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Theoretical and experimental studies on the self-healing properties of metallised capacitor films under multiple stresses

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High Voltage 2024年第6期9卷 1347-1356页

作者： Zhiyuan Wu Shangshu Liu Tong Tong Shaolong Zhong Jiantao Wang Hongbin Qi Zhimin Dang Wei Wang Beijing Key Laboratory of High Voltage and Electromagnetic Compatibility North China Electric Power UniversityBeijingChina State Key Laboratory of Power System Operation and Control Tsinghua UniversityBeijingChina

Metallised film capacitors,for the most important merits is the excellent self-healing property,have significant electrical insulation *** essential factors affecting the self-healing properties of metallised polypropylene film capacitors(MPPFCs)are first analysed,and a self-healing performance characterisation test platform for metallised polypropylene capacitor films was *** the voltage/current waveforms and discharge patterns of the self-healing process under multiple stresses including temperature,voltage and inter-layer pressure were recorded and *** correlation between self-healing performance characterisation and the carbon that appeared on the surface of the dielectric layer during the arc extinction time is ***,by virtue of an equivalent dynamic circuit model,the influence of square resistance and the equivalent capacitance of the power grid on self-healing has been theoretically studied.

关键词： films stresses film

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Two-stage Optimal Scheduling of Community Integrated Energy system Considering operation Sequences of Hydrogen Energy Storage systems

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Journal of Modern Power systems and Clean Energy 2025年第1期13卷 276-288页

作者： Wei Kong Kai Sun Jinghong Zhao School of Electrical Engineering Naval University of EngineeringWuhanChina Department of Electrical Engineering State Key Laboratory of Power System Operation and ControlTsinghua UniversityBeijingChina

The hydrogen energy storage system(HESS)integrated with renewable energy power generation exhibits low reliability and flexibility under source-load *** address the above issues,a two-stage optimal scheduling model considering the operation sequences of HESSs is proposed for commercial community integrated energy systems(CIESs)with power to hydrogen and heat(P2HH)*** aims to optimize the energy flow of HESS and improve the flexibility of hydrogen production and the reliability of energy supply for ***,the refined operation model of HESS is established,and its operation model is linearized according to the operation domain of HESS,which simplifies the difficulty in solving the optimization problem under the premise of maintaining high approximate ***,considering the flexible start-stop of alkaline electrolyzer(AEL)and the avoidance of multiple energy conversions,the operation sequences of HESS are ***,a two-stage optimal scheduling model combining day-ahead economic optimization and intra-day rolling optimization is established,and the model is simulated and verified using the source-load prediction data of typical days in each *** simulation results show that the two-stage optimal scheduling reduces the total load offset by about 14%while maintaining similar operating cost to the day-ahead economic optimal ***,by formulating the operation sequences of HESS,the operating cost of CIES is reduced by up to about 4.4%.

关键词： Community integrated energy system(CIES) hydrogen storage operation sequence two-stage optimal scheduling

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Generating High-Temperature Polymer Dielectrics with a Graph Convolution and Reinforcement Learning Framework

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Journal of Physical Chemistry C 2025年第22期129卷 10020-10026页

作者： Liu, Di-Fan Dong, Wen-Zhuo Wang, Xin-Jie Zhong, Shao-Long Dang, Zhi-Min State Key Laboratory of Power System Operation and Control Department of Electrical Engineering Tsinghua University Beijing100084 China

Generating molecular structures with certain desired properties is a fundamental problem for material science research. Deep learning models have demonstrated big potential to identify novel materials by exploring large chemical spaces efficiently. Here, we demonstrate the generation of hypothetical polymers with a high glass-transition temperature (Tg) and a wide band gap (Eg) using a general graph convolutional network-based model through reinforcement learning. Two forward property prediction models on Tg and Eg are employed to provide domain-specific rewards. We further incorporate prior knowledge in the form of adversarial rewards given by a generative adversarial network framework via a data set of exemplar polymer structures. The domain-specific rewards and adversarial rewards are optimized in a reinforcement learning framework through policy gradient methods. Rules of chemistry are incorporated in the molecule generation environment as hard constraints. The generation process is guided to generate promising high-temperature polymer dielectrics for energy storage applications by property targeting and constrained property optimization. This work demonstrates potential for exploring large chemical spaces for the discovery of polymers with desirable properties. © 2025 American Chemical Society.

