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Challenges and Reflection on Dielectric Materials for High-energy-density Film Capacitor Application

Gaodianya Jishu/High Voltage engineering 2025年第5期51卷 2210-2218页

作者： Dang, Zhimin Yang, Minhao State Key Laboratory of Power System Operation and Control Department of Electrical Engineering Tsinghua University Beijing100084 China Zhongyuan Electric Laboratory Xuchang461002 China National Innovation Platform for Industry-Education Integration of Energy Storage Technology North China Electric Power University Beijing102206 China

Film capacitors are important in high-tech fields such as power transmission and transformation systems, electric vehicles, and pulse power systems. Currently, the performance of capacitors is limited by the biaxially oriented polypropylene film, which leads to low energy storage density, poor temperature resistance, few charge and discharge cycles, and short lifespan of capacitors. This seriously affects the further improvement of the performance of metallized film capacitors and cannot meet the demands of high-energy-density metallized film capacitors in many fields. However, the key issues, including limited improvement in the comprehensive performance of dielectric materials for high-energy-density capacitors, and the difficulty in the industrial production of high-energy-density dielectric polymer materials from the small-sized samples produced in a laboratory, make it difficult to verify the comprehensive performance of metalized film capacitors. Therefore, several important perspectives and advice, including materials composite technology, materials chemical modification, and coating layers modification as well as the energy storage performance enhancement of dielectric films and high-energy-density capacitors design, are proposed in this article to guide the future research direction and promote the development of advanced dielectric materials for high-energy-density film capacitor application in China. © 2025 Science Press. All rights reserved.

关键词： Metallizing

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Flexible AC Traction Converter control Based on Active Disturbance Rejection control 1

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16th Annual Conference of China Electrotechnical Society, ACCES 2021

作者： Li, Zhanhe Li, Xiaoqian Li, Ziming Lin, Yunzhi Wei, Yingdong Li, Weirui Lu, Chao Li, Zengqin State Key Laboratory of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China China Railway Electrification Engineering Group Co. Ltd. Beijing China China Railway Electric Industry Co. Ltd. Baoding China

ISBN: (数字)9789811915321

ISBN: (纸本)9789811915314

The traditional out-of-phase traction power system has the problem of neutral sections and power quality, which seriously restricts the further development of electrified railways. With the development of flexible AC transmission systems, the flexible AC traction power system based on flexible AC traction converters is expected to break through the bottleneck of electrified railways’ development. However, because the power demand of rail vehicles is high and changeable, the DC voltage of AC-DC-AC flexible AC traction converters has a transient sag with the abrupt change of rail vehicles’ power. This paper focuses on flexible AC traction converters with modular multilevel converter (MMC) topology, adopts the active disturbance rejection control (ADRC) to estimate and compensate the uncertainty of the converter model and improves the current inner loop control, to solve the DC voltage sag. PSCAD/EMTDC is used to build the converter model with the ADRC controller. According to the simulation results, the controller proposed in this paper can achieve better dynamic performance and robustness. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

关键词： controllers

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The Optimal Design of the Second-Order Generalized Integrator Phase-Locked Loop Under power Voltage Distortion Conditions 5

The Optimal Design of the Second-Order Generalized Integrato...

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

作者： Zhang, Xin Gong, Lijiao Wang, Bin Si, Jindong College of Mechanical and Electrical Engineering Shihezi University Shihezi China Shihezi China State Key Laboratory of Safety Control and Simulation of Power Systems and Power Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China

ISBN: (纸本)9781665434256

Phase-locked loop (PLL) based on traditional second-order generalized integrator (SOGI) cannot obtain the voltage, frequency and phase information accurately when there are multiple harmonic interference and DC offset in grid voltage. To solve this problem, this paper proposes an improved PLL that can suppress harmonic and eliminate DC component to extract the synchronous signal accurately. First of all, based on the derivation of distorted grid voltage expression, the problem offluctuation in extracting synchronous signal from three-phase unbalanced voltage with harmonic by traditional PLL is analyzed. Then, the design of improved PLL is proposed, which is composed of an improved second-order generalized integrator and a frequency correction component which can suppress harmonics and eliminate disturbances under the condition of grid voltage distortion, and has self-adaptability in large frequency offset. Determine the control parameters to ensure that the proposed PLL structure has a better rejection to harmonic distortion than previous approaches, and realize accurate tracking of grid fundamental frequency synchronization information. Finally, the behavior of the proposed system is verified with MATLAB/Simulink simulation and Hardware-in-Loop Experimental Platform which prove the proposed PLL can realize the synchronous tracking performance of grid frequency and phase quickly and accurately in the non-ideal grid environment, and the results are consistent with the theoretical analysis. © 2021 IEEE

关键词： Phase locked loops

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Development of environmentally friendly high-capacity power cables

Nature Reviews Electrical Engineering

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Nature Reviews electrical engineering 2024年 565-566页

