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Improved Multi-Grained Cascade Forest Model for Transformer Fault Diagnosis

CSEE Journal of power and energy systems 2025年第1期11卷 468-476页

作者： Yiyi Zhang Yuxuan Wang Jiefeng Liu Heng Zhang Xianhao Fan Dongdong Zhang Guangxi Key Laboratory of Power System Optimization and Energy Technology Guangxi UniversityNanningGuangxi530004China

Dissolved gas analysis(DGA)is an effective online fault diagnosis technique for large oil-immersed ***,due to the limited number of DGA data,most deep learning models will be overfitted and the classification accuracy cannot be ***,this paper has introduced the idea of deep neural networks into the multi-grained cascade forest(gcForest),which is a tree-based deep learning model,and proposed an improved gcForest that can be accelerated by ***,in order to extract features more effectively and reduce memory consumption,the multi-grained scanning of gcForest is replaced by convolutional neural ***,the cascade forest(CasForest)is replaced by cascade eXtreme gradient boosting(CasXGBoost)to improve the classification ***,235 DGA samples are used to train and evaluate the proposed *** average fault diagnosis accuracy of the improved gcForest is 88.08%,while the average recall,precision,and Fl-score are 0.89,0.90,0.89,***,the proposed method still has high fault diagnosis accuracy for datasets of different sizes.

关键词： Convolutional neural networks dissolved gas analysis fault diagnosis multi-grained cascade forest(gcForest) power transformer

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Small Signal Equivalent Modeling for Large ES-Embedded DFIG Wind Farm With Dynamic Frequency Response

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IEEE Transactions on power systems 2025年第3期40卷 2324-2335页

作者： Dai, Wei Xu, Jun Goh, Hui Hwang Shi, Tonghui Zeng, Zhihong Guangxi University Guangxi Key Laboratory of Power System Optimization and Energy Technology Nanning530004 China

A simplified equivalent model that replaces detailed large-scale wind farms is an effective method for conducting complex simulation analyses and avoiding the dimensional catastrophe problem in power systems. In recent years, wind farms are equipped with the energy storage (ES) for improved primary frequency support action to react to low inertial power systems. Nonetheless, the existing equivalent models disregard the function of the ES, thus failing to capture the frequency response characteristics under the synergistic action of every doubly-fed induction generator (DFIG) and ES. This paper proposes a frequency response equivalent method for ES-embedded DFIG that takes into account coordinated control between ES and DFIG to accurately represent the primary frequency regulation capability. Based on a small signal model analysis, the general equivalent frequency response formula of ES-embedded DFIG system is derived. A multi-machine equivalent model is developed with variable operating states and the power response mutation resulting from ES intervention. To acquire the equivalent parameters of the preceding model, an improved two-stage parameter identification model is proposed to capture the accurate frequency response curve prior to and following ES action. Multiple large-scale wind farms are included in the two-area, four-generator system that validates the proposed method. © 1969-2012 IEEE.

关键词： Asynchronous generators

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MAPPO-ITD3-IMLFQ algorithm for multi-mobile robot path planning

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Advanced Engineering Informatics 2025年 65卷

作者： Hu, Likun Wei, Chunyou Yin, Linfei Guangxi Key Laboratory of Power System Optimization and Energy Technology Guangxi University Guangxi Nanning530004 China

With the development of robotics, mobile robots (MRs) are widely applied in industrial and agricultural production. Reasonable path planning (PP) algorithms are the prerequisite for multi-mobile robot (MMR) systems to accomplish tasks. However, the existing PP algorithms of MMR systems still have the problems of being unable to dynamically assign tasks, not comprehensively considering the needs of kinematic constraints and dynamic obstacle avoidance, and poorly coordinating path conflicts. This study proposes a multi-agent proximal policy optimization-artificial potential field twin delayed deep deterministic policy gradient-improved multi-level feedback queue (MAPPO-ITD3-IMLFQ) algorithm for the PP of MMR systems. The proposed MAPPO-ITD3-IMLFQ algorithm combines the multi-agent proximal policy optimization (MAPPO) algorithm, the improved twin delayed deep deterministic policy gradient (ITD3) algorithm, and the improved multi-level feedback queue (IMLFQ) algorithm to form a PP algorithm for MMR system. The MRs apply the MAPPO algorithm to calculate task assignment (TA) schemes and provide sub-goal points for ITD3 algorithm. The MRs apply the ITD3 algorithm to calculate the path of the MRs. When the paths of different MRs conflict, the MR applies the IMLFQ algorithm to coordinate the movement of the MRs. The proposed MAPPO-ITD3-IMLFQ algorithm realizes the dynamic TA of the MMR system, meets the kinematic constraints and dynamic obstacle avoidance requirements of MRs, and coordinates path conflicts among the MRs. In this study, the proposed MAPPO-ITD3-IMLFQ algorithm is applied to different environments for the PP of MMRs. Experimental results show that: compared to the Hungarian algorithm and the genetic algorithm, the proposed MAPPO-ITD3-IMLFQ algorithm reduces the time spent on assigned tasks by 75.25 % and 77.44 %, respectively. Compared to the PP algorithms for reinforcement learning, the proposed MAPPO-ITD3-IMLFQ algorithm reduces the length of the planned path

