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Coordinated Capacitor Voltage Balancing Method for Cascaded H-bridge Inverter with Supercapacitor and DC-DC Stage

第11届国际电机与系统学术会议

作者： Shutian Zhang~1,Qiongxuan Ge~1,yaohua li~1 1 institute of electrical engineering chinese academy of sciences,Beijing P.R.China

This paper present a high power three-level NPC inverter with the Integrated Gate-Commntated Thyristor(IGCT) *** power circuit consisted of a 12-pulse diodes rectifier and three-level NPC inverter with IGCT.A valid SVPWM control strategy filled with a TMS320F2407 DSP controller is proposed to improve power quality,reduce total harmonic distortion and overcome the problem of the minimum pulse *** to the three-level configuration and the valid SVPWM control method, the output harmonic is *** experimental of three phase system demonstrated that both the power circuit and control system designed are reasonable and valid.

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CES Transactions on electrical Machines and Systems 2024年第2期8卷 191-201页

作者： Ye Zhang Zixin li Fanqiang Gao Cong Zhao yaohua li IEEE Key Laboratory of High Density Electromagnetic Power and Systems(chinese academy of sciences) Institute of Electrical EngineeringChinese Academy of SciencesHaidian District University of chinese academy of sciences Shijingshan District

Cascaded H-bridge inverter(CHBI) with supercapacitors(SCs) and dc-dc stage shows significant promise for medium to high voltage energy storage applications. This paper investigates the voltage balance of capacitors within the CHBI, including both the dc-link capacitors and SCs. Balance control over the dc-link capacitor voltages is realized by the dcdc stage in each submodule(SM), while a hybrid modulation strategy(HMS) is implemented in the H-bridge to balance the SC voltages among the SMs. Meanwhile, the dc-link voltage fluctuations are analyzed under the HMS. A virtual voltage variable is introduced to coordinate the balancing of dc-link capacitor voltages and SC voltages. Compared to the balancing method that solely considers the SC voltages, the presented method reduces the dc-link voltage fluctuations without affecting the voltage balance of SCs. Finally, both simulation and experimental results verify the effectiveness of the presented method.

关键词： Cascaded H-bridge inverter(CHBI) Hybrid modulation strategy(HMS) Capacitor voltage balancing DClink voltage fluctuation Supercapacitor(SC)

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A Loss-model-based Efficiency Optimization Control Method for Induction Traction System of High-speed Train under Emergency Self-propelled Mode

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CES Transactions on electrical Machines and Systems 2024年第2期8卷 227-239页

作者： Yutong Zhu yaohua li institute of electrical engineering chinese academy of sciences Beijing 100190China University of chinese academy of sciences Beijing 100190China China academy of Railway sciences Corporation limited(Beijing Zongheng Electromechanical Technology Co.Ltd Beijing 100081 China IEEE

Increasing attention has been paid to the efficiency improvement of the induction traction system of high-speed trains due to the high demand for energy saving. In emergency self-propelled mode, however, the dc-link voltage and the traction power of the motor are significantly reduced, resulting in decreased traction efficiency due to the low load and low speed operations. Aiming to tackle this problem, a novel efficiency improved control method is introduced to the emergency mode of high-speed train traction system in this paper. In the proposed method, a total loss model of induction motor considering the behaviors of both iron and copper loss is established. An improved iterative algorithm with decreased computational burden is then introduced, resulting in a fast solving of the optimal flux reference for loss minimization at each control period. In addition, considering the parameter variation problem due to the low load and low speed operations, a parameter estimation method is integrated to improve the controller's robustness. The effectiveness of the proposed method on efficiency improvement at low voltage and low load conditions is demonstrated by simulated and experimental results.

