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Density functional theory investigation of oxygen interaction with boron-doped graphite

Applied Surface Science 2016年 390卷 273-282页

作者： Juan Liu Chen Wang Tongxiang Liang Wensheng Lai State Key Lab of New Ceramic and Fine Processing Institute of Nuclear and New Energy Technology Tsinghua University Beijing 100084 China Advanced Material Laboratory School of Materials Science & Engineering Tsinghua University Beijing 100084 China

Boron inserted as impurity by substitution of carbon atoms in graphite is known to change (improve or deteriorate) oxidation resistance of nuclear graphite, but the reason for both catalytic and inhibiting oxidation is still uncertain. As a first step, this work is more specially devoted to the adsorption and diffusion of oxygen atoms on the surface and related to the problem of oxygen retention on the pure and boron-containing graphite surfaces. Adsorption energies and energy barriers associated to the diffusion for molecular oxygen recombination are calculated in the density functional theory framework. The existence of boron modifies the electronic structure of the surface, which results in an increase of the adsorption energy for O. However, low boron loading makes it easier for the recombination into molecular oxygen. For high boron concentration, it induces a better O retention capability in graphite because the presence of B-B bonds decreases recombination of the adsorbed oxygen atoms. A possible explanation for both catalytic and inhibiting effects of boron in graphite is proposed.

关键词： Density functional calculations Chemisorption Graphite Boron Oxygen

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Design of High Power IGBT Interlocking Drive and Protect Circuit Supplied by Single Power Based on ACPL-332J

Design of High Power IGBT Interlocking Drive and Protect Cir...

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International Conference on Electrical Machines and Systems

作者： Yuan Zhu Kai Yang Dezhang Lou Tianbao Yu State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan 430074 R.P China

ISBN: (纸本)9781467388634

This paper proposes a novel design of high power IGBT interlocking drive and protect circuit supplied by single power based on ACPL-332J chip. Firstly, it introduces the basic principle of interlocking drive circuit. Then, peripheral protect circuit is presented in detail, including chip protect circuit and IGBT protect circuit. Why and how to choose parameters of each component also are described. A novel interlocking drive circuit, without adding any components, is designed to prevent short circuit of DC bus when gate drive signals of the upper and lower IGBTs in the same phase are turned on at the same time. This IGBT interlocking drive and protect circuit is proved to be stable and reliable in Servo drive system of PMSM by experiment.

关键词： permanent magnetic synchronous motor (PMSM) interlocking drive IGBT single power supply ACPL-332J over current protect circuit of IGBT

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13-3: Top-emitting Quantum-dot Light-emitting Diodes with all the p-i-n Functional Layers Deposited by Solution Processes

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SID Symposium Digest of Technical Papers 2017年第1期48卷

作者： Yibin Jiang Shuming Chen Hoi-Sing Kwok State Key Lab on Advanced Displays and Optoelectronics Department of Electronic and Computer Engineering The Hong Kong University of Science & Technology Clear Water Bay Kowloon Hong Kong Department of Electrical and Electronic Engineering Southern University of Science and Technology Shenzhen 518055 PR China

A green top-emitting quantum-dot light-emitting diode (TQLED) with conventional structure is demonstrated in this study with all its functional layers, including hole transportation layer, emitting layer and electron transportation layer, fabricated by spin-coating processes. This green QLED exhibits an external quantum efficiency (EQE) of 6.4 % and a maximum brightness of 200000 cd/m 2 , which is the highest values reported for green TQLEDs in literature. Besides, this is the first report of all-solution-processed TQLEDs.

关键词： quantum-dot light-emitting diodes top-emitting spin-coating all-solution-processed

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Interaction of boron with graphite: A van der Waals density functional study

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Applied Surface Science 2016年 379卷 402-410页

作者： Juan Liu Chen Wang Tongxiang Liang Wensheng Lai Beijing Key Lab of Fine Ceramics Institute of Nuclear and New Energy Technology Tsinghua University Beijing 100084 China State Key Lab of New Ceramic and Fine Processing Tsinghua University Beijing 100084 China Advanced Material Laboratory School of Materials Science & Engineering Tsinghua University Beijing 100084 China

