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International Conference on Renewable power Generation, RPG 2015

作者： Li, Hongping Wang, Fei Ren, Hui Sun, Hongbin Liu, Chun Wang, Bo Lu, Jing Zhen, Zhao State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Baoding Hebei Province071003 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Haidian District Beijing100084 China China Electric Power Research Institute Haidian District Beijing100192 China

ISBN: (纸本)9781785610400

Irradiance changes caused by clouds movement are the mam factors, which lead to mutation of photovoltaic power. In order to increase the accuracy of the ultra-short-term photovoltaic power prediction, based on of clouds images, the cloud identification for sky images is one of the primary aspects for improving photovoltaic power accuracy. A cloud identification model for sky images is established based on Otsu. Firstly, a series of sky images are collected by Total Sky Imager (TSI) with the regions of clouds and sky are distinguished. Secondly, the color features (based on RGB values) of pixels in sample images and the spectral and texture features of the whole image are extracted;Finally, we established a cloud identification model for sky images based on Otsu according to the clouds' and sky areas' division and the general characteristics featured by pixels and images. The simulated results show that the model in this paper can identify the clouds in a sky images effectively.

关键词： Pixels

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Short-term prediction model of module temperature for photovoltaic power forcasting based on support vector machine

Short-term prediction model of module temperature for photov...

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International Conference on Renewable power Generation, RPG 2015

作者： Sun, Yujing Wang, Fei Mi, Zengaiang Sun, Hongbin Liu, Chun Wang, Bo Lu, Jing Zhen, Zhao Li, Kangping State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Baoding Hebei Province071003 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Haidian District Beijing100084 China China Electric Power Research Institute Haidian District Beijing100192 China

ISBN: (纸本)9781785610400

To improve the prediction accuracy of photovoltaic (PV) power generation, the temperature of PV modules and its prediction is very important. A short-term step-wise temperature prediction model for PV module based on Support Vector Machine (SVM) is proposed in this paper. Firstly, the primary impact factors of PV module temperature are determined in terms of the PV module physical characteristics and the correlation coefficient between each factor and module temperature. Secondly, two kinds of prediction models, direct and step-wise models, are built to predict module temperature respectively. For direct model, the prediction model is based on SVM using the historical data. For step-wise one, the prediction models of the primary impact factors are built at the first step and then the mapping models between module temperature and the impact factors are established. In the end, the deviations of two different kinds of prediction models are analyzed and discussed based on actual operation data. The results indicate that the stepwise prediction model has better accuracy than the direct prediction model if other things are equal.

关键词： Forecasting

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Influences of temperature on Space Charge in Gas-to-Liquid Oil-Impregnated Paper

Influences of temperature on Space Charge in Gas-to-Liquid O...

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International Conference on High Voltage Engineering and Application, ICHVE

作者： Yuanxiang Zhou Xin Huang Ling Zhang Yunxiao Zhang Zhongliu Zhou Chenyuan Teng China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China

ISBN: (数字)9781728155111

ISBN: (纸本)9781728155128

Gas-to-liquid (GTL) transformer oil has been on trial in converter transformers. However, its influence on the space charge characteristic is not clear. This work aims at exploring space charge characteristics of GTL oil at different temperatures as well as comparing with commercial naphthenic oil (KI50X). Space charge distribution during the polarization and the dissipation process in the GTL oil-impregnated paper at different temperature was measured by the pulse electroacoustic method (PEA), which were contrasted with those of the KI50X oil-impregnated paper. Results illustrated that high temperature accelerated the injection and migration of charge carriers in the oil-impregnated paper. And the polarity of the accumulated charge in the vicinity of anode changed from positive to negative with the increase of temperature. It was perceived that oil-paper conductivity and carrier mobility grew with the increase of temperature, resulting in the easier migration of injected charge to another electrode. Furthermore, the space charge dissipation rate in the GTL oil-impregnated paper is lower than that in the naphthenic oil-impregnated paper at the same temperature. Thus, a longer time interval of tests or switch operation in the factory test and operation process may need if GTL oil is used rather than naphthenic oil.

