大型风电机组机组层AGC控制策略研究

针对传统控制策略下的风电机组输出波动性大、随机性强,需其他设备协调风电场出力的缺点,提出一种机组层WT-AGC控制策略,并对该控制策略的工作原理进行了详细的分析。在考虑风电机组运行状态及风电场调度要求的基础上,将WT-AGC策略下机组运行方式分为2种:调度指令高于机组最大出力能力的常规运行和调度指令低于机组最大出力能力的限功率运行。通过风电机组转速调节和变桨距机构动作配合,实现风电机组输出稳定,满足风电场调度要求,并对某实际双馈风电机组进行了仿真。结果表明该控制策略不但可以实现风电机组的可调度输出,而且提高风电机组并网后的功率稳定性,验证了所提策略的正确性。

风力机叶片翼型型线集成设计理论研究

在叶片翼型设计过程中,提出了翼型型线的集成设计理论和方法,阐述了保角变换理论及其在翼型设计过程中的应用,引入了级数思想,推导出了能够广泛应用的翼型集成表达式,构造出了三种典型的翼型曲线,最后对常用的两种翼型进行了集成表达,并比较分析了级数项对翼型形状的影响,验证了函数表达方程的集成性和通用性。该研究突破了现有翼型数学模型固有特性的限制,提出的函数集成表达方式能够表征翼型的本质特征,为风力机叶片翼型的优化设计理论与方法研究拓宽了思路。

基于CFD和NCPSO的复杂地形风电场微观选址优化

针对复杂地形条件下风电场微观选址技术难度大的问题,提出一种基于数值计算结果和高效优化方法的微观选址优化算法。将测风数据按风向等分成12个扇区,并利用平均风速和CFD对复杂地形的每个扇区进行数值模拟,得到风电场各扇区的风资源分布,提取轮毂高度处的风速和风向分布。优化中风力机的尾流影响采用Jensen尾流模型,风电场风能计算中风速按照威布尔分布处理,并考虑每个扇区风速的大小、概率密度。目标函数为整个风电场的输出功率倒数的对数,自变量为风力机在给定风电场中的位置坐标,约束条件为地形边界和风力机之间的最小距离,优化算法采用该文提出的改进小生境粒子群算法(NCPSO),优化风力机组微观选址的最优解。该文提出优化算法得到的结果与基于高度的经验布置方法(EX-TH)、基于风能密度的经验布置方法(EX-PH)以及普通粒子群算法(PSO)进行比较,证明在复杂地形条件下所提出方法的可靠性与有效性,并可应用于工程实践。

复杂地形风电场一体化优化设计研究

针对现阶段复杂地形风电场微观选址以及风力机布置等的密切关系,以风力机布置更加合理、上网电量更多、投资更加节省为目标,简要分析影响复杂地形风电场设计的主要因素,建立微观选址、集电线路、检修道路设计等一体化的优化问题数学模型,依托风电场区域内已有的1 a测风资料,运用遗传算法进行微观选址的优化,在风力机机位优化的基础上进一步利用单源最短路径算法、最小生成树算法等优化算法对集电线路和检修道路进行优化。实践表明,该文的研究结果可为实际的风电场建设前期工作提供重要的过程指导。

Asphaltenes: Separations, structural analysis and applications

Asphaltenes, complex aromatic compounds from various carbonaceous sources, could be obtained by solvent dissolution, filtration and adsorption. It was difficult to clarify the molecular structures and chemical properties of asphaltene due to its structural similarity, composition complexity and source dependences. Many techniques, like Mass spectrometry, Chromatography, Nuclear magnetic resonance spectroscopy, Infrared spectroscopy, Roman spectroscopy, Fluorescence spectroscopy, X-ray diffraction analysis and Small-angle scattering techniques and so on, have revealed some valuable descriptions of asphaltenes chemical compositions and fundamental structures. Moreover, advanced Mass spectrometry,Atomic force microscopy and Scanning tunneling microscopy could provide more clear and essential molecular compounds and structures in asphaltenes. In addition, several asphaltenes models have succeeded to illustrate aggregation properties asphaltene. In this work, the progress on asphaltene separation, characterization and application was summarized, and the similarities and differences between coal-derived asphaltenes and petroleum asphaltenes were compared. Furthermore, the reactivity of asphaltenes has been discussed in the aspect of hydroprocessing, pyrolysis and gasification. Asphaltene was excellent carbon precursor for functional carbon material due to its high aromaticity and carbon yield;several porous carbon nanosheets from asphaltenes that would be prospective electrode materials after being graphitized were shown. Pitch-based carbon fiber derived from coal-derived asphaltenes displayed a tensile strength of 1.0 GPa and elastic modulus of 350 MPa, respectively. These powerful advances will provide asphaltenes promising developments.