Boron doping has been widely investigated to improve oxidation resistance of graphite. In this work the interaction of boron with graphite is investigated by a van der Waals density-functional approach (vdW-DF). The traditional density-functional theory (DFT) is well accounted for the binding in boron-substituted graphite. However, to investigate the boron atom on graphite surface and the interstitial impurities require use of a description of graphite interlayer binding. Traditional DFT cannot describe the vdW physics, for instance, GGA calculations show no relevant binding between graphite sheets. LDA shows some binding, but they fail to provide an accurate account of vdW forces. In this paper, we compare the calculation results of graphite lattice constant and cohesive energy by several functionals, it shows that vdW-DF such as two optimized functionals optB88-vdW and optB86b-vdW give much improved results than traditional DFT. The vdW-DF approach is then applied to study the interaction of boron with graphite. Boron adsorption, substitution, and intercalation are discussed in terms of structural parameters and electronic structures. When adsorbing on graphite surface, boron behaves as π electron acceptor. The π electron approaches boron atom because of more electropositive of boron than carbon. For substitution situation, the hole introduced by boron mainly concentrates on boron and the nearest three carbon atoms. The B-doped graphite system with the hole has less ability to offer electrons to oxygen, ultimately resulted in the inhibition of carbon oxidation. For interstitial doping, vdW-DFs show more accurate formation energy than LDA. PBE functional cannot describe the interstitial boron in graphite reasonably because of the ignoring binding of graphite sheets. The investigation of electron structures of boron doped graphite will play an important role in understanding the oxidation mechanism in further study.

关键词： Graphite Boron van der Waals density functional Oxidation

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Unit commitment considering coordinated dispatch of large scale electric vehicles and wind power generation

Unit commitment considering coordinated dispatch of large sc...

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International Conference on Renewable Power Generation, RPG 2015

作者： Wang, Chun Wu, Ke Zhang, Xiangwen Sun, Haishun Zhang, Cong Xv, Xiaohui China Electric Power Research Institute Beijing100192 China State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan430074 China

ISBN: (纸本)9781785610400

Assuming that all electric vehicles (EVs) integrated to the grid are managed by aggregators, it is possible to make full use of the controllability of the charging EVs. Based on this. the charging load of each EV aggregator is defined as one of the optimal scheduling variables in the unit commitment (UC) model. This can be accomplished by assessing the upper and lower limit of charging load of each EV aggregator in different scenarios, which is simulated by Monte Carlo method. According to this, a UC model is proposed for optimal coordination of EV aggregators and wind generation, considering the EV owner's requirement, the range of charging load and the unit constraints. Using the10-units system as the test system, the results of UC models with different EVs charging strategies and the wind power integration indicators such as utilization rate are investigated. Simulation results show that both the abandoned wind power and the unit operating costs can be decreased more effectively in the proposed UC model.

关键词： Electric vehicles

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Research on frequency regulation using scheduling capacity of electric vehicles

Research on frequency regulation using scheduling capacity o...

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International Conference on Renewable Power Generation, RPG 2015

作者： He, Chenying Zhang, Xiangwen Sun, Haishun Xu, Xiaohui Liu, Haixuan Zhang, Cong State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan430074 China China Electric Power Research Institute Beijing100192 China

ISBN: (纸本)9781785610400

Nowadays, growing number of electric vehicles (EVs) can not only be controllable load to regulate power system, but also serve as distributed energy storage unit that can feedback to the grid by vehicle-to-grid (V2G). Therefore, ancillary services for the grid such as frequency regulation can potentially be provided by the use of EVs with scheduling capacity. However, the scheduling capacity is limited by factors such as the constraints of customers travel demand and the battery life. Based on this, a centralized control mode is applied for distributed EVs and a mathematical model with charging and discharging static frequency characteristics of aggregators is established, considering EVs scheduling capacity. According to this, load frequency control models both for single and two-area power systems are proposed. The simulation results show that using EVs scheduling capacity for frequency regulation can effectively help reducing the system frequency deviation and thus improving the electricity quality. Furthermore, the reserve capacity of traditional frequency regulation units can be decreased and especially power system economics has developed.

