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Pattern analysis of future HVDC grid development

Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2014年第34期34卷 6007-6020页

作者： Yao, Liangzhong Wu, Jing Wang, Zhibing Li, Yan Lu, Zongxiang China Electric Power Research Institute Haidian District Beijing100192 China State Key Lab of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Haidian District Beijing100084 China

The development of high voltage direct current (HVDC) grid is an effective approach to implement the large-scale long-distance power transmission, the large-scale renewable energy integration and accommodation, and the safe and stable operation of the interconnected AC grids. This paper reviewed the latest research progresses of DC transmission technologies, summarized the characteristics of DC grid, and discussed the current research status of DC grid. Then a typical topology of HVDC grid considering the integration of large-scale renewable generations over different regions was proposed. The technical requirements of such a HVDC grid was studied and refined accordingly. Furthermore, new types of key equipment, new control and protection technologies, reliability evaluation methods and standard system of such a HVDC grid were analyzed and the present research foundations and the future research directions of these relevant technologies were stated. It provides a technical reference for future research and construction of the DC grid in China. © 2014 Chin. Soc. for Elec. Eng.

关键词： HVDC power transmission

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Optimizing the Homogeneity and Efficiency of A Solid Oxide Electrolysis Cell Based on Multiphysics simulation and Data-Driven Surrogate Model

SSRN

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SSRN 2022年

作者： Chi, Yingtian Yokoo, Kentaro Nakajima, Hironori Ito, Kohei Lin, Jin Song, Yonghua State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing100087 China Department of Hydrogen Energy Systems Graduate School of Engineering Kyushu University Fukuoka Japan Department of Mechanical Engineering Faculty of Engineering Kyushu University Fukuoka Japan Tsinghua-Sichuan Energy Internet Research Institute Chengdu610213 China State Key Laboratory of Internet of Things for Smart City University of Macau 999078 China

Inhomogeneous current and temperature distributions are harmful to the durability of the solid oxide electrolysis cell (SOEC). Segmented SOEC experiments reveal that a high steam utilization, which is favorable for system efficiency, leads to local steam starvation and enhanced the inhomogeneity. It is necessary to consider inhomogeneity and efficiency jointly in optimization studies. Three-dimensional (3D) multiphysics models can simulate the inhomogeneity in a reliable manner, but they are unsuitable for optimization due to the high computational cost. This study proposes a method that combines segmented SOEC experiments, multiphysics simulation, and artificial intelligence to optimize the inhomogeneity and efficiency of SOEC. A 3D cell model is first built and verified by segmented SOEC experiments. Then, fast neural network surrogate models are built from the simulation data and integrated into a multi-objective optimization problem. Its solutions form a Pareto front reflecting the conflicting relationships among different objectives. It is found that the down-stream current is 60%-65% of the up-stream current when the steam utilization is 0.7. To increase the steam utilization to 0.8, the down-stream current further drops to 50%-60% of the up-stream current. The Pareto fronts enable system operators to achieve a balance between efficiency and inhomogeneity. © 2022, The Authors. All rights reserved.

关键词： Multiobjective optimization

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Optimizing the Homogeneity and Efficiency of an SOEC Based on Multiphysics simulation and Data-driven Surrogate Model

arXiv

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arXiv 2022年

Inhomogeneous current and temperature distributions are harmful to the durability of the solid oxide electrolysis cell (SOEC). Segmented SOEC experiments reveal that a high steam utilization, which is favorable for system efficiency, leads to local steam starvation and enhanced the inhomogeneity. It is necessary to consider inhomogeneity and efficiency jointly in optimization studies. Three-dimensional (3D) multiphysics models validated with experiments can simulate the inhomogeneity in a reliable manner, but they are unsuitable for optimization due to the high computational cost. This study proposes a method that combines segmented SOEC experiments, multiphysics simulation, and artificial intelligence to optimize the inhomogeneity and efficiency of SOEC jointly. A 3D cell model is first built and verified by segmented SOEC experiments. Then, fast neural network surrogate models are built from the simulation data and integrated into a multi-objective optimization problem. Its solutions form a Pareto front reflecting the conflicting relationships among different objectives. It is found that the down-stream current is 60%-65% of the up-stream current when the steam utilization is 0.7. To increase the steam utilization to 0.8, the down-stream current will further drop to 50%-60% of the up-stream current. The Pareto fronts enable system operators to achieve a balance between efficiency and inhomogeneity. Copyright © 2022, The Authors. All rights reserved.

