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Flexible region aggregation of adjustable loads via an adaptive convex hull strategy

Global Energy Interconnection 2025年第1期8卷 106-120页

作者： Yisha Lin Zongxiang Lu Ying Qiao Ruijie Chen State Key Lab of Power Systems Operation and Control (Department of Electrical Engineering Tsinghua University)BeijingPR China State Grid Quanzhou Electric Power Supply Company QuanzhouPR China

Increasing interest has been directed toward the potential of heterogeneous flexible loads to mitigate the challenges associated with the increasing variability and uncertainty of renewable *** the aggregated flexible region of load clusters managed by load aggregators is the crucial basis of power system scheduling for the system *** is because the aggregation result affects the qual-ity of the scheduling schemes.A stringent computation based on the Minkowski sum is NP-hard,whereas existing approximation meth-ods that use a special type of polytope exhibit limited adaptability when aggregating heterogeneous *** study proposes a stringent internal approximation method based on the convex hull of multiple layers of maximum volume boxes and embeds it into a day-ahead scheduling optimization *** numerical results indicate that the aggregation accuracy can be improved compared with methods based on one type of special polytope,including boxes,zonotopes,and ***,the reliability and economy of the power sys-tem scheduling can be enhanced.

关键词： Aggregation Flexible region Heterogeneous load power system scheduling

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Optimal Design of Full-Bridge Three-Level LLC Converter Based on Time-Domain Analysis 2

Optimal Design of Full-Bridge Three-Level LLC Converter Base...

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2nd IEEE International power Electronics and Application Symposium, PEAS 2023

作者： Liu, Zengyang Sun, Kai Yi, Zheyuan Tsinghua University State Key Laboratory of Power System Operation and Control Department of Electrical Engineering Beijing China

ISBN: (纸本)9798350313765

Fully DC wind turbine generator system is a promising substitute for conventional AC one. In the system, the LLC step-up converter plays a key role. Mode analysis and time-domain expressions can provide more accurate estimation of the resonant performance than the conventional First Harmonic Analysis method. The circuit works at different modes as the load rate varies. This paper categorizes these resonant behaviors into four modes, with time-domain expressions of each mode obtained. The variation regular of these modes is given and is applied in the program to realize recognizing the working mode automatically. The simulation and experiment have verified the effectiveness of the proposed method. © 2023 IEEE.

关键词： fully DC wind turbine generator system LLC converter mode analysis Pareto Front optimization time-domain expression

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Short-Term Photovoltaic Prediction Based on Transfer Learning and LSTM 7

Short-Term Photovoltaic Prediction Based on Transfer Learnin...

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7th IEEE Conference on Energy Internet and Energy system Integration, EI2 2023

作者： Zhang, Tianyu Zheng, Kedi Chen, Qixin Tsinghua University State Key Laboratory of Power System Operation and Control Department of Electrical Engineering Beijing China

ISBN: (纸本)9798350345094

With the proposal of carbon peaking and carbon neutrality goals, the proportion of renewable energy generation continues to increase and the number of new photovoltaic power stations is growing rapidly. Accurate photovoltaic power prediction is of great significance for the safe, stable and operation of power system. In order to solve the problem of insufficient historical data of newly constructed PV power plants, this paper proposes a short-term PV power prediction model based on Long Short Term Memory and transfer learning. The model uses meteorological data, numerical weather forecast data and PV power as features. According to the transfer learning theory, the Long Short Term Memory model is pre-trained using the historical data of other previously-built PV power plants, and then a small amount of local operation data is used to fine-adjust the model. Case study based on Hebei open source photovoltaic and meteorological data set proves that the proposed transfer learning model can effectively improve the short-term PV power prediction accuracy, and the MAPE can be improved by up to 15%. © 2023 IEEE.

