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Formulations and Approximations of Branch Flow Model for General power Networks

Journal of Modern power systems and Clean Energy 2022年第5期10卷 1110-1126页

作者： Zhao Yuan Electrical Power Systems Laboratory(EPS-Lab) Department of Electrical and Computer EngineeringUniversity of IcelandReykjavikIceland IEEE

The formulations and approximations of the branch flow model for general(radial and mesh) power networks(General-BranchFlow) are given in this paper. Using different sets of the power flow equations, six formats of the exact General-BranchFlow model are listed. The six formats are mathematically equivalent with each other. Linear approximation and second-order cone programming(SOCP) are then used to derive the six formats of the convex General-BranchFlow model. The branch ampacity constraints considering the shunt conductance and capacitance of the transmission line Π-model are derived. The key foundation of deriving the ampacity constraints is the correct interpretation of the physical meaning of the transmission line Π-model. An exact linear expression of the ampacity constraints of the power loss variable is derived. The applications of the General-BranchFlow model in deriving twelve formats of the exact optimal power flow(OPF) model and twelve formats of the approximate OPF model are formulated and analyzed. Using the Julia programming language, the extensive numerical investigations of all formats of the OPF models show the accuracy and computational efficiency of the General-BranchFlow model. A penalty function based approximation gap reduction method is finally proposed and numerically validated to improve the AC-feasibility of the approximate General-BranchFlow model.

关键词： Branch flow linear approximation second-order cone programming ampacity constraint optimal power flow radial network mesh network

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Abnormal Data Identification and Reconstruction Based on Wind Speed Characteristics

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CSEE Journal of power and Energy systems 2025年第2期11卷 612-622页

作者： Mao Yang Tian Peng Wei Zhang Xin Su Chao Han Fulin Fan Key Laboratory of Modern Power System Simulation and Control&Renewable Energy Technology Ministry of EducationNortheast Electric Power UniversityJilin 132012China Department of Electronic and Electrical Engineering University of StrathclYdeGlasgow G11XWUnited Kingdom

High availability of wind power data is the basis for wind power research, but there are a large number of abnormal data in actual collected data, which seriously affects analysis of wind power law and reduces prediction accuracy. Measured power data of wind farm are analyzed, influence of wind speed fluctuation characteristics on wind power is discussed, and abnormal points are identified for data of different wind types. The Cluster-Based Local Outlier Factor (CLOF) algorithm based on K-means is used to identify outlier abnormal points, and conditional constraints based on physical background are used to identify accumulation abnormal points. Reconstructed data segment is divided according to fluctuation of wind speed. The Bidirectional Gate Recurrent Unit (BiGRU) model with wind speed as input reconstructs fluctuation segment data, and bi-directional weighted random forest model reconstructs stationary segment data. Based on analysis of measured data of a wind farm, results show the method can effectively identify various abnormal data, and complete high-quality reconstruction of data, thereby improving accuracy of wind power prediction.

关键词： Abnormal data bidirectional weighted random forest BiGRU CLOF reconstruction wind power prediction wind speed characteristics

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Control and Stability of Large-scale power system with Highly Distributed Renewable Energy Generation:Viewpoints from Six Aspects

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CSEE Journal of power and Energy systems 2023年第1期9卷 8-14页

作者： Qing-Hua Wu Anjan Bose Chanan Singh Joe H.Chow Gang Mu Yuanzhang Sun Zhaoxi Liu Zhigang Li Yang Liu School of Electric Power Engineering South China University of TechnologyGuangzhou 510640China School of Electrical Engineering&Computer Science Washington State UniversityPullmanWA 99164USA Department of Electrical and Computer Engineering Texas A&M UniversityCollege StationTX 77843USA Department of Electrical Computer and Systems EngineeringRensselaer Polytechnic Institute(RPI)TroyNYUSA Key Laboratory of Modern Power System Simulation and Control&Renewable Energy Technology Ministry of Education(Northeast Electric Power University)Jilin 132012China School of Electrical Engineering and Automation Wuhan UniversityWuhan 430072China

power systems are moving toward a low-carbon or carbon-neutral future where high penetration of renewables is *** conventional fossil-fueled synchronous generators in the transmission network being replaced by renewable energy generation which is highly distributed across the entire grid,new challenges are emerging to the control and stability of large-scale power *** analysis and control methods are needed for power systems to cope with the ongoing *** the CSEE JPES forum,six leading experts were invited to deliver keynote speeches,and the participating researchers and professionals had extensive exchanges and discussions on the control and stability of power ***,potential changes and challenges of power systems with high penetration of renewable energy generation were introduced and explained,and advanced control methods were proposed and analyzed for the transient stability enhancement of power grids.

关键词： Distributed energy resources high converter penetration power system control renewable energy generation stability control transient stability

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Preventive power Outage Estimation Based on A Novel Scenario Clustering Strategy

Preventive Power Outage Estimation Based on A Novel Scenario...

