㊂为了达到这一目的,学者们提出了多种方法,包括无源阻尼法[21-23]和有源阻尼法[24-26]㊂其中,无源阻尼法需要引入附加无源元件,以改变变换器的阻抗特性,但附加阻尼电路会增加硬件成本,降低变换器效率;有源补偿法具有成本低㊁不增加损耗的优点,因而被广泛用于基于DAB 变换器的级联系统阻抗匹配优化设计中㊂文献[27]采用有源阻尼的优化思路对LC -DAB 级联系统进行阻抗重塑,提出基于一次侧电容电压的并联虚拟阻抗和一次电流串联虚拟阻抗控制策略,从而使得级联系统在全功率范围内均能稳定运行;文献[28]研究基于DAB 的储能系统稳定性,提出在窄带范围内对负载变换器DAB 的输入阻抗进行重塑,在提高稳定性的同时保证系统动态性能良好;文献[7]研究了用于电动汽车双向充放电的DAB 级联单相并网电压源变换器(voltage source converter,VSC)系统的阻抗稳定性,提出一种基于虚拟电阻的有源阻尼方法,以改变2电㊀机㊀与㊀控㊀制㊀学㊀报㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀第27卷㊀VSC的输出阻抗,提高级联系统在各种工作模式下的稳定性;文献[29]面向DAB级联三相VSG系统,通过构建与DAB转换器的输入阻抗并联或串联的虚拟阻抗以增加DAB输入阻抗幅值,从而满足稳定性准则㊂文献[30]针对具有电压调整单元的DAB 变换器提出一种基于超前-滞后的阻抗优化调节器用以抑制输出阻抗谐振尖峰,提升了系统运行可靠性,并优化了电流应力㊂总的来说,上述级联系统的稳定性增强方法都需要增加附加的控制过程,从而不可避免地增加了模型的复杂度,其设计方法仍存在进一步简化的空间㊂而DAB变换器的输入阻抗会受到其反馈控制器的影响,揭示二者之间的关联有助于简化阻抗匹配优化设计,但此方面的相关研究较少,并且缺乏深入的理论分析㊂针对上述问题,本文对双有源桥DC/DC变换器与单相并网逆变器组成的级联系统进行阻抗建模并进行稳定性分析㊂首先,建立采用双环控制策略的DAB输出阻抗模型和采用解耦电流控制策略的单相并网逆变器直流端输入阻抗模型,并将锁相环的相位波动考虑在内,通过扫频法验证阻抗模型的正确性㊂随后,建立阻抗交互模型,从理论上分析DAB变换器的PI参数对其输出阻抗波形的影响,结合Nyquist图和闭环根轨迹进一步讨论关键参数与系统稳定性之间的关联㊂分析结论表明,调节DAB电压外环比例系数可直接调节级联系统稳定性,基于此,提出通过优化DAB变换器的电压外环比例系数提高级联系统稳定性的方法,该方法无需任何额外的补偿器或控制回路,在兼顾系统动态性能的同时,有效实现了基于DAB的交直流级联系统的稳定性增强㊂MATLAB/Simulink仿真算例验证了稳定性改善方法的有效性㊂1㊀级联系统阻抗建模变换器阻抗的精确建模是稳定性分析的基础㊂图1所示的控制框图为级联系统的常规控制方案,其中,DAB变换器负责控制直流母线电压的稳定,单相并网逆变器负责控制功率输出[31-32]㊂本节将分别给出DAD输出阻抗和单相并网逆变器的直流侧输入阻抗的建模过程㊂1.1㊀DAB变换器输出阻抗建模DAB变换器的拓扑及控制方案如图1中左面虚线框所示㊂其输出功率[33-34]可表示为P=nV in v busL o f s dϕ(1-2dϕ)=v bus i2⓪㊂(1)式中:n为变压器变比;V in为DAB输入电压;v bus为输出电压;L o为变压器等效电感;f s为开关频率;dϕ为变压器两侧H桥输出电压之间的相移量(dϕ=ϕ/2π);i2为副边H桥输出电流, i2⓪表示其平均值㊂经小信号分析可得i2与占空比dϕ的关系为G i2d=i^2d^ϕ=nV in Lo f s(1-4Dϕ)㊂(2)式中符号^表示变量的小信号形式㊂采用内环电流加外环电压的双环控制模式㊂将控制器的内环传函记作G c1(s),外环传递函数记作G c2(s),其中:G c1(s)=k pi+k ii s;G c2(s)=k pv+k iv s㊂将负载变换器阻抗等效为R,则DAB控制回路小信号模型如图2所示,图中LPF为一阶低通滤波器,用于实现20dB/dec的环路增益[35](H LPF(s)= 1/(s/ωLPF+1),其中ωLPF为低通滤波器的截止频率)㊂图2㊀DAB控制回路小信号模型Fig.2㊀Small signal model of DAB control loop根据上述控制框图,得到DAB的输出阻抗为Z out_DAB=v^bus-i^bus=1C bus s+G c1G x㊂(3)式中G x=G c2G i2d1+G c2G i2d H LPF㊂1.2㊀单相并网逆变器直流侧输入阻抗建模基于SOGI的锁相环(PLL)模型如图3(a)所示㊂图中,v为自公共耦合点(PCC)电压(将其本身视为静止坐标系下的α轴分量,β轴虚拟分量与之垂直)㊂SOGI的传递函数为H e(s)=K SOGIω1ss2+K SOGIω1s+ω21㊂(4)式中:ω1为电网工频;K SOGI为闭环系数㊂在小扰动下,PLL输出与PCC实际相位存在相位差Δθ,其将导致控制系统中的各变量与功率系统中的相应变量存在差异㊂为以示区分,文中带有上标s的变量表示 电气量 ,带有上标c的变量表示 控制量 ㊂为了简化表达式,将成对变量以矢量形式编写,例如v s dq表示[v s d v s q]T,另外,变量的大写符3第12期刘㊀欣等:DAB级联单相逆变器系统的阻抗特性及稳定性分析号表示其自身静态工作点㊂图3㊀基于SOGI 的PLL 模型Fig.3㊀SOGI-based PLL model根据图1可得系统功率方程为:(Z L +Z g )i ^s dq =D dq v ^bus +d ^sdq V bus ;i ^bus=12(D T dq i ^s dq +I T dq d ^sdq )㊂}(5)式中:i ^s dq =[i ^s d i ^s q ]T 和d ^s dq =[d ^s d d ^s q ]T分别为交流侧电流与占空比的dq 轴分量构成的列向量;Z L =sL f +R f -ωL f ωL f sL f +R f éëêêùûúú;Z g =sL g +R g -ωL g ωL g sL g +R g éëêêùûúú;L f 和R f 为滤波电感及其等效内阻;L g 和R g 为电网内阻抗;i ^bus 为逆变器直流侧输入电流㊂将图3中Park 变换框图T θ1前移,得到其等效控制框图如图3(b)所示,图中:H edq (s )=A B-B A[];A =[H e (s +j ω1)+H e (s -j ω1)]/2;B =[j H e (s +j ω1)-j H e (s -j ω1)]/2㊂根据图3(b)可推导PCC 电压的 控制量v ^c dq与 电气量v ^sdq之间的关系为v ^c dq =G v PLL v ^sdq ㊂(6)式中:Gv PLL=v ^c dq v^s dq=A -V sqG s B B +V sqG s A -B +V sd G s B A -V sd G s Aéëêêùûúú;G s 为PLL 输出角度与PCC 电压q 轴分量的关系式;G s =sk p_PLL +k i_PLLs +V s d (sk p_PLL +k i_PLL ),k p_PLL 和k i_PLL 为锁相环PLL 的PI 参数㊂同理可得输出电流与占空比的 控制量 与 电气量 的小信号关系为:d ^sdq=d^cdq+G dPLL v ^s dq;i^c dq=Hedq i^s dq+GiPLL v ^s dq㊂}(7)式中:G d PLL =D s qG s B -D s qG s A -D sd G s B D sd G s Aéëêêùûúú;Gi PLL=-I sq G s B I s q G s A I sd G s B-I sd G s Aéëêêùûúú㊂令:H i =k p_INV +k i_INV /sk p_INV+k i_INV /s éëêêùûúú,其中:k p_INV 和k i_INV 为逆变器电流控制器的PI 参数;G ci=k p_INV +k i_INV /s ωL f-ωL fk p_INV+k i_INV /s éëêêùûúú㊂将解耦电流控制策略与PCC 电压前馈结合,得到考虑锁相环影响的逆变器控制回路的小信号模型如图4所示㊂图4㊀PLL 影响下电流控制回路小信号模型Fig.4㊀Small-signal model for current control loopwith PLL根据图4,得到逆变器控制部分的方程为d ^s dq =[(G v PLL -G ci G i PLL +V bus G dPLL )Z g -G ci H edq ]i ^s dq /V bus ㊂(8)联立式(5)㊁式(8)可得单相并网逆变器直流侧输入导纳为Y in_INV =i ^busv ^bus=12V busI T dq (Z L +Z g )+12D T dq[]㊃([Z L +G ci H edq -G PLL_V Z g ]-1D dq )-12V bus I Tdq D dq㊂(9)式中G PLL_V =G v PLL -G ci G i PLL +V bus G dPLL -E ,其中E为单位矩阵㊂相应的单相并网逆变器直流侧输入阻抗为Z in_INV =1/Y in_INV ㊂(10)1.3㊀阻抗模型的仿真验证基于MATLAB /Simulink 平台搭建了DAB 级联单相并网逆变器的仿真模型,采用扫频法对2个级联子系统的输出和输入阻抗模型分别进行验证,仿真参数如表1所示㊂图5给出了仿真扫频与理论模型的对比结果㊂可以看出,在1~10000Hz 频段,所得阻抗模型与扫频结果吻合较好,验证了所推得的DAB 输出阻抗和单相逆变器输入阻抗模型的正确性㊂4电㊀机㊀与㊀控㊀制㊀学㊀报㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀第27卷㊀图5㊀级联系统阻抗模型Fig.5㊀Impedance model of cascade system表1㊀级联系统电路参数Table1㊀Parameters of cascade system㊀㊀㊀参数数值DAB直流侧输入电压稳态值V in/V400直流母线电压稳态值V bus/V400直流母线电容C bus/μF1500 DAB变压器等效电感L o/μH30变压器变比n1ʒ1 DAB开关频率f s/kHz20低通滤波器截至频率ωLPF/(rad/s)4000π逆变器并网电压有效值V g/V220逆变器输出功率稳态值P/kW10逆变器滤波电感L f/mH及等效内阻R f/mΩ10,50电网内电感L g/mH及内电阻R g/mΩ1,152㊀级联系统稳定性分析2.1㊀级联系统阻抗交互模型级联系统的稳定性不仅取决于变换器各自的稳定性,还决定于源变换器(本文为DAB)输出阻抗与负载变换器(本文为单相逆变器)输入阻抗二者交互作用的影响㊂将DAB视为电压源,逆变器视为电流源,二者构成的级联系统阻抗相互作用示意图如图6所示㊂图6㊀级联系统等效阻抗示意图Fig.6㊀Equivalent impedance diagram of cascade system根据图6,可知级联系统开环传递函数为T m=Z out_DABZ in_INV㊂(11)式中T m也称为系统小环路增益㊂根据Middlebrook 判据[13],当源变换器和负载变换器各自稳定,并且系统的小环路增益T m满足Nyquist稳定判据时,该级联系统方是稳定的㊂图7为DAB输出阻抗和逆变器输入阻抗伯德图㊂由于逆变器采用恒功率控制,因此,除50Hz频点外,在f<f c3(f c3为逆变器电流控制器的截止频率)频率范围内逆变器直流端输入阻抗呈现阻值为-V2bus/P的负电阻特性;在f>f c3频率范围内呈现电感性质㊂而50Hz频点是一个特殊点,其阻抗幅值几乎为0,相位跃变到0㊂虽然逆变器与DAB的阻抗在50Hz频点处容易产生交叉,但二者相位之差小于180ʎ,因此不影响系统稳定性㊂此外,DAB输出阻抗在f<f r频段(f r为DAB输出阻抗谐振频率)呈现电感特性,在f>f r频段呈现电容特性㊂这使得DAB输出阻抗具有类似LC滤波器的阻抗特性㊂图7㊀级联系统阻抗伯德图Fig.7㊀Impedance Bode diagram of cascade