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Solid-state transformer-based new traction drive system and control

Jianghua FENG, Jing SHANG, Zhixue ZHANG, Huadong LIU, Zihao HUANG

《机械工程前沿（英文）》 2018年第13卷第3期页码 411-426 doi: 10.1007/s11465-018-0467-0

摘要：

A new type of traction drive system consisting of solid-state traction transformer (SSTT), inverter unit, auxiliary inverter, traction motor and other key components is built in order to suit the demand of developing the next-generation electric traction system which will be efficient and lightweight, with high power density. For the purpose of reducing system volume and weight and improving efficiency and grid-side power quality, an efficient SSTT optimized topology combining high-voltage cascaded rectifiers with high-power high-frequency LLC resonant converter is proposed. On this basis, an integrated control strategy built upon synchronous rotating reference frame is presented to achieve unified control over fundamental active, reactive and harmonic components. The carrier-interleaving phase shift modulation strategy is proposed to improve the harmonic performance of cascaded rectifiers. In view of the secondary pulsating existing in a single-phase system, the mathematical model of secondary power transfer is built, and the mechanism of pulsating voltage resulting in beat frequency of LLC resonant converter is revealed, so as to design optimum matching of system parameters. Simulation and experimental results have verified that the traction system and control scheme mentioned in this paper are reasonable and superior and that they meet the future application requirements for rail transit.

关键词： solid-state traction transformer high-voltage cascaded rectifier LLC resonant converter synchronous rotating reference frame carrier-interleaving phase shift control secondary pulsating voltage beat frequency

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中国动态大地坐标框架最优实现的方法与应用 Article

程鹏飞, 成英燕, 王晓明, 吴素芹, 徐彦田

《工程（英文）》 2020年第6卷第8期页码 879-897 doi: 10.1016/j.eng.2020.08.004

摘要：

2000国家大地坐标系（CGCS2000）作为正式发布的法定坐标系已运用了多年。在我国，所有基于全球导航卫星系统（GNSS）测站的坐标为了与CGCS2000框架保持一致，都需要进行坐标改正。实现最佳CGCS2000框架需采用不同的策略，而不同的策略会导致不同的结果，有的差异甚至达到几分米。GNSS测站坐标改正常用的两种方法是CGCS2000控制下的拟稳平差和板块运动改正，两种方法计算的结果相差超过10 cm。本文将监督聚类（supervised clustering）统计方法应用于GNSS基准站的选择，同时提出了GNSS测站大网数据处理分组的间距分区（partition spacing）法，并用板块运动改正将当前历元GNSS测站坐标归算至CGCS2000参考历元。结果表明，新的分区方法明显优于传统的地理分区方法。当以不分组的测站坐标为标准时，新分区方法得到的三维坐标分量的精度均优于2 mm。监督聚类法得到的x、y、z方向上的速度均方根（RMS）分别为0.19 mm·a^–1、0.45 mm·a^–1和0.32 mm·a^–1，远小于传统方法的0.92 mm·a^–1、0.72 mm·a^–1和0.97 mm·a^–1。此外，采用奇异谱分析（SSA）对位置非线性运动进行建模和预测。在东、北、高（E、N和U）方向，SSA的建模精度分别优于3 mm、2 mm和5 mm，在水平方向和垂直方向的预测精度分别优于5 mm和1 cm。

关键词：参考框架优化实现中国板块模型 CGCS2000维持非线性运动建模

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Nonlinear dynamic behavior of rotating blade with breathing crack

Laihao YANG, Zhu MAO, Shuming WU, Xuefeng CHEN, Ruqiang YAN

《机械工程前沿（英文）》 2021年第16卷第1期页码 196-220 doi: 10.1007/s11465-020-0609-z

摘要： This study aims at investigating the nonlinear dynamic behavior of rotating blade with transverse crack. A novel nonlinear rotating cracked blade model (NRCBM), which contains the spinning softening, centrifugal stiffening, Coriolis force, and crack closing effects, is developed based on continuous beam theory and strain energy release rate method. The rotating blade is considered as a cantilever beam fixed on the rigid hub with high rotating speed, and the crack is deemed to be open and close continuously in a trigonometric function way with the blade vibration. It is verified by the comparison with a finite element-based contact crack model and bilinear model that the proposed NRCBM can well capture the dynamic characteristics of the rotating blade with breathing crack. The dynamic behavior of rotating cracked blade is then investigated with NRCBM, and the nonlinear damage indicator (NDI) is introduced to characterize the nonlinearity caused by blade crack. The results show that NDI is a distinguishable indicator for the severity level estimation of the crack in rotating blade. It is found that severe crack (i.e., a closer crack position to blade root as well as larger crack depth) is expected to heavily reduce the stiffness of rotating blade and apparently result in a lower resonant frequency. Meanwhile, the super-harmonic resonances are verified to be distinguishable indicators for diagnosing the crack existence, and the third-order super-harmonic resonances can serve as an indicator for the presence of severe crack since it only distinctly appears when the crack is severe.

