基于V2-OCC的BUCK变换器的斜坡补偿控制研究

针对BUCK变换器的电压模式控制中,电力电子开关工作在大占空比下不稳定,易引起次谐波振荡,提出了一种基于V2-OCC的BUCK变换器斜坡补偿控制方法。增加斜坡补偿环节,在电流内环引入基于负载前馈的纹波补偿,通过匹配控制参量参数达到稳态无差调节。通过对输出电压进行补偿设计,不仅提高了系统的带载能力,同时也提高了系统的鲁棒性与稳态精确性。为验证所设计控制器的性能,在Matlab/Simulink里搭建仿真模型,并将控制效果与传统PID控制以及V2-OCC控制效果相比较,仿真结果表明引入斜坡补偿环节的控制方法具有更强的鲁棒性与带载能力。     

基于最优效率的双有源桥变换器参数设计优化方法

V2G作为一种新的分布式储能模式,能够有效参与电网的负荷平抑、峰谷调节,位置灵活且易于产生巨大的经济效益。双有源桥变换器是V2G中重要的组成部分,具有良好的电气隔离、电能变换能力。然而,在V2G这种功率双向、输出电压范围宽、恒功范围宽的工作场合,双有源桥变换器的设计成为了一大难题。提出一种基于最优效率的双有源桥变换器参数设计优化方法,能够综合频率、器件、功率、磁性器件、控制方法、输出电压范围、输入输出电压匹配关系等优化参数,设计出最优效率的双有源桥变换器。     

测试稿件

为筛选NaCl胁迫对葡萄影响的主要指评价指标。     

一种Buck变换器输出电容故障在线预测方法

提出一种基于特征参数退化的Buck变换器输出电容故障在线预测方法。首先,分析输出电容的失效机理,选取反映电容退化规律的等效串联电阻(ESR)RESR和电容值(C)为退化特征参数。然后,根据Buck连续导通模式,提出一种新的利用输出电压纹波分量计算特征参数ESR值RESR和C的在线提取方法,该方法可高效无电流传感器实现ESR值RESR和电容C在线监测。最后,利用特征参数ESR值RESR和C的时间序列,采用最小二乘支持向量机、BP神经网络和灰色模型实现Buck变换器输出电容故障值预测。仿真实例及试验验证该方法的有效性和准确性。     

串联补偿式电力节电器的研制

设计一电力节电器,由双向交流BUCK斩波器与变压器串联组成。该串联型的电力变换器采用ATmega128来产生PWM开关信号和完成整个电路的电压闭环智能控制;新颖的PWM开关驱动方式使得此节电器可适用于任何负载,且节电效果明显。实验结果表明此节电器的节电率可达30%。     

基于电动汽车V2G技术的多端口集成车载变换器研究

双向功率变换器是实现电动汽车V2G(Vehicle to grid)技术的关键性设备。引入集成技术,利用共享车载驱动电机和驱动电力电子变换装置,提出一种新的集成式双向车载功率变换器。它既可以将电动汽车蓄电池能量回馈给电网,又可完成蓄电池充电功能。集成式功率变换器具有单相、三相充/放电接口,实现了一机多口,增强了车载系统的紧凑性。分析不同充/放电模式下的集成功率变换器拓扑,给出了充/放电模式下的控制策略。最后,给出了仿真和试验结果,验证了多端口集成车载功率变换器的可行性。     

通风空调系统分步带载控制策略的优化

介绍了田湾核电站柴油机带载控制策略的现状。通过排查一期通风空调系统柴油机带载中发生通风设备失控,造成试验失败的原因是接口设计不匹配,尤其是驱动模块的设计和设备驱动回路的供电设计问题;通过采取修改仪控逻辑、优化通风空调系统分步带载控制策略等措施,弥补了控制柜供电电源当初设计的不足。建议分布式控制系统成套商加强与设计院的技术交流,充分发挥分布式控制系统的强大功能。     

以SCADA系统为基础的变电站无功电压闭环优化控制

随着无人值班变电站的不断增加,变电站综合自动化系统也在不断完善,功能亦不断强大.为了实现全电网的无功优化控制,提高系统运行的可靠性和经济性,最好的无功控制方式为集中式控制,即调度中心对各个变电站的变压器的分接头和无功补偿设备进行统一的控制.     