关键词： Oils Space charge power transformer insulation Oil insulation Electric fields Distortion Temperature measurement

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Optimization of tool-path generation for material extrusion-based additive manufacturing technology

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Additive Manufacturing 2014年 1卷 32-47页

作者： Jin, Yu-an He, Yong Fu, Jian-zhong Gan, Wen-feng Lin, Zhi-wei The State Key Lab of Fluid Power Transmission and Control Systems Department of Mechanical Engineering Zhejiang University Hangzhou310027 China Zhejiang Province's Key Laboratory of 3D Printing Process and Equipment Department of Mechanical Engineering Zhejiang University Hangzhou310027 China

In this study, we propose a tool-path generation approach for material extrusion-based additive manufacturing (AM) that considers the machining efficiency and fabrication precision, which are inherent drawbacks of general AM techniques compared with conventional manufacturing methods. The proposed approach aims to tackle the generation of direction-parallel tool-paths for the interior filling of simple connected areas, which comprises three main steps: (1) determining the inclination of reference lines;(2) generating and grouping tool-path segments into individual sub-paths;and (3) linking sub-paths based on specific requirements. These three modules interact to affect the efficiency and precision of AM significantly. In order to find an optimal inclination, we first analyze the impacts on the fabrication efficiency and manufacturing accuracy with different inclinations. A comparatively accurate building time model is developed subsequently to obtain the optimal tool-path inclination, but without compromising the machining precision, based on the analysis of a geometrical accuracy model. The proposed approach employs different inclinations in distinct layers according to specific manufacturing scenarios and technological requirements. After determining the reference lines, the tool-path segments are selected and grouped based on some characteristics (e.g., the number of intersections between reference lines and boundaries) to make up individual sub-paths, which are then connected to a zigzag-shaped path with short line segment connections. In the module for sub-path linking, some strategies are introduced to decrease the number of useless tool-paths, i.e., uncut paths, which could jeopardize the manufacturing quality by frequently turning the print head on and off. In addition, parametric curves are used to link the final sub-paths to avoid deceleration/acceleration processes in the end/starting parts of the sub-paths. The proposed approach has been used in practice

关键词： 3D printers

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Analysis and Suppression of Subsynchronous Oscillation of RuDong Wind power Through MMC-HVDC system

Analysis and Suppression of Subsynchronous Oscillation of Ru...

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2021 Annual Meeting of CSEE Study Committee of HVDC and power Electronics, HVDC 2021

作者： Li, Jingyi Xie, Xiaorong Yang, Jianjun Li, Haozhi Shi, Zhaohui Wang, Ke Fu, Chunxiang Yang, Wenbin Key Laboratory of Far-shore Wind Power Technology of Zhejiang Province Huadong Engineering Corporation Limited Power China Zhejiang Province Hangzhou310014 China Dept. of Electrical Engineering Tsinghua University State Key Lab of Control and Simulation of Power Systems and Generation Equipment Haidian District Beijing100084 China

ISBN: (纸本)9781839537035

There may be complex interaction between the converter control systems of wind power and MMC-HVDC, which will lead to sub-/super-synchronous oscillation and threaten the safe and stable operation of the system. The relevant events have been reported in Guangdong Nan'ao, Shanghai Nanhui and Zhangbei projects. Rudong offshore wind power project is the first offshore wind power transmission system in China, and it is still under construction. Therefore, it is of great significance to carry out the research on the risk analysis and suppression measures of sub-synchronous oscillation in Rudong wind power MMC-HVDC system. First, the time-domain simulation model of Rudong wind power MMC-HVDC system is built in the PSCAD/EMTDC simulation model. Then, the effects of the number of wind turbine generators, wind power output and the parameters of MMC-HVDC controller on the sub-/supersynchronous oscillation characteristics of the system are further analyzed. Finally, the suppression measures based on supplementary frequency dependent gain control are proposed, the application position of the controller is discussed, and the parameter optimization method of the controller is given. The research content provides a certain guiding significance for the operation and control of Rudong wind power MMC-HVDC. © 2021 IET Conference Proceedings. All rights reserved.

