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Capacitor Voltage Imbalance Mechanism and Balancing Control of MMC When Riding Through PTG Fault

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CSEE Journal of power and Energy Systems 2024年第2期10卷 778-785页

作者： Zhen He Maozeng Lu Lijun Hang Pingliang Zeng Yanhua Liu Hangzhou Dianzi University Hangzhou 310018China Shandong University of Technology Zibo 255000China state grid Hangzhou power Supply company State GridHangzhou 310000China

Modular multilevel converter (MMC) based fault ride through (FRT) control is a promising solution to deal with the pole-to-ground (PTG) fault in high voltage direct current (HVDC) system. However, when MMC switches to the FRT control, capacitor voltage imbalance between upper and lower arms will occur, resulting in the deterioration of FRT performance. This letter provides a comprehensive analysis for the imbalance issue from the perspective of fundamental frequency circulating current (FFCC). It is found the imbalance during FRT stage will not expand continuously, but converge to a certain value gradually. The specific imbalance degree is closely associated with the amplitude of FFCC. In order to solve the imbalance issue, an open-loop balancing control is proposed. By introducing a fundamental frequency feedforward item to the inherent circulating current control, the proposed method can not only balance the capacitor voltages, but also minimize the amplitude of FFCC, and consequently the power loss of MMC during FRT process can be reduced. Finally, simulation results of PSCAD/ EMTDC verify the validity of theoretical analysis.

关键词： Balancing control capacitor voltage imbalance FFCC FRT control HVDC system PTG fault

Multi-Time Scale Operation and Simulation Strategy of the Park Based on Model Predictive Control

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Energy Engineering 2024年第3期121卷 747-767页

作者： Jun Zhao Chaoying Yang Ran Li Jinge Song grid Center State Grid Shanxi Electric Power Company Electric Power Science Research InstituteTaiyuan030000China

Due to the impact of source-load prediction power errors and uncertainties,the actual operation of the park will have a wide range of fluctuations compared with the expected state,resulting in its inability to achieve the expected *** paper constructs an operating simulation model of the park power grid operation considering demand response and proposes a multi-time scale operating simulation method that combines day-ahead optimization and model predictive control(MPC).In the day-ahead stage,an operating simulation plan that comprehensively considers the user’s side comfort and operating costs is proposed with a long-term time scale of 15 *** order to cope with power fluctuations of photovoltaic,wind turbine and conventional load,MPC is used to track and roll correct the day-ahead operating simulation plan in the intra-day stage to meet the actual operating operation status of the ***,the validity and economy of the operating simulation strategy are verified through the analysis of arithmetic examples.

关键词： Demand response model predictive control multiple time scales operating simulation

Optical Fibre Communication Feature Analysis and Small Sample Fault Diagnosis Based on VMD-FE and Fuzzy Clustering

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Energy Engineering 2024年第1期121卷 203-219页

作者： Xiangqun Li Jiawen Liang Jinyu Zhu Shengping Shi Fangyu Ding Jianpeng Sun Bo Liu Gannan power Supply company of state grid Gansu electric power Supply company Hezuo747000China Digital Communication Department Gannan Power Supply Company of State Grid Gansu Electric Power Supply CompanyHezuo747000China

To solve the problems of a few optical fibre line fault samples and the inefficiency of manual communication optical fibre fault diagnosis,this paper proposes a communication optical fibre fault diagnosis model based on variational modal decomposition(VMD),fuzzy entropy(FE)and fuzzy clustering(FC).Firstly,based on the OTDR curve data collected in the field,VMD is used to extract the different modal components(IMF)of the original signal and calculate the fuzzy entropy(FE)values of different components to characterize the subtle differences between *** fuzzy entropy of each curve is used as the feature vector,which in turn constructs the communication optical fibre feature vector matrix,and the fuzzy clustering algorithm is used to achieve fault diagnosis of faulty optical *** VMD-FE combination can extract subtle differences in features,and the fuzzy clustering algorithm does not require sample *** experimental results show that the model in this paper has high accuracy and is relevant to the maintenance of communication optical fibre when compared with existing feature extraction models and traditional machine learning models.

