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Impact of Different AC Voltage Control Modes of Wind-farm-side MMC on Stability of MMC-HVDC with Offshore Wind Farms

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Journal of Modern Power Systems and Clean Energy 2023年第5期11卷 1687-1699页

作者： Hongfei Lin tao xue Jing Lyu Xu Cai Key Laboratory of Control of Power Transmission and Conversion Ministry of EducationDepartment of Electrical EngineeringShanghai Jiao Tong UniversityShanghai 200240China Department of Electrical Engineering Shanghai Jiao Tong UniversityShanghaiChina Department of Electrical Engineering The Hong Kong Polytechnic UniversityHong KongChina

Wind-farm-side modular multilevel converters(WFMMCs) used in modular multilevel converter based highvoltage direct current(MMC-HVDC) transmission systems must be able to control the AC grid voltage in offshore wind farms. Different AC voltage control strategies can significantly affect the dynamic characteristics of WFMMCs. However, existing studies have not provided a general methodology of controller parameter design, and few comparative studies have been conducted on control performance under varying operating conditions as well as the effects of different AC voltage control modes(AVCMs) on the stability of MMC-HVDCs with offshore wind farms. This paper provides a controller parameter design method for AVCMs, which is tested in various operating scenarios. Sequence impedance models of offshore wind farms and WFMMCs under different AVCMs are then developed. The effects of AVCMs on the small-signal stability of the interconnected system are then analyzed and compared using the impedance-based method. Finally, case studies are conducted on a practical MMC-HVDC system with offshore wind farms to verify the theoretical analysis.

关键词： Offshore wind farm modular multilevel converter based high-voltage direct current(MMC-HVDC) AC voltage control stability dynamic response

T-Q diagram analyses and entransy optimization of the organic flash cycle(OFC)

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Science China(Technological Sciences) 2015年第4期58卷 630-637页

作者： WANG Wen Hua CHENG xue tao LIANG Xin Gang Key Laboratory for Thermal Science and Power Engineering of Ministry of Education School of AerospaceTsinghua University

The electrical power generation from low temperature heat source attracts more and more attentions but the temperature mismatching between the heat sources and working medium in the organic Rankine cycle(ORC)becomes an *** organic flash cycle(OFC)is an effective solution to this *** this paper,the OFC is analyzed by the concept of entransy loss and the T-Q(temperature-heat flow rate)diagram for the heat-work *** equations for cycles of the basic OFC and the OFC whose heat source is the exhaust gas of the turbine in a Brayton cycle(the combined cycle)are derived theoretically and the results indicate that larger entransy loss rate leads to larger output power with prescribed inlet parameters of the hot stream in the discussed cases,which is displayed by the T-Qdiagram *** numerical examples demonstrate that the optimal mass flow rate of the working medium for the maximum entransy loss rate is the same as that for the maximum output *** T-Qdiagram analyses is in accordance with the numerical *** concept of entransy loss can be used as the criteria for the OFC optimization.

关键词： OFC T. Q diagram entransy loss combined cycle optimization

Uniformity principle of temperature difference field in heat transfer optimization

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Chinese Physics B 2019年第6期28卷 245-253页

作者： xue-tao Cheng Xin-Gang Liang Department of Science and Technology of Anhui Province Hefei 230091China Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Engineering MechanicsTsinghua UniversityBeijing 100084China

The uniformity principle of temperature difference field is very useful in heat exchanger analyses and *** this paper, we analyze some other heat transfer optimization problems in the thermal management system of spacecrafts,including the cooling of thermal components, the one-stream series-wound heat exchanger network, the volume-to-point heat conduction problem, and the radiative heat transfer optimization problem, and have found that the uniformity principle of temperature difference field also holds. When the design objectives under the given constraints are achieved, the distributions of the temperature difference fields are uniform. The principle reflects the characteristic of the distribution of potential in the heat transfer optimization problems. It is also shown that the principle is consistent with the entransy theory. Therefore, although the principle is intuitive and phenomenological, the entransy theory can be the physical basis of the principle.

关键词： heat transfer optimization uniformity principle of temperature difference field equipartition of potential entransy theory

Speech emotion recognition with unsupervised feature learning

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Frontiers of Information Technology & Electronic Engineering 2015年第5期16卷 358-366页

作者： Zheng-wei HUANG Wen-tao xue Qi-rong MAO Department of Computer Science and Communication Engineering Jiangsu University

Emotion-based features are critical for achieving high performance in a speech emotion recognition(SER) system. In general, it is difficult to develop these features due to the ambiguity of the ground-truth. In this paper, we apply several unsupervised feature learning algorithms(including K-means clustering, the sparse auto-encoder, and sparse restricted Boltzmann machines), which have promise for learning task-related features by using unlabeled data, to speech emotion recognition. We then evaluate the performance of the proposed approach and present a detailed analysis of the effect of two important factors in the model setup, the content window size and the number of hidden layer nodes. Experimental results show that larger content windows and more hidden nodes contribute to higher performance. We also show that the two-layer network cannot explicitly improve performance compared to a single-layer network.

关键词： Speech emotion recognition Unsupervised feature learning Neural network Affect computing

Entransy: its physical basis, applications and limitations

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Chinese Science Bulletin 2014年第36期59卷 5309-5323页

作者： xue-tao Cheng Xin-Gang Liang Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Engineering MechanicsTsinghua University

In this paper, the physical basis and application conditions of the entransy theory are reviewed and discussed. Entransy can be obtained from the analogy between heat and electrical conductions. It is a state value and the‘‘potential energy'' of heat. From the viewpoint of thermomass, it reflects the thermal energy of the thermomass in an object. Furthermore, it was also related to the microstate number and is a single value function of the microstate number. The concepts of entransy, entransy flux and entransy dissipation can be used to express the least action of heat transfer. The entransy balance equations for heat transfer and thermodynamic processes and their applications to thermal systems are also reviewed. The differences between the entransy theory, constructal theory, entropy generation minimization, exergy analyses method, principle of uniformity of temperature difference field and field synergy(coordination) principle are also discussed. The entransy theory is different from the other discussed theories. The limitations of the entransy theory are also discussed.

