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Algorithms to Calculate the Most Reliable Maximum Flow in Content Delivery Network

Computer systems Science & Engineering 2022年第5期41卷 699-715页

作者： Baili Zhang Keke Ling Pei Zhang Zhao Zhang Mingjun Zhong School of Computer Science and Engineering Southeast UniversityNanjing211189China State Key Laboratory of Smart Grid Protection and Control Nanjing211106China Nari Group Corporation Nanjing211106China Department of Computing Science University of AberdeenAberdeenAB243UEUK

Calculating the most reliable maximum flow(MRMF)from the edge cache node to the requesting node can provide an important reference for selecting the best edge cache node in a content delivery network(CDN).However,SDBA,as the current state-of-the-art MRMF algorithm,is too complex to meet real-time computing *** paper proposes a set of MRMF algorithms:NWCD(Negative Weight Community Deletion),SCPDAT(Single-Cycle Preference Deletion Approximation algorithm with Time constraint)and SCPDAP(Single-Cycle Preference Deletion Approximation algorithm with Probability constraint).NWCD draws on the“flow-shifting”algorithm of minimum cost and maximum flow,and further defines the concept of negative weight *** algorithm continuously deletes the negative weight communities,which can increase reliability while keeping the flow constant in the residual *** is proven that when all negative weight communities are deleted,the corresponding maximum flow is the *** tries to approach the optimal solution to the greatest extent possible within the limited time,while SCPDAP tries to reach the probability threshold in the shortest amount of *** of these adopt the strategy of first deleting single-cycle communities(which contribute more to the reliability with lower time cost).Experiments show that,compared with SDBA,NWCD combined with the probabilistic pruning achieves an order of magnitude improvement in time cost,while SCPDAT and SCPDAP demonstrate better time performance and increased applicability.

关键词： Content delivery network uncertain graph maximum flow flow reliability

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Regulation performance of virtual synchronous generator applied in renewable energy system

Regulation performance of virtual synchronous generator appl...

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2021 International Conference on Information Technology and Intelligent control, CITIC 2021

作者： Qi, WeiZhi Zha, Daojun Wu, Tonghua Dai, Wei Li, Xindong Hou, Xiaofan State Grid Jiangsu Electric Power Co. Ltd. Nanjing210024 China State Key Laboratory of Smart Grid Protection and Control Nanjing Nanjing 211106 China Nanjing211106 China

The conventional synchronous generator (SG) can regulate the active and reactive power for frequency and voltage stability, when the system fluctuates. In renewable energy generation system (RES), the stability problem of RES can be solved by adding virtual inertia and damping in the control strategy of the grid-connected inverter. The grid-connected inverter and renewable energy system with this kind of control strategy, called as virtual synchronous generator (VSG), acts as a synchronous generator. In this paper, the topology of grid-connected PV array and energy storage system is proposed. The VSG used in grid-connected inverter, is modelled as stator and rotor model by stator voltage equation and rotor motion equation, respectively. Meanwhile, the VSG control mechanism, based on droop control and model of VSG, can be divided as active power-frequency and reactive power-voltage control. Besides, the system stability is analyzed based on small signal model, for the design of inertia and damping. The simulation model is designed by MATLAB/Simulink for the implementation of VSG. In simulation, it is compared that the dynamic regulation performance of VSG with different control coefficient, such as virtual inertia, virtual damping, droop coefficient and integral coefficient. The optimization for regulation performance in simulation provides an appropriate selection method of the control coefficient for VSG. © 2021 Institute of Physics Publishing. All rights reserved.

关键词： Synchronous generators

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A Dual-Objective Optimization control Strategy with Markov Forecast for Battery Energy Storage system to Mitigating Wind Farm Fluctuations 6th

A Dual-Objective Optimization Control Strategy with Markov F...

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6th PURPLE MOUNTAIN FORUM on smart grid protection and control, PMF2021

作者： Gu, Haotian Hou, Kai Jiang, Yingwei Yin, Hang Liu, Jing Zhong, Xu NARI Group Corporation/State Grid Electric Power Research Institute Jiangsu Province Nanjing211000 China State Key Laboratory of Smart Grid Protection and Control Jiangsu Province Nanjing211000 China

ISBN: (纸本)9789811671555

In a renewable energy power system dominated by a high proportion of wind power, the configuration of energy storage system is an effective solution to mitigate wind power fluctuations, ensure the safe and stable operation of the grid, and improve the dispatch ability of wind power. This paper proposes a battery energy storage system (BESS) control strategy with the consideration of the impact of future wind power. To achieve maximum bidirectional output capability and minimum output of BESS, multi-objective hybrid optimization model is built on base of first-order low-pass filter’s variable time constant Tf, which contains two weight coefficients c1 and c2 to flexibly adjust BESS output. Markov chain prediction model is introduced to forecast the future multi-step wind power and PSO optimization algorithm is used to obtain the optimal BESS output power in real-time rolling calculation. Finally, the effectiveness of the proposed control strategy is verified through case studies. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

