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Optimal Planning of Hybrid AC/DC Low-voltage Distribution Networks Considering DC Conversion of Three-phase Four-wire Low-voltage AC Systems

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Journal of Modern Power Systems and Clean Energy 2024年第1期12卷 141-153页

作者： Bo Zhang Lu Zhang Wei Tang Gen Li Chen Wang the College of Information and Electrical Engineering China Agricultural UniversityBeijing 100083China the Electric Energy Group Department of Engineering TechnologyTechnical University of Denmark(DTU)2750 BallerupDenmark the Power Distribution Technology center State Grid Beijing Electric Power Research InstituteBeijing 100075China

The increasing integration of distributed household photovoltaics(PVs)and electric vehicles(EVs)may further ag gravate voltage violations and unbalance of low-voltage distribu tion networks(LVDNs).DC distribution networks can increase the accommodation of PVs and EVs and mitigate mutilple pow er quality problems by the flexible power regulation capability of voltage source converters.This paper proposes schemes to es tablish hybrid AC/DC LVDNs considering the conversion of the existing three-phase four-wire low-voltage AC systems to DC op eration.The characteristics and DC conversion constraints of typical LVDNs are analyzed.In addition,converter configura tions for typical LVDNs are proposed based on the three-phase four-wire characteristics and quantitative analysis of various DC configurations.Moreover,an optimal planning method of hybrid AC/DC LVDNs is proposed,which is modeled as a bi-level programming model considering the annual investments and three-phase unbalance.Simulations are conducted to verify the effectiveness of the proposed optimal planning method.Sim ulation results show that the proposed optimal planning method can increase the integration of PVs while simultaneously reduc ing issues related to voltage violation and unbalance.

关键词： Optimal planning low-voltage distribution net work three-phase unbalance DC conversion

Multi-Branch Fault Line Location Method Based on Time Difference Matrix Fitting

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Energy Engineering 2024年第1期121卷 77-94页

作者： Hua Leng Silin He Jian Qiu Feng Liu Xinfei Huang Jiran Zhu School of Electrical and Information Engineering Hunan UniversityChangsha410082China Distribution Network technical center State Grid Hunan Electric Power Research InstituteChangsha410007China technical center China Energy Construction Group Hunan Thermal Power ConstructionZhuzhou412011China School of Electrical and Information Engineering Changsha University of Science and TechnologyChangsha410076China

The distribution network exhibits complex structural characteristics,which makes fault localization a challenging task.Especially when a branch of the multi-branch distribution network fails,the traditional multi-branch fault location algorithm makes it difficult to meet the demands of high-precision fault localization in the multi-branch distribution network system.In this paper,the multi-branch mainline is decomposed into single branch lines,transforming the complex multi-branch fault location problem into a double-ended fault location problem.Based on the different transmission characteristics of the fault-traveling wave in fault lines and non-fault lines,the endpoint reference time difference matrix S and the fault time difference matrix G were established.The time variation rule of the fault-traveling wave arriving at each endpoint before and after a fault was comprehensively utilized.To realize the fault segment location,the least square method was introduced.It was used to find the first-order fitting relation that satisfies the matching relationship between the corresponding row vector and the first-order function in the two matrices,to realize the fault segment location.Then,the time difference matrix is used to determine the traveling wave velocity,which,combined with the double-ended traveling wave location,enables accurate fault location.

关键词： Multi-branch lines distribution network fault location double-ended traveling wave positioning least square method

Challenges and prospects for room temperature solid-state sodiumsulfur batteries

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Nano Research 2024年第3期17卷 1402-1426页

作者： Yashuang Qiu Jing Xu Research center of grid Energy Storage and Battery Application School of Electrical and Information EngineeringZhengzhou UniversityZhengzhou 450001China

Room temperature sodium-sulfur(Na-S)batteries,known for their high energy density and low cost,are one of the most promising next-generation energy storage systems.However,the polysulfide shuttling and uncontrollable Na dendrite growth as well as safety issues caused by the use of organic liquid electrolytes in Na-S cells,have severely hindered their commercialization.Solid-state electrolytes instead of liquid electrolytes are considered to be the most direct and effective solution to solve the above problems.However,its practical application is still greatly challenged due to the poor interfacial compatibility between the all-solid-state electrolytes and the anode/cathode,ionic conductivity,and the shuttle effect caused by the presence of liquid phase in the quasi-solid-state electrolytes.This paper presents a comprehensive review of solid-state Na-S batteries from the perspective of regulating interfacial compatibility and improving ionic conductivity as well as suppressing polysulfide shuttle.According to different components,solid-state electrolytes were divided into five categories:solid inorganic electrolytes,solid polymer electrolytes,polymer/inorganic solid hybrid electrolytes,gel polymer electrolytes,and liquid–solid inorganic hybrid electrolytes.Finally,the prospect of developing high performance solid-state electrolytes to improve the cycling stability of room temperature Na-S cells is envisaged.