关键词： Wind power

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Medium and long-term wind energy forecasting method considering multi-scale periodic pattern 10

Medium and long-term wind energy forecasting method consider...

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2020 10th International Conference on power, Energy and Electrical Engineering, CPEEE 2020

作者： Lin, Yisha Lu, Zongxiang Qiao, Ying Li, Mingjie Liang, Zhifeng State Key Lab of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Haidian District Beijing100084 China State Grid Corporation of China Haidian District Beijing100031 China

Medium and long-term weather sequence forecast becomes unreliable beyond two weeks since the weather is a chaotic system. Using values of same months for electricity prediction of wind power is the usual method. This approach defaults wind power output with annual cycle law. However, the periodic pattern can be very complicated in fact with multiple time scales. This paper proposes an approach with multi-scale periodic pattern considered. The application of parametric estimation on cumulative distribution function avoids the difficulty of predicting the power curve. Meteorological condition is considered to some extent via multi-scale periodic pattern explored basing on historical energy data. This work is an exploration for medium and long-term wind power forecasting that can well adapt to existing conditions. It has better prediction accuracy than the method without multi-scale periodicity considered. © 2020 The Authors, published by EDP Sciences.

关键词： Wind power

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Precise regulation of acid pretreatment for red mud SCR catalyst:Targeting on optimizing the acidity and reducibility

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Frontiers of Environmental Science & Engineering 2022年第7期16卷 61-71页

作者： Xiang Zhang Yue Xuan Bin Wang Chuan Gao Shengli Niu Gaiju Zhao Dong Wang Junhua Li Chunmei Lu John C.Crittenden National Engineering Laboratory for Coal-Burning Pollutants Emission Reduction School of Energy and Power EngineeringShandong UniversityJinan250061China School of Civil and Environmental Engineering and the Brook Byers Institute for Sustainable Systems Georgia Institute of TechnologyAtlantaGA30332USA State Key Joint Laboratory of Environment Simulation and Pollution Control National Engineering Laboratory for Multi Flue Gas Pollution Control Technology and EquipmentSchool of EnvironmentTsinghua UniversityBeijing100084China Energy Institute Qilu University of Technology(Shandong Academy of Sciences)Jinan250013China

Red mud(RM),as an alkaline waste,was recently proved to be a promising substitute for the SCR *** could improve the acidity and reducibility of red mud,which were critical for SCR ***,the dealkalization effect depended on the reaction between acid solution and red *** this study,we realized the directional control of the chemical state of active sites through tuning the acid pretreatment(dealkalization)*** pretreatment endpoint was controlled at pH values of 3–5 with diluted nitric *** the pH values of red mud were 3 and 5(CRM-3 and CRM-5),activated catalysts showed NOx conversion above 90%at 275℃–475℃.The high initial reaction rate,Ce^(3+)/(Ce^(3+)+Ce^(4+))ratio,and surface acidity accounted for the excellent SCR performance of CRM-5 ***,more Fe^(3+) on the CRM-3 surface improved the NH_(3) *** was a strong interaction between Al and Fe in both CRM-5 and CRM-3 *** results showed that the adsorption capacity of the Al-O_(3)-Fe for NH_(3) and NO is stronger than that of Fe-O_(3)-Fe,which enhanced the NOx conversion of the ***,the almandine was formed in CRM-4,consumed part of Fe^(3+) and Al^(3+),and the interaction between Al and Fe was ***,deposited almandine on the catalyst surface covered the active sites,thus leading to lower NH_(3)-SCR activity.