关键词： Efficiency optimization Induction motor Loss model control Motor drives Traction system

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Tunneling conductance in graphene ferromagnet/p wave superconductor junctions

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Science China(Physics,Mechanics & Astronomy) 2012年第4期Mechanics & Astronomy) .卷 649-653页

作者： li XiaoWei 1,2*,CHEN HuaBao 1 & liU ShuJing 1 1 School of Physics and Electronic electrical engineering,Huaiyin Normal University,Huaian 223300,China 2 State Key Laboratory of Functional Materials for Informatics,Shanghai institute of Microsystem and Information Technology,chinese academy of sciences,Shanghai 200050,China School of Physics and Electronic electrical engineering Huaiyin Normal University Huaian China State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences Shanghai China

Using the extended Blonder-Tinkham-Klapwijk formalism,we investigate the conductance spectra of graphene ferromagnet/p wave superconductor *** is found that the conductance spectra are affected by the p wave pairing *** ferromagnetic exchange energy in the ferromagnet can suppress Andreev retroreflection but enhance the specular Andreev reflection in graphene ferromagnet/p wave superconductor *** conductance decreases with increasing exchange energy Eh for EhEF.

关键词： graphene ferromagnet p wave superconductor tunneling conductance

Preparation and characterization of PZT thick film enhanced by ZnO nanowhiskers for MEMS piezoelectric generators

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Progress in Natural Science:Materials International 2011年第2期21卷 159-163页

作者： Zhong-xia DUAN~1,Guo-qin YU~2,Jun-biao liU~1,Jun liU~2,Xiao-wen DONG~2,li HAN~1,Peng-yun JIN~1 1.institute of electrical engineering,chinese academy of sciences,Beijing 100190,China 2.Shanghai Municipal Electric Power Company,Shanghai 200025,China institute of electrical engineering Chinese Academy of Sciences Beijing 100190 China Shanghai Municipal Electric Power Company Shanghai 200025 China

A hybrid sol-gel route which was used to fabricate PZT thick film for MEMS piezoelectric generators was investigated. （100）-oriented Pb(Zr0.52Ti0.48)O3thick films enhanced by ZnO nanowhiskers（ZnOw） were successfully prepared on Pt/Cr/SiO2/Si substrates via spin-coating ZnOwsuspension and PZT *** influences of film thickness on the microstructure and electrical properties of composite thick film were *** results show that PZT composite thick films have（100）-oriented perovskite *** results show that,the surface of as-prepared（100）-oriented PZT piezoelectric composite thick film is smooth,compact and crack-free,and the cross section is *** composite thick films exhibit good ferroelectric,dielectric and piezoelectric properties.2 urn-thick（100）-oriented PZT piezoelectric composite thick film has the remnant polarization intensity and coercive field of 6.7μC/cm2and 92.5 kV/cm,the dielectric constant and dielectric dissipation of 1 431 and 0.44,respectively,and piezoelectric constant d33is calculated to be 151.0 pC/*** composite thick film is good to meet the use of MEMS piezoelectric generators.

关键词： PZT thick film ZnO nanowhisker electrical properties piezoelectric generator

Salient region detection and segmentation for general object recognition and image understanding

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Science China(Information sciences) 2011年第12期54卷 2481-2490页

作者： HUANG TieJun 1 , TIAN YongHong 1 , li Jia 2 & YU HaoNan 11 National engineering Laboratory for Video Technology, School of electrical engineering and Computer Science, Peking University, Beijing 100871, China 2 Key Laboratory of Intelligent Information Processing, institute of Computing Technology, chinese academy of sciences, Beijing 100190, China National engineering Laboratory for Video Technology School of Electrical Engineering and Computer Science Peking University Beijing China Key Laboratory of Intelligent Information Processing Institute of Computing Technology Chinese Academy of Sciences Beijing China

General object recognition and image understanding is recognized as a dramatic goal for computer vision and multimedia retrieval. In spite of the great efforts devoted in the last two decades, it still remains an open problem. In this paper, we propose a selective attention-driven model for general image understanding, named GORIUM (general object recognition and image understanding model). The key idea of our model is to discover recurring visual objects by selective attention modeling and pairwise local invariant features matching on a large image set in an unsupervised manner. Towards this end, it can be formulated as a four-layer bottom-up model, i.e., salient region detection, object segmentation, automatic object discovering and visual dictionary construction. By exploiting multi-task learning methods to model visual saliency simultaneously with the bottom-up and top-down factors, the lowest layer can effectively detect salient objects in an image. The second layer exploits a simple yet effective learning approach to generate two complementary maps from several raw saliency maps, which then can be utilized to segment the salient objects precisely from a complex scene. For the third layer, we have also implemented an unsupervised approach to automatically discover general objects from large image set by pairwise matching with local invariant features. Afterwards, visual dictionary construction can be implemented by using many state-of-the-art algorithms and tools available nowadays.