关键词： Deep reinforcement learning

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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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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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Optimal Scheduling of Active-Reactive Power for PV-BES system Considering Voltage Support and Frequency Regulation 50

Optimal Scheduling of Active-Reactive Power for PV-BES Syste...

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50th Annual Conference of the IEEE Industrial Electronics Society, IECON 2024

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

ISBN: (纸本)9781665464543

The voltage support capability of renewable resources (RES) is emphasized by grid codes for stable and secure operation faced with grid faults. However, there is another problem occurs when the penetration of RES is boosting. The capability occupation due to injected power for voltage support leads to the decrease of output power for loads, which may result in frequency issues when the inertia of the system decreases. To guarantee the voltage and frequency security during fault ride through (FRT) process, this paper proposes an optimal scheduling scheme for PV-BES system considering voltage support and frequency regulation. In the optimal model, in order to map the voltage and frequency constraints into power constraints, the evaluation model of required injected power for voltage support is formulated firstly. Based on center of inertia theorem and time scale characteristics of FRT, the frequency deviation is represented by distributed generator (DG) adjustment. The voltage and frequency constraint are incorporated into the optimal scheduling model and the quasi-steady-state of the PV-BES system during FRT can be analyzed. The proposed method is fully tested, and the results demonstrate that with the proposed method, the voltage and frequency security can be well guaranteed. © 2024 IEEE.

关键词： Renewable energy

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A Modulation Scheme of CLLC Converters for Bidirectional Power Transfer with Reduced Switching Frequency Range

A Modulation Scheme of CLLC Converters for Bidirectional Pow...

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2024 IEEE Energy Conversion Congress and Exposition, ECCE 2024

作者： Wang, Leheng Chen, Huan Sun, Kai Tsinghua University State Key Laboratory of Power System Operation and Control Department of Electrical Engineering Beijing China

ISBN: (纸本)9798350376067

CLLC converters are broadly used in battery energy storage systems (BESS), where the capabilities of bidirectional operation and voltage regulation are desired. In the existing bidirectional power transfer scheme, pulse frequency modulation (PFM) is used to realize the reciprocal gain of forward and backward directions. It leads to not only large frequency modulation range but also asymmetric transfer characteristics. In this paper, a novel modulation scheme of CLLC converters for bidirectional power transfer is proposed. In the proposed backward power transfer scheme, the driving signals of primary and secondary-side switches are aligned at the falling-edge, which brings about symmetrical characteristics as forward scheme. This symmetry further ensures the identical switching frequency in both directions, which simplifies parameter design, minimizes switching frequency range, and improves efficiency. A 10-kW prototype is built and the experimental results validate the effectiveness of the proposed scheme, offering potential for cost-effective and efficient applications. © 2024 IEEE.

关键词： Switching frequency

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Influence of Thermal Conductivity of Multi-scale Particles Epoxy Composites on High-Frequency Electrical Insulation Property 5

Influence of Thermal Conductivity of Multi-scale Particles E...

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5th IEEE International Conference on Dielectrics, ICD 2024

作者： Song, Yan-Hui Dang, Zhi-Min Tsinghua University State Key Laboratory of Power System Operation and Control Department of Electrical Engineering Beijing China

ISBN: (纸本)9798350308976

Epoxy, with excellent electrical insulation properties, processing performance, and low price, is commonly used for transformers (110kV and below) and power electronic transformers (high-frequency transformers) as the primary insulating material. Since the thermal conductivity of epoxy resins is only 0.2 W/(m·K), the electrical insulation properties decline significantly at high frequency. Preparing epoxy composites with high thermal conductivity and excellent electrical insulation at high frequencies is a great challenge for industrial production. It is considered that SiO2 (9 eV), BN (5.9 eV), and Al2O3 (7.2-8.8 eV) are thermally conductive particles with good electrical insulation properties. The materials filled with different micron-scale particles have higher thermal conductivity than the nanofilled materials. In this study, 5 μm SiO2, 25 μm BN, and 40 μm Al2O3 were used as fillers, and the filler ratios were calculated according to the Dinger-Funk model, focusing on the effects of the variation of filler content on thermal conductivity and electrical insulation properties. The thermal conductivity of the epoxy composites improved with the increase of filler content up to 1.003 W/(m·K), while the AC breakdown field strength gradually decreased. However, the breakdown time at 20 kHz, 35 kV/mm bipolar square wave appeared to increase and then decrease with the increase of content. Therefore, the optimum content of fillers allows the preparation of efficient epoxy composites as insulating materials for power electronic transformers. This study provides ideas for designing thermally conductive composites operating at high frequency and high voltage fields. © 2024 IEEE.