关键词： Electric power system control

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Hydrogen Electrocatalysis: Self‐Assembly of Large‐Area 2D Polycrystalline Transition Metal Carbides for Hydrogen Electrocatalysis (Adv. Mater. 50/2018)

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advanced Materials 2018年第50期30卷

作者： Xining Zang Wenshu Chen Xiaolong Zou J. Nathan Hohman Lujie Yang Buxuan Li Minsong Wei Chenhui Zhu Jiaming Liang Mohan Sanghadasa Jiajun Gu Liwei Lin Research Laboratory of Electronics Massachusetts Institute of Technology Cambridge MA 02139 USA Mechanical Engineering University of California Berkley Berkeley CA 94704 USA State Key Laboratory of Metal Matrix Composites Shanghai Jiao Tong University Shanghai 200240 China Tsinghua–Berkeley Shenzhen Institute Shenzhen 518055 China The Molecular Foundry Lawrence Berkeley National Lab Berkeley CA 94704 USA Advanced Light Source Lawrence Berkeley National Lab Berkeley CA 94704 USA U.S. Army RDECOM AMRDEC Redstone Arsenal AL 35898 USA

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Active Damping of Output LCL Filter in PWM Inverter-Fed Drive System With Long Motor Cable

Active Damping of Output LCL Filter in PWM Inverter-Fed Driv...

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International Conference on Electrical Machines and Systems

作者： Guangqiang Kan Shenghua Huang Xunhao Zou State Key Laboratory Ratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan 430074 R.P. China

ISBN: (纸本)9781467388634

In the PWM inverter-fed drive systems, overvoltage easily occur at the terminal of motor because of the high change rate of the inverter output voltage. Especially, when there is a long motor cable between the inverter and motor in some application, voltage reflection makes such phenomenon much more obvious. Overvoltage will lead to the failure of the motor and cable insulation. The LCL filter is often used to make the voltage sinusoidal, suppressing overvoltage. However, the LCL filter may causes the oscillation or resonance at system resonant frequency. One of the methods to solve the problem is passive damping. Although passive damping is simple and reliable, it will result in the loss of power. In this paper, a feasible and simple active damping algorithm for permanent magnet synchronous motor (PMSM) vector control system with LCL filter is proposed. The high-frequency component of the inverter side inductor current is multiplied by the virtual resistance to simulate the resistance drop. Meanwhile, the fundamental component of the inductor current inverter side can be used in the motor control. Compared with the traditional active damping, the proposed algorithms can save a set of sensors. The proposed algorithm is irrelevant to the design of standard vector control. Simulation results show that the proposed algorithm is feasible.

关键词： Active damping (AD) LCL filter long motor cable vector control

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DFIG WT electromechanical transient behaviour influenced by PLL: Modelling and analysis

DFIG WT electromechanical transient behaviour influenced by ...

引用

International Conference on Renewable Power Generation, RPG 2015

作者： Wang, Yajing Hu, Jiabing Zhang, Dongliang Ye, Chao Li, Qing State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Eelectronic Engineering Huazhong University of Science and Technology Wuhan430074 China China Electric Power Research Institute Beijing100192 China

ISBN: (纸本)9781785610400

With increasing wind power penetrations, WTGs shoulder a higher responsibility. Traditional WTG control and modelling is generally designed assuming that the external grid is strong enough. However, in the case of weak grid in which power variations between synchronous generators (SG) and DFIG are more intense, more appropriate DFIG model needs to be built for electromechanical transient stability analysis of power system. Phase-locked loop (PLL) is typically employed in modern megawatt WTGs and tracks the WT's terminal voltage phase change, so as to provide reference frame for active/reactive power control. Thus power output of DFIG as well as other power source in the system subjects to PLL's dynamic responses. This work establishes a DFIG-based WT's electromechanical transient model considering the dynamic influence of PLL, and analyses its dynamic response which influences WTG electromechanical transient behaviour and system stability.

关键词： Phase locked loops

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Research and Design of High Power Factor Induction Motor Drive Based on V/f Control

Research and Design of High Power Factor Induction Motor Dri...

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International Conference on Electrical Machines and Systems

作者： Xiaoguang Wang Fang Wei Jun Yang Cheng Luo Dezhang Lou Kai Yang State Key Laboratory of Advanced Electromagnetic Engineering and Technology *Huazhong University of Science and Technology Wuhan 430074 R.P.China Wuhan Polytechnic

ISBN: (纸本)9781467388634

This paper presented the design and implementation of an induction motor drive. In order to improve energy efficiency of this drive, system configuration comprised a single to three-phase converter with additional circuitry for PFC. In this design, using TI's UC3854 as the PFC controller chip, and the related parameters were designed. The control scheme was based on V/f control using two low-cost resistance current sensors. Only stator current measurements were needed to compensate for stator resistance drop. Regardless of changes in frequency or load, the magnitude of the stator flux can be constant by vectorially modifying the stator voltage. Furthermore, the hardware and software design were presented in detail. Experiments results showed that the proposed control system had high power factor and excellent performance.

关键词： induction motor PFC V/f control

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