system综合以上阻抗特性可知,DAB输出阻抗的谐振峰以及逆变器在低频段的负阻抗特性是导致交直流级联系统稳定性降低的主要原因㊂一旦DAB输出阻抗的谐振峰与逆变器输入阻抗发生交叉,就会因5第12期刘㊀欣等:DAB级联单相逆变器系统的阻抗特性及稳定性分析相位裕度无法满足稳定条件而造成系统振荡失稳㊂2.2㊀DAB 变换器的控制参数分析由图7可知,平抑DAB 输出阻抗的谐振峰将有效提高级联系统稳定性㊂为了达成这一目的,本节将详细分析DAB 反馈控制器的PI 参数与谐振峰之间的关联,为级联系统的稳定性分析及控制器参数优化设计奠定基础㊂当DAB 电流内环截止频率与一阶低通滤波器LPF 带宽相等时,经控制器定量设计可得电流控制器比例系数k pi 为0㊂将k pi =0代入式(3),并且忽略含有C bus 和T LPF 的高阶项,整理得到DAB 输出阻抗的简化表达式为Zᶄout_DABʈ1G i2d k ii s (s +G i2d k ii )C bus s 2+k pv s +k iv㊂(12)图8给出了DAB 输出阻抗的理论模型和简化模型的对比图㊂可以看出,在1~200Hz 频率范围内,二者阻抗模型基本吻合,结合图7可知,影响系统稳定性的频段为几十赫兹,因此说明上述简化模型可胜任稳定性分析需求㊂图8㊀DAB 理论模型和简化模型对比Fig.8㊀Comparison of theoretical and simplified Bodediagrams of DAB设定DAB 电流内环截至频率f c1为2000Hz,相位裕度P m1为45ʎ,同时电压外环截至频率f c2为20Hz,相位裕度P m2为45ʎ时,经设计所得DAB 的控制参数如表2所示㊂表2㊀DAB 控制器PI 参数Table 2㊀PI parameters of DAB controller㊀㊀㊀㊀参数数值电流控制器比例系数k pi 0电流控制器积分系数k ii 30.443电压控制器比例系数k pv 0.102电压控制器积分系数k iv24.35㊀㊀将s =j ω代入式(12),得到DAB 阻抗的模值为|Z ᶄout_DAB (j ω)|=ωaω2(C bus ω2-k iv +ak pv )2+(ω2k pv -C bus ω2a +ak iv )2(-C bus ω2+k iv )2+ω2k 2pv㊂(13)式中a =G i2d k ii ㊂令Z ᶄout_DAB (j ω)虚部为0,得到谐振点频率为ω=G i2d k ii k ivC bus G i2d k ii -k pv㊂(14)根据式(13)和式(14)可得DAB 输出阻抗的谐振频率及谐振峰值分别与控制参数的关系曲线如图9所示㊂结合式(27)㊁式(28)和图9,可得如下结论:当电压外环比例系数k pv 增大时,谐振频率几乎不变,谐振峰值陡然降低;当电压外环积分系数k iv 增大时,谐振频率增大,谐振峰值维持不变;当电流环积分系数k ii 改变时,二者均基本不发生改变㊂上述分析表明,参数k pv 是平抑DAB 输出阻抗谐振峰的关键参数,而参数k iv 是改变谐振频点的关键参数㊂图9㊀谐振频率及谐振峰值与DAB 控制参数的关系曲线Fig.9㊀Relationship curves of resonant frequency andresonant peak with DAB control parameters为了佐证此结论,图10给出了不同控制参数下的DAB 输出阻抗伯德图㊂可以看出,当比例系数k pv 从0.02逐渐增大到0.4,且其余参数与表1和表2保持一致时,DAB 输出阻抗谐振峰值急剧减小,但谐振频点基本保持不变;当积分系数k iv 从10增大到120,且其余参数与表1和表2保持一致时,DAB 输出阻抗谐振频率逐渐增大,而谐振峰值几乎不变㊂6电㊀机㊀与㊀控㊀制㊀学㊀报㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀第27卷㊀图10㊀不同控制参数作用下DAB输出阻抗伯德图Fig.10㊀DAB output impedance Bode diagram of differ-ent control parameters综上所述,DAB电压外环控制器参数直接决定了其输出阻抗谐振峰值的大小及位置㊂其中,参数k pv与谐振峰幅值大小具有强相关性,适度增大参数k pv将显著降低DAB输出阻抗谐振峰,从而避免与逆变器输入阻抗发生交叉㊂据此可推断,参数k pv是作为影响级联系统稳定性的关键参数,对其进行优化设计可实现系统稳定控制,且设计过程也最为简单,相关分析及验证将在2.3节给出㊂2.3㊀DAB电压外环比例系数对系统稳定性的影响本节进一步讨论k pv对级联系统稳定性的影响㊂根据式(11)可知系统的特征方程为1+T m=0㊂(15)将式(3)和式(10)代入式(15),可得sC bus s2+(k pv s+k iv)G x+Z in_INV=0㊂(16)由于参数k pv直接体现在系统特征方程中,因此可结合基于闭环传递函数的根轨迹和开环传递函数的Nyquist图进行分析㊂对式(16)进行等效变换,保证特征方程不变,得到系统等效的开环传递函数为D(s)=k pv sG x Z in_INVs+Z in_INV(Cs2+k iv G x)㊂(17)根据式(17),得到当参数k pv从0逐渐变化至+ɕ时系统闭环传递函数的特征根在复平面的变化轨迹如图11所示㊂此时DAB电流内环控制参数与表2中相同,电压外环积分系数为98.3㊂可以看出,当k pv<0.0634时,级联系统存在右半平面极点,系统处于不稳定状态;当k pv>0.0634时,系统方可稳定;当k pv=0.0634时,复平面上出现位于虚轴上的闭环极点(0,ʃj251),说明系统处于临界稳定状态,这意味着系统中将会出现251rad/s(约40Hz)的振荡频率㊂图11㊀系统关于参数的k pv的根轨迹图Fig.11㊀Root trajectory diagram of the system with re-spect to the parameter k pv图12给出了此临界稳定状态下系统开环传递函数T m的Nyquist图,在此参数状态下,Nyquist曲线恰好穿越(-1,j0)点㊂分析结果说明,增大DAB电压外环比例系数k pv有助于增强级联系统稳定性,反之,将使级联系统稳定性变差㊂图12㊀系统开环传递函数的Nyquist图Fig.12㊀Nyquist diagram of the open-loop transferfunction为了验证上述分析结论,在MATLAB/Simulink 中搭建DAB与单相并网逆变器级联系统的仿真模7第12期刘㊀欣等:DAB级联单相逆变器系统的阻抗特性及稳定性分析型㊂电路参数如表1所示㊂图13给出了当其余参数保持不变,DAB 电压外环比例系数k pv 分别为2㊁0.258㊁0.0634和0.03时直流母线电压和交流侧输出电流的时域仿真波形㊂可以看出,当k pv 为2和0.258时,系统运行在稳定状态;当k pv 为0.0634时,系统处于临界稳定状态;当k pv 减小到0.03时,系统振荡失稳㊂这与图11中的参数根轨迹分析结果相符㊂图13㊀k pv 减小时直流母线电压和交流电流时域波形Fig.13㊀Waveforms of DC bus voltage and AC currentwhen k pv decreases取时间窗为0.2s,对图13中各个时间段的直流母线电压的时域波形进行频谱分析,所得结果如图14所示㊂可以看出,当k pv >0.0634时,直流母线电压主要含有直流分量和单相交直流系统中固有的二倍频分量;当k pv =0.0634时,在直流母线电压中出现可观的40Hz 频率分量,与图11中临界稳定状态下的系统振荡频率基本吻合;当k pv <0.0634时,直流母线电压中谐波分量杂乱繁多,系统失去稳定性㊂此外,还需特别说明的是,系数k pv 在影响系统稳定性的同时,也会影响系统动态响应速度㊂观察图11中根轨迹局部放大图可知,当k pv 小于0.258时,随着k pv 增大,主导极点的根轨迹从右半平面逐渐变化到左半平面并远离虚轴;当k pv 大于0.258时,根轨迹方向转变并逐渐靠近虚轴㊂因此,当k pv =0.258时,系统具有最佳的动态性能㊂若k pv 持续增大,越过最佳运行点,虽仍可保证稳定,但系统稳定速度将滞缓,这说明需兼顾稳定性和动态性能进行k pv 的参数设计㊂为了验证这一结论,图15给出了k pv 取值变化时系统有功功率波形的变化,从有功功率角度说明系数k pv 对系统稳定性及动态响应速度的影响㊂比较图15(a)㊁(b)和(c)可知,当0.0634<k pv <0.258时,系统动态响应速度随着k pv 的增大而加快,并且k pv 越大,系统稳定速度越快㊂比较图15(c)和图15(d)可知,当k pv 取2时,系统的稳定速度相较于图15(c)变慢,说明此时k pv 取值已越过了最佳运行点,进而验证了前述理论分析的正确性㊂图14㊀直流母线电压FFT 分析Fig14㊀FFT analysis of DC busvoltage图15㊀不同k pv 作用下的有功功率曲线Fig.15㊀Active power waveforms with different k pv8电㊀机㊀与㊀控㊀制㊀学㊀报㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀第27卷㊀3㊀级联系统稳定性改善方法第2.3节中的分析结论表明,增大DAB 电压外环比例系数k pv 将显著提高级联系统稳定性㊂因此,当级联系统面临振荡失稳问题时,一种简单而可靠并且无需任何额外的补偿器或控制回路的稳定性改善方法为:增大DAB 电压外环比例系数k pv ㊂根据2.1节的分析,若要使系统满足稳定性要求,应保证增大k pv 后,DAB 输出阻抗的峰值小于V 2bus /P ,从而避免与逆变器输入阻抗发生交叉,并保证系统具有足够的相位裕度㊂本节将结合具体的仿真算例验证此稳定性改善方法的有效性㊂仿真算例中基本电路参数如表1所示,DAB 控制器的相关参数列于表2之中㊂图16给出了算例中直流母线电压和交流电流时域波形,图17则给出了与之对应的级联系统阻抗伯德图㊂如图16中0.2~0.5s 时间窗内波形所示,当系统传输功率为5kW 时,系统稳定运行,直流母线电压包含400V 的直流分量和二倍频分量㊂若传输功率增加为10kW,系统将发生振荡失稳,如图16中0.5~0.7s 的波形所示㊂图17中曲线Z in_INV1与Z in_INV2分别为功率改变前后逆变器输入阻抗伯德图㊂可以看出,负载的加重造成逆变器在低频段的阻抗幅值减小,因此与DAB 输出阻抗发生交叉㊂图16㊀稳定性改善前后的时域仿真波形Fig.16㊀Time domain simulation waveforms before andafter stability improvement为了改善系统稳定性,应当增大DAB 电压外环比例系数㊂图18为传输功率为10kW 时,级联系统关于参数k pv 的根轨迹曲线㊂可以看出,要想保证系统稳定运行,k pv 的取值必须大于0.0645,并且当k pv 取0.452时,系统具有最佳动态性能㊂观察图16中0.7~1.1s 时域波形可知,在0.8s 时,将DAB 电压外环比例系数调整为最佳参数0.452,其余参数保持不变,由于DAB 输出阻抗的谐振峰值降低,系统又重新恢复至稳定运行状态㊂图17㊀稳定性改善前后的级联子系统阻抗伯德图Fig.17㊀Impedance Bode diagram before and after sta-bility improvement of the cascadesubsystem图18㊀传输功率为10kW 时系统闭环根轨迹Fig.18㊀Closed-loop root trajectory of the system at10kW transmission power上述仿真算例进一步验证了稳定性改善方法的可行性㊂在系统控制器设计中,应当根据DAB 和单相并网逆变器的阻抗特性,利用阻抗伯德图和系统关于参数k pv 的闭环根轨迹进行直观判断,综合考虑系统的稳定性和动态响应速度,以确定适合的控制参数㊂4㊀结㊀论本文分别建立了DAB 输出阻抗模型和考虑锁相环相位波动影响的单相并网逆变器的直流端输入阻抗模型,提高了模型的准确度,并通过扫频法对阻抗模型进行验证;此外,通过理论分析获得了DAB 输出阻抗谐振频率及谐振峰值的计算公式,从原理9第12期刘㊀欣等:DAB 级联单相逆变器系统的阻抗特性及稳定性分析。