关键词： Mobile robots

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Thermal fault diagnosis of power equipment through improved instance segmentation and deep neural network temperature fitting

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Dianji yu Kongzhi Xuebao/Electric Machines and Control 2025年第2期29卷 116-125页

作者： Zheng, Hanbo Hu, Junhao Li, Jinheng Liang, Yanshen Huang, Junjie Guangxi Key Laboratory of Power System Optimization and Energy Technology Guangxi University Nanning530004 China Electric Power Research Institute State Grid Hubei Electric Power Co. Ltd. Wuhan430077 China

The malfunctioning equipment displays anomalous temperatures at the fault location, posing a significant risk to the security and stability of the power system. To evaluate the thermal status of power equipment, a method for diagnosing thermal faults was proposed. This approach was implemented through instance segmentation and temperature fitting. Firstly, a dataset was constructed based on the infrared images of power equipment collected at the substation, and an improved instance segmentation model was developed. The enhanced model achieves a 3. 6% improvement in the mean average precision of masks and a 2. 5% improvement in the boxes, while the model’s floating point operation is maintained at only 12. 1 GFLOPs. Secondly, a method for fitting the temperature values of the equipment based on deep neural networks was proposed. This method achieved better fitting accuracy than other methods, with an R-square of 0. 999 7 and a fitting temperature deviation of approximately 3% . Finally, a method for automatically diagnosing thermal abnormalities was proposed in accordance with the current industrial guidelines. This algorithm was founded upon kernel density estimation for the obtainment of temperature parameters. The experimental findings indicate that our algorithm precisely detects and is alert to the fault breaker, thus increasing operational safety. © 2025 Editorial Department of Electric Machines and Control. All rights reserved.

关键词： Deep neural networks

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Cepstrum Lifting and Coherent Averaging-based Instantaneous Frequency Estimation of Low-Amplitude Signal Components for Rotating Machinery

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IEEE Sensors Journal 2025年第10期25卷 17479-17490页

作者： Liu, Shaokang Liu, Shuai Wu, Yingjie Liu, Weiliang Liu, Changliang Luo, Zhihong University of North China Electric Power Control and Computer Engineering Department Beijing102200 China Baoding key Laboratory of State Detection and Optimization Regulation for Integrated Energy System Baoding071000 China University of Northeast Electric Power Automation Engineering Department Jilin132000 China Inner Mongolia University of Technology Electric Power Department Hohhot010080 China

Instantaneous frequency (IF) serves multiple critical functions in the prognostic and health management of rotating machinery. Current IF estimation methodologies primarily concentrate on enhancing estimation accuracy at the algorithmic level. However, in practical industrial applications, the target signal component is often influenced by varying operating conditions, structural resonances, and background noise, causing it to become submerged or even disappear, ultimately resulting in the failure of conventional IF estimation techniques. To address these challenges, a novel IF estimation approach incorporating signal quality enhancement is developed. First, the complementary multi-source vibration signal is processed by the proposed segmented cepstrum lifting method to overcome the submersion of the resonant frequency band on the target component. Then, processed segmented signals are fused using coherent averaging technology to enhance the amplitude of the target component. Finally, leveraging the first-order approximation capability of the short-time fractional Fourier transform (STFrFT) for nonlinear frequency modulation modes, precise IF estimation is achieved. Verified by field data, the proposed method outperforms mainstream methods in both accuracy and applicability, highlighting its industrial application prospects. © 2025 IEEE.

