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Joint limiting Control Strategy Based on Virtual Impedance Shaping for Suppressing DC Fault Current and Arm Current in MMC-HVDC Systems

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Journal of Modern Power Systems and Clean Energy 2023年第6期11卷 2003-2014页

作者： Qin Jiang Yan Tao baohong li Tianqi liu Zhe Chen Frede Blaabjerg Peng Wang IEEE College of Electrical Engineering Sichuan UniversityChengdu 610065China Smart Grid Key Laboratory of Sichuan Province Chengdu610065China State Grid Jiangsu Electric Power Company Research Institute Nanjing 211103China Department of Energy Technology Aalborg UniversityAalborg 9920Denmark School of Electrical and Electronic Engineering Nanyang Technological UniversitySingapore 639798Singapore

This paper proposes a joint limiting control strategy for suppressing DC fault current and arm current in modular multilevel converter-based high-voltage direct current(MMC-HVDC) systems, which includes two target-oriented current limiting controls. To limit the DC fault current in the early fault stage, an equivalent modular multilevel converter(MMC) impedance is obtained, and its high-frequency part is reshaped by introducing virtual impedance, which is realized by adjusting the inserted submodules adaptively. Following the analysis of MMC control characteristics, the arm current limiting strategy is investigated, with results showing that the inner-loop control has significant effects on arm current and that a simple low-pass filter can reduce the arm current in the fault period. Finally, by combining the virtual impedance shaping and innerloop control, the fault currents of DC lines and MMC arms can be suppressed simultaneously, which can not only alleviate the interrupting pressure of the DC circuit breaker, but also prevent the MMC from being blocked by the arm overcurrent. Theoretical analysis conclusions and the proposed strategy are verified offline by a digital time-domain simulation on Power Systems Computer Aided Design/Electromagnetic Transients including DC platform, and experiment on a real-time digital simulator platform.

关键词： Modular multilevel converter(MMC) highvoltage direct current(HVDC)transmission direct current fault fault current limitation arm current suppression virtual impedance direct current circuit breaker

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Impact of Grid Topology on Pole-to-ground Fault Current in Bipolar DC Grids:Mechanism and Evaluation

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Journal of Modern Power Systems and Clean Energy 2023年第2期11卷 434-445页

作者： Yingmin Zhang Wenxin Zhang Qiao Peng baohong li Yan Tao Min Zhang Tianqi liu Frede Blaabjerg College of Electrical Engineering Sichuan UniversityChengdu 610065China Electric Power Research Institute State Grid Shanxi Electric Power CompanyTaiyuan 030001China AAU Energy Aalborg UniversityAalborg 9920Denmark

The fault current level analysis is important for bipolar direct current(DC)grids,which determines the operation and protection *** DC grid topology significantly impacts the current path and then the fault current level of the grid,which makes it possible to limit the fault current by optimizing the grid ***,the corresponding discussion in the literature is *** at this point,the impact of grid topology,i.e.,the connecting scheme of converters,on the pole-to-ground fault current in bipolar DC grids,is investigated in this paper,and the ground-return-based and metallic-return-based grounding schemes are considered,***,the decoupled equivalent model in frequency domain for fault current analysis is ***,the impacts of converters with different distances to the fault point on the fault current can be analyzed according to the high-frequency impedance *** on the analysis results,a simplified fault current index(SFCI)is proposed to realize the fast evaluation of impact of grid topology on the fault current *** SFCI is then applied to evaluate the relative fault current ***,the simulation results validate the model,the analysis method,and the SFCI,which can effectively evaluate the relative fault current level in a direct and fast manner.