第 54 卷第 4 期2023 年 4 月中南大学学报(自然科学版)Journal of Central South University (Science and Technology)V ol.54 No.4Apr. 2023离散颗粒抑制热喷流红外辐射的大涡模拟胡峰1，孙文静1, 2，张靖周1，单勇1(1. 南京航空航天大学 能源与动力学院，江苏 南京，210016；2. 中国航天科工飞航技术研究院 北京动力机械研究所，北京，100074)摘要：为了探究气溶胶离散颗粒对飞行器排气喷管热喷流3~5 μm 波段的红外辐射的抑制效果，设计地面状态下气溶胶颗粒投射的仿真环境，采用大涡模拟和颗粒离散相模型对含气溶胶颗粒的飞行器排气喷管尾部气固两相剪切流进行数值模拟研究，系统地分析颗粒的质量流量、粒径和喷射速度对离散颗粒空间分布形态以及热喷流红外辐射抑制的影响规律。

研究结果表明：颗粒的质量流量和粒径对于红外抑制效率的影响较为明显，增加颗粒质量流量对颗粒的空间分布形态影响较小，但能够显著提升红外抑制效率；当颗粒粒径大于1.0 μm 时，颗粒空间分布均匀，红外抑制效率最高；颗粒的喷射速度对于颗粒的空间分布以及红外抑制效率的影响较小。