关键词：应用程序物理基础微观状态数热力学过程平衡方程构形理论火用分析热系统

Synthesis and structure analysis of aluminum doped zinc oxide powders

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Science China Chemistry 2008年第9期51卷 823-828页

作者： NIE DengPan xue tao ZHANG Yu LI XiangJun Guizhou Institute of Metallurgy and Chemical Engineering Guiyang 550002China School of Chemical Engineering Guizhou UniversityGuiyang 550003China College of Chemistry and Chemistry Engineering Graduate University of Chinese Academy of SciencesBeijing 100049China

Hexagonal Al-doped zinc oxide (ZnO) powders with a nominal composition of Zn1?x Al x O (0?x?0.028) were synthesized by the co-precipitation method. The contents of the Al element in the samples were measured by the inductively coupled plasma-optical emission spectroscopy (ICP-OES) technique. The structures of the Zn1?x Al x O (0?x?0.028) compounds calcined at 1000 and 1200°C have been determined using the Rietveld full-profile analysis method. Rietveld refinements of the diffraction data indicated that the addition of Al initially has a considerably positive effect on the decreasing of the lattice parameters a and c of Zn1?x Al x O, but the effect becomes very slight and even negative with the further increase of the Al content. The solid solubility limit of Al in ZnO (mole fraction y) is 2.2l%, resulting in Zn0.978Al0.22O. It seems that when the Al content is excessive, Al prefers to form a ZnAl2O4 compound with ZnO, but not to incorporate into the ZnO lattice to occupy the Zn2+ cites. Two phases, [ZnO] (or Al-doped ZnO) and [ZnAl2O4], are obviously segregated in Zn1?x Al x O while the value of x is larger than 0.024. The UV-Vis absorption spectra show that the Al-doped ZnO exhibits a red-shift in the absorption edge without reduced transmission compared with pure ZnO, which also confirms that Al ions enter the ZnO lattice and form a Zn1?x Al x O solid solution.

关键词： Al-doped zinc oxide (ZnO) co-precipitation method X-ray diffraction crystal structure

Health-oriented strategies are needed to optimize China’s 2025 clean air action plan

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Science Bulletin 2024年第13期69卷 2007-2008页

作者： tao xue Ning Kang Wei Wan Tong Zhu Institute of Reproductive and Child Health/National Health Commission Key Laboratory of Reproductive Health and Department of Epidemiology and Biostatistics/Ministry of Education Key Laboratory of Epidemiology of Major Diseases(PKU) School of Public HealthPeking University Health Science CentreBeijing 100191China State Environmental Protection Key Laboratory of Atmospheric Exposure and Health Risk Management Center for Environment and HealthPeking UniversityBeijing 100871China Advanced Institute of Information Technology Peking UniversityHangzhou 311215China Clean Air Asia Beijing 100600China College of Environmental Sciences and Engineering Peking UniversityBeijing 100871China

Recently,China’s State Council issued the Continuous Improvement of Air Quality Action Plan(hereafter,the third action plan),which follows the Air Pollution Prevention and Control Action Plan(2013–2017)(hereafter,the first action plan)and the Three-Year Action Plan for Winning the Blue Sky Defense Battle(2018–2020)(hereafter the second action plan).The first two action plans yielded nationwide health benefits[1–3],from improving lung function[4]to saving medical expenditures[5].Based on our previous estimates[6],due to reductions in the fine particulate matter(PM2.5)level,implementation of the first and second action plans was expected to increase life expectancy by 2.11 and 3.68 months.

关键词： action hereafter nationwide

Improving the numerical stability of the MAGIC model

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Journal of Environmental Sciences 2001年第2期13卷 189-191页

作者： DENG Yi- xiang CHEN Ji- ning HU xue- tao Department of Envi ronment Sciences and Engineering T singhua University Bei jing 100084 China

MAGIC is one of the most widely used models for forecasting long-term acidification. The model's code, however, has been experiencing numerical instability, though this might not be widely known to the public users. The major instability comes from the analytical solution to two cubic equations for calculating SO42- concentration and the exchangeable fraction of Al on the soils. The mathematical algorithm for calculating the concentration of SO42- from a quadratic equation is also found instable. This paper is aimed at improving the instability above through proved numerical algorithms.

关键词： MAGIC model numerical instability

Preparation and characterization of Ti3C2Tx with SERS properties

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Science China(Technological Sciences) 2019年第7期62卷 1202-1209页

作者： XIE XiaoJing ZHU YuMei LI Fang ZHOU XiaoWei xue tao School of Materials Science and Engineering Tianjin University Tianjin 300072 China Center for Analysis and Tests Tianjin University Tianjin 300072 China

During the preparation of MXenes, the control of the amounts of metal atoms and functional groups has a great influence on the properties of Surface Enhancement Raman Scattering(SERS) substrate materials. A freestanding Ti3C2 Txmembrane with good uniformity was prepared by HF etching of Ti3AlC2. The effect of etching time on the removal of Al atoms and the functional groups bonded to Ti3C2 was precisely characterized by XRD. In addition, by using Ti3C2 Txas the SERS substrate, a quadratic relationship between the enhancement intensity and concentration of the dye molecule rhodamine was achieved.

关键词： MXene Ti3C2Tx SERS controlling terminations