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2024 IEEE power and Energy Society General Meeting, PESGM 2024

作者： Wang, Xiaofei Liu, Weijia Ding, Fei Yao, Yiyun Zhao, Junbo Power System Engineering Center National Renewable Energy Laboratory Golden United States Department of Electrical and Computer Engineering University of Connecticut Storrs United States

The increasing occurrence of extreme weather events is challenging power grid operation. For extreme weather events, the system operator is responsible for estimating the power outages and scheduling the restoration resources. This paper proposes an outage evaluation framework to identify the possible unserved load profiles, vulnerable areas, and mobile energy adequacy. The outputs of an outage prediction model tool are used to generate numerous faulted line scenarios. Next, each scenario's nodal unserved load profile is obtained by solving a three-phase restoration model that considers repair crews and mobile energy resources (MERs). Then, a novel scenario clustering strategy is developed to cluster the unserved load profiles into multiple representative profiles which the system operator can focus on. Finally, case studies on a distribution system evaluate the damage caused by an extreme weather event and verify the effectiveness of the proposed scenario clustering strategy. © 2024 IEEE.

关键词： Mobile energy resources (MERs) power system resilience preventive outage evaluation scenario clustering

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Inhibiting liquid permeation into silicone rubber by superhydrophobic coating for prolonged service life

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High Voltage 2023年第5期8卷 986-996页

作者： Shuming Liu Ying Zhou Zhou Zuo Shuqi Liu Qian Wang Zhong Chen Xidong Liang State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical EngineeringTsinghua UniversityBeijingChina School of Material Science and Engineering Nanyang Technological UniversitySingaporeSingapore

Liquid permeation into silicone rubber(SR)may lead to the degradation or complete failure of the composite *** to inhibit liquid permeation,two kinds of superhydrophobic coatings are applied to the SR *** liquid permeation properties of SR with different types of liquids are investigated,and the Langmuir diffusion model is applied to analyse the experimental *** results show that the composite superhydrophobic coating can effectively inhibit liquid permeation by reducing the contact area between the surface and liquid,and the stable structure of the composite coating can maintain the performance after the liquid permeation and ***,the nano‐particle coating without the polymer binder experiences severe performance degradation during the immersion test,and it cannot restrain the liquid permeation anymore after it loses the *** a validation of the effective protection,the insulation resistivity change was *** resistivity decreases sharply for the pristine SR after water permeation;however,the decrease is much smaller for the coated *** current study not only provides new insight into the liquid permeation properties of SR with different surface wettability but also suggests an effective measure to prevent liquid permeation into SR.

关键词： coating permeation liquid

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A Simple Open-loop Soft Startup Method Based on Operation Mode Analysis for LCC Converters Used in High-voltage DC power Supply 10

A Simple Open-loop Soft Startup Method Based on Operation Mo...

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10th IEEE International power Electronics and Motion Control Conference, IPEMC 2024 ECCE Asia

作者： Zhang, Kai Liu, Hanyu Sun, Kai Tsinghua University State Key Laboratory of Power System Operation and Control Department of Electrical Engineering China

ISBN: (纸本)9798350351330

LCC converters incorporate the stray parameters of high frequency transformer and are commonly employed as the initial stage of high-voltage DC power supplies, enhancing both efficiency and power density. However, the significant overshoot that occurs during the startup phase of high-voltage DC power supply poses considerable difficulties for the circuit. In this article, a simple open-loop soft startup control method is proposed: First, the operation mode analysis method is used to accurately solve the time-domain model of the LCC converter under different duty cycles in continuous current mode (CCM). Second, an open-loop variable duty cycle soft startup control strategy from the energy transmitted view is derived. Finally, soft startup process corresponding to different startup time requirements are verified on a 200V/20kV experimental prototype. © 2024 IEEE.

关键词： Time domain analysis

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Efficient economic operation based on load dispatch of power systems using a leader white shark optimization algorithm

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Neural Computing and Applications 2024年第18期36卷 10613-10635页

作者： Hassan, Mohamed H. Kamel, Salah Selim, Ali Shaheen, Abdullah Yu, Juan El-Sehiemy, Ragab Ministry of Electricity and Renewable Energy Cairo Egypt Department of Electrical Engineering Faculty of Engineering Aswan University Aswan81542 Egypt Department of Electrical Power Engineering Faculty of Engineering Suez University Suez43533 Egypt State Key Laboratory of Power Transmission Equipment and System Security and New Technology College of Electrical Engineering Chongqing University Chongqing China Department of Electrical Engineering Faculty of Engineering Kafrelsheikh University Kafrelsheikh33516 Egypt

This article proposes the use of a leader white shark optimizer (LWSO) with the aim of improving the exploitation of the conventional white shark optimizer (WSO) and solving the economic operation-based load dispatch (ELD) problem. The ELD problem is a crucial aspect of power system operation, involving the allocation of power generation resources to meet the demand while minimizing operational costs. The proposed approach aims to enhance the performance and efficiency of the WSO by introducing a leadership mechanism within the optimization process, which aids in more effectively navigating the complex ELD solution space. The LWSO achieves increased exploitation by utilizing a leader-based mutation selection throughout each generation of white sharks. The efficacy of the proposed algorithm is tested on 13 engineer benchmarks non-convex optimization problems from CEC 2020 and compared with recent metaheuristic algorithms such as dung beetle optimizer (DBO), conventional WSO, fox optimizer (FOX), and moth-flame optimization (MFO) algorithms. The LWSO is also used to address the ELD problem in different case studies (6 units, 10 units, 11 units, and 40 units), with 20 separate runs using the proposed LWSO and other competitive algorithms being statistically assessed to demonstrate its effectiveness. The results show that the LWSO outperforms other metaheuristic algorithms, achieving the best solution for the benchmarks and the minimum fuel cost for the ELD problem. Additionally, statistical tests are conducted to validate the competitiveness of the LWSO algorithm. © The Author(s) 2024.