关键词： Bipolar DC grid pole-to-ground fault grid topology fault current evaluation simplified fault current index

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印染废水原水磁混凝沉淀预处理工程改造实例

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给水排水 2024年第6期50卷 99-104页

作者：曾祥专黄义勋王俊先龚志辉邓伟权李宝宏郭春胜卢思敏广东恩维乐环境科技有限公司广州510320 佛山市顺德区前进实业有限公司佛山528303 华南师范大学广州510006

广东顺德某印染企业废水处理站原设计采用普通斜管沉淀池作为印染废水预处理措施。由于污泥量大,沉淀池跑泥现象较为严重,抗冲击负荷能力弱,土地利用效率不高。为改善预处理出水效果,同时也为了给未来深度处理改造工程腾出用地,该厂设... 详细信息

广东顺德某印染企业废水处理站原设计采用普通斜管沉淀池作为印染废水预处理措施。由于污泥量大,沉淀池跑泥现象较为严重,抗冲击负荷能力弱,土地利用效率不高。为改善预处理出水效果,同时也为了给未来深度处理改造工程腾出用地,该厂设计采用磁混凝工艺替代原有斜管沉淀池对进水进行混凝沉淀预处理。改造工程运行结果表明,在节省占地50%的情况下,改造后污水磁混凝预处理系统出水效果稳定,COD去除率稳定在40%~50%,出水水质优于改造前。磁混凝后物化污泥浓度高,经过调理后,污泥浓缩性能较好,污泥压滤处理系统负荷相对改造前变化不大。改造项目的调试与运行实践表明,磁混凝工艺用于高污泥产量的工业废水原水预处理需要同时考虑表面负荷与固体负荷两个重要参数。

关键词：磁混凝印染废水原水预处理表面负荷固体负荷

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Anti-biofouling NH_(3) gas sensor based on reentrant thorny ZnO/graphene hybrid nanowalls

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Microsystems & Nanoengineering 2020年第1期6卷 706-716页

作者： Tian Hang Jiangming Wu Shuai Xiao baohong li Hongbo li Chengduan Yang Cheng Yang Ning Hu Yonghang Xu Yu Zhang Xi Xie State Key Laboratory of Optoelectronic Materials and Technologies School of Electronics and Information TechnologyGuangdong Province Key Laboratory of Display Material and TechnologySun Yat-Sen UniversityGuangzhou 510006China School of Materials Science and Energy Engineering Foshan UniversityFoshan 528000China The First Affiliated Hospital of Sun Yat-Sen University Guangzhou 510080China

Since toxic gas leakage may cause ecological environmental problems and even life-threatening damage,effective monitoring of toxic gas is of great importance and subject to increasing ***,complicated environmental factors,as well as various coexisting interferences can easily affect the sensitivity and selectivity of gas sensors,hindering their *** reports have successfully demonstrated the development of hierarchical nanostructures with desirable self-cleaning properties,yet gas sensors that can resist contamination have rarely been ***,we developed a reentrant thorny ZnO/graphene hybrid nanowall structure that simultaneously repels liquid contamination and possesses NH_(3) gas sensing *** unique reentrant and hierarchical structure,featuring an interconnected vertical graphene nanowall framework with numerous ZnO nanospikes branched on the top nanowall,is highly repellent to liquids,even biofluids with low surface *** hierarchical structure consisting of gas sensing graphene and ZnO can be successfully applied as an NH_(3) gas sensor at room temperature,exhibiting not only excellent sensitivity,selectivity,and repeatability,but also outstanding stability even after bacterial *** study provides a versatile method for fabricating reentrant and hierarchical structures with excellent liquid repellency,and offers a promising method for designing reliable gas sensors with anti-biofouling properties.

关键词： fouling walls versatile

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Unlocking supercapacitive energy storage potential:Catalyzing electrochemically inactive manganese oxides to active MnO_(2)via heterostructure reconstruction

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Nano Research 2024年第7期17卷 5897-5906页

作者： baohong Zhang Tao Jiang Xinyan Zhou Xiaoyu Fan Binbin Jia lidong li School of Chemistry Beihang UniversityBeijing 100191China College of Materials and Chemical Engineering Key Laboratory of Inorganic Nonmetallic Crystalline and Energy Conversion MaterialsChinaThree Gorges UniversityYichang 443002China Chinese Academy of Sciences(CAS)Key Laboratory of Nanosystem and Hierarchy Fabrication CAS Center for Excellence in NanoscienceNational Center for Nanoscience and TechnologyBeijing 100190China Shanghai GTX Semiconductor Co. Ltd.Shanghai 201806China