A Facile Self-assembly Synthesis of Hexagonal ZnO Nanosheet Films and Their Photoelectrochemical Properties

Here, large-scale and uniform hexagonal zinc oxide(ZnO) nanosheet films were deposited onto indium tin oxide(ITO)-coated transparent conducting glass substrates via a facile galvanic displacement deposition process. Compared with other commonly used solution methods, this process avoids high temperature and electric power as well as supporting agents to make it simple and cost-effective. The as-fabricated ZnO nanosheet films have uniform hexagonal wurtzite structure. The photoelectrochemical(PEC) cell based on ZnO nanosheet film/ITO photoelectrode was also fabricated and its performance was improved by optimizing the solution concentration. A higher photocurrent density of*500 l A cm^(-2)under AM 1.5 G simulated illumination of 100 m W cm^(-2)with zero bias potential(vs. Ag/AgCl electrode) was obtained, which may ascribe to the increased surface-to-volume ratio of disordered Zn O nanosheet arrays. Our developed method may be used to deposit other oxide semiconductors, and the Zn O nanosheet film/ITO PEC cell can be used to design low-cost optoelectronic and photoelectrochemical devices.

Fast Growth of Highly Ordered TiO2 Nanotube Arrays on Si Substrate under High-Field Anodization

Highly ordered TiO_2 nanotube arrays(NTAs) on Si substrate possess broad applications due to its high surfaceto-volume ratio and novel functionalities, however, there are still some challenges on facile synthesis. Here, we report a simple and cost-effective high-field(90–180V) anodization method to grow highly ordered TiO_2 NTAs on Si substrate,and investigate the effect of anodization time, voltage, and fluoride content on the formation of TiO_2 NTAs. The current density–time curves, recorded during anodization processes, can be used to determine the optimum anodization time. It is found that the growth rate of TiO_2 NTAs is improved significantly under high field, which is nearly 8 times faster than that under low fields(40–60 V). The length and growth rate of the nanotubes are further increased with the increase of fluoride content in the electrolyte.

Identification of nitrogen-polyaromatic compounds in asphaltene from co-processing of coal and petroleum residue using chromatography with mass spectrometry

Abstract Asphaltene, from co-processing of coal and petroleum residues is one of the most precious and complex molecular mixtures existing, with tremendous economic relevance. Asphaltene was separated by Soxhlet extraction with methylbenzene and then divided into three parts by distillation. Gas chromatography （GC） and high-performance liquid chromatography （HPLC） were coupled with quadrupole time-of-flight mass spectrometry （Q-TOF MS） to separate and characterize organic nitrogen species in the distillates of asphaltene at molecular level. Molecular mass of compounds was mainly distributed from 150 to 600 ~t. Number of rings plus double bonds （rdb） and synchronous fluorescence spectra indicated that most of the organonitrogen compounds （NPAC） contained heterocyclic aromatic rings, including pyridines, anilines, quinolins, pyrroles, carbazoles and indoles plus various alkyl groups. Constant-wavelength synchronous fluo- rescence spectrometry （CWSFS） indicated NPAC with 2-3 rings were the main structures of organonitrogen compounds and the corresponding structural information was proposed. Some organic nitrogen isomers were separated and identified by atmospheric pressure chemical ionization （APCI） GC-Q-TOF MS and electrospray ionization （ESI） HPLC-Q-TOF MS. The methodology applied here contained chromatographic injection of the diluted sample using conventional columns sets and Data Analysis 4.2 software. Identifying molecular structures provides a foundation to understand all aspects of coal- derived asphaltene, enabling a first-principles approach to optimize resource utilization.

Airfoil Trailing Edge Noise Generation and Its Surface Pressure Fluctuation

In the present work, Large Eddy Simulation (LES) of turbulent flows over a NACA 0015 airfoil is performed. The purpose of such numerical study is to relate the aerodynamic surface pressure with the noise generation. The results from LES are validated against detailed surface pressure measurements where the time history pressure data are recorded by the surface pressure microphones. After the flow-field is stabilized, the generated noise from the airfoil Trailing Edge (TE) is predicted using the acoustic analogy solver, where the results from LES are the input. It is found that there is a strong relation between TE noise and the aerodynamic pressure. The results of power spectrum density show that the fluctuation of aerodynamic pressure is responsible for noise generation.