关键词： Electric load dispatching

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A Core Loss Estimation Method Based on Data-driven Technology with Multi-head Attention Mechanism 10

A Core Loss Estimation Method Based on Data-driven Technolog...

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10th IEEE International power Electronics and Motion Control Conference, IPEMC 2024 ECCE Asia

作者： Su, Bowen Sun, Kai Yang, Min Xiao, Yunhao Zhang, Kai Liu, Bo Tsinghua University State Key Laboratory of Power System Operation and Control Department of Electrical Engineering China

ISBN: (纸本)9798350351330

Magnetic components play an important role in power electronic equipment, but there is still lack of accurate magnetic core loss estimation model. The data-driven methods are well-developed in recent years, and they are also more robust and accurate than conventional model-driven methods like Steinmetz Equation (SE) and improved Generalized Steinmetz Equation (iGSE). However, existing data-driven methods often focus on single excitation waveform like sinusoidal excitation waveform, which is not robust enough when facing complex excitation waveform with many high-frequency harmonic waveform. This paper presents a data-driven model based on attention mechanism which can capture the inner relationship within the input excitation waveform to present a more accurate core loss estimation results. And the comparison results with Multi-layer Perceptron (MLP) and Long Short-Term Memory(LSTM) models indicates that the proposed model has much more accuracy when facing complex excitation waveform. The proposed model can help to design magnetic components. © 2024 IEEE.

关键词： Facings

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Effects of Temperature-Induced Crystalline Phase Transition on the Space Charge Characteristics of Isotactic Polypropylene 14

Effects of Temperature-Induced Crystalline Phase Transition ...

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14th International Conference on the Properties and Applications of Dielectric Materials, ICPADM 2024

作者： Zhou, Yuanxiang Hou, Xuzhao Cheng, Jiayu Zhang, Ling Tsinghua University State Key Laboratory of Power System Department of Electrical Engineering Beijing100084 China

ISBN: (纸本)9798350374605

Isotactic polypropylene (iPP), especially its β - crystal form, has demonstrated outstanding advantages in terms of electrical insulation properties. However, under certain conditions, the metastable β -crystal form may transform into the more stable α -crystal form, which could affect the insulating properties of iPP and potentially threaten the safe and reliable operation of power cables. This study focuses on the temperature-induced crystalline phase transition behavior of iPP, first exploring the specific conditions for temperature-induced phase transition. Based on the determined conditions for temperature-induced phase transition, further research was conducted on the performance changes of iPP after constant-temperature phase transition treatment. The research found that the higher the temperature of the constant-temperature phase transition treatment, the more complete the transition from β phase to α phase, with an increase in melting temperature and no significant impact on crystalline properties. Under a field of -30 kV/mm, with the increase of constant-temperature, the space charge injection amount of iPP increased, as did the field distortion rate. The data and analysis obtained from this study provide reference information for the regulation of the crystal form of iPP and its impact on electrical insulation properties. © 2024 IEEE.

关键词： Crystalline materials

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Influence of Crosslinking Parameters on the Space Charge Characteristics of Hindered Phenol Antioxidant Grafted Polyethylene 14

Influence of Crosslinking Parameters on the Space Charge Cha...

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14th International Conference on the Properties and Applications of Dielectric Materials, ICPADM 2024

作者： Zhou, Yuanxiang Hou, Xuzhao Cheng, Jiayu Zhang, Ling Tsinghua University State Key Laboratory of Power System Department of Electrical Engineering Beijing100084 China

ISBN: (纸本)9798350374605

Cross-linked polyethylene (XLPE) insulation materials are used widely in high-voltage cables. To slow down the thermal-oxidative aging of XLPE, it is common practice in engineering to add an appropriate amount of antioxidant during the preparation of XLPE masterbatches. Antioxidant 300 was selected and added to low-density polyethylene, with the antioxidant 300 being grafted onto the polyethylene molecular chains through a chemical reaction during the crosslinking process. The effects of different crosslinking temperatures and times on the crosslinking rate, mechanical properties, physicochemical properties, and space charge distribution characteristics of the XLPE were studied. The results show that with the increase of crosslinking temperature or the extension of crosslinking time, the gel content and tensile strength of XLPE increase, while the crystallinity decreases, and the height of the hydroxyl absorption peak in the infrared spectrum curve reduces, leading to increasingly severe electric field distortions caused by space charges. These findings provide data support for scientific research and engineering fields. © 2024 IEEE.

关键词： Grafting (chemical)

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