Advancing supercapacitor system performance hinges on the innovation of novel electrode materials seamlessly integrated within distinct ***,we introduce a direct approach for crafting nanorod arrays featuring crystalline/amorphous CuO/MnO_(2)−*** reconfigured heterostructure results in an elevated content of electrochemically active MnO_(2).The nanorod arrays serve as efficient capacitive anodes and are easily prepared via low-potential electrochemical *** resulting structure spontaneously forms a p–n heterojunction,developing a built-in electric field that dramatically facilitates the charge transport *** intrinsic electric field,in conjunction with the crystalline/amorphous architecture,enables a large capacitance of 1.0 F·cm^(−2)at 1.0 mA·cm^(−2),an ultrahigh rate capability of approximately 85.4%at 15 mA·cm^(−2),and stable cycling performance with 92.4%retention after 10,000 *** calculations reveal that the presence of heterojunctions allows for the optimization of the electronic structure of this composite,leading to improved conductivity and optimized OH−adsorption *** work provides new insights into the rational design of heterogeneous nanostructures,which hold great potential in energy storage applications.

关键词： reconfiguration active MnO_(2) crystalline/amorphous structure p-n heterojunction supercapacitor

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Simulation on Peak-to-Average Power Ratio for Orthogonal Frequency Division Multiplexing

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Wuhan University Journal of Natural Sciences 2006年第6期11卷 1873-1876页

作者： SHAN Weifeng MENG baohong liU Ningning li Hui ZHANG Hongwei Department of Command Communication and Command Academy Wuhan 430010 Hubei China

Clipping is a simple and convenient PAPR （peak-to-average power ratio） reduction method for high speed OFDM （orthogonal frequency division multiplexing） communication system. In this paper, we propose a new PAPR reduction method for Wireless-MAN（metropolitan area network）-OFDM system based on IEEE 802.16, which is over-sampling clipping arithmetic. Simulation and performance of the over-samples clipping＇s PAPR reduction capability, BER effect is given. The simulation indicates that the PAPR of at least 99.9% OFDM symbol is below 6dB after 2 Nyquist rate clipping, and the performance of BER has 1dB SNR（signal noise ratio） loss. The results prove that this method has better capacity to reducing PAPR. So it can be well used in WMAN-OFDM system.

关键词： peak-to-average power ratio OFDM(orthogonal frequency divisior multiplexing) clipping

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基于等效电流源的级联混合直流馈入系统强度影响分析

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电网技术 2024年第3期48卷 1244-1252页

作者：何遥张英敏李保宏江琴刘天琪王洪耀张婉欣四川大学电气工程学院四川省成都市610065

级联型混合直流系统受端的模块化多电平换流器高压直流系统(modular multilevel converter high voltage direct current,MMC-HVDC)和电网换相换流器高压直流系统(line commutated converter high voltage direct current,LCC-HVDC)会因馈入点电气距离较近而存在强相互作用关系。为明确级联型混合直流馈入系统中MMC-HVDC对LCC-HVDC系统强度的影响,提出考虑幅值和相位的MMC等效电流源的简化等效方法,基于所提MMC等效原理将级联型混合直流馈入系统等效成单馈入LCC-HVDC系统,分析等效单馈入系统的参数计算方法,并提出等效单馈入短路比评估指标。最后通过该指标分析归纳了不同控制方式、不同电气距离下等效单馈入系统的系统强度变化情况,即为MMC-HVDC对LCC-HVDC系统强度的影响规律。机理分析和基于PSCDAD/EMTDC、MATLAB的仿真结果表明,所提等效方法具有有效性且所提指标能很好地反应MMC-HVDC对LCC-HVDC系统强度的影响。

关键词：级联型混合直流系统相互作用关系系统强度 MMC等效电流源等效单馈入短路比

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Fluorescence detection of Escherichia coli on mannose modified ZnTe quantum dots

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Chinese Chemical Letters 2020年第6期31卷 1504-1507页