关键词： rotating blade breathing crack nonlinear vibration nonlinear damage indicator

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New method of fault diagnosis of rotating machinery based on distance of information entropy

Houjun SU, Tielin SHI, Fei CHEN, Shuhong HUANG

《机械工程前沿（英文）》 2011年第6卷第2期页码 249-253 doi: 10.1007/s11465-011-0124-3

摘要：

This paper introduces the basic conception of information fusion and some fusion diagnosis methods commonly used nowadays in rotating machinery. From the thought of the information fusion, a new quantitative feature index monitoring and diagnosing the vibration fault of rotating machinery, which is called distance of information entropy, is put forward on the basis of the singular spectrum entropy in time domain, power spectrum entropy in frequency domain, wavelet energy spectrum entropy, and wavelet space feature entropy in time-frequency domain. The mathematic deduction suggests that the conception of distance of information entropy is accordant with the maximum subordination principle in the fuzzy theory. Through calculation it has been proved that this method can effectively distinguish different fault types. Then, the accuracy of rotor fault diagnosis can be improved through the curve chart of the distance of information entropy at multi-speed.

关键词： rotating machinery information fusion fault diagnosis Information entropy distance of the information entropy

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Imbalanced fault diagnosis of rotating machinery using autoencoder-based SuperGraph feature learning

《机械工程前沿（英文）》 2021年第16卷第4期页码 829-839 doi: 10.1007/s11465-021-0652-4

摘要： Existing fault diagnosis methods usually assume that there are balanced training data for every machine health state. However, the collection of fault signals is very difficult and expensive, resulting in the problem of imbalanced training dataset. It will degrade the performance of fault diagnosis methods significantly. To address this problem, an imbalanced fault diagnosis of rotating machinery using autoencoder-based SuperGraph feature learning is proposed in this paper. Unsupervised autoencoder is firstly used to compress every monitoring signal into a low-dimensional vector as the node attribute in the SuperGraph. And the edge connections in the graph depend on the relationship between signals. On the basis, graph convolution is performed on the constructed SuperGraph to achieve imbalanced training dataset fault diagnosis for rotating machinery. Comprehensive experiments are conducted on a benchmarking publicized dataset and a practical experimental platform, and the results show that the proposed method can effectively achieve rotating machinery fault diagnosis towards imbalanced training dataset through graph feature learning.

关键词： imbalanced fault diagnosis graph feature learning rotating machinery autoencoder

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―Summary of investigations on rotating cavity at IDG, RWTH Aachen University

Dieter BOHN, Jing REN,

《能源前沿（英文）》 2009年第3卷第4期页码 489-497 doi: 10.1007/s11708-009-0040-y

摘要： Annular cavities are found inside rotor shafts of turbomachines with an axial or radial throughflow of cooling air, which influences the thermal efficiency and system reliability of the gas turbines. The flow and heat transfer phenomena in those cavities should be investigated in order to minimize the thermal load and guarantee the system reliability. An experimental rig is set up in the Institute of Steam and Gas Turbines, RWTH Aachen University, to analyze the flow structure inside the rotating cavity with an axial throughflow of cooling air. The corresponding 3D numerical investigation is conducted with the in-house flow solver CHTflow, in which the Coriolis force and the buoyancy force are implemented in the time-dependent Navier-Stokes equations. Both the experimental and numerical results show that the whole flow structure rotating slower than the cavity rotating speed. The flow passing the observation windows in the experimental and numerical results indicates the quite similar trajectories. The computed sequences and periods of the vortex flow structure correspond closely with those observed in the experiment. Furthermore, the numerical analysis reveals a flow pattern changing between single pair, double pair, and triple pair vortices. It is suggested that the vortices inside the cavity are created by the gravitational buoyancy force in the investigated case, while the number and strength of the vortices are controlled mainly by the Coriolis force.