关键词： Air pollution control Nitrogen oxides Selective catalytic reduction Red mud Solid waste utilization

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Short-Term Prediction of Wind power Based on NWP Error Correction with TimeGAN and LSTM-TCN 4th

Short-Term Prediction of Wind Power Based on NWP Error Corre...

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4th International Conference on Energy power and Automation Engineering, ICEPAE 2023

作者： Li, Shuona Ma, Wei Liu, Zhao Duan, Yuge Tian, Chengwei School of Electrical Engineering Beijing Jiaotong University Beijing China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments of Electrical Engineering Tsinghua University Beijing China

ISBN: (纸本)9789819988778

The data quality of numerical weather prediction has a great influence on the accuracy of wind power prediction technology. In order to improve the short-term forecasting effect of wind power, we proposed a combined LSTM-TCN forecasting model based on NWP error correction model with TimeGAN. First, minimal redundancy maximal relevance (mRMR) algorithm is used to extract original NWP features and measured meteorological features, respectively. Then, TimeGAN is used to correct initial NWP data according to the internal hidden associations with the measured weather features. After that, the corrected NWP features combined with historical wind power are applied to establish a wind power short-term prediction hybrid model based on LSTM and TCN network. Finally, the performance of the hybrid model is tested by a wind farm dataset in China, which verified effectiveness of this method. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.

关键词： Wind power

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Phase Segmentation of Ni/YSZ Anode for Solid Oxide Fuel Cells by Deep Learning

Phase Segmentation of Ni/YSZ Anode for Solid Oxide Fuel Cell...

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243rd ECS Meeting

作者： Wang, Y. Matsui, Y. Hosomizo, A. Kishimoto, M. Han, M. Iwai, H. Department of Mechanical Engineering and Science Kyoto University Nishikyo-ku Kyoto615-8540 Japan State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Energy and Power Engineering Tsinghua University Beijing100084 China

ISBN: (纸本)9781607685395

A deep learning network is implemented for the phase segmentation of Ni/YSZ anode of solid oxide fuel cells (SOFCs), as manual segmentation of focused ion beam-scanning electron microscopy (FIB-SEM) images is time-consuming. Segmentation is performed on two samples with different volume ratios of Ni to YSZ. The mean intersection over union (mIoU) reaches 0.9363, indicating good agreement between the predicted images and the manually segmented images. Furthermore, the impact of image augmentation on segmentation accuracy is investigated, and it is found that augmentation is necessary when the number of images in the training set is small or the training and testing sets come from different samples. Furthermore, mixing a sixth of manually segmented images from a new sample into the training set can significantly improve the accuracy of automated segmentation for the new sample. This strategy reduces the number of images requiring manual segmentation and improves processing efficiency. © The Electrochemical Society.

关键词： Solid oxide fuel cells (SOFC)

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Design Optimization of Ferrite Rings for VFTO Mitigation

Design Optimization of Ferrite Rings for VFTO Mitigation

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作者： He, Jiaxi Guan, Yonggang Liu, Weidong Chen, Weijiang Li, Zhibing The Department of Electrical Engineering State Key Lab of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing100084 China State Grid Corporation of China Beijing100031 China China Electric Power Research Institute Beijing100192 China

very-fast transient overvoltage (VFTO)-related problems are raising growing concerns in China with the development of ultra-high voltage. The practice of fitting ferrite rings on gas-insulated switchgear busbars for VFTO mitigation has long been proposed but few investigations on its design optimization were conducted. Based on theoretical analysis of the simplified model, the optimal damping condition of ferrite rings is proposed, which is conducive to the type selection. The number of rings to be employed to ensure visible suppressing effects is given through simulations and the influence of the saturation is discussed. Impact on the power frequency is analyzed to be negligible. Finally, comparisons are made between the theoretical conclusions and existing experiment results, which approve the optimal damping condition and agree with the number of rings to be employed. © 2014 IEEE.

关键词： Damping

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