关键词： Low pass filters

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Influence of Generator-tripping Time on Transient Stability

Influence of Generator-tripping Time on Transient Stability

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2019 IEEE PES Innovative smart grid Technologies Asia, ISGT 2019

作者： Xue, Yusheng Zhu, Xueqiong Li, Ze NARI Group Corporation State Grid Electric Power Research Institute China State Key Laboratory of Smart Grid Protection and Control Nanjing China School of Electrical Engineering Southeast University Nanjing China

ISBN: (纸本)9781728135205

Study the influence of generator-tripping time on transient stability is of great significance for guiding the setting of the optimal generator-tripping time. Based on the extended equal area criterion (EEAC), the paper points out that the generator-tripping operation affects transient power angle stability margin of the system by changing the equivalent electromagnetic power, the equivalent mapping rotor angle and its corresponding energy accumulation interval, and clarifies accordingly the paths of generator-tripping time affects transient power angle stability margin. For the first swing of angle instability of the Hamiltonian system, the complex influences of generator-tripping time on the control effect are revealed. As generator-tripping time increases, the transient power angle stability margin may present an evolution situation that first increases and then decreases, and reaches a maximum value when generator-tripping time equals to the fault clearing time, and may also present decreases monotonically. The analysis conclusions are verified by simulation experiments. © 2019 IEEE.

关键词： Transients

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Distributed Continuation Power Flow for High Penetration New Energy Power grid 6

Distributed Continuation Power Flow for High Penetration New...

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6th International Conference on Power and Energy Technology, ICPET 2024

作者： Dai, Zemei Chen, Tianhua Tang, Yi Zhao, Jinquan State Key Laboratory of Smart Grid Protection and Control NARI Group Corporation State Grid Electric Power Research Institute Nanjing China College of Power and Electrical Engineering Hohai University Nanjing China

ISBN: (纸本)9798350375855

The high penetration of new energy integration into the power grid has highlighted the problem of voltage stability. Continuation Power Flow (CPF) is an important tool for Voltage Stability Analysis (VSA). As the scale of new energy grid integration continues to expand, the method of power equivalent modeling of the aggregated grid in the main transmission network fails due to the neglect of the network structure and new energy models. This paper proposes a distributed voltage stability assessment method for high proportion new energy grids based on Distributed Continuation Power Flow (DCPF). The proposed method decomposes the global grid at the Point of Common Coupling (PCC) into new energy Sub-grids (SGs) and the transmission Main-grid (MG), achieving distributed computation of global grid voltage stability assessment by exchanging state information at the PCC between MG and SGs. Simulation results of the global power system show that the proposed method is effective. © 2024 IEEE.

关键词： Power grids

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Modified distance backup protection fused with DC control information 7

Modified distance backup protection fused with DC control in...

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7th Asia Conference on Power and Electrical Engineering, ACPEE 2022

作者： Gongye, Lingjiao Zhang, Dahai Li, Wei Wang, Xueqin Wu, Chuanjian Beijing Jiaotong University School of Electrical Engineering Beijing China Skl of Sgpc Nari Group Corporation State Key Laboratory of Smart Grid Protection and Control Nanjing China

ISBN: (纸本)9781665418195

The removal of the DC line may lead to power flow transfer, which leads to the wrong operation of the AC line distance III protection. To solve this problem, a modified distance backup protection that integrates DC control information is proposed. First, analyze the characteristics of DC side control information and propose a power flow transfer identification scheme that integrates DC control information. Subsequently, the modified distance backup protection is constructed using the identification results of the power flow transfer. Finally, an AC/DC hybrid model was established to verify the feasibility and fault resistance capability of the proposed scheme. © 2022 IEEE.