关键词： sodium-sulfur batteries solid-state electrolytes ionic conductivity polysulfide shuttling interfacial compatibility

Review on birefringence in borates based on birefringence-active functional groups and arrangements

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Science China Chemistry 2024年第7期67卷 2155-2170页

作者： Qianzhen Zhang Ran An Zhihua Yang Xifa Long Shilie Pan Yun Yang Research center for Crystal Materials State Key Laboratory of Functional Materials and Devices for Special Environmental ConditionsXinjiang Key Laboratory of Functional Crystal MaterialsThe Xinjiang Technical Institute of Physics&ChemistryChinese Academy of SciencesUrumqi 830011China center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China

As a fundamental parameter of the optical crystals,birefringence plays a vital role in many optical applications,such as phase modulation,light splitting,and polarization,especially the phase matching process of the nonlinear optical crystals.The big birefringence not only benefits to the miniaturization of related devices,but also broadens the phase-matching wavelength range of nonlinear optical crystals.The design and synthesis of crystals with large birefringence becomes a hot research topic due to its more and more important applications in the optical modulation and laser technology fields.Herein,crystals with birefringence greater than 0.05 in the borate system are reviewed and classified according to different birefringent active groups,and the relationship between structure and properties is thoroughly explored.It is hoped that this review will provide a clear understanding of what kinds of building units and arrangements would have more opportunity to get adequate birefringence in borate systems and provide the statistical references to encourage the emergence of better crystal materials with large birefringence.

关键词： birefringence borate optical functional crystal structural anisotropy arrangement of functional units

Distributed Dispatch of Multiple Energy Systems Considering Carbon Trading

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CSEE Journal of Power and Energy Systems 2023年第2期9卷 459-469页

作者： Yue Xiang Mengqiu Fang Junyong Liu Pingliang Zeng Ping Xue Gang Wu College of Electrical Engineering Sichuan UniversityChengdu 610065China School of Automation Hangzhou Dianzi UniversityHangzhou 310018China state grid sichuan technical training center Chengdu 610072China state grid sichuan Economic Research Institute Chengdu 610065China

As an integrated carrier of energy production,transmission,distribution,conversion,storage,and utilization,multiple energy systems(MESs)have significant low-carbon potential.This paper proposes a hierarchical distributed dispatch model of MESs considering carbon trading,which is composed of the lower autonomous operation level of each MES and the upper coordinated control level.Different carbon emission sources are considered,including combined heat and power(CHP)units,gas boilers,and power to gas(P2G)devices.The transactive control(TC)mechanism is used to solve the model by introducing a virtual price signal.In the case study based on a 3-MES system,the effectiveness of the proposed distributed method is proved by comparison with a centralized algorithm.Meanwhile,the impacts of different carbon prices on MESs with different resource endowments are analyzed from the aspects of scheduling results,carbon emissions,clean energy consumption rate,and comprehensive operating costs.

关键词： Carbon trading distributed optimal dispatch transactive control multiple energy systems

Bi-GRU Relation Extraction Model Based on Keywords Attention

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Data Intelligence 2022年第3期4卷 552-572页

作者： Yuanyuan Zhang Yu Chen Shengkang Yu Xiaoqin Gu Mengqiong Song Yu Peng Jianxia Chen Qi Liu technical training center of state grid Hubei Electric Power Co. Ltd.Wuhan 430070China Hubei University of Technology School of Computer ScienceWuhan 430068China

Relational extraction plays an important role in the field of natural language processing to predict semantic relationships between entities in a sentence. Currently, most models have typically utilized the natural language processing tools to capture high-level features with an attention mechanism to mitigate the adverse effects of noise in sentences for the prediction results. However, in the task of relational classification, these attention mechanisms do not take full advantage of the semantic information of some keywords which have information on relational expressions in the sentences. Therefore, we propose a novel relation extraction model based on the attention mechanism with keywords, named Relation Extraction Based on Keywords Attention(REKA). In particular, the proposed model makes use of bi-directional GRU(Bi-GRU) to reduce computation, obtain the representation of sentences, and extracts prior knowledge of entity pair without any NLP tools. Besides the calculation of the entity-pair similarity, Keywords attention in the REKA model also utilizes a linear-chain conditional random field(CRF) combining entity-pair features, similarity features between entity-pair features, and its hidden vectors, to obtain the attention weight resulting from the marginal distribution of each word. Experiments demonstrate that the proposed approach can utilize keywords incorporating relational expression semantics in sentences without the assistance of any high-level features and achieve better performance than traditional methods.