关键词：红外抑制；高速剪切流；大涡模拟；气溶胶颗粒分布；气固相互作用中图分类号：V231.1 文献标志码：A 开放科学(资源服务)标识码(OSID)文章编号：1672-7207（2023）04-1576-16Large eddy simulation of discrete particles suppressing infraredradiation from thermal jetsHU Feng 1, SUN Wenjing 1, 2, ZHANG Jingzhou 1, SHAN Yong 1(1. College of Energy and Power, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China;2. Beijing Power Machinery Institute, China Aerospace Institute of Science and Technology, Beijing 100074, China)Abstract: To investigate the effect of aerosol discrete particles on the infrared radiation suppression in the 3~5 μm band of thermal jets of aircraft exhaust nozzles, the simulation environment of aerosol particle projection under ground conditions was designed. The large eddy simulation(LES) and particle discrete phase model(DPM) were used to numerically simulate the gas-solid two-phase shear flow at the tail of the aircraft exhaust nozzle containing aerosol particles, and the effect law of particle mass flow, size and jet speed on the spatial distribution of discreteparticles and the suppression of infrared radiation of thermal jets was systematically analyzed. The results show收稿日期： 2022 −05 −14； 修回日期： 2022 −07 −23基金项目(Foundation item)：中国博士后科学基金特别资助(站前)项目(2020TQ0143)；江苏省自然科学基金青年基金资助项目(BK20200448) (Project(2020TQ0143) supported by the Postdoctoral Science Foundation of China; Project(BK20200448) supported by the Youth Fund of Jiangsu Natural Science Foundation)通信作者：孙文静，博士，讲师，从事气固两相湍流、湍流燃烧、流动强化传热研究；E-mail ：**************.cnDOI: 10.11817/j.issn.1672-7207.2023.04.033引用格式： 胡峰, 孙文静, 张靖周, 等. 离散颗粒抑制热喷流红外辐射的大涡模拟[J]. 中南大学学报(自然科学版), 2023, 54(4): 1576−1591.Citation: HU Feng, SUN Wenjing, ZHANG Jingzhou, et al. Large eddy simulation of discrete particles suppressing infrared radiation from thermal jets[J]. Journal of Central South University(Science and Technology), 2023, 54(4): 1576−1591.第 4 期胡峰，等：离散颗粒抑制热喷流红外辐射的大涡模拟that the effect of particle mass flow and size on infrared radiation suppression rate is obvious. With the increase of particle mass flow, its effect on the spatial distribution of particles is small, but the infrared suppression efficiency is significantly improved. When the particle diameter is 1.0 μm, the particle space distribution is uniform and the highest infrared suppression rate is achieved. However, the particle injection speed has less effect on the spatial distribution of particles and infrared radiation suppression efficiency.Key words: infrared suppressing; high-speed shear flow; large eddy simulation; aerosol particle distribution; gas-solid interactions气溶胶红外隐身技术是一种主动型应急红外对抗技术，该技术利用附加的机载引气装置，将细微颗粒喷射在发动机热喷流周围形成气溶胶云，借此对排气喷管热内腔和热喷流的强红外辐射进行遮蔽和散射。

氦氖激光器的谱线竞争效应
氦氖激光器的谱线竞争效应是指当两个或多个氦氖激光器同时工作时，由于它们产生的光谱线位置重叠，会导致光谱线的强度减弱。

在氦氖激光器中，氦原子和氖原子被激发到高能级上，然后通过受激辐射跃迁回低能级，释放出能量并发出特定波长的光。

这些光的波长由激光器的谐振腔长度和氦氖原子的能级差决定。

当两个或多个氦氖激光器同时工作时，它们产生的光谱线位置可能会重叠。

这意味着一些光线会被吸收或散射，从而使它们的强度减弱。

这种现象被称为谱线竞争效应。

要减轻谱线竞争效应的影响，可以采取以下措施：
1. 使用不同的激光器：选择不同波长的激光器可以避免它们产生的光谱线重叠。

2. 使用光纤放大器：将多个激光器的信号传输到一个光纤放大器中，可以增强信号并减少谱线竞争效应的影响。

3. 调整激光器的参数：通过调整激光器的谐振腔长度、增益和相位等参数，可以优化激光器的输出，并减少谱线竞争效应的影响。

谱线竞争效应还可以通过使用非线性光学器件来减轻。

例如，可以使用具有非线性放大作用的二极管或晶体管来增加激光器的输出功率，并减少谱线竞争效应的影响。

此外，还可以使用光隔离器来分离多个激光器的输出信号，以避免它们之间的干扰和相互影响。

在实际应用中，谱线竞争效应可能会对某些特定的实验产生影响，因此需要根据实验的具体需求进行优化和调整。

例如，在医学成像领域中，需要使用高分辨率的光谱仪来分析人体组织的分子结构，而谱线竞争效应可能会影响到这种分析的精度和可靠性。

因此，需要采取一些特殊的措施来避免或减轻谱线竞争效应的影响，以确保实验结果的准确性和可靠性。

不平衡电压条件下并网逆变器多目标协同控制崔金豹(鄂尔多斯市和效电力设计有限责任公司，内蒙古鄂尔多斯017000)摘要：为提高电压不平衡条件下并网逆变器的运行性能，提出一种功率振荡与当前谐波抑制的多目标协同控制策略。

首先建立了基于无波动条件下平衡电流、有功功率、无功功率的数学模型，并将峰值限制在安全范围内。

然后，针对传统离散傅里叶算法运算复杂度高的缺点，提出一种适用于电压正负不平衡序列的简化滑动递归离散傅里叶变换（SRDFT)算法，准确、快速地分离正、负序向量分量。

实验结果表明，在电压不平衡的情况下，并网逆变器的输出电能质量可以得到显著改善，在抑制电流畸变、减小功率波动的同时，保证了系统的安全快速响应，实现了多目标协同控制。