关键词： object recognition image understanding visual saliency salient object segmentation visual dictionary

Square Wave Control of 3-Level NPC Inverter for Large Capacity High-Speed Drive Systems

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Square Wave Control of 3-Level NPC Inverter for Large Capaci...

2005国际电机与系统学术会议

作者： Haishan li yaohua li institute of electrical engineering. chinese academy of sciences Beijing 100080 China Graduate School of chinese academy of sciences Beijing 100080 China

＜正＞This paper presents an improved method to achieve the high control performance of 3-level inverter for large capacity high-speed drive systems. Usually, due to the limit switching frequency of high voltage high power devices, the output frequency of the inverter is low in most cases. To achieve higher output frequency, the square wave modulation （SWM） is adopted. However, the use of the normal SWM decreases the control performance of the inverter and deteriorates the dynamic behavior of the drive systems because of less control freedom in per fundamental period. The proposed method with the improvement of the normal SWM has twelve freedoms and the optimum operation region of this method is given. Experimental results show that the proposed method can be applied in three level NPC inverters especially for large capacity highspeed drive systems.

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变长分段直线感应电机数学建模

中国电机工程学报 2024年第13期44卷 5338-5347,I0027页

作者：徐飞李子欣孔甘霖史黎明李耀华中国科学院电力电子与电气驱动重点实验室(中国科学院电工研究所) 北京市海淀区100190 中国科学院大学北京市石景山区100049 齐鲁中科电工先进电磁驱动技术研究院山东省济南市250100

变长分段直线感应电机参数具有不连续、快速时变及强耦合特性,这给电磁暂态建模带来挑战。该文引入3种时变因子推导出具有参数时变特性的变长分段直线感应电机数学表达式。通过分析变长分段直线感应电机定子与动子的电磁耦合特性及时变... 详细信息

变长分段直线感应电机参数具有不连续、快速时变及强耦合特性,这给电磁暂态建模带来挑战。该文引入3种时变因子推导出具有参数时变特性的变长分段直线感应电机数学表达式。通过分析变长分段直线感应电机定子与动子的电磁耦合特性及时变因子与状态变量之间的耦合关系,建立定子、动子及时变因子相互解耦的数学模型。仿真结果表明,该数学模型计算的电压、电流和速度与有限元计算结果差别小于6%,验证了数学模型的准确性。硬件在环实验结果表明,在高速工况下数学模型可以准确模拟系统的电磁暂态特性,验证了数学模型的解耦能力及数值运算稳定性。

关键词：变长分段直线电机时变因子解耦数学建模

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On adjacent-vertex-distinguishing total coloring of graphs

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Science China Mathematics 2005年第3期48卷 289-299页

作者： ZHANG Zhongfu, CHEN Xiang’en, li Jingwen, YAO Bing, LU Xinzhong & WANG Jianfang College of Mathematics and Information Science, Northwest Normal University, Lanzhou 730070, China Department of Computer, Lanzhou Normal College, Lanzhou 730070, China institute of Applied Mathematics, Lanzhou Jiaotong University, Lanzhou 730070, China College of Information and electrical engineering, Lanzhou Jiaotong University, Lanzhou 730070, China institute of Applied Mathematics, chinese academy of sciences, Beijing 100080, China College of Mathematics and Information Science Northwest Normal University Lanzhou China Department of Computer Lanzhou Normal College Lanzhou China institute of Applied Mathematics Lanzhou Jiaotong University Lanzhou China College of Information and electrical engineering Lanzhou Jiaotong University Lanzhou China institute of Applied Mathematics Chinese Academy of Sciences Beijing China

In this paper, we present a new concept of the adjacent-vertex-distinguishing total coloring of graphs (briefly, AVDTC of graphs) and, meanwhile, have obtained the adjacent-vertex-distinguishing total chromatic number... 详细信息

关键词： graph, proper total coloring, adjacent-vertex-distinguishing total coloring, adjacent-vertex-distinguishing total chromatic number.

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