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Zhongxu Wang,Huai Wang,Yi Zhang,Frede Blaabjerg 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
In order to increase the efficiency and to improve the reliability of modular multilevel converters in medium voltage applications, this paper proposes an adaptive control method to choose an optimal carrier frequency dynamically according to power loading conditions of the modular multilevel converter. By evaluating the impact of the carrier frequency on the output current harmonic performance and the capacitor voltage ripple analytically, the proposed adaptive control can reduce the power loss and the thermal stress on the power semiconductors. Meanwhile, the electrical operation requirements can still be fulfilled. One-year mission profile is utilized to assess the energy efficiency and the reliability performance between the proposed and the traditional control scheme. Moreover, theoretical analyses and simulation results are presented to demonstrate the effectiveness of the proposed control.
Zhongxu Lian,Jinkai Xu,Peng Yu,Zhanjiang Yu,Zuobin Wang,Huadong Yu 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.11
As two typical special wettability materials, superhydrophobic and superoleophobic surfaces are the most widely studiedinterfaces because of their excellent water-or oil-repellent ability. However, how to use a simple strategy to obtain thosesurfaces is still a huge challenge. On the other hand, corrosion tend to occur while using metallic materials, resulting in poorperformance of metallic equipment and even serious safety hazards. In this work, a one-step strategy of nanosecond laserablation was presented to construct the microstructures acquired by superhydrophobic and superoleophobic aluminum alloysurfaces. The superhydrophobic and superoleophobic properties of microstructured surfaces were obtained via high temperatureand fluorosilane treatments on laser-processed surfaces, respectively, and the oil-repellent and corrosion resistanceproperties of both substrates were studied. The potentiodynamic polarization test shows that the superoleophobic surfacehad a better corrosion resistance than the superhydrophobic surface, which will provide an effective protection for the barealuminum alloy. Meanwhile, the superoleophobic surface had good chemical stability. It is believed that the nanosecond lasertechnology can offer an effective strategy for constructing the microstructures acquired by large-area superhydrophobic andsuperoleophobic surfaces on aluminum alloy materials.
A Hybrid Energy Storage System for an Electric Vehicle and Its Effectiveness Validation
Chunhua Zheng,Yafei Wang,Zhongxu Liu,Tianfu Sun,Namwook Kim,Jongryeol Jeong,차석원 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.6
A hybrid energy storage system (HESS), which consists of a battery and a supercapacitor, presents good performances on both the power density and the energy density when applying to electric vehicles. In this research, an HESS is designed targeting at a commercialized EV model and a driving condition-adaptive rule-based energy management strategy (EMS) is proposed for the HESS, which takes into account the superiority achievement of each ESS and also the protection to each ESS. The effectiveness of the HESS plus the EMS compared to the single battery case is validated by both the computer simulation and the semi-physical rapid control prototype (RCP) test bench. An electric loading equipment is adopted in the RCP experiment validation for simulating the vehicle driving cycle instead of the traditional combination of a motor and a dynamometer. Both validation results show that compared to the single battery case, the working status of the battery is stabilized by the addition of the supercapacitor in the HESS case during both the propelling and regeneration modes and the battery energy is also saved. A dynamic degradation model for the battery is adopted in order to evaluate the life cycle cost of the HESS. Results show that the HESS plus the EMS has the effect of prolonging the battery lifetime and the HESS is economically effective compared to the single battery case.
Ammonia etched petroleum pitch-based porous carbon as efficient catalysts for CO2 electroreduction
Ning Hui,Guo Zhihao,Wang Wenhang,Wang Xiaoshan,Yang Zhongxue,Ma Zhengguang,Tian Yangming,Wu Chenghao,Hao Jian,Wu Mingbo 한국탄소학회 2022 Carbon Letters Vol.32 No.3
Electrochemical reduction of carbon dioxide to valuable chemicals is a promising way of storing renewable energy through electric-to-chemical energy conversion, while its large-scale application is in urgent need of cheap and high-performance catalysts. Herein, we invent a convenient method to synthesize N-doped porous carbon by ammonia etching the pyrolysis carbon of petroleum pitch. We found the ammonia etching treatment not only increase the pyridinic-N content, but also enlarge the specific surface area of the petroleum pitch-based porous carbon. As a cheap and easily available catalyst for carbon dioxide electroreduction, up to 82% of Faradaic efficiency towards carbon monoxide was obtained at − 0.9 V vs the reversible hydrogen electrode in 0.1 M KHCO3. After a long time electrocatalysis of more than 20 h, the Faradaic efficiency of carbon monoxide remains 80%, indicating the porous carbon as made have an ultra-high stability as catalyst for carbon dioxide reduction. Our work provides a new technology to economically prepare efficient electrocatalysts for carbon dioxide reduction.