ANovel Non-Isolated Cubic DC-DC Converter with High Voltage Gain for Renewable Energy Power Generation System

In recent years,switched inductor(SL)technology,switched capacitor(SC)technology,and switched inductor-capacitor(SL-SC)technology have been widely applied to optimize and improve DC-DC boost converters,which can effectively enhance voltage gain and reduce device stress.To address the issue of low output voltage in current renewable energy power generation systems,this study proposes a novel non-isolated cubic high-gain DC-DC converter based on the traditional quadratic DC-DC boost converter by incorporating a SC and a SL-SC unit.Firstly,the proposed converter’s details are elaborated,including its topology structure,operating mode,voltage gain,device stress,and power loss.Subsequently,a comparative analysis is conducted on the voltage gain and device stress between the proposed converter and other high-gain converters.Then,a closed-loop simulation system is constructed to obtain simulation waveforms of various devices and explore the dynamic performance.Finally,an experimental prototype is built,experimental waveforms are obtained,and the experimental dynamic performance and conversion efficiency are analyzed.The theoretical analysis’s correctness is verified through simulation and experimental results.The proposed converter has advantages such as high voltage gain,low device stress,high conversion efficiency,simple control,and wide input voltage range,achieving a good balance between voltage gain,device stress,and power loss.The proposed converter is well-suited for renewable energy systems and holds theoretical significance and practical value in renewable energy applications.It provides an effective solution to the issue of low output voltage in renewable energy power generation systems.

Effects of stress dependent electrochemical reaction on voltage hysteresis of lithium ion batteries

Intercalation of lithium ions into the electrodes of lithium ion batteries is affected by the stress of active materials, leading to energy dissipation and stress dependent voltage hysteresis. A reaction-diffusion-stress coupling model is established to investigate the stress effects under galvanostatic and potentiostatic operations. It is found from simulations that the stress hysteresis contributes to the voltage hysteresis and leads to the energy dissipation. In addition, the stress induced voltage hysteresis is small in low rate galvanostatic operations but extraordinarily significant in high rate cases. In potentiostatic operations, the stresses and stress induced overpotentials increase to a peak value very soon after the operation commences and decays all the left time. Therefore,a combined charge-discharge operation is suggested, i.e., first the galvanostatic one and then the potentiostatic one. This combined operation can not only avoid the extreme stress during operations so as to prevent electrodes from failure but also reduce the voltage hysteresis and energy dissipation due to stress effects.

High Linear Voltage Gain in QZNC Through Synchronizing Switching Circuits

The solar powered systems require high step-up converter for efficient energy transfer.For this,quasi-impedance network converter has been introduced.The quasi-impedance network converter(QZNC)is of two types:type-1 and type-2 configuration.Both the type-1 and type-2 QZNC configurations have drooping voltage gain profile due to presence of high switching noise.To overcome this,a new quasi-impedance network converter synchronizing the switching circuit with low frequency noise has been proposed.In this paper,the proposed QZNC con-figuration utilizes the current controlling diode to prevent the output voltage drop.Thus,the suggested topology provides linear high voltage gain profile,low load voltage ripple,and reduced impedance network stress and device stress.There-fore,the efficiency of proposed QZNC has been improved.The topology descrip-tion,working principle,parameter design and comparison with traditional converters are illustrated.Andfinally,both simulation and practical results are presented to confirm the converter characteristics and performance.From the results,it has been found that the performance of the suggested topology is better as it achieves a higher efficiency of 81%and hence,it is suitable for high power applications.

Sensitivity analysis of pull-in voltage for RF MEMS switch based on modified couple stress theory

An approximate analytical model for calculating the pull-in voltage of a stepped cantilever-type radio frequency （RF） micro electro-mechanical system （MEMS） switch is developed based on the Euler-Bernoulli beam and a modified couple stress theory, and is validated by comparison with the finite element results. The sensitivity functions of the pull-in voltage to the designed parameters are derived based on the proposed model. The sensitivity investigation shows that the pull-in voltage sensitivities increase/decrease nonlinearly with the increases in the designed parameters. For the stepped cantilever beam, there exists a nonzero optimal dimensionless length ratio, where the pull-in voltage is insensitive. The optimal value of the dimensionless length ratio only depends on the dimensionless width ratio, and can be obtained by solving a nonlinear equation. The determination of the designed parameters is discussed, and some recommendations are made for the RF MEMS switch optimization.

Low voltage substrate current： a monitor for interface states generation in ultra-thin oxide n-MOSFETs under constant voltage stresses

The low voltage substrate current （Ib） has been studied based on generation kinetics and used as a monitor of interface states （Nit） generation for ultra-thin oxide n-MOSFETs under constant voltage stress. It is found that the low voltage Ib is formed by electrons tunnelling through interface states, and the variations of Ib（△Ib） are proportional to variations of Nit （△Nit）. The Nit energy distributions were determined by differentiating Nit（Vg）. The results have been compared with that measured by using gate diode technique.