关键词：并网逆变器；协同控制；傅里叶变换；不平衡电压中图分类号：TM464 文献标识码：A 文章编号：1000-100X(2021)05-0105-05Multi-objective Cooperative Control of Grid Connected Inverter UnderUnbalanced VoltageCUI Jin-bao(Ordors City Power Design Co. y Ltd., Ordors017000, China)A bstract： In order to improve the operation performance of grid connected inverter under unbalanced voltage, a multi­objective cooperative control strategy of power oscillation and current harmonic suppression is proposed.Firstly, the mathematical model of balancing current, active power and reactive power under the condition of no fluctuation is est­ablished, and the peak value is limited in the safe range.Then, aiming at the disadvantage of high computational com­plexity of traditional discrete Fourier transform algorithm, a simplified sliding recursive discrete Fourier transform (SR - DFT) algorithm is proposed to separate the positive and negative sequence vector components accurately and quickly. The experimental results show that the output power quality of the grid connected inverter can be significantly im­proved in the case of unbalanced voltage, which can suppress the current distortion and reduce the power fluctuation, ensure the safe and rapid response of the system,and realize the multi-objective cooperative control.Keywords ： grid connected inverter ；cooperative control ；Fourier transform ；unbalanced voltageFoundation Project ： Supported by National Natural Science Foundation of China (No.51277069)l引言电压源并网逆变器具有输出正弦度高,有功、无功功率大等优点，广泛应用于分布式发电、高压直流输电等电力系统或装置中||]。

