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    Fault Detection in Power Distribution Systems Based on Gated Recurrent Attention Network
    CHEN Haolan, JIN Bingying, LIU Yadong, QIAN Qinglin, WANG Peng, CHEN Yanxia, YU Xijuan, YAN Yingjie
    Journal of Shanghai Jiao Tong University    2024, 58 (3): 295-303.   DOI: 10.16183/j.cnki.jsjtu.2022.091
    Abstract346)   HTML13)    PDF(pc) (2938KB)(3016)       Save

    To improve fault identification accuracy in power distribution systems, a model named gated recurrent attention network is proposed. First, a higher weight is put on the key cycles of fault phase based on the attention mechanism, making the model focus more on these key messages by weight assignment. Then, the gated recurrent network is adopted, which controls the memory transmission with gate signal and constructs the relationship between input waveform and probability of events at different stages to process the waveform sequence, thereby improving recognition accuracy. Experiments based on both simulation and field data show that the proposed method, under the small-sample-learning condition, is much better than other commonly-used classification models, such as support vector machine, gradient boosting decision tree, and convolutional neural network, providing new insights into fault identification technology in power distribution systems.

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    Joint Policy Optimization of Quality Control, Condition-Based Maintenance and Spare Ordering for a Degradation System
    HAN Mengying, MA Shugang, YANG Jianhua, LI Wei, MA Zhichao
    Journal of Shanghai Jiao Tong University    2024, 58 (3): 361-370.   DOI: 10.16183/j.cnki.jsjtu.2022.356
    Abstract234)   HTML9)    PDF(pc) (5697KB)(2898)       Save

    A joint policy of quality control, condition-based maintenance and spare ordering is proposed for a degradation system subject to the delay time concept. First, considering the fact that product quality is largely dependent on system state, a two-stage inspection policy is proposed, in which the system state is detected during the initial deterioration process, but the product quality is checked after the defective state is found by an inspection. Then, based on the condition inspection information, quality information and failure information, the corresponding maintenance activity is chosen. Combining the state of the spare part when the system replacement is required, all possible events during an inspection interval are discussed and then a mathematical model of average cost rate is established. Afterwards, a simulation-based optimization approach coupling discrete event simulation and response surface methodology is devised to obtain a near optimal joint policy. Finally, a numerical example is provided to demonstrate the effectiveness and applicability of the proposed policy by comparing it with the comparative policy.

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    Modeling of Multi-Modal Knowledge Graph for Assembly Process of Wind Turbines with Multi-Source Heterogeneous Data
    HU Zhiqiang, LIU Mingfei, LI Qi, LI Xinyu, BAO Jinsong
    Journal of Shanghai Jiao Tong University    2024, 58 (8): 1249-1263.   DOI: 10.16183/j.cnki.jsjtu.2023.062
    Abstract533)   HTML19)    PDF(pc) (11842KB)(1526)       Save

    The assembly process information of wind turbines is usually scattered in process documents consisting of multi-modal information, such as 3D models, natural texts, and images. Therefore, the cost of maintaining data and extracting process knowledge is high while the efficiency is low. To solve this problem, a multi-modal knowledge graph-based modeling method for the assembly process knowledge of wind turbines is proposed with multi-source heterogeneous data. First, the concepts in multi-modal process knowledge graph of wind turbine (MPKG-WT) are defined by analyzing the process characteristics of wind turbines to complete the construction of ontology. Then, based on the characteristics of multi-source heterogeneous data and multi-modal information, data analysis, knowledge extraction, and semantic similarity calculation are leveraged to realize the automatic instantiation of the graph. Finally, taking the process data of a wind turbine enterprise as an example, MPKG-WT is constructed and verified by implementing an auxiliary system for process design. The results show that MPKG-WT is more informative than the single-modal graph, and the data in different modals can complement each other, which leads to significant improvements in the efficiency of process design.