作者： Yao Zhou Jinliang He State Key Laboratory of Electrical Insulation and Power Equipment School of Electrical Engineering Xi’an Jiaotong University Xi’an China State Key Laboratory of Power System Operation and Control Department of Electrical Engineering Tsinghua University Beijing China

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An Online Compensation Method of DC Drift for Three-Phase Current Reconstruction with DC-Link Resistance

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Chinese Journal of Electronics 2020年第5期29卷 982-990页

作者： HUANG Lili ZHENG Lianqing LI Pengwei Department of Electric Machine and Electric Apparatus School of Electrical Engineering Chongqing University State Key Laboratory of Power Transmission Equipment & System Security and New Technology Chongqing University

In a three-phase power convertor system,phase current reconstruction technique using a DC-link resistance can reduce the cost and weight of the diving system. The three-phase current without DC offset in normal condition is introduced in this paper *** on this premise, the DC-link current offset is considered and the logical relationship between threephase voltage, three-phase current, and DC offset are analyzed and depicted. The DC offset introduced during the sampling processes a distortion into phase current,which is composed of fundamental and harmonic frequency based on FFT analysis. The fundamental component of the distortion shares the same phase angle with counterpart voltage, which distorts power factor and amplitude of three-phase currents. The harmonic components of the distortion can be transformed into 6th harmonic components in synchronous dq axes and undermine the performance of the controlling system. After that, a practical method is proposed to solve this problem, namely sampling the DC offset signal during the period of the zero voltage vectors. An analogy sample circuit is designed and tested. This method can avoid the DC offset from the source. Finally, its effectiveness is verified via simulation and experiment.

关键词： synchronous dq axes DC drift phase angle power grids DC offset signal compensation FFT analysis electric current control power convertors DC offset PWM power convertors fast Fourier transforms Current deviation power system harmonics DC-link resistance three-phase current reconstruction phase current reconstruction technique three-phase power convertor system harmonic components power supply quality Phase current reconstruction

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Performance of a siphon-like water supplying solar distiller with helium gas enhancing the reverse film evaporation process

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Desalination 2023年第1期564卷

作者： Yuan, Xi Zheng, Hongfei Wang, Ge Zhao, Yunsheng Kong, Hui School of Mechanical Engineering Beijing Institute of Technology Beijing100081 China College of Energy and Power Engineering Nanjing University of Aeronautics and Astronautics Nanjing210016 China School of Physics and Electronics Nanning Normal University Nanning530021 China State Key Laboratory of Power System Operation and Control Department of Thermal Engineering Tsinghua-BP Clean Energy Center Tsinghua University Beijing100084 China

The multistage solar desalination method based on the interface local thermal method is an attractive and efficient desalination method. However, there are still problems such as the upward diffusion of water vapor in the air and the downward irradiation of solar light, which make the multistage device fail to effectively condense and interface salt crystallization cannot be effectively eliminated, hindering the development of large-scale and sustainable applications of this technology. Here, we use a cheap nanofiber super-hydrophilic material to promote the flow of seawater at the interface and promote the discharge of salt crystallization under the siphon-like effect. At the same time, the water vapor‑helium space is constructed by filling helium to promote the downward diffusion of water vapor in the space and solve the problem of insufficient multistage condensation. In this work, a two-stage and three-stage reverse mass transfer solar seawater desalination system with solar hot film evaporation was built, and the corresponding theoretical calculation and experimental verification were carried out. The experimental results show that under sunlight irradiation of 800 W m−2, the three-stage experimental system filled with helium can effectively enhance the condensation of water so that the GOR value of the system vapor is 1.54, the first-stage evaporation efficiency reaches 67.9 %, and the water productivity reaches 1.85 kgm−2h−1. In this study, injecting low molecular weight gas to achieve efficient condensation of the system to improve the performance of the interfacial evaporation desalination system provides a new method and reference. © 2023 Elsevier B.V.

关键词： Condensation

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Robust operation of Integrated Electric-Gas systems Considering Frequency Regulation 2

Robust Operation of Integrated Electric-Gas Systems Consider...

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2nd IEEE China International Youth Conference on electrical engineering, CIYCEE 2021

作者： Jia, Qiyue Zhang, Rui Wang, Cheng Bi, Tianshu University of North China Electric Power University Electrical Engineering Department Beijing China North China Electric Power University State Key Laboratory of Alternate Electrical Power System Renewable Energy Sources Beijing102206 China

ISBN: (纸本)9781665400640

This paper addresses the secure and economic operation problem of integrated electricity and natural gas system (IEGS), considering its participation in the power system's frequency regulation (FR). IEGS can make profits by participating in the Frequency Regulation Auxiliary Service Market (FRASM) through the power reserve (PR) of the gas turbine (GT). However, the time required for FR is uncertain, which poses a challenge for its safe operation. We establish a robust model to balance security and the economy. Since the gas network is described by highly nonlinear partial differential equations that hinder the solution, we linearized the gas network by the difference method. Then the solution is obtained through a two-stage robust optimization algorithm. Our proposed model introduces the dynamic security concept into the IEGS operation optimization when participating in FRASM for the first time. The simulation results verify the effectiveness and necessity of the proposed model and algorithm. © 2021 IEEE.