关键词： Multiobjective optimization

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Contaction of Atoms for Outstanding Dielectric Characteristics in Kx-Passivated Polymer Dielectrics

SSRN

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SSRN 2022年

作者： Li, Xiao-Fen Wang, Tian-Yu Liu, Bai-Xin Liu, Jian-Bo Zhang, Gui-Xin Wang, Zhong Lin School of Materials Science and Engineering Tsinghua University Beijing100084 China State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing100084 China CAS Center for Excellence in Nanoscience Beijing Institute of Nanoenergy and Nanosystems Chinese Academy of Sciences Beijing100083 China School of Nanoscience and Technology University of Chinese Academy of Sciences Beijing100049 China School of Material Science and Engineering Georgia Institute of Technology AtlantaGA30332 United States

High dielectric characteristics polymer dielectrics are crucial for high-power, high-integration, and high-energy storage density electrical devices and film capacitors. However, polymer dielectrics accumulate much charge during operation, causing local electric field distortion and flashover or breakdown. The deep-level defect state (electron/hole accumulation center) is a fundamental factor affecting dielectric strength. Unfortunately, related research, especially on passivating deep-level defects in polymer dielectrics, is minimal. In this paper, based on experiments and first-principles calculations, it is found that KX (X=F, Cl, Br, I) effectively passivates deep-level defect states in polymer dielectrics. Further analysis of the physical passivation mechanism reveals that the deep-level defect cation passivation principle is the cation dipole effect on polymers. The principle of anion passivation of deep-level defects by suspending anions and cations is the key to producing more stable C covalent bonds. This stable covalent bond transfers the local charge from the C with the lone electron pair that originally contains the hanging bond. Therefore, some transfer occurs and the anion implements effective passivation. This paper addresses the design of high-performance polymer dielectrics, providing a reference for experimental and theoretical analyses. © 2022, The Authors. All rights reserved.

关键词： Passivation

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Improved Blade Tip Timing in Blade Vibration Monitoring with Torsional Vibration of the Rotor

引用

Journal of Physics: Conference Series 2012年第1期364卷

作者： Chao Liu Dongxiang Jiang State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Thermal Engineering Tsinghua University Beijing 100084 People's Republic of China

Due to the complex conditions in rotating machinery, the blades usually encounter fluctuating loads, and failures may occur in the operation. Blade vibration is rarely monitored in the practical rotating machinery in power plants as the traditional blade vibration method using strain gauge method is hard to be applied in long-time and online monitoring. The blade tip timing method is a promising approach to monitor the blade vibration and several special sensors are developed to realize the online monitoring. Based on the traditional blade tip timing method, an improved approach is established in this work. The proposed method can modify the expected arriving time when the torsional vibration exists. The accuracy is therefore improved in the torsional vibration case. Then the blade vibration monitoring with the traditional blade tip timing method and the proposed method are carried out in the test rig in laboratory. The results validate that, the torsional vibration influences the expected arriving time, and the proposed method can modify the expected arriving time and improve the accuracy of the blade vibration monitoring.

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Crack Growth Prediction of the Steam Turbine Generator Shaft

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Journal of Physics: Conference Series 2011年第1期305卷

作者： Dongxiang Jiang Chao Liu State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Thermal Engineering Tsinghua University Beijing 100084 People's Republic of China

The power network in China is encountering great changes and large-scale network is increasingly implemented for long distance power transmission as well as various kinds of power electronic devices, which bring in the risk of the torsional vibration of the turbine generator shafts, may cause the fatigue damage and cracks in the product life cycle. The paper analyzed the failed coupling of some 600MW steam turbine generator and calculated the local stress of the assembly under torsional load caused by the network disturbance. Then the crack propagation was analyzed with the predicted crack initiation position and crack propagation routine. The assembled coupling contains shaft, coupling and keys with interferences between the parts. Therefore the contact analysis was included. Extended Finite Element Method (X-FEM) is used to calculate the crack propagation and that the mesh needs not to be regenerated with the crack propagation, which is beneficial for engineering applications.

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Optimal Sizing and Pricing of Renewable power to Ammonia systems Considering the Limited Flexibility of Ammonia Synthesis

arXiv

引用

arXiv 2022年

作者： Yu, Zhipeng Lin, Jin Liu, Feng Li, Jiarong Zhao, Yuxuan Song, Yonghua Song, Yanhua Zhang, XinZhen The State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing100087 China Sichuan Energy Internet Reasearch Institute Tsinghua University Chengdu610213 China The Department of Electrical and Computer Engineering University of Macau 999078 China The Department of Electrical Engineering Tsinghua University Beijing100087 China Shenzhen Edo Renewable Co. Ltd Shenzhen518067 China

Converting renewable energy into ammonia has been recognized as a promising way to realize "green hydrogen substitution" in the chemical industry. However, renewable power to ammonia (RePtA) requires an essential investment in facilities to provide a buffer against the strong volatility of renewable energy and the limited flexibility of ammonia synthesis, which involves the three main stakeholders, namely, power, hydrogen, and ammonia. Therefore, the sizing and pricing of RePtA play a core role in balancing the interest demands of investors. This paper proposes an optimal sizing and pricing method for RePtA system planning. First, power to ammonia (P2A) is modeled as a flexible load, especially considering the limited flexibility of ammonia synthesis, which has been verified using real dynamic regulation data. Second, the multi-investor economic (MIE) model is established considering both external and internal trading modes. Then, a two-stage decomposed sizing and pricing method is proposed to solve the problem caused by the strong coupling of planning, operation, and trading, and information gap decision theory (IGDT) method is utilized to handle the uncertainty of renewable generation. Finally, real data from a real-life system in Inner Mongolia are utilized to verify the proposed approach. The results show that the system proposed has a yield of 8.15%. Copyright © 2022, The Authors. All rights reserved.