关键词： epoxy resin high frequency bipolar square wave inorganic particle compounding thermal conductive electrical insulation

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Modeling method of photovoltaic power generation grid connection based on particle swarm optimization neural network

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Energy Informatics 2024年第1期7卷 88页

作者： Zhang, Jie Lu, Yuanhong Huang, Libin Guo, Haiping Tu, Liang State Key Laboratory of HVDC China Southern Power Grid Guangzhou510000 China Guangdong Provincial Key Laboratory of Intelligent Operation and Control for New Energy Power System China Southern Power Grid Guangzhou510000 China CSG Key Laboratory for Power System Simulation China Southern Power Grid Guangzhou510000 China

Aiming at the complex structure, numerous equipment, intricate control and protection logic, as well as the existence of numerous unmodeled dynamics and black-box device models in photovoltaic (PV) grid-connected systems, a modeling method based on Particle Swarm Optimization Neural Network (PSO-NN) is proposed to address the inability of pure mechanism models to accurately simulate their operational dynamics. Utilizing the differences in active power response waveforms under Voltage-Frequency (Vf) control, Power-Reactive Power (PQ) control, and Droop control as criteria for control strategy identification, a PSO-NN model is constructed for PV grid-connected systems, with inputs comprising temperature, humidity, light intensity, voltage, and frequency disturbances, and outputs being active and reactive power. To validate the model's effectiveness, a PV grid-connected system model is built in a self-developed simulation software and connected to an IEEE 14-bus distribution network for simulation verification. The results demonstrate that the proposed PV grid-connected model can effectively identify the types of Vf control, PQ control, and Droop control strategies, and accurately reflect the dynamic response characteristics of active and reactive power under various voltage and frequency disturbances. © The Author(s) 2024.

关键词： Particle swarm optimization (PSO)

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Characteristics of perfluoromethyl vinyl ether:A new eco-friendly alternative gas for SF_(6)

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High Voltage 2024年第3期9卷 509-517页

作者： Song Xiao Yijiang Chen Mingjun Tang Shuangshuang Tian Haoran Xia Yifan Wang Ju Tang Yi Li Xiaoxing Zhang State Key Laboratory of Power Grid Environmental Protection School of Electrical Engineering and AutomationWuhan UniversityHubeiChina Key Laboratory for High-Efficiency Utilization of Solar Energy and Operation Control of Energy Storage System School of Electrical and Electronic EngineeringHubei University of TechnologyWuhanChina

The exploration of eco-friendly insulating gas to substitute the most potent greenhouse gas sulphur hexafluoride(SF6)has consistently garnered significant ***,the au-thors evaluated the feasibility of utilising perfluoromethyl vinyl ether(PMVE,C_(3)F_(6)O)as a new branch of eco-friendly insulating gas for the first *** primary dielectric and stability characteristics of PMVE regarding AC breakdown,partial discharge,dielectric recovery,and decomposition properties were revealed under various gas pressure and electrical field *** was found that PMVE demonstrated superior dielectric strength,with the AC breakdown and PD inception voltage(PDIV)1.10 and 1.14 times that of pure SF_(6).Furthermore,the dielectric strength of PMVE exhibits stability even after undergoing 100 cycles of AC breakdowns,and there is no observable formation of solid precipitation on the electrode *** discharge decomposition of PMVE mainly generates fluorocarbon(CF_(4),C_(2)F_(6),C_(3)F_(6),C_(3)F_(8),etc.)and ***,the exceptional insulation stabilityandno absence of solidprecipitation featuresendow PMVE tobe utilised as a new eco-friendly gas for SF_(6)-free gas-insulated equipment.

关键词： surface dielectric vinyl

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