基于Kisssoft的V带传动的设计

KISSSOFT是一款用于机械传动设计分析的软件,计算操作过程简便,计算结果精确。文中借助其V带设计专家系统对V带传动进行参数设计和传动准确性进行校核,重点介绍了该系统参数化设计的过程,进而提高产品的开发效率。     

V型双缸发动机惯性力测试及其调整方法研究

在分析V型双缸发动机惯性力数学模型的基础上,研究了理论惯性力曲线“力椭圆”和实验惯性力曲线“力八字”的关系,研究了曲柄连杆机构的合成旋转质量的位置及与往复质量的比值这两个重要的设计参数与一次最大惯性力、主趋角、不平衡率的变化关系,讨论了V型双缸发动机惯性力参数选择依据,提出了惯性力参数的实验校正算法。     

Energy-efficient conversion of propane to propylene and ethylene over a V2O5/CeO2/SA5205 catalyst in the presence of limited oxygen

Oxidative conversion of propane to propylene and ethylene over a V₂O₅/CeO₂/SA5205 (V:Ce=1:1) catalyst, with or without steam and limited O₂, has been studied at different temperatures (700–850 °C), C₃H₈/O₂ ratio (4.0), H₂O/C₃H₈ ratio (0.5) and space velocity (3000 cm³ g⁻¹ h⁻¹). The propane conversion, selectivity for propylene and net heat of reaction (ΔHr) are strongly influenced by the reaction temperature and presence of steam in the reactant feed. In the presence of steam and limited O₂, the process involves a coupling of endothermic thermal cracking and exothermic oxidative conversion reactions of propane which occur simultaneously. Because of the coupling of exothermic and endothermic reactions, the process operates in an energy-efficient and safe manner. The net heat of reaction can be controlled by the reaction temperature and concentration of O₂. The process exothermicity is found to be reduced drastically with increasing temperature. Due to the addition of steam in the feed, no coke formation was observed in the process.     

Hydrothermal synthesis of SnO2–V2O5 mixed oxide and electrochemical screening of carbon nano-tubes (CNT), V2O5, V2O5–CNT,and SnO2–V2O5–CNT electrodes for supercapacitor applications

Nano-scaled SnO₂–V₂O₅ mixed oxide is synthesized by a hydrothermal method in an autoclave. For comparative evaluation, V₂O₅ single oxide is prepared by a conventional process from ammonium vanadate. The capacitive behaviour of the following electrodes is studied by cyclic voltammetry in 0.1 M KCl solutions: carbon nano-tubes (CNT), V₂O₅, V₂O₅–CNT, and SnO₂–V₂O₅–CNT. At a scan rate of 100 mV s⁻¹, the SnO₂–V₂O₅–CNT electrode provides the best performance, viz., 121.4 F g⁻¹. The nano-scaled mixed oxide is characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Raman spectra.     

Ion beam sputter deposition of V2O5 thin films

V₂O₅ thin films were deposited by means of dc-ion beam sputtering. To determine the influence of various deposition parameters, samples were characterized by X-ray diffractometry and transmission electron microscopy. Using electron energy loss spectroscopy, the oxidation state of vanadium was quantified based on the chemical shift of absorption edges. Measurement of in-plane direct current showed that the electronic conductivity varies over several orders of magnitude depending on the preparation conditions. The desired structure suitable for battery applications is achieved by sputtering under partial pressure of oxygen and suitable post-annealing under ambient atmosphere. Reversible intercalation of Li into the produced thin films was demonstrated.     

Studies on dehydrogenation characteristic of Mg(NH2)2/LiH mixture admixed with vanadium and vanadium based catalysts (V,V2O5 and VCl3)

In the present study, we have investigated the effect of vanadium and its compounds (V, V₂O₅ and VCl₃) on desorption characteristics of 1:2 magnesium amide (Mg(NH₂)₂) and lithium hydride (LiH) mixture. The hydrogen storage characteristics of 1:2 Mg(NH₂)₂/LiH mixture gets enhanced with admixing of V, V₂O₅ and VCl₃ separately. The VCl₃ has been found to be the most effective followed by V and V₂O₅. The activation energy for dehydrogenation process of 1:2 Mg(NH₂)₂/LiH mixture with and without catalyst has been evaluated using a method suggested by Ozawa et al. [25]. Based on the experimental results, schematic reaction scheme for decomposition of Mg(NH₂)₂ in the presence of VCl₃ has also been proposed.     