A method of convolutional neural network based on frequency segmentation for monitoring the state of wind turbine blades

Wind turbine blades are prone to failure due to high tip speed,rain,dust and so on.A surface condition detecting approach based on wind turbine blade aerodynamic noise is proposed.On the experimental measurement data,variational mode decomposition filtering and Mel spectrogram drawing are conducted first.The Mel spectrogram is divided into two halves based on frequency characteristics and then sent into the convolutional neural network.Gaussian white noise is superimposed on the original signal and the output results are assessed based on score coefficients,considering the complexity of the real environment.The surfaces of Wind turbine blades are classified into four types:standard,attachments,polishing,and serrated trailing edge.The proposed method is evaluated and the detection accuracy in complicated background conditions is found to be 99.59%.In addition to support the differentiation of trained models,utilizing proper score coefficients also permit the screening of unknown types.

大气稳定度对山地风力机功率影响研究

大气稳定度对风力机功率影响较为显著,但该影响在复杂地形中的研究尚不深入。本文通过分析某一山地风电场运行数据和流场测量数据,定量研究了大气稳定度通过风加速因子、湍流强度和风切变指数对风力机功率的影响。受地形影响,风力机来流风速不能直接按上游测风塔轮毂高度风速处理,使用机舱风速根据机舱风速传递函数推算。研究表明,非中性与中性条件下的风加速因子的差值与中性条件下地形效应正相关,且由风加速因子不同造成的来流风速每改变1%可引起功率改变3%。对于同一来流风速,中性时的功率最大,稳定条件时功率略微降低,而在不稳定条件下功率降低显著可达到8%。这一差异可能与风力机最大功率追踪的控制系统参数按中性条件设置相关。

Highlights of mainstream solar cell efficiencies in 2023

This article continues our highlights last two years[1,2]on the highest independently confirmed mainstream(silicon,perovskite,and organic)solar cell efficiencies in 2023.The world record power conversion efficiency(PCE)of the single-junction silicon and perovskite/silicon tandem solar cells has reached over 27%and close to 34%,respectively,in 2023.We have also witnessed the rapid mass-production development of the silicon passivating contact and silicon back contact solar cells,as well as further progress with perovskite solar cells(PSCs).

基于风轮平均风速的风电场致动盘模型

针对风电场空气动力学计算中致动盘模型参考风速难以确定的问题,本文提出了一种根据风轮平均风速计算致动盘动量源项的方法。该模型使用体积修正因子对致动盘区域动量源项进行修正,降低致动盘区域网格辨识误差对模拟的影响;结合拓展k-ε湍流模型,改进ε源项参数的分布规律,提高模型对于风电场尾流模拟可靠性。Nibe-B风力机和Homs I近海风场的尾流计算结果表明所提出的模型能够较为准确地模拟风电场空气动力场分布。

基于致动面模型的风力机尾流数值研究

致动面模型利用无厚度的平面代替风力机叶片,在平面上施加不连续压力来模拟叶片对气流的作用,结合N-S方程,在FLUENT中进行数值模拟计算,是对致动线方法的延伸与改进。运用该方法能够简化风力机的模型,从而减少网格数量和计算时间。采用线性分布下的致动面模型,提出一种致动面网格的辨识方法,对单台Nibe A型风力机的远近尾流区域进行模拟计算,包括尾流风速变化,湍流强度,涡结构,并将数值模拟的结果与致动线模型计算结果以及实验数据进行对比分析,主要是风轮后特定距离截面的风速变化,验证了致动面方法的优越性以及用于风力机尾流场计算的可行性。

Type-ll Metacaspases Mediate the processing of Plant Elicitor Peptides in Arabidopsis

Plants can produce animal cytokine-like immune peptides,among which plant elicitor peptides(Peps)derive from the C termini of their precursors(PROPEPs).Recently,the functions of Peps have been expanded beyond plant immunity.However,a long-standing enigma is how PROPEPs are processed into Peps.Here,we report that the Ca2+-dependent type-ll metacaspases(MCs)constitute the proteolytic enzymes to mediate PROPEP processing in Arabidopsis.In protoplasts,co-expression of PROPEP1 with type-ll MCs,including MC4 to MC9,can promote the generation of processed Pep1.Destruction of the catalytic cysteine residue in MC4 or the conserved arginine residue preceding the Pep1 sequence blocks PROPEP1 cleavage,whereas the bacterial elicitor flg22 enhances the MC4-mediated PROPEP1 processing.MC4 cleaves PROPEP1 in vitro and also cleaves PROPEP2 to PROPEP8,but,surprisingly,not PROPEP6 in protoplasts.Domain swapping between PROPEP1 and PROPEP6 suggests a hidden role of the sequence context upstream of the Pep sequence for PROPEP processing.flg22-induced PROPEP1 processing and B otrytis cinerea resistance are severely impaired in the m c4/5/6/7 quadruple-mutant plants.Taken together,our study identifies the type-ll MCs as new players in Pep signaling,and lays the foundation for understanding the regulation of multifaceted functions of Peps in plant immunity and beyond.

