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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

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 requirements.The 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 topology.However,the corresponding discussion in the literature is indigent.Aiming 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,respectively.Firstly,the decoupled equivalent model in frequency domain for fault current analysis is obtained.Then,the impacts of converters with different distances to the fault point on the fault current can be analyzed according to the high-frequency impedance characteristics.Based 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 level.The SFCI is then applied to evaluate the relative fault current level.Finally,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

Dual innervation of spinal ganglion neurons on perineum and bladder

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Chinese Science Bulletin 1998年第2期43卷 137-140页

作者： Guowei Lü Zhuo Meng baohong li Zhigao Jin Capital Univ Med Sci Dept Neurobiol Beijing 100054 Peoples R China Chinese Acad Tradit Chinese Med Inst Acupuncture Beijing 100700 Peoples R China

Experiments were performed on 13 Wister rats. Fastblus (FB) was injected into subcutaneous tissue in perineum area and nuclear yellow (NY) was injected into subserous lamina of the bladder wall, respectively. FB, NY and FB+NY were mostly found in the spinal ganglions of L6, S1 ans S2 segments. The numbers of FB,NY and FB+NY labeled cells were 146, 186 and 81, in a total of 463 labeled cells and their proportion was 40%, 51% and 9%, respectively. The result indicates that the spinal ganglion neurons dually innervate both the somatic and visceral tissues, and the convergence of somato_visceral sensory pathways might occur in the spinal ganglion cells.

关键词： spinal ganglion double fluorescent labeling somatovisceral interaction.

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酸酐酰化胶原蛋白的制备与表征及应用

中国组织工程研究 2024年第15期28卷 2430-2436页

作者：李炜钊周慧彭新生李宝红广东医科大学药学院广东省东莞市523808

背景:胶原蛋白是一种具有良好生物相容性、低毒性、低免疫活性且高细胞亲和力的生物医药材料,然而亲水性和热稳定性较差等缺陷是其在生物医学、组织工程等应用领域亟需解决的关键技术难题之一。目的:阐述酰化胶原蛋白的制备方法、表征... 详细信息

背景:胶原蛋白是一种具有良好生物相容性、低毒性、低免疫活性且高细胞亲和力的生物医药材料,然而亲水性和热稳定性较差等缺陷是其在生物医学、组织工程等应用领域亟需解决的关键技术难题之一。目的:阐述酰化胶原蛋白的制备方法、表征及应用的进展。方法:利用PubMed、X-mol和中国知网数据库,检索有关酰化胶原蛋白制备方法、表征及应用的文献,检索时间为1992年1月至2023年5月,英文检索词为“acylated collagen,modified collagen,water-soluble collagen,acetic anhydride”,中文检索词为“酰化胶原蛋白,改性胶原蛋白,水溶性胶原蛋白”。根据纳入与排除标准对所有文章进行初筛后,保留相关性较高的53篇文章进行综述。结果与结论:①酰化胶原蛋白的制备主要是通过酸酐类进行酰化反应所得,反应的位点主要是胶原蛋白的ε-氨基和N端-氨基,同时酰化反应的反应环境需要在碱性环境下进行;②琥珀酸酐是酰化胶原蛋白的首选反应物,同时近几年挖掘出降冰片烯二酸酐、柠檬酸酐以及具有酰化能力的双官能团改性剂来满足各种要求,但仍局限于实验室中制备,复杂的制备流程难以工业化,还需后续研究不断完善;③酰化胶原蛋白的表征手段与胶原蛋白类同,但针对酰化胶原蛋白的水溶性表征仍缺乏标准;④近年来酰化胶原蛋白逐步被用于镜片、水凝胶和敷料的制备及化妆品原料,但关于酰化胶原蛋白的应用研究仍然较少,缺乏完整的体内实验来验证酰化胶原蛋白的实用性。

关键词：胶原蛋白酰化酸酐酰化胶原蛋白表征应用领域综述

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 demand.However,complicated environmental factors,as well as various coexisting interferences can easily affect the sensitivity and selectivity of gas sensors,hindering their performance.Recent reports have successfully demonstrated the development of hierarchical nanostructures with desirable self-cleaning properties,yet gas sensors that can resist contamination have rarely been realized.Here,we developed a reentrant thorny ZnO/graphene hybrid nanowall structure that simultaneously repels liquid contamination and possesses NH_(3) gas sensing properties.The 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 tension.The 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 contamination.This 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

基于生态翻译学“十化”译法的佛经典籍英译研究——以《般若波罗蜜多心经》两个英译本为例

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法音 2024年第5期 65-70页

作者：王娟李宝宏西安理工大学人文与外国语学院

佛教典籍是中国文化的重要组成部分,在中国文化“走出去”的大战略背景下,其译介对传播中国文化、促进人文交流发挥着重要作用。《般若波罗蜜多心经》(以下简称“《心经》”)浓缩了大乘佛教的核心要义,内容虽短,但义理丰富,是大乘佛教... 详细信息