Control of interface of glass-ceramic electrolyte/liquid electrolyte for aqueous lithium batteriesTonghuan Yang a ,Xingjiang Liu a ,b ,*,Lin Sang b ,Fei Ding ba School of Chemical Engineering and Technology,Tianjin University,Tianjin 300072,China bNational Key Lab of Power Source,Tianjin Institute of Power Source,Tianjin 300384,Chinah i g h l i g h t sThe water-stable lithium electrodes (WSLE)were prepared with LAGP and LATP glass-ceramic plates. A modi fied layer was deposited at glass-ceramic/organic electrolyte interface by magnetron sputtering. The discharge performance of WSLE was improved 70e 80%by the modi fied layer.a r t i c l e i n f oArticle history:Received 29November 2012Received in revised form 15March 2013Accepted 13April 2013Available online 20April 2013Keywords:Lithium-air batteryWater-stable lithium electrode Glass-ceramic electrolyte Interfacial modi ficationa b s t r a c tThe discharge performance of the water-stable lithium electrode (WSLE)is improved by introducing the surface modi fication of the glass-ceramic plate (LAGP and LATP).The water-stable lithium electrodes are prepared with the NASICON-type glass-ceramic plates as protection layer,and using organic electrolyte as interlayer.The glass-ceramic plates with ionic conductivity of 4Â10À4À5.7Â10À4S cm À1are water-stable and 300e 500m m thick.The modi fied layer is deposited onto the glass-ceramic plates by RF magnetron sputtering from a Li 4Ti 5O 12target.The modi fied layer is analyzed by XRD,SEM-EDX,Raman and XPS.The Li-air test-cells are assembled with an SCE as reference electrode in aqueous solution.In the Li-air test-cells,the AC impedance and constant polarization potential measurements are carried out to identify the improvement of modi fication.The impedance of interface between the glass-ceramic plate and organic electrolyte decreases about 20e 50%.Consequently,the discharge current is promoted about 70e 80%.Then,by introducing interfacial modi fication of glass-ceramic plate,the power performance of WSLE is remarkably promoted.Ó2013Elsevier B.V.All rights reserved.1.IntroductionThe lithium-air and lithium-water battery has attracted many researchers ’attention,as the extremely high speci fic energy stor-age system in principle.Although the energy potentiality is high comparing with other electrochemical systems,the practical implementation still has to face several issues regarding both the electrodes and electrolytes.One of the issues,which have to be solved,is that the discharge product Li 2O 2is insoluble in organic electrolyte and clogs the porous air-electrode gradually.Visco et al.and Imanishi et al.proposed a water-stable lithium anode protected by Li 3M 2(PO 4)solid electrolyte,which conquered this issue [1e 4].The Li 3M 2(PO 4)with NASICON-type structure is akind of water-stable lithium-ion super conductor.And since the Li 3M 2(PO 4)has reduction reaction with lithium metal in con-tact,a lithium-ion conductive interlayer was employed between Li 3M 2(PO 4)and the Li-metal.At first solid-state lithium-ion con-ductors have been proposed as protective interlayer,such as LiPON etc.However,the solid-state interlayer has low ionic conductivity and can ’t adapt to the surface-morphological changes of Li-metal electrode during discharge.Subsequently,the polymer electrolyte and organic electrolyte was proposed as the interlayer for better lithium-ion conductivity and surface-morphological adaptability [5e 10].In our previous work,it is found that the interface imped-ance between the solid electrolyte plate and the organic electrolyte is dominant during discharge in WSLE,which is controlling the current density [11].Then,the interface impedance between the solid electrolyte and organic electrolyte became important.For improving the performance of water-stable lithium anode pro-tected by solid electrolyte plate,the interface impedance must be reduced.*Corresponding author.National Key Lab of Power Source,Tianjin Institute of Power Source,Tianjin 300384,China.Tel.:þ86(0)2223383783;fax:þ86(0)2223959300.E-mail addresses:xjliu@ ,klpsc@ (X.Liu).Contents lists available at SciVerse ScienceDirectJournal of Power Sourcesjournal h omepage:www.elsevier.co m/lo cate/jp owsour0378-7753/$e see front matter Ó2013Elsevier B.V.All rights reserved./10.1016/j.jpowsour.2013.04.071Journal of Power Sources 244(2013)43e 49In this work,the water-stable electrolyte plates were prepared by a Li2O e Al2O3e TiO2e P2O5(LATP)or Li2O e Al2O3e TiO2e P2O5 (LAGP)system glass-ceramic,which primarily consisted of Li1þx Ti2-x Al x(PO4)3(x¼0.3)or Li1þx Ge2-x Al x(PO4)3(x¼0.5)respectively.Andthe thickness was about300e500m m.The surface of the glass-ceramic plates was modified to promote the electrochemical per-formance of the interface between glass-ceramic plate and organic electrolyte.2.Experimental2.1.Glass-ceramic plate preparationThe LATP glass-ceramic[14Li2O9Al2O338TiO239P2O5(mol%)] exhibits high lithium-ion conductivity and has been prepared into thin plates in reports[12e14].The14Li2O9Al2O338TiO239P2O5 glass-ceramic was synthesized by reagent grade chemicals, including Li2CO3,Al2O3,TiO2,and NH4H2PO4.The synthesis process is same with the report by Thokchom et al.[13,14].The LATP glass-ceramic plates were refined shape and polished to a300e500m m thick plate.The LAGP glass-ceramic[0.8Li2O0.25Al2O3 1.5GeO2 1.5P2O5 (mol%)]has the same structure with LATP and was made into thin electrolyte plates[15e17].In this work,the LAGP plates were synthesized by Li2CO3,Al2O3,GeO2,and NH4H2PO4.The four raw materials were weighted and mixed by the stoichiometry of 0.8Li2O0.25Al2O31.5GeO21.5P2O5.To begin with,the mixed raw materials were heated slowly to723K and kept for1.5h to release gaseous production.Subsequently,the mixture was heated up to 1723K and melted for2h.And then the molten mixture was poured in a heated plate mold and pressed by another one.The glass plate,which was casted by the molten mixture,was annealed at823K for2h and cooled in furnace.After being annealed,the glass plate crystallized at1223K for12h and became a dense opaque white specimen.This specimen was refined shape and polished to a300e500m m thick plate[11].2.2.Glass-ceramic plate surface modificationA thinfilm of lithium titanium oxide(LTO)was deposited onto glass-ceramic plate surface by RF magnetron sputtering in argon (Ar:50%)/oxygen(O2:50%)plasmas.The sputtering targets were prepared by compressing Li4Ti5O12powder(99.9%)into a100mm diameter pellet and were sintered at1023K for6h in air.The vacuum chamber was evacuated to a base pressure10À3Pa.The Ar/ O2mixture gas pressure was maintained at1Pa.The deposition rate was15 A minÀ1at300W RF power.2.3.CharacterizationsIn all physical and electrochemical measurements,a big glass-ceramic plate was cut into10e20pieces of small ones(about 1cm2each)in order to exclude the effect of different batches of the glass-ceramic plate.Half of them were tested after surface modi-fication;others were tested in same way for comparison.The surface morphology of the glass-ceramics with and without modification was characterized by a Hitachi S-4800field emission scanning electron microscopy(SEM-EDX).The X-ray diffraction (XRD)patterns of LAGP,LATP and modified layer were recorded by a Rigaku TTRAXⅢdiffractometer employing a Cu e K a source.Raman spectra of samples were recorded on a Jobin-Yvon T64000double monochromator equipped with a spatialfilter.The modified layer samples,prepared for Raman testing,were deposited on nickel plate to avoid the influence of glass-ceramic plate substrate.2.4.Electrochemical measurementsThe ionic conductivity of glass-ceramic plate was measured by AC impedance.A0.5m m thick Ag coating was evaporated onto both sides of the glass-ceramic plate.The Ag coated platefixed by two stainless blocking electrodes in a cell.At the room temperature (298K),the impedance measurements were carried out on the cell using a Solartron instrument(model1470Eþ1455A)in0.1to106 frequency range.The electrochemical impedance spectra were fitted using Zview software.A test-cell was designed for electrochemical measurements,as shown in Fig.1.The test-cell was separated into a Li electrode area and an air-electrode area by0.25cm2glass-ceramic plate with a thickness of300e500m m.The Li electrode area contained a Li-metal electrode in organic electrolyte(EC:DEC:EMC¼1:1:1, 1M LiPF6);the air-electrode area contained an air-electrode(Super-P carbon loaded Ni foam)and a reference electrode(an SCE con-nected by salt bridge)in water solution(0.5M LiOH and0.5M KCl).3.Results and discussionFig.2(LAGP)shows an XRD patterns of the LAGP plate which consists of Li1þx Al x Ge2-x(PO4)3(x¼0.5)and AlPO4crystals[15e17]. The Li1þx Al x Ge2-x(PO4)3(x¼0.5)phase is dominant in LAGP glass-ceramic,and other peaks indicate the presence of an AlPO4phase. Fig.2(LATP)provides an XRD patterns of the LATP plate,which consists of Li1þx Ti2-x Al x(PO4)3(x¼0.3)and AlPO4phases,the peaks corresponding to them are observed in XRD patterns[13,14].The Li1þx Ti2-x Al x(PO4)3(x¼0.3)phase is dominant in LATP glass-ceramics.The peak around36 indicates the presence of an AlPO4 phase.Fig.3shows the morphology of the LAGP surface(a,b)and LATP surface(c,d).The LAGP and LATP surface is close-grained and has visible traces of polishing.Few chips of LAGP/LATP glass-ceramic attach on surface,which were produced by polishing.Figs.4and 5is the impedance spectrum of LAGP and LATP plate by blocking electrode test.The ionic conductivity of LAGP and LATP plate can be calculated and can reach5.7Â10À4S cmÀ1and4Â10À4S cmÀ1, respectively.[The formula:ε¼d/(S$R);d:thickness of electrolyte plate;S:area of electrolyte plate;R:resistance of electrolyte plate].Fig.6shows the small angle XRD patterns obtained from modified layer on LATP.The XRD pattern suggests that the LTO modified layer is amorphous,because it is prepared by RF magnetron sputtering.Fig.7shows the surface morphology of the LTO modified layer on SiO2plate(a)and LAGP plate(b,c,d).The surface of SiO2is Fig.1.A schematic representation of the3electrode Li-air test-cell.T.Yang et al./Journal of Power Sources244(2013)43e49 44smoother than LAGP and LATP plate.It ’s better for the analysis of the LTO modi fied layer ’s morphology without the in fluence of morphology of the LAGP and LATP surface.As shown in Fig.7(a),the modi fied layer,which is deposited onto the surface of SiO 2sub-strate,is continuous and uniform.Fig.7(b)is a SEM cross-section of a modi fied layer on the LAGP substrate.The cross-section shows a modi fied layer is deposited onto the surface of the LAGP substrate.The thickness of the modi fied layer is about 400nm.Fig.7(c,d)shows the SEM top view images of the modi fied layer on the LAGP surface.The modi fied layer is composed of many small grains and rougher than the LAGP surface.The modi fied layer would change the electrochemical characteristic of the interface between the organic electrolyte and LAGP plate,which covered on both hills and valleys of the whole LAGP surface.According to the observation of SEM images,the LAGP surface is completely covered by the modi-fied layer which is prepared by RF magnetron sputtering from aLi 4Ti 5O 12target.And the modi fied layer is a continuous,close-grained and uniform deposition layer,which closely growing on the LAGP surface.Fig.8shows an EDX mapping of the modi fied layer on the LAGP for Ti element and Ge element.Existence of the Ti element of modi fied layer is observed and uniformly distributed.And exis-tence of the Ge element of the LAGP substrate can also be observed,because the analysis depth of EDX is 1e 2m m which is more than the 400nm thickness of the modi fied layer.As Fig.9(b)shows,a Raman spectrum of the Li 4Ti 5O 12target has six characteristic bands which appear at 165,239,344,430,674,and 754cm À1.The bands at 239cm À1can be assigned to the bending vibrations of O e Ti e O bonds;the bands at 674and 754cm À1are attributed to vibrations of Ti e O bonds in TiO 6octa-hedra,the bands at 344and 430cm À1are attributed to the stretching vibrations of the Li e O bonds in LiO 4and LiO 6polyhedra,respectively [18].The weak feature at 165cm À1is attributed to bending vibrations of O e Li e O bonds and 274cm À1assigned to F2g modes [18e 21].In Fig.9(a),the evolution of the Raman spectrum is caused by the structural changes that occurred in the LTO modi fied layer upon the RF magnetron sputtering.The Raman spectrum of the modi fied layer still has the bands at 674and 754cm À1,which can be attributed to vibrations of Ti e O bonds in TiO 6octahedra.The band at 430cm À1disappears due to the absent of LiO 6polyhedra by the RF magnetron sputtering.And the Raman spectrum shows the bands at 200and 360cm À1and the absence of the bands at 239and 344cm À1.As Julien et al.report,the Li 7Ti 5O 12displays a tetragonal structure with 141/amd (D 194h)space group,which induces three typical Raman bands located at 200,360and 465cm À1[21].When x >1.4of Li 4þx Ti 5O 12,the Raman spectrum displays the bands at 200and 360cm À1and the bands at 239and 344cm À1disappear.The lack of band at 465cm À1could be attributed to the weak Raman-activity of it [21].The band at 1096cm À1can be assigned to the vibration of CO 32Àwhich is formed at surface in reaction be-tween super fluous lithium and CO 2.Then,the modi fied layer should consist of Li 4þx Ti 5O 12(1.4<x <3).Fig.3.SEM images of the LAGP plate (a,b)and the LATP plate(c,d).Fig.2.XRD patterns of the LAGP and the LATP.T.Yang et al./Journal of Power Sources 244(2013)43e 4945To obtain direct information about Ti valence of the modi fied layer,a modi fied layer is deposited