Enhancing Stress Intensity Factor Reduction in Cracks Originating from a Circular Hole in a Rectangular Plate under Uniaxial Stress through Piezoelectric Actuation

Circular holes are commonly employed in engineering designs;however, they often serve as locations where cracks initiate and propagate. This paper explores a novel approach to structural repair by utilizing piezoelectric actuators. The primary focus of this study is to investigate the influence of an adhesively bonded piezoelectric actuator patch placed above a circular hole on the stress intensity factor (SIF) in an aluminium plate. The plate is subjected to uniaxial tensile stress, while the piezoelectric actuator is excited with varying voltage levels. The analysis is conducted using the finite element method (FEM), a powerful numerical technique for simulating complex structures. The study assesses the stress distribution and employs the SIF as an adequate criterion for evaluating the impact of different patch configurations. The results indicate a strong correlation between the applied voltage and the SIF. Whether the SIF increases or decreases depends on the polarization of the piezoelectric actuator. Particularly noteworthy is the finding that rectangular patches in a horizontal orientation significantly reduce the SIF compared to other patch geometries. Moreover, double-sided patches exhibit a pronounced decrease in the SIF compared to single-sided patches. In summary, this research underscores the potential of piezoelectric actuators in mitigating stress intensity in structures with circular hole with crack initiation. It offers valuable insights into the influence of applied voltage, patch geometry, and patch placement on the SIF, thereby contributing to developing effective strategies for enhancing structural integrity.

The jointing stress analysis of one-shot seal-off high-voltage vacuum interrupters

The free shrinkage of ceramic or metal is restricted due to solidification of the solder. Hence the shrinkage stress arises and the jointing strength is reduced during the brazing of high-voltage vacuum interrupters （HVVIs）. The solder bound contour was gained by solved energy bound equation. The finite element model of weld beads was established with Surface Evolver software. Then the stress in two different cooling techniques （ natural cooling and force cooling） was calculated with ANSYS. Comparing the stress, a better cooling technique was selected for HVVIs. Its cooling time is shortened by 3 hours while the jointing stress doesn＇ t increase and the tensile strength of ceramic to metal seal is not decreased. The stress-rupture tests have validated the calculated results. More important, a method is found, by which the brazing technique could be improved in advance instead of blind experiments.

基于电应力损伤特征值的XLPE绝缘电压耐受指数评估方法研究

XLPE绝缘的电压耐受指数n表征绝缘电寿命特性,对加速寿命试验中获取的失效数据进行分析可以获取n值,然而,加速寿命试验中的外施场强与试验所获失效数据的分析方法影响n值的准确性。本文研究电压耐受指数n的评估方法,对XLPE绝缘试样分别进行恒定应力试验与步进应力试验,提出基于损伤特征值的试验数据分析方法,该方法通过损伤矩阵建立试验中累积损伤阈值(Dc)与n的映射关系,以矩阵秩的变化作为n值的选取依据。结果表明:本文所提方法在恒定应力试验中获取的XLPE绝缘电压耐受指数n2=12.43,在步进应力试验中获取的XLPE绝缘电压耐受指数n3=12.04,较线性拟合获取的XLPE绝缘电压耐受指数n1=12.83仅相差3%与6%,且本文所提方法能够节省75%以上的试验时间,验证了该方法的有效性。

基于DAB的蓄电池最小电流应力控制策略研究

双有源桥(DAB)变换器是一种适用于蓄电池充电的双向DC/DC变换器。为减小蓄电池充电过程中的功率损耗并提高传输效率,提出了双重移相(DPS)最小电流应力控制策略,分析DAB变换器全部开关管的零电压开通(ZVS)的电感电流约束条件,求解得到ZVS区域内电流应力最小时的移相比组合,能够减小蓄电池的充电损耗,提高充电效率,并通过理论对比验证了优化效果。仿真与实验结果均表明,所提优化策略可以实现开关管ZVS以及最小电流应力,从而减小损耗,提高变换器的性能。

新型高增益耦合电感二次型变换器

将开关-耦合电感单元引入二次型变换器,采用一个耦合电感和两个独立电感,在开关管关断时,电感为电容充电;导通时,利用电容为负载供电。与传统变换器相比,所提出的变换器采用更少的器件,能得到高电压增益效果与低占空比。采用了降低电压应力的电容,二极管和半导体开关,开关管应力更低。提出了稳态和比较性能分析,制作了一台140W实验平台,给出实验数据与结论,验证了理论分析的正确性。