关键词： Long short-term memory

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25%-Efficiency flexible perovskite solar cells via controllable growth of SnO_(2)

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iEnergy 2024年第1期3卷 39-45页

作者： Ningyu Ren Liguo Tan Minghao Li Junjie Zhou Yiran Ye Boxin Jiao Liming Ding Chenyi Yi State Key Laboratory of Power System Operation and Control Department of Electrical EngineeringTsinghua UniversityBeijing 100084China Center for Excellence in Nanoscience(CAS) Key Laboratory of Nanosystem and Hierarchical Fabrication(CAS)National Center for Nanoscience and TechnologyBeijing 100190China

High power conversion efficiency(PCE)flexible perovskite solar cells(FPSCs)are highly desired power sources for aerospace crafts and flexible ***,their PCEs still lag far behind their rigid ***,we report a high PCE FPSC by controllable growth of a SnO_(2)electron transport layer through constant pH chemical bath deposition(CBD).The application of SnSO_(4)as tin source enables us to perform CBD without strong acid,which in turn makes it applicable to acid-sensitive flexible indium tin ***,a mild and controllable growth environment leads to uniform particle growth and dense SnO_(2)deposition with full coverage and reproducibility,resulting in a record PCE of up to 25.09%(certified 24.90%)for FPSCs to *** as-fabricated FPSCs exhibited high durability,maintaining over 90% of their initial PCE after 10000 bending cycles.

关键词： Flexible perovskite solar cells chemical bath deposition SnO_(2) electron transport layer

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electrical tree degradation of MgO/epoxy resin composites at different voltage frequencies

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High Voltage 2024年第3期9卷 581-590页

作者： Yunxiao Zhang Wenxin Lin Yuanxiang Zhou Weiwei Xing Jiayu Cheng Chenyuan Teng College of Electrical Engineering and Automation Fuzhou UniversityFujian Key Laboratory of New Energy Generation and Power ConversionFuzhouChina State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical EngineeringTsinghua UniversityBeijingChina

electrical tree degradation is one of the main causes of insulation failure in high-frequency *** tree degradation is studied on pure epoxy resin(EP)and MgO/EP composites at frequencies ranging from 50 Hz to 130 *** results show that the tree initiation voltage of EP decreases,while the growth rate and the expansion coefficient increase with ***,the bubble phenomenon at high frequencies in EP composites is *** with trap distribution character-istics within the material,the intrinsic mechanism of epoxy composites to inhibit the growth of the electrical tree at different frequencies is *** can be concluded that more deep traps and blocking effect are introduced by doping nano-MgO into EP bulks,which can improve the electrical tree resistance performance of EP composites in a wide frequency range.

关键词： composites tree electrical

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Characteristics of controlled Bridge Circuit and Its Application in Magnetic Field Induction Measurement

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Tsinghua Science and Technology 2024年第4期29卷 1105-1117页

作者： Yanchu Li Qingqing Ding Mingchen Yan Jiyao Wang Jun Xu Xinzhou Dong Department of Electrical Engineering Tsinghua UniversityBeijing 100084China State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua UniversityBeijing 100084China School of Electrical and Electronic Engineering North China Electric Power UniversityBeijing 100096China

The article designs a new type of bridge circuit with a controlled source—when the resistance on the bridge arm of the controlled source bridge circuit meets the bridge balance condition, and the bridge branch contains only one Current-controlled Current Source (CCCS), a Voltage-controlled Current Source (VCCS), a Current-controlled Voltage Source (CCVS), or a Voltage-controlled Voltage Source (VCVS), the circuit is called a controlled bridge circuit, which has the characteristics of bridge balance. Due to the relationship between the controlled source and the bridge arm, the sensitivity of the components on the bridge is higher mathematically and logically. When applied to measurement, engineering, automatic control, and other fields, the controlled bridge circuit has higher control ac-curacy. Mathematical derivation and simulation results prove the correctness of the bridge balance conclusion and the special properties of this bridge when applied to the measurement field.

关键词： bridge bircuit bridge circuit applications bridge balanced condition controlled bridge circuit magnetic field induction measurement

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Effect of Photoionization Mechanism on Numerical Simulation of Transformer Oil Streamer Discharge 19th

Effect of Photoionization Mechanism on Numerical Simulation ...

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19th Annual Conference of China Electrotechnical Society, ACCES 2024

作者： Liang, Shaobin Zhou, Yuanxiang Chen, Jianning He, Zhiyang Li, Yuhang School of Electrical Engineering Xinjiang University Urumqi China State Key Laboratory of Power System Operation and Control Beijing China Department of Electrical Engineering Tsinghua University Beijing China