关键词： Gases

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power-absorption mechanism and coupling effects in dual-wavelength laser-sustained plasma

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Physical Review Applied 2025年第5期23卷 054083-054083页

作者： Dongheyu Zhang (张东荷雨) Jinbao Liu (刘金宝) Yangyang Fu (付洋洋) Department of Electrical Engineering Tsinghua University 100084 Beijing China State Key Laboratory of Power System Operation and Control Department of Electrical Engineering Tsinghua University 100084 Beijing China

Dual-wavelength laser-sustained plasma (LSP), which absorbs energy from lasers with two different wavelengths, is promising as a high-performance light source for wafer optical inspection; however, the mechanisms of power absorption from two lasers are still not well understood. Here a fully coupled laser-thermal-hydrodynamic fluid model is established to investigate the formation characteristics of dual-wavelength LSP. The model is validated by our comparing the laser power absorption results from the simulation and those from experiments. The simulation results show that the near-infrared (915-nm) laser heats a relatively large area of the LSP. In contrast, the visible (435-nm) laser can penetrate the LSP bulk and deposit energy mainly at the focal point, resulting in a smaller, hotter, and higher-radiance LSP core. The time-dependent evolution of the dual-wavelength LSP and the energy components of laser power absorption are presented; moreover, the coupling effects of the two lasers are observed. The near-infrared laser can sustain a large-area background plasma at a relatively low temperature (approximately 15 000 K), which increases the visible laser power absorption at the LSP core, reaching the highest temperature of approximately 30 000 K. The results from this work indicate that dual-wavelength LSP can be a competitive candidate for developing high-performance broadband and high-intensity radiative light sources.

关键词： Laser produced plasmas

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Feasible Region Identification Approach for the Regional Integrated Energy system Considering Flexible Ramping Constraints Based on Polyhedral Projection Algorithm

SSRN

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SSRN 2024年

作者： Xiong, Zhan Zhang, Chunyan Qiu, Dawei Wang, Lingling Jiang, Chuanwen Zhou, Shichao Key Laboratory of Control and Power Transmission and Converstion Shanghai Jiao Tong University Shanghai China State Grid Shanghai Municipal Electric Power Company China Department of Electrical and Electronic Engineering Imperial College London London United Kingdom

The low-carbon agenda promotes the increasing penetration of renewable energy, this however also results in a rapid decrease in the flexibility of power systems with less controllable generation. The regional integrated energy system (RIES) has multi-time scale characteristics in the energy transmission process and contains rich flexibility capacity. Fully exploiting the flexibility potential of RIES can effectively improve the integration of renewable energy. However, identifying feasible regions and optimizing operations for an RIES remains challenging, particularly considering its complex multi-energy coupling effects and highly uncertain characteristics resulting from multi-energy load profiles and distributed renewable energy resources. This paper proposes a novel approach to tackle this challenge by introducing a projection method based on second-order cone programming. The approach aims to describe the interactive energy and flexible reserve feasible regions of an RIES. Specifically, a max-min optimization problem is formulated to identify the maximum set of the RIES feasible region. Subsequently, the duality principle and Karush-Kuhn-Tucker (KKT) optimality conditions are leveraged to reformulate the max-min optimization problem into a solvable second-order cone programming problem. Additionally, to address uncertainties within the RIES, a chance-constrained programming approach is proposed. This approach introduces a set of chance constraints to represent the operational risk associated with system uncertainties. Case studies conducted on an RIES incorporating a 33-bus distribution network and a 7-node natural gas network demonstrate the effectiveness and efficiency of the proposed approach in projecting the feasible region in terms of both operating costs and computational time. © 2024, The Authors. All rights reserved.

关键词： Second-order cone programming

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Big data service capability of enterprise-scale data middle platform

Big data service capability of enterprise-scale data middle ...

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Tsinghua University-IET electrical engineering Academic Forum: Constructing Green and Sustainable Energy system 2021

作者： Chen, Lianfu Wang, Xuan Peng, Fang Liu, Shi State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing China Department of Electrical Engineering Tsinghua University Beijing China Big Data Center of State Grid Corporation of China Beijing China

ISBN: (纸本)9781839536199

With the rapid development of technologies such as big data, cloud computing, Internet of things and artificial intelligence, electric power enterprises are faced with the strategic deployment of digital transformation. By upgrading IT architecture, power grid companies build the data middle platform, and separate the data operation and product technology from its front platform. Through service reusing and data sharing, the business capability can be shared, which providing technical support for power enterprises to serve a variety of complex business scenarios. This paper focuses on the architecture design of data middle platform in power grid companies, and analyzes its service capability. In addition, this paper sorts out the capability output framework of big data middle platform, and analyzes the data service requirements and application modellings for data middle platform in different business scenarios. © 2021 Institution of engineering and Technology. All rights reserved.

关键词： Big data

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