关键词： Relation extraction Bi-GRU CRF keywords attention Hidden similarity

Behavioural analysis and dynamic simulation of the debris flow that occurred in Ganluo County(sichuan, China) on 30 August 2020

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Journal of Mountain Science 2022年第6期19卷 1495-1508页

作者： LI Nuo-dong LIU Wei ZHAO Jin-heng Chengdu Power Supply Company of state grid sichuan Electric Power Company Chengdu 610041China Key Laboratory of Mountain Hazards and Surface Process Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengdu 610041China University of Chinese Academy of Sciences Beijing 100049China state Key Laboratory of Hydraulics and Mountain River Engineering Sichuan UniversityChengdu 610065China Department of Water Hydropower and Construction Engineering Skill Training Center of State Grid Sichuan Electric Power CompanyChengdu 610000China

On August 30, 2020, a high-intensity storm that dropped 45.4 mm of rain in 5 hours hit the Heixiluo basin and triggered a landslide-generated debris flow event, causing fatalities and damage. The original source of the debris flow was a large slope collapse on a steep hillside. The fallen debris mass was enlarged through sediment entrainment and slope collapse and ultimately buried a bridge at the gully entrance. Approximately 6.9×10;m;of material, including sediments and collapsed slope deposits in the gullies, was entrained, and the maximum erosion depth reached 17 m. A geomorphological analysis was initially performed based on a detailed field investigation to recognize the liquid and solid sources of the debris flow and the areas subjected to deposition and erosion. A map of the erosiondeposition distribution was obtained based on preand post-event DEMs. Using the rainfall estimated by the nearest rain gauge and the solid source estimated by the DEMs, runoff and debris flow propagation was simulated using a liquid-solid two-phase model that considers the effects of runoff and entrainment. The similarity between the estimated and simulated deposition-erosion volumes was satisfactory. The behaviour of debris flows captured in the simulation is broadly in line with the main features of the observed event.

关键词： Debris flow Formation analysis Two-phase model Dynamic simulation

PSO-LSSVM-based Online SOC Estimation for Simulation Substation Battery

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Structural Durability & Health Monitoring 2022年第1期16卷 37-51页

作者： Qiang Zhang Xianguang Zha Jun Wu Liang Zhang Wei Dai Gang Ren Shiqian Li Ning Ji Xiangjun Zhu Fengwei Tian state grid Jiangsu Electric Power Co. Ltd.Nanjing210024China state grid Jiangsu Electric Power Company Research Institute Nanjing211103China Technican training center of state grid Jiangsu Electric Power Co. Ltd.Suzhou215004China

As the emergency power supply for a simulation substation,lead-acid batteries have a work pattern featuring noncontinuous operation,which leads to capacity regeneration.However,the accurate estimation of battery state of charge(SOC),a measurement of the amount of energy available in a battery,remains a hard nut to crack because of the non-stationarity and randomness of battery capacity change.This paper has proposed a comprehensive method for lead-acid battery SOC estimation,which may aid in maintaining a reasonable charging schedule in a simulation substation and improving battery’s durability.Based on the battery work pattern,an improved Ampere-hour method is used to calculate the SOC during constant current and constant voltage(CC/CV)charging and discharging.In addition,the combined Particle Swarm Optimization(PSO)and Least Squares Support Vector Machine(LSSVM)model is used to estimate the SOC during non-CC discharging.Experimental results show that this method is workable in online SOC estimation of working batteries in a simulation substaion,with the maximum relative error standing at only 2.1%during the non-training period,indicating a high precision and wide applicability.

关键词： Simulation substation lead-acid batteries SOC PSO LSSVM

Leveraging Continuous Prompt for Few-Shot Named Entity Recognition in Electric Power Domain with Meta-Learning

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Data Intelligence 2023年第2期5卷 494-509页

作者： Yang Yu Wei He Yu-meng Kang You-lang Ji Metrology center State Grid Jiangsu Market Service Center Nanjing Jiangsu 210019China

Conventional named entity recognition methods usually assume that the model can be trained with sufficient annotated data to obtain good recognition results.However,in Chinese named entity recognition in the electric power domain,existing methods still face the challenges of lack of annotated data and new entities of unseen types.To address these challenges,this paper proposes a meta-learning-based continuous cue adjustment method.A generative pre-trained language model is used so that it does not change its own model structure when dealing with new entity types.To guide the pre-trained model to make full use of its own latent knowledge,a vector of learnable parameters is set as a cue to compensate for the lack of training data.In order to further improve the model's few-shot learning capability,a meta-learning strategy is used to train the model.Experimental results show that the proposed approach achieves the best results in a few-shot electric Chinese power named entity recognition dataset compared to several traditional named entity approaches.

关键词： Named Entity Recognition Pre-trained model Prompt-Tuning Meta-Learning Few-Shot