关键词： Optical fibre fault diagnosis OTDR curve variational mode decomposition fuzzy entropy fuzzy clustering

A Simple and Effective Surface Defect Detection Method of power Line Insulators for Difficult Small Objects

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Computers, Materials & Continua 2024年第4期79卷 373-390页

作者： Xiao Lu Chengling Jiang Zhoujun Ma Haitao Li Yuexin Liu state grid Jiangsu electric power Co. Ltd.Nanjing210024China state grid Changzhou power Supply company Changzhou213003China

Insulator defect detection plays a vital role in maintaining the secure operation of power *** address the issues of the difficulty of detecting small objects and missing objects due to the small scale,variable scale,and fuzzy edge morphology of insulator defects,we construct an insulator dataset with 1600 samples containing flashovers and *** a simple and effective surface defect detection method of power line insulators for difficult small objects is ***,a high-resolution featuremap is introduced and a small object prediction layer is added so that the model can detect tiny ***,a simplified adaptive spatial feature fusion(SASFF)module is introduced to perform cross-scale spatial fusion to improve adaptability to variable multi-scale ***,we propose an enhanced deformable attention mechanism(EDAM)*** integrating a gating activation function,the model is further inspired to learn a small number of critical sampling points near reference *** the module can improve the perception of object *** experimental results indicate that concerning the dataset of flashover and breakage defects,this method improves the performance of YOLOv5,YOLOv7,and *** practical application,it can simply and effectively improve the precision of power line insulator defect detection and reduce missing detection for difficult small objects.

关键词： Insulator defect detection small object power line deformable attention mechanism

Influence characteristics of water penetration on fibre-reinforced polymer/rigid polyurethane foam interface of the composite cross-arm considering natural ageing

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High Voltage 2024年第1期9卷 81-93页

作者： Jun Xie Zhe Zhou Ziqian Liu Haonan Tian Sigang Zhang Qing Xie Hebei Provincial Key Laboratory of power Transmission Equipment Security Defense North China Electric Power UniversityBaodingChina state grid Gansu electric power company LanzhouChina

Fibre-reinforced polymer(FRP)/rigid polyurethane foam(RPUF)interface is susceptible to moisture intrusion in addition to natural ageing during *** study investigated the influence of moisture intrusion on the FRP/RPUF interface under natural ageing using experiments and molecular dynamics(MD)*** absorption,shear strength,and leakage current tests were used to clarify the changes in the interface *** degradation mechanism of moisture intrusion at the interface under natural ageing was revealed by MD simulation and *** results show that the natural ageing of interfacial materials will slightly reduce the quality of the interface but will reduce the water resistance of the material and promote the process of water intrusion into the *** addition,water mainly invades the interface through *** water penetration,the interfacial bonding strength and insulation performance significantly *** and hydrolysis of interfacial materials are the main reasons for decreased interfacial *** can cause irreversible damage to the interface,increasing interface defects and water *** vicious cycle of material hydrolysis is the ultimate cause of interfacial *** polar molecules produced by this process and the water absorbed by the interface caused the degradation of the interface insulation performance.

关键词： interface polyurethane interfacial

Energy Economic Dispatch for Photovoltaic-Storage via Distributed Event-Triggered Surplus Algorithm

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Energy Engineering 2024年第9期121卷 2621-2637页

作者： Kaicheng Liu Chen Liang Naiyue Wu Xiaoyang Dong Hui Yu China electric power Research Institute Beijing100192China electric power Research Institute of state grid Gansu electric power company Lanzhou730000China state Key Laboratory of power grid Safety Beijing100084China

This paper presents a novel approach to economic dispatch in smart grids equipped with diverse energy *** method integrates features including photovoltaic(PV)systems,energy storage coupling,varied energy roles,and energy supply and demand *** systemmodel is developed by considering energy devices as versatile units capable of fulfilling various functionalities and playing multiple roles *** strike a balance between optimality and feasibility,renewable energy resources are modeled with considerations for forecasting errors,Gaussian distribution,and penalty ***,this study introduces a distributed event-triggered surplus algorithm designed to address the economic dispatch problem by minimizing production *** in surplus theory and finite time projection,the algorithm effectively rectifies network imbalances caused by directed graphs and addresses local inequality *** algorithm greatly reduces the communication burden through event triggering ***,both theoretical proofs and numerical simulations verify the convergence and event-triggered nature of the algorithm.