佛教典籍是中国文化的重要组成部分,在中国文化“走出去”的大战略背景下,其译介对传播中国文化、促进人文交流发挥着重要作用。《般若波罗蜜多心经》(以下简称“《心经》”)浓缩了大乘佛教的核心要义,内容虽短,但义理丰富,是大乘佛教最重要的经书之一,其中以玄奘译本在国内流传最为广泛。自近代以来,《心经》开始被译为英文。

关键词：大乘佛教《心经》佛教典籍波罗蜜般若生态翻译学人文交流战略背景

基于多类型换流设备的受端电网耦合鲁棒阻尼控制策略

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电力自动化设备 2024年第3期44卷 210-216页

作者：孙天一李保宏江琴张英敏张敏王腾鑫四川大学电气工程学院四川成都610065 国网山西省电力公司电力科学研究院山西太原030001

针对混合级联直流馈入与柔性输电设备密集接入的受端电网,为增强其特定振荡模式的阻尼,利用不同换流设备控制回路间的相互作用,提出了一种基于多输入多输出系统模型的耦合鲁棒阻尼控制器设计方法。根据主模比指标选取振荡抑制效果最佳... 详细信息

针对混合级联直流馈入与柔性输电设备密集接入的受端电网,为增强其特定振荡模式的阻尼,利用不同换流设备控制回路间的相互作用,提出了一种基于多输入多输出系统模型的耦合鲁棒阻尼控制器设计方法。根据主模比指标选取振荡抑制效果最佳的反馈信号作为控制器输入信号;利用总体最小二乘-旋转不变技术识别系统的振荡模式并辨识系统降阶模型;采用混合H_(2)/H_(∞)方法设计耦合鲁棒控制阻尼器。控制器采用平衡截断法进行降阶,兼具鲁棒性能与实际工程应用。混合级联直流与受端江苏电网互联系统的时域仿真结果表明,相比于传统超前-滞后控制器,耦合鲁棒阻尼控制器在多种扰动和故障下均能有效抑制低频振荡,使系统快速恢复稳定运行。

关键词：交直流互联电网柔性输电设备低频振荡混合H2/H∞方法耦合鲁棒阻尼控制

级联型混合直流与UPFC的柔性潮流协调控制策略

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工程科学与技术 2024年第2期56卷 80-90页

作者：黑玉鹏张英敏李保宏江琴张婉欣张敏王腾鑫四川大学电气工程学院四川成都610065 国网山西省电力科学研究院山西太原030002

级联型混合直流输电系统具有能抑制换相失败、传输大容量功率的优势。但当级联型混合直流低端模块化多电平换流器(MMC)采用主从控制时,若系统发生交直流故障或负荷突增,可能会产生电流不平衡问题,导致受端交流侧功率出现大范围反向传输... 详细信息

级联型混合直流输电系统具有能抑制换相失败、传输大容量功率的优势。但当级联型混合直流低端模块化多电平换流器(MMC)采用主从控制时,若系统发生交直流故障或负荷突增,可能会产生电流不平衡问题,导致受端交流侧功率出现大范围反向传输及电压支撑能力下降。为解决该问题并增强受端电网的稳定性,针对级联型混合直流输电系统,提出一种基于统一潮流控制器(UPFC)的柔性潮流协调控制策略。研究了基于柔性交流输电(FACTS)设备统一潮流控制器(UPFC)的级联型混合直流系统柔性潮流控制特性,针对系统故障及大扰动时出现的功率返送及电压稳定性问题,提出基于UPFC的频率支撑策略和基于动态限幅的电压支撑策略。该策略将送端侧故障带来的功率扰动转移到受端交流系统UPFC所在线路,利用UPFC功率补偿能力进行协调,同时基于动态限幅控制策略,采用无功优先控制方式提高换流站无功输出能力。最后,在PSCAD–EMTDC平台搭建了含受端交流系统的级联型混合直流输电系统模型。首先,仿真了LCC直流电流指令值下降过程,结果表明,本文所提基于UPFC的协调控制策略可以有效地减小交流系统频率波动,抑制功率返送现象;其次,仿真了系统负荷突增过程,验证了动态限幅控制策略能更好地提升MMC对交流系统的电压支撑能力;最后,仿真了连锁故障过程,结果表明,所提协调控制策略能有效地实现对系统频率和电压支撑,抑制功率波动,提高了级联型混合直流系统及受端电网的稳定性。因此,本文提出的级联型混合直流与UPFC的柔性潮流协调控制策略具有有效性和可行性。

关键词：混合直流输电系统统一潮流控制器(UPFC) 动态限幅协调控制策略电压支撑

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