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    Dynamic Equivalence Modeling of Short-Circuit Faults in Wind Farms Considering Wake Effects
    YU Hao, LI Canbing, YE Zhiliang, PENG Sui, REN Wanxin, CHEN Sijie, TANG Binwei, CHEN Dawei
    Journal of Shanghai Jiao Tong University    2024, 58 (6): 798-805.   DOI: 10.16183/j.cnki.jsjtu.2022.476
    Abstract1254)   HTML11)    PDF(pc) (2071KB)(1473)       Save

    Fast and accurate analysis of the short-circuit characteristics of large wind farms has important engineering application value, and the short-circuit characteristics of wind farms under the influence of the wake effect vary greatly. Therefore, it is necessary to establish a wind farm short-circuit fault time equivalence model. A wind farm short-circuit fault dynamic equivalence method considering the effect of wake effect is proposed. First, the wake effect factor is defined to reflect the degree of the unit affected by the wake effect. Then, the wake effect factor is used as the grouping basis to reduce the variability of operating state of the units within the group under the influence of the wake effect. A positive- negative- zero-sequence network equivalence method is analyzed to improve the effectiveness of the equivalence model in asymmetric short-circuit faults. An equivalence method suitable for zero-sequence network is proposed and a platform is built for verification. The simulation results show that the dynamic short-circuit fault equivalence model proposed can accurately reflect the active and reactive short-circuit output characteristics of wind farms under the influence of the wake effect.

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    Cited: CSCD(1)
    An Identification Method for DC-Link Capacitor Capacitance of Grid Connected Inverter
    ZHU Chenghao, WANG Han, SUN Guoqi, WEI Xiaobin, WANG Fuwen, CAI Xu
    Journal of Shanghai Jiao Tong University    2022, 56 (6): 693-700.   DOI: 10.16183/j.cnki.jsjtu.2021.515
    Abstract1240)   HTML1284)    PDF(pc) (5050KB)(1401)       Save

    DC-link for the capacitor is one of the most vulnerable components of the grid connected converter, whose capacitance identification will help to improve the system reliability by finding and replacing the aging capacitor in time. An identification method for the DC-link capacitor capacitance of the grid connected inverter based on pre-charging circuit is proposed. By analyzing the relationship between the capacitance and the charging current, charging voltage during pre-charging process, and combining the historical operating data, the set of capacitance state feature vector is built. The support vector regression (SVR) model is trained and the regression prediction relationship between the state value and the capacitance is set. The model is optimized by using the particle swarm optimization (PSO) algorithm, which can be used for capacitance identification of the DC-link capacitor. Simulation and experiments results show that the proposed method can implement the accurate capacitance identification of the DC-link capacitor of the grid connected inverter, with an identification error of less than 0.95%. This method does not need to add hardware circuit and change the control algorithm, and has a certain practical value.

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    Cited: CSCD(1)
    Challenges of Distributed Green Energy Carbon Trading Mechanism and Carbon Data Management
    LI Xingzhi, HAN Bei, LI Guojie, WANG Keyou, XU Jin
    Journal of Shanghai Jiao Tong University    2022, 56 (8): 977-993.   DOI: 10.16183/j.cnki.jsjtu.2021.450
    Abstract1291)   HTML900)    PDF(pc) (2604KB)(1377)       Save

    To achieve the double carbon goal of “carbon peaking and carbon neutrality”, the construction of the power system which is based on the green energy needs to be accelerated. With the growth of the system scale, the distributed green energy carbon trading mechanism and the carbon data management technology based on the blockchain technology can effectively encourage the development of green energy and become effective means for the implementation of low-carbon electricity. The accurate and real-time carbon emission calculation will further provide data support for the accuracy and security of carbon trading information. First, the current research status of green certificate trading and carbon asset management is introduced. Next, the adaptability analysis of the key technologies of the blockchain technology in the four directions of green electricity traceability, green certificate trading, carbon trading, and joint market of green certificate and carbon assets is performed. Afterwords, the specific mathematical models of carbon emission calculation is studied, and the data availability of carbon source traceability methods applicable to the blockchain architecture are discussed. Finally, some suggestions for the future development of carbon emission flow analysis are proposed.

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    Cited: CSCD(8)
    Online Steady-State Scheduling of New Power Systems Based on Hierarchical Reinforcement Learning
    ZHAO Yingying, QIU Yue, ZHU Tianchen, LI Fan, SU Yun, TAI Zhenying, SUN Qingyun, FAN Hang
    Journal of Shanghai Jiao Tong University    2025, 59 (3): 400-412.   DOI: 10.16183/j.cnki.jsjtu.2023.344
    Abstract1265)   HTML1)    PDF(pc) (4192KB)(1349)       Save

    With the construction of new power systems, the stochasticity of high-proportion renewable energy significantly increases the uncertainty in the operation of the power grid, posing severe challenges to its safe, stable, and economically efficient operation. Data-driven artificial intelligence methods, such as deep reinforcement learning, are becoming increasingly important for regulating and assisting decision-making in the power grid in the new power system. However, current online scheduling algorithms based on deep reinforcement learning still face challenges in modeling the high-dimensional decision space and optimizing scheduling strategies, resulting in low model search efficiency and slow convergence. Therefore, a novel online steady-state scheduling method is proposed for the new power system based on hierarchical reinforcement learning, which reduces the decision space by adaptively selecting key nodes for adjustment. In addition, a state context-aware module based on gated recurrent units is introduced to model the high-dimensional environmental state, and a model with the optimization objectives of comprehensive operating costs, energy consumption, and over-limit conditions is constructed considering various operational constraints. The effectiveness of the proposed algorithm is thoroughly validated through experiments on three standard test cases, including IEEE-118, L2RPN-WCCI-2022, and SG-126.