关键词： Fully distributed algorithm economic dispatch directed graph renewable energy resource

Analysis and Modeling of Time Output Characteristics for Distributed Photovoltaic and Energy Storage

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Energy Engineering 2024年第4期121卷 933-949页

作者： Kaicheng Liu Chen Liang Xiaoyang Dong Liping Liu China electric power Research Institute Beijing100192China electric power Research Institute State Grid Gansu Electric Power CompanyLanzhou730000China state Key Laboratory of power grid Safety Beijing100084China

Due to the unpredictable output characteristics of distributed photovoltaics,their integration into the grid can lead to voltage fluctuations within the regional power ***,the development of spatial-temporal coordination and optimization control methods for distributed photovoltaics and energy storage systems is of utmost importance in various *** paper approaches the issue from the perspective of spatiotemporal forecasting of distributed photovoltaic(PV)generation and proposes a Temporal Convolutional-Long Short-Term Memory prediction model that combines Temporal Convolutional Networks(TCN)and Long Short-Term Memory(LSTM).To begin with,an analysis of the spatiotemporal distribution patterns of PV generation is conducted,and outlier data is handled using the 3σ ***,a novel approach that combines temporal convolution and LSTM networks is introduced,with TCN extracting spatial features and LSTM capturing temporal ***,a real spatiotemporal dataset from Gansu,China,is established to compare the performance of the proposed network against other *** results demonstrate that the model presented in this paper exhibits the highest predictive accuracy,with a single-step Mean Absolute Error(MAE)of 1.782 and an average Root Mean Square Error(RMSE)of 3.72 for multi-step predictions.

关键词： Photovoltaic power generation spatio-temporal prediction temporal convolutional network long short-term memory network

Inverse-time Backup Protection Based on Unified Characteristic Equation for Distribution Networks with High Proportion of Distributed Generations

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Journal of Modern power Systems and Clean Energy 2024年第1期12卷 202-212页

作者： Nana Chang Guobing Song Zhongxue Chang Yuping Zheng Xingang Yang the School of electrical Engineering Xi’an Jiaotong UniversityXi’anChina state Key Laboratory of Smart grid Protection and Control NARI Group CorporationNanjingChina electric power Research Institute of state grid Shanghai electric power company ShanghaiChina

The setting work of backup protection using steady-state current is tedious,and mismatches occasionally occur due to the increased proportion of distributed generations(DGs)connected to the power ***,there is a practical need to study a backup protection technology that does not require step-by-step setting and can be adaptively *** paper proposes an action sequence adaptive to fault positions that uses only positive sequence fault component(PSFC)*** the influence of DGs,the unified time dial setting can be obtained by selecting specific *** protection performance is improved by using the adjacent upstream and downstream protections to meet the coordination time interval in the case of metallic faults at the near-and far-ends of the ***,the expression and implementation scheme for inverse-time backup protection(ITBP)based on the unified characteristic equation is *** results show that this scheme can adapt to DG penetration scenarios and can realize the adaptive coordination of multi-level relays.

关键词： Inverse-time backup protection(ITBP) distributed generation(DG) positive sequence fault component(PSFC)voltage unified characteristic equation adaptive coordination

Study on the influence of mechanism dispersion on transient recovery voltage distribution of modular DC vacuum circuit breakers

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High Voltage 2024年第2期9卷 346-355页

作者： Chongyang Huang Yongshuai Yin Shuxin Liu Hanwen Du Zengyu Shan Yundong Cao Shurui Yang Key Laboratory of Special electric Machines and High Voltage Apparatus in the Ministry of Education Shenyang University of TechnologyShenyangChina Shenyang power Supply company of state grid Liaoning electric power Co. LtdShenyangChina Chifeng power Supply company of state grid Mongolia electric power Co. LtdChifengChina

A simulation analysis and an experiment are carried out to investigate how the gap difference between the breaks of a direct current vacuum circuit breakers with multi-breaks(MB-DC VCB)caused by the mechanism dispersion of the breaker influences the distribution of TRV among the *** interruption model of MB-DC VCB,combining the continuous transition model,is established to analyse the rising rate of transient recovery voltage and the dielectric strength recovery speed of the breaks for MB-DC VCB under different gap difference *** on the experimental platform of dual break DC vacuum circuit breaker breaking,the correctness of the simulation model is verified on a DC VCB with the double-breaks interruption experimental ***,a model is applied to the non-synchronous interruption simulation of a DC VCB with *** relationship between the TRVs of the breaks under different gap difference conditions is analysed using the comparative analysis method,obtaining the maximum gap difference at the moment of breaking *** results of this study show that large-gap breaks have a higher TRV than small-gap breaks(the fracture of the action delay module),with double fractures reaching 1.4 times and triple fractures reaching a maximum of 1.52 times;the ability of small-gap breaks to withstand TRV is weak,giving rise to re-breakdown or even interruption failure;as the number of fractures increases,the maximum gap difference also *** the synchronous interruption ability of the MB-DC VCB is conducive to improving the interruption performance and interruption success rate of this type of a circuit breaker.

关键词： TRV transient distribution