关键词： Costs

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A massive grid-connected power accumulator battery testing system using hybrid AC-DC microgrid

引用

Diangong Jishu Xuebao/Transactions of China Electrotechnical Society 2014年 29卷 449-453页

作者： Long, Bo Sun, Hongbin Wang, Bin Yao, Shuqing Fang, Xu Yao, Gaoxiang University of Electronic Science and Technology Chengdu610054 China State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing100084 China Bohai New Century Machinery Manufacturing Co. Ltd. TianJin300280 China

Nowadays, the network mode of the most energy recovery power battery testing instruments adopts AC-microgrid, which has the drawbacks of low energy recovery efficiency, complicated power circuit topology, cumbersome of the control algorithms. Aiming at these issues, a hybrid AC-DC microgrid system which is based on the power battery testing system has been put forward in this paper. The proposed scheme is composed by an energy storing system, a bidirectional DC-DC converter for test experiment, the grid-side loads, compared with conventional scheme, the proposed scheme has the merits of higher energy recovery efficiency, simplified power circuit for testing instruments. ©, 2014, Diangong Jishu Xuebao/Transactions of China Electrotechnical Society. All right reserved.

关键词： DC-DC converters

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Evaluation Model for Smart Distribution Network Planning under Energy Interconnection

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IOP Conference Series: Earth and Environmental Science 2019年第4期300卷

作者： Yan Zhang Zefu Jiang Jinsen Liu Wenxia Liu Hua Gao Yanmin Wang Power Grid Planning Research Center of Guizhou Power Grid Co. Ltd Guiyang Guizhou 550003 China State Key Laboratory of Power System and Power Generation Equipment Control and Simulation Department of Electrical Engineering Tsinghua University Haidian Beijing 100084 China

Due to the development of the energy interconnection, smart distribution networks (SDNs) should needs be transformed and upgraded to meet new demands. In order to assess the SDN planning, a new index system was conducted from the five attributes. The quantitative methods of all criteria were also defined. An evaluation model was proposed based on AHP weighting and TOPSIS methods. Empirical analysis was performed to verify the feasibility of the evaluation system.

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Optimization of hydrogen yield of a high-temperature electrolysis system with coordinated temperature and feed factors at various loading conditions: a model-based study☆

arXiv

引用

arXiv 2018年

作者： Xing, Xuetao Lin, Jin Song, Yonghua Hu, Qiang Zhou, You Mu, Shujun State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing100084 China Department of Electrical and Computer Engineering University of Macau Macau China Tsinghua-Sichuan Energy Internet Research Institute Chengdu610213 China National Institute of Clean and Low Carbon Energy Beijing102211 China Zhejiang Zhentai Energy Tech. Co. Ltd. Lishui Zhejiang Province321400 China

High-temperature electrolysis (HTE) is a promising technology for achieving high-efficiency power-to-gas, which mitigates the renewable curtailment while promoting decarbonization by transforming wind or solar energy into fuels. Different from low-temperature electrolysis, a considerable amount of the input energy is consumed by auxiliary equipment in an HTE system for maintaining the temperature, so the studies on systematic energy description and parameter optimization of HTE are essentially required. A few published studies investigated HTE’s systematic optimization based on simulation, yet there is not a commonly used analytical optimization model which is more suitable for integration with power grid. To fill in this blank, a concise analytical operation model is proposed in this paper to coordinate the necessary power consumptions of auxiliaries under various loading conditions of an HTE system. First, this paper develops a comprehensive energy flow model for an HTE system based on the fundamentals extracted from the existing work, providing a quantitative description of the impacts of condition parameters, including the temperature and the feedstock flow rates. A concise operation model is then analytically proposed to search for the optimal operating states that maximize the hydrogen yield while meeting the desired system loading power by coordinating the temperature, the feedstock flows and the electrolysis current. The evaluation of system performance and the consideration of constraints caused by energy balances and necessary stack requirements are both included. In addition, analytical optimality conditions are obtained to locate the optimal operating states without performing nonlinear programming by further investigating the optimization method. In the case study, a numerical case of an HTE system is employed to validate the proposed operation model and optimization method, which proves that the proposed operation strategies not only improve the overal

关键词： Hydrogen production

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