基于SEPIC的新型高增益DC-DC变换器及衍生拓扑分析

针对光伏并网系统中单开关升压变换器(如SEPIC、Boost、准Z源、二次型)电压增益低和半导体器件电压应力大的问题,提出1种基于SEPIC的外部升压型高增益DC-DC变换器。首先对所提变换器在电感电流连续导通模式和断续导通模式下的工作原理和稳态特性进行详细分析,并与其他新型拓扑进行性能对比。在此基础上,给出了基于外部升压网络的衍生拓扑。最后,通过搭建1台400 V/200 W的实验样机证明了理论分析的准确性。所提变换器利用阻抗网络和开关电容单元构成的外部升压网络提升了SEPIC变换器的电压增益,并改善了半导体器件电压应力大的缺点。

高轻载效率少功率器件的可模块化扩展ZVS高增益变换器

提出一种高轻载效率且少功率器件的可模块化扩展零电压开关高增益Boost变换器。该变换器可以通过增加升压模块数量n,极大地提高变换器的升压能力;具有2个开关管和n+1个二极管,且各功率管承受相同的电压应力,均为[(n+1)U_(in)+U_(o)]/(n+2);输入电感工作在连续导通模式,其余电感工作在双向导通模式,且反向峰值电流之和大于输入电感电流的谷值,从而实现所有功率管的软开关。所提变换器采用柔性开关频率控制策略,即根据输入电压和负载大小适当地调整开关频率,使电感电流脉动量维持在合适的范围内,既确保实现功率管的软开关,又具有较小的通态损耗,因此在整个负载范围内均具有较高的运行效率。以一个扩展模块为例,对所提变换器的工作原理、稳态特性、软开关条件、控制方法进行深入分析,并通过一台250 W的样机实验验证了理论分析的正确性。

少开关低电压应力电流连续且共地的高增益Buck/Boost变换器

传统Buck/Boost双向直流变换器的升压能力较弱,且开关管承受较高的电压应力(等于高压侧电压),导致变换效率较低,同时高压侧电流存在较大的脉动,电容电流应力较大,需要增大滤波电容,降低了可靠性。文章提出了一种改进的Buck/Boost双向变换器,其在传统拓扑的基础上增加了一个开关管、一个电感和两个电容,实现了连续的输入输出电流特性,减小了高压侧电容的电流应力。此外,Boost模式下的电压增益被提升,且所有开关管的电压应力均降低为高压侧和低压侧电压的差值,从而改善了变换效率。文章详细分析了所提双向变换器的工作原理、稳态特性、控制策略,建立了小信号数学模型,并通过一台100 W/120 kHz的样机验证了其可行性。实验结果表明,其在宽工作范围内均具有较高的效率,且最高效率达到95.6%。

等离子冲击波作用下红砂岩的动态破裂行为试验与数值模拟研究

为了研究等离子冲击波作用下岩石的破裂行为,开展了不同放电间距下的高压脉冲击穿红砂岩试验。利用超高速相机观测了红砂岩试件的裂纹扩展过程,讨论了放电间距对等离子冲击波作用下红砂岩试样表面裂纹密度的影响。随后,利用数值模拟软件LS-DYNA建立与实验条件一致的有限元模型,对比了模拟和实验结果,再现了试验过程。结果表明:等离子冲击波作用下,垂直放电通道方向的两个表面上的破坏主要是径向裂纹;平行放电通道的四个侧面则是横向裂纹占主导。随着放电间距的增大,试件表面的裂纹密度逐渐增大。依据数值模拟结果对试件内部的破裂过程及应力波的衰减进行了分析。结果表明:随着放电间距的增加,等离子冲击波在红砂岩试样内部形成的有效应力呈现出指数型衰减,在自由面附近有效应力峰值趋于稳定。

双有源桥串联谐振变换器的暂态过程与控制

基于移相控制的双有源桥串联谐振变换器(dual-bridge series resonant converter,DBSRC)在传输功率的快速调控过程中,移相角将发生较大的阶跃变化,导致谐振腔出现大幅度长时间的振荡过程,不仅严重恶化了变换器的动态性能,电路元件也会面临严重的过电压和过电流风险。该文首先基于基波分析法推导DBSRC暂态过程的通用计算模型,分析暂态过程中的振荡特性,精确估算暂态过程中的谐振电压峰值、谐振电流峰值以及暂态过渡时间,评估暂态过程中的过电压与过电流程度。基于暂态过程计算模型,提出一种振荡的抑制方法,使变换器在一个开关周期后能够到达新的稳定状态,有效地避免了过电压与过电流的风险,并且大幅改善了闭环控制的动态特性。最后,通过仿真与实验结果验证理论分析和所提出的控制方法。