关键词： Electric load flow

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Cyber-attack-tolerant Frequency control of Power systems

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Journal of Modern Power systems and Clean Energy 2021年第2期9卷 307-315页

作者： Chunyu Chen Kaifeng Zhang Ming Ni Ying Wang the School of Electrical and Power Engineering China University of Mining and TechnologyXuzhou 221116China the School of Automation Southeast UniversityNanjing 210096China NARI Group Corporation(State Grid Electric Power Research Institute) Nanjing 211106China NARI Technology Co. Ltd.Nanjing 211106China State Key Laboratory of Smart Grid Protection and Control Nanjing 211106China

Cyber attacks are emerging threats in the Internet of Things applications,and power systems are typical cyber attack *** one of the most essential operation functions,frequency control is threatened by cyber intrusions,and the existing centralized control mode cannot effectively address cyber *** this study,a new distributed cyber-attack-tolerant frequency control scheme is *** distributed control mode also serves as a convenient tool for attack *** designed cyber-attack-tolerant frequency controller adopts the idea of passive fault attenuation,thus simplifying the design *** the aid of graph theory and consensus techniques,distributed integral based and model predictive control(MPC)based controllers are *** with the integral type,the MPC-based controller can simultaneously improve the dynamic responses and the tolerance ability under *** proposed controller is validated via an IEEE benchmark system,and the effectiveness of its application in actual power systems is verified.

关键词： Frequency control cyber attack distributed control passive fault attenuation cyber-attack-tolerant frequency control

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A Fault Ride-Through Method of Paralleled Synchronous and Virtual Synchronous Generators in Islanded Microgrids 5

A Fault Ride-Through Method of Paralleled Synchronous and Vi...

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5th IEEE Conference on Energy Internet and Energy system Integration, EI2 2021

作者： Ru, Yanfei Zhao, Feng Jin, Zhangtao State Key Laboratory of Smart Grid Protection and Control Nari Group Corporation Nanjing211106 China College of Electrical and Information Engineering Hunan University Changsha410082 China

ISBN: (纸本)9781665434256

With the development of distributed power generation technologies, parallel operations of virtual synchronous generators (VSGs) and synchronous generators (SGs) become increasingly common in a microgrid. Due to the low overcurrent capacity of VSGs, fault ride-through (FRT) is necessary for microgrids, which makes the transient stability of SG-VSG-based microgrids be different from the traditional power system. In this paper, a new abnormal overcurrent phenomenon caused by FRT is discovered in SG-VSG-based islanded microgrids. Then, characteristics of the output current of the VSG which uses different parameters are compared and analyzed. Furthermore, an optimized FRT method is proposed, which suppresses the abnormal overcurrent. Finally, a simulation is performed to verify the effectiveness of the proposed method on the PSCAD/EMTDC. © 2021 IEEE

关键词： Synchronous generators

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Correction of Wind Power Prediction Error Under the Extreme Weather Based on K-nearest Neighbor Algorithm 1

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8th Purple Mountain Forum on smart grid protection and control, PMF 2023

作者： Ye, Wenjie Liu, Gang Yang, Dongmei Liang, Yiheng Yang, Yize Tang, Chenghong Chen, Yizhi State Key Laboratory of Smart Grid Protection and Control Nanjing211106 China Nanjing211106 China NARI Technology Development Co. Ltd Nanjing211106 China

ISBN: (数字)9789819992515

ISBN: (纸本)9789819992508

Extreme weather, such as cold waves and frosts, can significantly impact the output of wind farms. To address this issue, this paper proposes a short-term power prediction and correction method suitable for wind farms during extreme weather, based on the K-nearest neighbor algorithm and multiple linear regression model. By verifying that wind power output is affected by wind speed, temperature, humidity, wind power kurtosis, and other factors, the K-nearest neighbor algorithm is used to obtain the sample set of similar days on the day to be measured. The regression model of influencing factors and output errors is established to improve the power prediction accuracy. A wind farm in northwest China is used as a test example to verify the effectiveness of the output correction method. © 2024, state grid Electric Power.

关键词： Nearest neighbor search

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Remote closed-loop test method of safety and stability control system based on step-by-step implementation 2

Remote closed-loop test method of safety and stability contr...

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2nd International Conference on Digital Society and Intelligent systems, DSInS 2022

作者： Zhao, Wei Hou, Yuqiang Chen, Xiong Xue, Feng Chen, Wei Chen, Luofei Nanjing211106 China State Key Laboratory of Smart Grid Protection and Control Nanjing211106 China PONOVO Power Co. Ltd. Beijing100000 China

ISBN: (纸本)9781510663244

The safe operation of the safety stability control system is an important means to ensure the safe and stable operation of AC and DC power grids. Aiming at the shortage of existing test methods that cannot perform closed-loop testing of field safety stability control systems, a remote closed-loop test method for safety stability control systems based on step-by-step implementation is proposed. Using the simulation results of real-time digital simulation system (RTDS) as the signal source, a remote test platform architecture integrating laboratory and field safety and stability control devices is designed, key modules such as platform management system, test master and test terminal are developed, specific solutions are given for platform communication, and a remote closed-loop test procedure is formulated. Finally, a pilot application is carried out with an actual power grid security and stability control system as an example, and the effectiveness of the proposed method is verified. © 2023 SPIE.

关键词： Real time systems

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