Highlights of mainstream solar cell efficiencies in 2021

Solar photovoltaic(PV)technology is expected to play a key role in global carbon neutrality.The global new installed solar PV capacity over the past 20 years has grown at a compound annual growth rate of approximately 40%,far outpacing other energy sources such as coal,oil,natural gas,and wind[1].The strong momentum of the PV industry comes from its rapidly decreased levelized cost of electricity due to technological improvement and large-scale application.

Nitrogen slow-release behavior of oxamide granules in two different types of paddy soils

Oxamide is a potential slow-release nitrogen(N)fertilizer,especially under waterlogged conditions,due to its low solubility in water and the slow-release of ammonium by soil amidases.To investigate the effects of oxamide granules(2.00-2.38 mm in diameter)as a single basal fertilizer(180 or 144 kg N ha^(-1))on rice growth,soil properties,and N use efficiency in terms of N recovery efficiency(NRE),we conducted field experiments on two different types of paddy soils over two rice-growing seasons.Results showed that the fertilization effects of oxamide granules varied between the two types of paddy soils.In the red clayey paddy soil,the grain yields for both rice-growing seasons were high with a significantly higher NRE in the oxamide treatment than in the urea treatment.However,in the alluvial sandy paddy soil,the grain yields in the oxamide treatment were slightly lower than those in the urea treatment.Furthermore,oxamide produced little improvement in NRE in the alluvial sandy paddy soil.Soil incubation experiments over 98 d were also carried out to evaluate the factors affecting the N release behavior of oxamide granules in the two types of paddy soils.We found that the amidase activity was higher and,therefore,the oxamide hydrolysis rate was faster in the alluvial sandy paddy soil,which had a higher soil pH value and organic matter content,compared to the red clayey paddy soil.The faster N release and the longer growth period resulted in a mismatch between N supply by oxamide and rice demand,which,in turn,led to little improvement in NRE and a decreased grain yield in the alluvial sandy paddy soil,especially in the reduced oxamide treatment.These results could help select the appropriate size of oxamide granules for use as a slow-release N fertilizer depending on the soil properties and growth period of rice.

Highlights of mainstream solar cell efficiencies in 2022

The world record power conversion efficiency(PCE)of both the single-junction silicon and perovskite/silicon tandem solar cells was broken in 2022,and the massproduction of the passivating contact and perovskite solar cells(PSCs)was also significantly developed in 2022.Continuing to the first viewpoint on the highest independently confirmed PCE of mainstream and emerging solar cells in 2021[1],this paper highlights the certified PCE in 2022 of silicon,perovskite,and organic solar cells and analyzes the progress of each cell technology.

SiO2 passivation layer grown by liquid phase deposition for silicon solar cell application

Surface passivation is one of the primary requirements for high efficient silicon solar cells. Though the current existed passivation techniques are effective, expensive equipments are required. In this paper, a comprehensive understanding of the SiO2 passivation layer grown by liquid phase deposition （LPD） was presented, which was cost-effective and very simple. It was found that the post-annealing process could significantly enhance the passivation effect of the LPD SiO2 film. Besides, it was revealed that both chemical passivation and field-effect passivation mechanisms played important roles in outstanding passivation effect of the LPD SiO2 film through analyzing the minority carrier lifetime and the surface recombination velocity of n-type and p-type silicon wafers. Although the deposition parameters had little influence on the passivation effect, they affected the deposition rate. Therefore, appropriate deposition para- meters should be carefully chosen based on the compromise of the deposition rate and fabrication cost. By utilizing the LPD SiO2 film as surface passivation layer, a 19.5%-efficient silicon solar cell on a large-scale wafer （156 mm × 156 mm） was fabricated.

Monolithic perovskite/c-Si tandem solar cell:Progress on numerical simulation

Perovskite/c-Si tandem solar cell(TSC)has gradually become the hottest research topic in photovoltaic field for global carbon neutrality.Here we review the recent progress of numerical simulation studies of monolithic perovskite/c-Si TSC in terms of the methodology,light harvesting management,and energy yield aspects.It is summarized that the integration of physical fundamentals of the methodology,optimization of modeling and parameter correction can bring simulation results closer to experiments.Based on theoretical analysis of light harvesting management,we have demonstrated that textures can enhance light trapping capability and resonance absorption.The advances of bifacial perovskite/c-Si TSC have been particularly reviewed in simulation calibration(current matching loss approach)and low-cost strategy(ultrathin Si).Finally,through the energy yield analysis of the monofacial and bifacial TSC,we have innovatively proposed that spectral variables,effective albedo and top-cell bandgap should be integrated into cell preparation and module installation.This in-depth numerical simulation review provides a guidance for experimental preparation of low-cost and high-efficiency perovskite/c-Si TSC.