关键词： rotating cavity buoyancy unsteady flow

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Design and realization of a remote monitoring and diagnosis and prediction system for large rotating

Shaohong WANG, Tao CHEN, Jianghong SUN

《机械工程前沿（英文）》 2010年第5卷第2期页码 165-170 doi: 10.1007/s11465-009-0090-1

摘要： Traditional on-site fault diagnosis means cannot meet the needs of large rotating machinery for its performance and complexity. Remote monitoring and diagnosis technology is a new fault diagnosis mode combining computer technology, communication technology, and fault diagnosis technology. The designed remote monitoring and diagnosis and prediction system for large rotating machinery integrates the distributed resources in different places and breaks through shortcomings as the offline and decentralized information. The system can make further implementation of equipment prediction technology research based on condition monitoring and fault diagnosis, provide on-site analysis results, and carry out online actual verification of the results. The system monitors real-time condition of the equipment and achieves early fault prediction with great significance to guarantee safe operation, saves maintenance costs, and improves utilization and management of the equipment.

关键词： large rotating machinery remote monitoring fault diagnosis prediction system

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Convective mass transfer from a horizontal rotating cylinder in a slot air jet flow

Hongting MA , Dandan MA , Na YANG ,

《能源前沿（英文）》 2009年第3卷第3期页码 289-296 doi: 10.1007/s11708-009-0019-8

摘要： The effects of air jet impinging on the mass transfer characteristics from a rotating spinning cylinder surface were experimentally investigated. The effects of rotational Reynolds number

关键词： air jet impinging rotating cylinder critical point mass transfer characteristics

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Metallic wastewater treatment by sulfate reduction using anaerobic rotating biological contactor reactor

Mothe Gopi Kiran, Kannan Pakshirajan, Gopal Das

《环境科学与工程前沿（英文）》 2018年第12卷第4期 doi: 10.1007/s11783-018-1073-4

摘要：

An-RBC reactor is highly suited to treat metallic wastewater.

Metal removal is due to sulfide precipitation via sulfate reduction by SRB.

Cu(II) removal was the best among the different heavy metals.

Maximum metal removal is achieved at low metal loading condition.

Metal removal matched well with the solubility product values of respective metal sulfide salts.

关键词： Factorial design analysis sulfate reducing bacteria multi-metal solution heavy metal removal anaerobic rotating biological contactor reactor high metal loading.

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simulated flue gas using aqueous persulfate with activation of ferrous ethylenediaminetetraacetate in the rotating

《化学科学与工程前沿（英文）》 2023年第17卷第4期页码 460-469 doi: 10.1007/s11705-022-2224-5

摘要： Nitric oxide being a major gas pollutant has attracted much attention and various technologies have been developed to reduce NO emission to preserve the environment. Advanced persulfate oxidation technology is a workable and effective choice for wet flue gas denitrification due to its high efficiency and green advantages. However, NO absorption rate is limited and affected by mass transfer limitation of NO and aqueous persulfate in traditional reactors. In this study, a rotating packed bed (RPB) was employed as a gas–liquid absorption device to elevate the NO removal efficiency (η_NO) by aqueous persulfate ((NH₄)₂S₂O₈) activated by ferrous ethylenediaminetetraacetate (Fe²⁺-EDTA). The experimental results regarding the NO absorption were obtained by investigating the effect of various operating parameters on the removal efficiency of NO in RPB. Increasing the concentration of (NH₄)₂S₂O₈ and liquid–gas ratio could promoted the oxidation and absorption of NO while the η_NO decreased with the increase of the gas flow and NO concentration. In addition, improving the high gravity factor increased the η_NO and the total volumetric mass transfer coefficient (K_Gα) which raise the η_NO up to more than 75% under the investigated system. These observations proved that the RPB can enhance the gas–liquid mass transfer process in NO absorption. The correlation formula between K_Gα and the influencing factors was determined by regression calculation, which is used to guide the industrial scale-up application of the system in NO removal. The presence of O₂ also had a negative effect on the NO removal process and through electron spin resonance spectrometer detection and product analysis, it was revealed that Fe²⁺-EDTA activated (NH₄)₂S₂O₈ to produce •SO₄^–, •OH and •O₂^–, played a leading role in the oxidation of NO, to produce NO₃^– as the final product. The obtained results demonstrated a good applicable potential of RPB/PS/Fe²⁺-EDTA in the removal of NO from flue gases.