作者： Dudu Wu Dongming Wang Xiaomei Ye Kangrui Yuan Yuling Xie baohong li Chaobo Huang Tairong Kuang Zhiqiang Yu Zhi Chen School of Pharmacy Guangdong Medical UniversityDongguan 523808China College of Chemical Engineering Nanjing Forestry University Nanjing 210037China College of Materials Science and Engineering Zhejiang University of TechnologyHangzhou 310014China School of Pharmaceutical Sciences Guangdong Provincial Key Laboratory of New Drug ScreeningSouthern Medical UniversityGuangzhou 510515China State Key Laboratory of Polymer Materials Engineering Sichuan UniversityChengdu 610065China

Rapid detection and identification of Escherichia coli(***)is essential to prevent its quickly *** this study,a novel fluorescence probe based on ZnTe quantum dots(QDs)modified by mannose(MAN)had been prepared for the determination of *** results showed that the obtained QDs showed excellent selectivity toward ***,and presented a good linearity in range of 1.0×10~5~1.0×10~8 CFU/*** optimum fluorescence intensity for detecting *** was found to be at pH 7.0 with a temperature of25℃and incubation time of 20 *** these optimum conditions,the detection limit of *** was4.6×10~4 CFU/*** quenching was discussed to be a static quenching procedure,which was proved by the quenching efficiency of QDs decreased with the temperature increasing.

关键词： ZnTe quantum dots Fluorescence intensity Probe Mannose Escherichia coli

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Assessment of Toxicity of BSA-conjugated Zinc Oxide Quantum Dots for C2C12 Cells

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Journal of Wuhan University of Technology(Materials Science) 2019年第3期34卷 736-743页

作者： CHEN Zhi WU Dudu School of Pharmacy Guangdong Medical University

Colloidal semiconductor nanoparticles (quantum dots, QDs) have attracted a lot of interests in numerous biological and medical applications due to their potent fluorescent properties. However, the possible toxic effects of quantum dots remain an issue of debate. In this study, we aimed to evaluate the cytocompatibility of bovine serum albumin (BSA) conjugated zinc oxide QDs for C2C12 cells. In the experiment, ZnO QDs were synthesized by using BSA as the structure directing agent, and the morphology and crystal phase of ZnO QDs were determined by transmission electron microscopy, X-ray diffractograms and Fourier transform infrared spectrograph techniques. The inverted fluorescence microscope results showed that ZnO QDs were distributed inside the cells. The toxicity of ZnO QDs was assessed by MTT methods, which revealed that ZnO QDs were highly cytocompatible in the concentration less than 200 μM. However, when the concentration of QDs was higher than 1 000 μM ZnO QDs showed significantly toxicity, which was ascribed to generation of free zinc and formation of reactive oxygen species (ROS). Furthermore, the morphological observations exhibited that cells treated with ZnO QDs showed altered morphology, depolymerized cytoskeleton and irregular-shaped nuclei. This study provides helpful guidances on the future safe use and manipulation of QDs to make them suitable tools in nanomedicine.

关键词： zinc oxide bovine serum albumin quantum dots toxicity cells

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矿山应急救援虚拟仿真虚实互动技术及实现途径

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现代矿业 2024年第6期40卷 1-4,8页

作者：孙颍昊毋晓军李保宏李玉良崔豫楠党煜太原理工大学安全与应急管理工程学院山西省晋中市0306001 陕煤集团神南产业发展有限公司

虚实互动技术是虚拟仿真的重要组成部分,现有矿山虚拟互动技术存在交互单一、跟手性差等不足,实际应用表现不佳。为此,提出了适用于矿山应急救援虚拟仿真虚实互动技术的实现途径,以多模态交互技术为基础,运用虚拟多角色协同作业交互技... 详细信息

虚实互动技术是虚拟仿真的重要组成部分,现有矿山虚拟互动技术存在交互单一、跟手性差等不足,实际应用表现不佳。为此,提出了适用于矿山应急救援虚拟仿真虚实互动技术的实现途径,以多模态交互技术为基础,运用虚拟多角色协同作业交互技术与环境漫游系统。通过运用这些技术,极大提升了矿山应急救援虚拟仿真虚实互动的交互效率与沉浸感,为智慧矿山建设提供技术支撑。

关键词：虚实互动多模态交互非接触感知矿山应急救援

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