ISBN: (纸本)9789819613861

Discharge in transformer oil is one of the primary causes of transformer failures. The physical mechanisms of oil discharges are not yet fully understood. However, the prevailing electrohydrodynamics models primarily adopt field ionization and collision ionization, neglecting photoionization, which could potentially affect the discharge of liquid dielectric streamers. To reveal the discharge characteristics of transformer oil, this paper improves the field ionization term in electrohydrodynamics model, establishes a function of the ionization energy of transformer oil in relation to the recombination strength of carriers, and proposes a simulation model of streamer discharge in oil considering photoionization. The effects of photoionization on the characteristics of streamer discharge in transformer oil are studied, by examining the morphology and propagation velocity of streamers. The results show that the introduction of the photoionization mechanism promotes the formation of streamer branches and makes the energy in the streamer channel more concentrated. Moreover, photoionization facilitates the rapid propagation of streamers, which is key to the formation of the third mode of streamers. © Beijing Paike Culture Commu. Co., Ltd. 2025.

关键词： Electrohydrodynamics

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Analysis and Suppression of Voltage Overshoot in Symmetrical Hybrid Five-level Converter 10

Analysis and Suppression of Voltage Overshoot in Symmetrical...

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

作者： Liu, Nianzhou Zhang, Mingqi Pang, Jupeng Xie, Pengfei Qiu, Changqing Wang, Kui Li, Yongdong State Key Laboratory of Electromagnetic Energy Wuhan430064 China Tsinghua University State Key Laboratory of Power System Operation and Control Department of Electrical Engineering Beijing100084 China

ISBN: (纸本)9798350351330

This paper analyzes the device voltage overshoot in the symmetrical hybrid five-level converter. Owing to the presence of stray inductance, the voltage that the power devices need to withstand during switching operations may exceed their rated values. To address this issue, a device voltage overshoot suppression method suitable for the topology is proposed in this paper. This method suppresses SiC MOSFET voltage overshoot through adjustment of switching speed and the utilization of snubber capacitance, and it employs the design of RC and dual-RCD snubber circuits to suppress Si IGBT voltage overshoot. Simulation and experimental results certificate the effectiveness of the proposed method in suppressing device voltage overshoot. © 2024 IEEE.

关键词： Capacitance

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A Parameter Design Strategy Based on operation Mode Analysis Method for LCC Converter Used in High-Voltage DC power Supply

A Parameter Design Strategy Based on Operation Mode Analysis...

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2023 IEEE PELS Students and Young Professionals Symposium, SYPS 2023

作者： Zhang, Kai Liu, Hanyu Sun, Kai Tsinghua University State Key Laboratory of Power System Operation and Control Department of Electrical Engineering Beijing10084 China

ISBN: (纸本)9798350307832

LCC converter has the characteristics of both series resonance and parallel resonance, which is often used as the front stage of high voltage DC power supply. A three-stage boosting circuit using LCC converter, high-frequency transformer and voltage multiplier circuit is applied to a high-voltage source. In order to realize the design of core resonant cavity parameters, firstly, the working process of LCC converter in continuous current mode (CCM) is solved by using the operation mode analysis method. On this basis, considering the integrated design of stray parameters such as stray capacitance and leakage inductance of high-frequency transformer, the resonant cavity design flow of LCC converter is given. Finally, an experimental platform is built to test the LCC converter and the whole boosting circuit, and the voltage transmission ratio of 20V/10kV is verified. © 2023 IEEE.

关键词： Cavity resonators

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Inertia Support Strategy for DC Collecting system of Wind Turbine Generator

Inertia Support Strategy for DC Collecting System of Wind Tu...

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2024 CPSS and IEEE International Symposium on Energy Storage and Conversion, CPSS and ISESC 2024

作者： Liu, Zenyang Sun, Kai Wang, Huan Lu, Junlong Tsinghua University State Key Laboratory of Power System Operation and Control Department of Electrical Engineering Beijing China Institute of Electrical Engineering Chinese Academy of Sciences Renewable Energy Power Generation System Research Department Beijing China

ISBN: (纸本)9798350380514

In wind turbine generators system, lacking of inertia is a common problem. In AC collecting system, some researches have been done to solve this problem. However, in DC collecting system, few researches were done. This paper analyzes the analogies between AC and DC collecting system and the virtual capacitor control corresponding to the virtual synchronous generator control. Small signal models of different precision are proposed considering the LLC resonant converter used for stepping-up. The virtual capacitance provided by the control is calculated using the small signal model and this verifies the effectiveness of the control quantitively and demonstrates that the small signal models are useful. © 2024 IEEE.

关键词： Wind Turbine Generators

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