关键词： Frequency estimation

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Electrochemical extraction of strontium from molten salts using reactive zincand aluminum electrodes

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International Journal of Minerals,Metallurgy and Materials 2025年第4期32卷 892-901页

作者： Yongcheng Zhang Taiqi Yin Lei Zhang Xiaochen Zhang Tao Bo Xiaoli Tan Mei Li Wei Han Zhejiang Key Laboratory of Data-Driven High-Safety Energy Materials and Applications Ningbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo 315201China College of Materials Science and Chemical Engineering Harbin Engineering UniversityHarbin 150001China MOE Key Laboratory of Resources and Environmental System Optimization College of Environmental Science and EngineeringNorth China Electric Power UniversityBeijing 102206China Qianwan Institute of CNITECH Ningbo 315336China

Herein, the electrochemical behaviors of Sr on inert W electrode and reactive Zn/Al electrodes were systematically investig-ated in LiCl–KCl–SrCl2molten salts at 773 K using various electrochemical methods. The chemical reaction potentials of Li and Sr on re-active Zn/Al electrodes were determined. We observed that Sr could be extracted by decreasing the activity of the deposited metal Sr onthe reactive electrode, although the standard reduction potential of Sr(II)/Sr was more negative than that of Li(I)/Li. The electrochemicalextraction products of Sr on reactive Zn and Al electrodes were Zn13Sr and Al4Sr, respectively, with no codeposition of Li *** on the density functional theory calculations, both Zn13Sr and Al4Sr were identified as stable intermetallic compounds with Zn-/Al-rich phases. In LiCl–KCl molten salt containing 3wt% SrCl2, the coulombic efficiency of Sr in the Zn electrode was ~54%. The depolar-ization values for Sr on Zn and Al electrodes were 0.864 and 0.485 V, respectively, exhibiting a stronger chemical interaction between Znand Sr than between Al and Sr. This study suggests that using reactive electrodes can facilitate extraction of Sr accumulated while elec-trorefining molten salts, thereby enabling the purification and reuse of the salt and decreasing the volume of the nuclear waste.

关键词： strontium reductive extraction molten salt depolarization effect reactive electrode

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An Enhancing Stability Control Strategy of VSG-Based power Source Under PWM Rectifier Load

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IEEE Transactions on Consumer Electronics 2025年

作者： Li, Gaoxiang Liu, Bowen Song, Wenhao Jining, Chen Liu, Xiao Guangxi University Guangxi Key Laboratory of Power System Optimization and Energy Technology School of Electrical Engineering Nanning530004 China Guangxi Zhuang Autonomous Region Information Center Guangxi Key Laboratory of Digital Infrastructure Nanning530200 China Guangxi University Guangxi Key Laboratory of Multimedia Communications and Network Technology Guangxi Colleges and Universities Key Laboratory of Multimedia Communications and Information Processing School of Computer Electronics and Information Nanning530004 China

Under PWM rectifier load, the power source based on virtual synchronous generator (VSG) is prone to cause mid-frequency oscillation. Firstly, the system oscillation mechanism and characteristic of the VSG-based power source are analyzed based on impedance method. Due to the negative resistance and capacitive characteristic in the middle frequency range, the PWM rectifier load is prone to interact with the VSG-based power source, which can lead to impedance resonance. Secondly, to improve the stability of the VSG-based power source under the PWM rectifier load, a voltage differentiation feedforward control is proposed. In addition, since the mid-frequency impedance magnitude decrease obviously, the improved VSG-based power source is closer to the ideal voltage source, which can automatically suppress the middle harmonics induced by uncontrollable rectifier load. Finally, the proposed control and the corresponding theoretical analysis are verified by simulations and experiments. © 1975-2011 IEEE.

关键词： Synchronous generators

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An active power control of DFIG-based wind turbine generators for frequency regulation with expected dynamic performance

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Applied energy 2025年 391卷

作者： Zhao, Teyang Liu, Hui Wang, Ni Su, Jinshuo Luo, Zhiqiang Ma, Siyu School of Electrical Engineering Guangxi University Nanning530004 China Guangxi Key Laboratory of Power System Optimization and Energy Technology Guangxi University Nanning530004 China The State Key Laboratory of Internet of Things for Smart City and Department of Electrical and Computer Engineering University of Macau 519000 China