大功率高频变压器绝缘问题研究综述

高频变压器是电力电子变换系统中负责电气隔离和电压变换的关键器件。大功率高频变压器紧凑化的结构使其复合绝缘或浇注绝缘承受严苛的电、热和机械应力,给绝缘设计带来很大挑战。该文首先回顾了高频变压器的应用背景和结构形式,然后分析了高频变压器主绝缘和纵绝缘承受的电压应力,指出变压器局部介电损耗的问题,从优化设计的角度表明了功率密度与绝缘可靠性之间的矛盾,并阐明了高频变压器绝缘承受机械应力。提取了近年来高频变压器样机的绝缘设计中常用的绝缘材料、绝缘形式、绝缘等级,分析了绝缘设计对变压器体积、电场分布及寄生参数等的影响,提出绝缘设计流程的改进方向。高频电压下聚合物绝缘的介电损耗、局部放电和空间电荷特性是目前相关研究的关注重点,而这些因素之间通常互相耦合。分析归纳了高频方波波形参数和温度等条件对局部放电、绝缘寿命、空间电荷和电树枝发展规律的影响,指出研究领域的空白。最后,对高频变压器应力特点、绝缘设计和绝缘问题研究现状进行了总结。

一种基于开关电容的十三电平逆变器

针对现有多电平逆变器拓扑体积大、成本高和结构复杂的问题,文中提出一种基于开关电容的十三电平逆变器。所提拓扑由1个直流输入电源、3个电容器及14个开关器件组成,可实现6倍升压的十三电平输出,在具有较低成本和较小体积的同时减少了系统输出谐波的含量,且无需H桥即可实现逆变即可降低开关管的电压应力。所提逆变器无需任何辅助方法就能实现电容电压自平衡,简化控制的复杂度。文中通过与其他传统多电平逆变器的对比分析,验证了所提拓扑的优越性。仿真和样机平台的实验结果证明所提逆变器在稳态和动态情况下均具有良好的性能。

新型电压自均衡开关电容多电平逆变器

为了使用更少的器件实现更多的输出电平,同时解决传统多电平逆变器开关器件在高电压下工作时,其电压应力较大,容易损坏的问题,提出一种新型单电源开关电容多电平逆变器拓扑。该开关电容逆变器拓扑通过研究开关电容技术与级联H桥逆变器的结合,采用脉宽调制的方式经过逻辑组合进行调制,实现了高效的电压增益和电平输出。在保证电容电压自均衡的前提下,仅使用单个直流电源输入,产生三倍电压增益的七电平输出。然后,为了进一步拓展该逆变器的应用范围,介绍所提逆变器的扩展结构,并简要分析其工作模式。同时与其他类似拓扑进行对比,证明该拓扑优势。最后为了验证理论分析的正确性,设计了仿真和实验样机,对逆变器的性能进行了详细测试。

一种两级式宽范围输入的高位取能电源设计

介绍了一种用于模块化多电平换流器(Modular Multilevel Converter,MMC)的宽范围输入高位取能电源设计方法,根据电源高电压、宽范围输入和多路小功率输出的特点,电源采用两级式结构。第一级源变换器采用输入串联输出并联(Input-Series Output-Parallel,ISOP)的反激拓扑,主要实现降压功能;第二级负载变换器采用三路单独的反激电路,保证精准调压。在此基础上,设计了一台输入电压DC 400~3 500 V、输出电压DC 15 V/15 V/400 V的高位取能电源样机。通过最高输入电压下开关管源漏极电压波形和不同负载下输出电压波形,证明了该设计方案可在宽输入范围内可靠运行,有效地减小了单个开关管所承受的电压应力并且具有优良的带载性能。

基于恒流源的增强型GaN动态导通电阻特性研究

动态导通电阻现象会导致GaN器件导通电阻增加,不仅会增大器件通态损耗,还会使器件温升更加显著,是限制GaN器件在高频度变换器中应用的重要因素之一。针对该现象,设计一种基于高速脉冲恒流源的动态导通电阻测试平台,并利用该平台分析了两款不同电压等级器件的导通电阻对断态电压应力、断态电压持续时间以及环境温度的影响。研究结果表明:当断态电压应力增大到两款器件各自额定电压的60%,两款器件的导通电阻分别较各自的标称值变化了15%和25%;断态电压持续时间增至100 s,两款器件的导通电阻分别较各自标称值变化了40%和81%;随着环境温度增大到125℃,两款器件的导通电阻分别较各自的标称值变化了102%和105%。GaN器件动态导通电阻现象较为显著,因此有必要在设计变换器时慎重地考虑GaN器件的工况,以保证在符合系统指标的前提下降低动态导通电阻的影响,从而提高GaN器件的效率。