关键词： rotating packed bed Fe²⁺-EDTA sulfate radical hydroxyl radical NO removal efficiency

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Cholera: an overview with reference to the Yemen epidemic

Ali A. Rabaan

《医学前沿（英文）》 2019年第13卷第2期页码 213-228 doi: 10.1007/s11684-018-0631-2

摘要： Cholera is a secretory diarrhoeal disease caused by infection with , primarily the O1 El Tor biotype. There are approximately 2.9 million cases in 69 endemic countries annually, resulting in 95 000 deaths. Cholera is associated with poor infrastructure and lack of access to sanitation and clean drinking water. The current cholera epidemic in Yemen, linked to spread of O1 (Ogawa serotype), is associated with the ongoing war. This has devastated infrastructure and health services. The World Health Organization had estimated that 172 286 suspected cases arose between 27th April and 19th June 2017, including 1170 deaths. While there are three oral cholera vaccines prequalified by the World Health Organization, there are issues surrounding vaccination campaigns in conflict situations, exacerbated by external factors such as a global vaccine shortage. Major movements of people complicates surveillance and administration of double doses of vaccines. Cholera therapy mainly depends on rehydration, with use of antibiotics in more severe infections. Concerns have arisen about the rise of antibiotic resistance in cholera, due to mobile genetic elements. In this review, we give an overview of cholera epidemiology, virulence, antibiotic resistance, therapy and vaccines, in the light of the ongoing epidemic in Yemen.

关键词： cholera epidemic multi-drug resistant catechin luteolin ToxT CTX&Fcy

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reference tracking control design for a class of nonlinear systems with time-varying delays

Mei-qin LIU,Hai-yang CHEN,Sen-lin ZHANG

《信息与电子工程前沿（英文）》 2015年第16卷第9期页码 759-768 doi: 10.1631/FITEE.1500053

摘要： This paper investigates the trajectory tracking control for a class of nonlinear systems with timevarying delays by virtue of Lyapunov-Krasovskii stability theory and the linear matrix inequality (LMI) technique. A unified model consisting of a linear delayed dynamic system and a bounded static nonlinear operator is introduced, which covers most of the nonlinear systems with bounded nonlinear terms, such as the one-link robotic manipulator, chaotic systems, complex networks, the continuous stirred tank reactor (CSTR), and the standard genetic regulatory network (SGRN). First, the definition of the tracking control is given. Second, the performance analysis of the closed-loop system including this unified model, reference model, and state feedback controller is presented. Then criteria on the tracking controller design are derived in terms of LMIs such that the output of the closed-loop system tracks the given reference signal in the sense. The reference model adopted here is modified to be more flexible. A scaling factor is introduced to deal with the disturbance such that the control precision is improved. Finally, a CSTR system is provided to demonstrate the effectiveness of the established control laws.

关键词： H∞ reference tracking Nonlinear system State feedback control Time-varying delays Unified model

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Modeling and control of a permanent magnet synchronous generator dedicated to standalone wind energy

Louar FATEH,Ouari AHMED,Omeiri AMAR,Djellad ABDELHAK,Bouras LAKHDAR

《能源前沿（英文）》 2016年第10卷第2期页码 155-163 doi: 10.1007/s11708-016-0410-1

摘要： The interest for the use of renewable energies has increased, because of the increasing concerns of the environmental problems. Among renewable energies, wind energy is now widely used. Wind turbines based on an asynchronous generator with a wound rotor present the inconvenience of requiring a system of rings and brooms and a multiplier, inferring significant costs of maintenance. To limit these inconveniences, certain manufacturers developed wind turbines based on synchronous machines with large number of pairs of poles coupled directly with the turbine, avoiding using the multiplier. If the generator is equipped with permanent magnets, the system of rings and brooms is eliminated. The control of the permanent magnet synchronous generator (PMSG) can be affected with the implementation of various techniques of control. This paper presented a new approach mainly based on the control strategy of power production system based on the PMSG. In fact, a mathematical model that simulates the Matlab chain was established with the introduction of control techniques, such as direct control of the torque (DTC) to control the load side converter (LSC), the control of the speed of the turbine and the DC-bus voltage ensured by PI regulators. To show the performance of the correctors used, some simulation results of the system were presented and analyzed.

关键词： wind turbine permanent magnet synchronous generator (PMSG) converter proportional-integral (PI) control direct control of the torque (DTC) regulation

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A reliable and practical reference objective for the deviation diagnosis of energy system parameters

Liping LI, Zheng LI,

《能源前沿（英文）》 2009年第3卷第4期页码 440-445 doi: 10.1007/s11708-009-0051-8

摘要： The core objective to optimize a complex energy system is to set the reference target to guide the parameter adjustment of system operation. In this paper, a new case-based approach is proposed based on an online performance assessment program and its long-term operation data for a large power unit. The online model of a coal-fired power unit’s performance assessment is demonstrated, and the distribution pattern of the performance index is revealed by statistical analysis of the abundant data. The fundamental issues (representation of the similarity of two thermal processes, similarity measure, etc.) are tackled. The key sections and key parameters for the completion of similarity determination are proposed, which are essential to realize a case-based strategy. A full-scope simulator of power unit is used to test the availability of the method. The advantage of the case-based approach is the integrality of information over other methods.

关键词： energy system case-based optimization power unit operation performance