The escalating wind power penetration presents a substantial challenge in ensuring the system frequency stability. Although wind turbine generators (WTGs) can offer rapid frequency support by the presetting power trajectory response (PPTR), it will result in a secondary frequency dip (SFD) while facing the demand of restoring rotor speed after frequency regulation. Moreover, the frequency overshoot will occur due to the fixed power increment provided by PPTR under minor disturbances. In this paper, an active power control strategy of DFIG-based WTGs is proposed for eliminating frequency overshoot and mitigating SFD while providing power support for the system frequency. A rotor-speed-based power increment and power attenuation trajectory are designed to enhance the primary frequency nadir while ensuring the operation stability of WTGs. After that, SFD will be mitigated by the proposed parabolic-formed compensation power. Moreover, a power increment control mode is proposed to eliminate the frequency overshoot by a membership-function-based global controller, which can smoothly switch the combined inertial response and the improved PPTR to provide a flexible power increment. Finally, the validity of the proposed strategy in improving frequency nadir, eliminating frequency overshoot, and mitigating SFD are verified by simulations under different wind power penetration levels, disturbances, and wind conditions. © 2025

关键词： Frequency stability

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A Harmonic Current Self-Compensation Control Strategy of DC Active power Filter

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IEEE Journal of Emerging and Selected Topics in power Electronics 2025年

作者： Li, Gaoxiang Wu, Huanchao Chen, Jining Liu, Xiao Guangxi University Guangxi Key Laboratory of Power System Optimization and Energy Technology School of Electrical En-gineering Nanning530004 China Guangxi Zhuang Autonomous Region Information Center Guangxi Key Laboratory of Digital Infrastructure Nanning530200 China Guangxi Key Laboratory of Multimedia Communications and Network Technology Guangxi Colleges and Universities Key Laboratory of Multimedia Communications and Information Processing School of Computer Electronics and Information Guangxi Uni-versity Nanning530004 China

Due to the diversity of nonlinear loads, the harmonic frequency of the DC microgrid is unpredictable, which poses a challenge to traditional DC active power filters (DC-APF). Firstly, the harmonic compensation mechanism and characteristics of the DC-APF with classical control strategy are analyzed. For the classical DC-APF, the voltage control and harmonic extraction are independent of each other, which may lead to their conflict and reduce the harmonic compensation performance. To address this issue, a harmonic current self-compensation control strategy of DC-APF is proposed, which uses a first-order inertia controller in the voltage loop and can simultaneously achieve voltage control and harmonic extraction. Then, the mechanism, characteristics, and parametric design method of the proposed harmonic current self-compensation control are introduced in detail. Compared with the classical DC-APF, the proposed DC-APF does not require any harmonic extraction filter and has better harmonic current compensation performance. Finally, the proposed control strategy and theoretical analysis are verified by simulation and experiment. © 2025 IEEE. All rights reserved.

关键词： Active filters

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Molecular Dynamics Study of the Viscosity Characteristics of Soybean Oil-Based Natural Ester Insulating Oil

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IEEE Transactions on Dielectrics and Electrical Insulation 2025年

作者： Zheng, Hanbo Lan, Hongce Wang, Ke Cai, Shengwei Yang, Tao Li, Yi Wang, Yang Guangxi University Guangxi Key Laboratory of Power System Optimization and Energy Technology Nanning53004 China China Electric Power Research Institute Beijing100192 China State Grid Corporation of China State Grid Henan Electric Power Research Institute Zhengzhou450000 China

Many studies have shown that natural ester insulating oil is an excellent transformer oil with a superior flash point, fire resistance, and renewability compared to mineral insulating oil. However, due to their molecular properties, the high viscosity of natural ester insulating oils results in poor heat transfer, limiting their safe application in transformers. In this paper, the viscosity values of the soybean oil-based natural ester insulating oil are measured experimentally in the temperature range of 293 K to 433 K. The micro-mechanisms affecting the viscosity of natural ester insulating oil are investigated in conjunction with molecular dynamics simulations. We also conducted a correlation analysis between specific heat and viscosity and the simulation results. In addition, the kinematic viscosity of natural ester insulating oils as a function of temperature is also obtained in this paper by the free volume theory. The temperature ranges from 293 K to 433 K, and the functional model closely agrees with the experimental measurements. The research in this paper can be informative for the study and prediction of the viscosity of natural ester insulating oils as well as for the study of thermal conductivity. © 2025 IEEE.

关键词： Fatty acid methyl ester

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