Direct synthesis of nanostructured V2O5 films using solution plasma spray approach for lithium battery applications

We demonstrate for the first time, the synthesis of vanadium pentoxide (V₂O₅) nanoparticles and nanorods in the films using a high throughput solution plasma spray deposition approach. The scalable plasma spray method enables the direct deposition of large area nanostructured films of V₂O₅ with controllable particle size and morphology. In this approach, the solution precursors (vanadium oxychloride and ammonium metavanadate) were injected externally into the plasma jet, which atomizes and pyrolyzes the precursors in-flight, resulting in the desired films on the current collectors. The microstructure analysis of the as synthesized films revealed pure nanocrystalline phase for V₂O₅ with particles in the size range of 20-50 nm. The V₂O₅ film based electrodes showed stable reversible discharge capacity in the range of 200-250 mAh g⁻¹ when cycled in the voltage window 2-4 V. We further discuss the mechanism for controlling the particle growth and morphology, and also the optimization of reversible lithium storage capacity. The nanorods of V₂O₅ formed after the anneal treatment also show reversible storage capacity indicative of the potential use of such film based electrodes for energy storage.     

Preparation and properties of V2O5 thin films for energy-efficient selective-surface applications

Thin V₂O₅ films have been prepared by thermal evaporation onto glass substrates at a pressure of about 1.99×10⁻³ Pa. The temperature dependence of electrical measurements exhibits an anomaly in resistivity at a temperature around 329 K. Temperature co-efficient of resistance (TCR) studies show positive values, so indicating semi-metallic behaviour up to a temperature of 363 K and the negative thereafter so indicating semi-conducting behaviour. Thickness-dependent resistivity measurement follows the Fuchs-Sordheimer size-effect theory. X-ray diffraction studies show that the material is amorphous. Optical studies show the material is highly transparent both in the visible and infrared regions. The integrated value of T_lum and T_sol is high, so indicating that the material is a potential candidate for selective surface applications.     

Effect of dry/wet-phase inversion method on fabricating polyetherimide-derived CMS membrane for H2/N2 separation

The research investigated carbon molecular sieve (CMS) membranes through the dry/wet-phase inversion method from the casting polyetherimide (PEI) on alumina support for hydrogen separation. Different coating techniques such as dry method (slide casting followed by drying under vacuum; and spin coating followed by drying under vacuum); and wet method (spin coating and then later kept in an isopropyl alcohol (IPA)/water coagulating bath) at different pyrolysis temperatures of 550, 600, 650 °C min⁻¹ were also investigated.     

n-Si/SnO2 junctions based on macroporous silicon for photoconversion

For the first time it is demonstrated that a photovoltaic junction can be formed by spraying a thin, transparent, conductive SnO₂ layer onto macroporous n-type silicon produced by photoelectrochemical etching. With a macropore density of 10⁷ cm⁻², and an average pore diameter in the range 1–2 μm, the cell reflectivity spectrum is flat and drops to a few percent in the visible and near infrared spectral range. EDX analysis and impedance measurements show that charge separation and current collection occur in the upper part of the pores and in the interpore region, whereas the bottom of the pores only acts as a photon absorber. The active junction area is found to be four times larger than with a mirror-polished substrate. A solar cell equipped with just a front ring contact was realized, which attains a solar conversion efficiency of 10% under AM 1.5 conditions.     

石墨烯包封Na3V2(PO4)3用作钠离子电池负极材料的电化学性能探究

具有三维网络结构的NASICON型Na₃V₂(PO₄)₃材料,由于其稳定的电压平台,较高的理论容量(117 mA·h/g),被视为一种具有良好应用前景的钠离子电池负极材料。采用溶剂热和进一步热处理的方式,获得石墨烯包封Na₃V₂(PO₄)₃的复合材料[Na₃V₂(PO₄)₃/G],有效提高了Na₃V₂(PO₄)₃的电子导电性。在0.01～3.00 V电压区间,0.2 C倍率进行测试时,Na₃V₂(PO₄)₃/G复合材料在230圈循环后,其放电比容量保持在100.9 mA·h/g,容量保持率高达68.4%,即使在5 C倍率,其放电比容量仍可达65.2 mA...