onto nickel plate and studied by XPS,and the corresponding Ti 2p spectra are shown in Fig.10.In Fig.10,the XPS spectrum of the modi fied layer has two peaks at 458.8and 464.6eV.The two peaks of Ti 2p binding energies is mixed-valence of Ti (þⅣ)and Ti (þⅢ).The binding energies at 458.8and 464.8eV indicate the existence of Ti (þⅣ)[22,23].The peaks locate at 462.8and 456.8eV belongs to Ti (þⅢ),which demonstrate the existence of Ti (þⅢ)[22e 25].According to the analysis of each peak,the Ti (þⅢ)occupy about 36e 50%.This suggests that the x of Li 4þx Ti 5O 12should be 1.8e 2.5,because the x of Li 4þx Ti 5O 12is equal to the number of Ti 3þin each five Ti-atoms.Thus,the modi fied layer includes Ti 3þand Ti 4þ,and the x of Li 4þx Ti 5O 12is 1.8e 2.5,which agrees with the analysis result of Raman spectra,but more accurate.According to the analysis of EDX mapping,XRD patterns,Raman spectra and XPS spectra,the modi fied layer is amorphous and composed of Li 4þx Ti 5O 12(1.8<x <2.5).The water-stable lithium metal electrode consists of lithium metal,organic electrolyte,and glass-ceramics electrolyte plate,in which the organic electrolyte is employed as an interlayer to reduce the contact resistance between the glass-ceramic plate and lithium electrode,and to protect the reduction of LATP by lithium metal [2].Fig.11shows impedance spectra of three-electrode test-cell with the LAGP and the modi fied LAGP plate.The impedance spectra of test-cell with the LAGP display a small semicircle at high frequency and a large semicircle at low frequency which may be a pressed semicircle or two overlapped semicircles.The impedance spectrum of test-cell with the modi fied LAGP shows a small semicircle at high frequency,a half semicircle at middle frequency and a large semi-circle at low frequency.The modi fied layer between the LAGP plate and the organic electrolyte has made an impedance decrease of test-cell,which should be corresponding to the half semicircle at middle frequency.And the large semicircle of the LAGP test-cell should be two overlapped semicircle.The equivalent circuit,proposed for fitting,is similar with re-ports,which include Re,Rg,Rint and Rsei with respective constant phase element (CPE1,CPE2and CPE3),and W (represent a Warburg resistance)[5e 7].Re represents the bulk resistance of the LAGP plate,organic electrolyte and wires,which is corresponding to the intercept of the small semicircle with the real axis.Rg is the grain boundary resistance in LAGP plate,which is corresponding to the small semicircle.The large circle includes two overlapped semi-circles,which represent the interfacial resistance of the LAGP plate at middle frequency range (Rint),and the interfacial resistance of the lithium electrode at low frequency range (Rsei).While dis-charging,the SEI impedance (Rsei)decreased with polarization potential,but the organic electrolyte/LAGP impedance (Rint)changed a little and became the major impedance [11].The impedance of electrolyte/LAGP interface controlled the discharge current density [11].Then,the improvement of modi fication can be estimated by the contrast of Rint,which is corresponding to the middle frequency semicircle.The simulated impedance spectra of the equivalent circuit fit with the impedance spectra well,and the parameter of the equivalent circuit is listed in Table 1.In Table 1,Re,Rg and Rsei of the test-cell with the LAGP plate are roughly equal to the one with the modi fied LAGP plate.However,the Rint with modi fied LAGP is decreased 40%e 50%(about 220U ).Accordingly,the discharge current of the test-cell with the modi fiedFig.5.Impedance spectra of theLATP.Fig.6.XRD patterns of the LTO modi fiedlayer.Fig.4.Impedance spectra of the LAGP.T.Yang et al./Journal of Power Sources 244(2013)43e 4946LAGP plate should increase.Then,some tests about discharge cur-rent have been carried out.Fig.12shows two constant potential polarization curves of the WSLE with and without interface modi fication.At À2.9V vs.SCE (about 0.4V vs.Li/Li þ),the current of the WSLE with interface modi fication is about 100%more than the one without.At the samepolarization potential,the current curves of the WSLE with and without interface modi fication could represent the power perfor-mance when discharging.Then,the power performance of the WSLE can be remarkably promoted by introducing the modi fied layer,which is deposited by RF magnetron sputtering from the Li 4Ti 5O 12target.The 50%decrease of Rint resulted in the 100%in-crease of discharge current,which is also an evidence of our pre-vious results that the organic electrolyte/LAGP impedance controlled the current density when discharging [11].At the interface of solid-state electrolyte or organic electrolyte,the ionic conduction phenomena have been explained by two different theories respectively.At the interface of solid-state electrolyte,the phenomena are characterized by the term “nanoionics ”to describe about ionic conduction [26].At the interface,two kinds of solid-stateionicFig.7.SEM images of the modi fied layer:(a)on SiO 2;(b)a cross-section of the modi fied layer on the LAGP plate (c,d)on the LAGPplate.Fig.8.EDX mapping images of the modi fied layer on the LAGPplate.Fig.9.Raman spectra of the LTO raw material and the LTO modi fied layer.T.Yang et al./Journal of Power Sources 244(2013)43e 4947conductor correspond to two different phenomena of ionic conduction.One is the contact of the electron-insulating ionic conductors.And one example is that two kinds of F Àion conductor (BaF 2and CaF 2)were brought into contact with each other [27].The com-positions and structures of solid electrolytes have been well tailored to achieve high ionic conductivities.However,the com-positions deviate from the optima at the space-charge layer.And therefore,the conductivity should be lower than that of bulk,increasing the interfacial resistance [28].For reducing the interfa-cial resistance,the Li 4Ti 5O 12or LiNbO 3layer is introduced as the buffer layer.Because the interposition of buffer layer can suppress the development of space-charge layer,the interfacial resistance is obviously reduced [28,29].The other one is the contact of the mixed conductors,which are materials with a signi ficant fraction of ionic as well as electronic.For instance,a space-charge layer in the LiCoO 2should vanish when in contact with a mixed conductor,because the electronic con-duction resolves the concentration gradient of the Li þions [28].Similar nanoionic phenomena should take place at the LAGP side of interface between the LAGP and the organic electrolyte,developing a space-charge layer.When the LAGP is in contact with the organic electrolyte,the large difference between their chemical potentials can make Li þions accumulate at LAGP interface,further developing the space-charge layer and resulting in a very large interfacial resistance.The interposition of buffer layer is a strategy which has been reported to suppress the space-charge layer [28,29].The buffer layer introduces two interfaces:LAGP/LTO and LTO/organic electrolyte.The space-charge layers at both interfaces will be less developed,because the former consists of solid-state oxides with similar chemical potentials,and the latter consists of mixed conductor materials.And the electronic conductivity of Li 4þx Ti 5O 12(x ¼1.8e 2.5)is enhanced via the generation of mixed-valence titanium [Ti (Ⅲ)/Ti (Ⅳ)].Then,the energy barrier of Li-ion transfer between the LAGP and organic electrolyte is divided into two smaller energy barriers,which are the energy barriers of LAGP/LTO interface and LTO/organic electrolyte interface.The actual process may be more complex,which needed further study.And the Li 4þx Ti 5O 12(1.8<x <2.5)should be a zero strain compound,which has the similar characteristic of Li 4Ti 5O 12[30].In that case,even if the formation of space-charge layer made lithium-ion unhomogeneously distribute,there still has no strain to break the modi fied layer.Fig.13shows the impedance spectra of the three-electrode test-cell with the LATP and the modi fied LATP plate.The impedance spectrum of test-cell with the LATP and the modi fied LATP displays a small semicircle at high frequency,a half semicircle at middle frequency,and a large semicircle at low frequency which is corre-sponding to the SEI impedance.Same to LAGP plate,the equivalent circuit include Re,Rg,Rint and Rsei with respective constant phase elements (CPE1,CPE2and CPE3),and W (represents a Warburg resistance).Re is corresponding to the intercept of the small semicircle with the real axis,and Rg is corresponding to the small semicircle.Rint is corresponding to the half semicircle,and RseiisFig.10.XPS patterns of Ti 2p of the modi fied layer.Table 1The parameter of the equivalent circuit of test-cell with LAGP and modi fied LAGP.Re (U )Rg (U )Rint (U )Rsei (U )LAGP27258557770Modi fied LAGP28234338771Fig.11.Impedance spectra of the WSLE with the LAGP and the modi fied LAGP in the three-electrodetest-cell.Fig.12.Constant potential polarization curves of the WSLE with the LAGP and the modi fied LAGP at À2.9V vs.SCE at 298K.T.Yang et al./Journal of Power Sources 244(2013)43e 4948corresponding to the large semicircle at the low frequency.The fitting lines of impedance spectra are also showed in Fig.13,and the analysis results of impedance are listed in Table 2.In Table 2,Rint with LATP is more than LAGP,which should be attributed to the low Li-ion conductivity of LATP and could also be different from actual area.Rint with modi fied LATP decreased about 240U which is 20e 30%of Rint without modi fication.Fig.14shows two constant potential polarization curves of the WSLE protected by the LATP with and without interface modi fica-tion.At À2.9V vs.SCE (about 0.4V vs.Li/Li þ),the current of the WSLE with interface modi fication is about 80%more than the one without.Then,the power performance of WSLE can be remarkably promoted by the modi fied layer,which is similar as the modi fica-tion of LAGP plate Fig.12.4.ConclusionBy using the modi fication of the interface between the glass-ceramic (LAGP/LATP)plate and the organic electrolyte,the discharge performance of the WSLE can be remarkably promoted in aqueous solution.The modi fied layer decreased the interfacial impedance between the glass-ceramic plate and organic electrolyte.The modi fied layer Li 4þx Ti 5O 12(1.8<x <2.5)can offer more lithium-ions and vacancy sites and has electronic conduction.And,it introduced two in-terfaces,such as glass-ceramic plate/LTO and LTO/organic electro-lyte,at which the space-charge layer was less developed.Because the Li 4þx Ti 5O 12(1.8<x < 2.5)the modi fied layer is a mixed conductor and covered the whole LAGP plate,which buffered the direct contact between the glass-ceramic plate and organic elec-trolyte.Then,the energy barrier of Li-ion transfer between the LAGP and organic electrolyte become two relative small energy barriers.References[1]S.J.Visco, E.Nimon, B.Katz,L.C.D.Jonghe,M.Y.Chu,Abstract 0389,TheElectrochemical Society Meeting Abstracts vol.2006e 2,Cancun,Mexico,2006.Oct.29e Nov.3.[2]S.J.Visco,E.Nimon,B.Katz,L.C.D.Jonghe,M.Y.Chu,Abstract 53,The 12thInternational Meeting on Lithium Batteries Abstracts,Nara,Japan,2004.[3]T.Zhang,N.Imanishi,S.Hasegawa,A.Hirano,J.Xie,Y.Takeda,O.Yamamoto,N.Sammes,J.Electrochem.Soc.155(2008)A965.[4]S.Hasegawa,N.Imanishi,T.Zhang,J.Xie,A.Hirano,Y.Takeda,O.Yamamoto,J.Power Sources 189(2009)371.[5]T.Zhang,N.Imanishi,S.Hasegawa,A.Hirano,J.Xie,Y.Takeda,O.Yamamoto,N.Sammes,Electrochem.Solid-State Lett.12(2009)A132.[6]T.Zhang,N.Imanishi,Y.Shimonishi,A.Hirano,J.Xie,Y.Takeda,O.Yamamoto,N.Sammes,J.Electrochem.Soc.157(2010)A214.[7]T.Zhang,N.Imanishi,A.Hirano,Y.Takeda,O.Yamanoto,Electrochem.Solid-State Lett.14(2011)A45.[8]Y.Wang,H.Zhou,J.Power Sources 195(2010)358.[9]P.He,Y.Wang,H.Zhou,mun.12(2010)1686.[10]P.He,Y.Wang,H.Zhou,J.Power Sources 196(2011)5611.[11]T.Yang,L.Sang,F.Ding,J.Zhang,X.Liu,Electrochim.Acta.81(2012)179.[12]J.Fu,Solid State Ionics 96(1997)195.[13]J.S.Thokchom,B.Kumar,Solid State Ionics 177(2006)727.[14]J.S.Thokchom,B.Kumar,J.Electrochem.Soc.154(2007)A331.[15]G.Y.Aleshin, D.A.Semenenko, A.I.Belova,T.K.Zakharchenko, D.M.Itkis,E.A.Goodilin,Y.D.Tretyakov,Solid State Ionics 184(2011)62.[16]K.He,Y.H.Wang,C.K.Zu,Y.H.Liu,H.F.Zhao,B.Han,J.Chen,Chin.J.Inorg.Chem.27(2011)2484.[17]J.Kumar,B.Kumar,J.Power Sources 194(2009)1113.[18]P.P.Posini,R.Mancini,L.Petrucci,V.Contini,P.Villano,Solid State Ionics 144(2001)185.[19] C.Julien,136-137,Solid State Ionics (2000)887.[20]T.Yi,L.Jiang,J.Liu,M.Ye,H.Fang,A.Zhou,J.Shu,Ionics 17(2011)799e 802.[21] C.M.Julien,M.Massot,K.Zaghid,J Power Sources 136(2004)72e 79.[22]P.W.Seo,S.S.Kim,S.C.Hong,Korean J.Chem.Eng.27(2010)1220.[23]J.Y.Luo,L.J.Chen,Y.J.Zhao,P.He,Y.Y.Xia,J.Power Sources 194(2009)1075.[24] C.Trapalis,V.Kozhukharov,B.Samuneva,J.Mater.Sci.28(1993)1276.[25]R.Cai,S.Jiang,X.Yu,B.Zhao,H.Wang,Z.Shao,J.Mater.Chem.22(2012)8013.[26]J.Maier,Nat.Mater.4(2005)805.[27]N.Sata,K.Eberman,K.Eberl,J.Maier,Nature 408(2000)946.[28]N.Ohta,K.Takada,L.Zhang,R.Ma,M.Osada,T.Sasaki,Adv.Mater.18(2006)2226.[29]Y.Seino,T.Ota,K.Takada,J Power Sources 196(2011)6488.[30]T.Ohzuku,A.Ueda,N.Yamamoto,J.Electrochem.Soc.142(1995)1431.Table 2The parameter of the equivalent circuit of test-cell with LATP and modi fied LATP.Re (U )Rg (U )Rint (U )Rsei (U )LATP421949791160Modi fied LATP382057321128Fig.13.Impedance spectra of the WSLE with the LATP and the modi fied LATP in the three-electrodetest-cell.Fig.14.Constant potential polarization curves of the WSLE with the LATP and the modi fied LATP at À2.9V vs.SCE at 298K.T.Yang et al./Journal of Power Sources 244(2013)43e 4949。

科技视界Science&Technology VisionScience&Technology Vision科技视界0引言太阳能是取之不尽、用之不竭的能源。

太阳照射到地球上一天的能原谅,就足够全人类使用一整年。

因此,太阳能受到了人们越来越多的关注。

光伏发电就是利用半导体将太阳能直接转化成电能的一项技术。

光伏电池制造所需的硅元素在地球上很充足,其含量高达26%,故不存在资源短缺、耗尽的问题。

所以光伏发电是目前世界上发展前景最好的一门发电技术。

而光伏系统现在存在一个主要的问题就是发电效率低,因此,如何提高光伏电池转换效率是光伏发电系统的主要研究方向。

太阳能光伏发电系统的最大功率点跟踪(MPPT-MaximumPower Point Tracker)就是其中一个尤为重要的课题。

1光伏电池输出特性分析光伏电池的输出特性曲线如图1所示:其中图(a)为不同温度(这里的温度表示光伏电池内部PN结处的温度)时的P-V特性曲线,图(b)为不同日照强度下的P-V特性曲线。

从图中我们可以得知,光伏电池输出特性曲线具有较强的非线性。

光伏电池的输出变化受温度、日照强度变化影响。

当日照强度增大时,电池的开路电压基本保持不变,短路电流明显增加,最大输出功率也增加。

当温度升高时,电池的开路电压下降,短路电流略有增加,最大输出功率减小。

故当温度和日照强度不变时,光伏电池有最大功率点,能输出当前条件下的最大功率。

(a)不同温度时的特性曲线(b)不同日照强度时的特性曲线图1光伏电池的输出特性曲线2最大功率跟踪控制方法研究光伏阵列的最大功率跟踪通常都是通过DC-DC变化电路实现的,常见的DC-DC变换电路有Buck、Cuk及Boost等等。

由于Boost电路较为简单,可以工作在连续模式,而且相对其它电路转换效率要略高一些,故我们采用Boost电路实现最大功率跟踪。

2.1Boost电路简介升压斩波电路(Boost Chopper)的原理图及工作波形如图2所示。