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    Depth Distribution Characteristics of Particle Velocity Field Intensity in Shallow Sea
    ZHANG Haigang, XIE Jinhuai, LIU Jiaqi, GONG Lijia, LI Zhi
    Journal of Shanghai Jiao Tong University    2024, 58 (7): 995-1005.   DOI: 10.16183/j.cnki.jsjtu.2023.073
    Abstract1571)   HTML9)    PDF(pc) (6512KB)(1308)       Save

    The depth distribution characteristics of particle velocity field intensity have had a significant impact on underwater acoustic detection and estimation. In this paper, based on the approximate conditions of the incoherent normal modes sum transformation to angular integration, the angular integration form of incoherent normal modes of particle velocity was derived, which avoided the complex calculations of eigenvalues and eigenfunctions while revealing the physical mechanism behind the significant variations in particle velocity intensity with source depth and symmetrical depth. The numerical results demonstrate that the analytical expression of the angular integration of incoherent particle velocity can facilitate fast computation and effectively characterize the depth distribution characteristics of particle velocity intensity. Additionally, due to the superposition effect of the amplitude function of normal modes, there are notable differences in the depth distribution of vertical and horizontal particle velocity. Subsequently, focusing on the intensity difference of particle velocity, the study analyzed the effects of parameters such as horizontal distance, source frequency, sound speed profile, and water depth on the depth distribution characteristics of particle velocity field intensity. The findings provide a theoretical basis for passive target depth estimation based on vector fields.

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    Multi-Objective Optimization Strategy of Trajectory Planning for Unmanned Aerial Vehicles Considering Constraints of Safe Flight Corridors
    HUANG Yuhao, HAN Chao, ZHAO Minghui, DU Qiankun, WANG Shigang
    Journal of Shanghai Jiao Tong University    2022, 56 (8): 1024-1033.   DOI: 10.16183/j.cnki.jsjtu.2021.154
    Abstract1168)   HTML44)    PDF(pc) (5684KB)(1291)       Save

    Aimed at the problem of generating a smooth, safe, and dynamically feasible continuous-time trajectory for unmanned aerial vehicles (UAV) in complex environments, a trajectory planning algorithm is proposed to minimize a multi-objective function based on safe flight corridors. The safe flight corridor represented by a collection of convex polyhedra is built based on the initial discrete waypoints generated by the improved rapidly-exploring random tree(RRT), namely the RRT* algorithm. The safety objective function is established according to the constraints of limiting the trajectory inside safe flight corridors. In combination with the flight smoothness, dynamic characteristics, and time performance, a multi-objective function is built. The gradient-based convex optimization algorithm is used to derive the continuous-time trajectory expressed as a piece-wise polynomial by optimizing the position, velocity, acceleration of waypoints, and time allocation. The effectiveness and performance of the proposed algorithm is tested and compared under complex environments such as the coal mine. The test results demonstrate that the proposed algorithm has a better comprehensive performance in comparison with existing algorithms.

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    Cited: CSCD(2)
    Low Carbon Economy Optimization of Integrated Energy System Considering Electric Vehicle Charging Mode and Multi-Energy Coupling
    ZHANG Cheng, KUANG Yu, CHEN Wenxing, ZHENG Yang
    Journal of Shanghai Jiao Tong University    2024, 58 (5): 669-681.   DOI: 10.16183/j.cnki.jsjtu.2022.364
    Abstract1433)   HTML14)    PDF(pc) (4514KB)(1195)       Save

    In order to enable a multi-energy coupling integrated energy system (IES) to meet the needs of load diversity in low-carbon economic operation, a bi-level optimal configuration method for low-carbon economic operation of multi-energy coupling IES in different charging modes of electric vehicles (EVs) is proposed. First, an IES including cold-thermal-electric-gas coupling is established. Then, in the day-to-day operation stage, factors such as hierarchical carbon trading mechanism and different charging modes of EVs are considered to achieve the lowest daily scheduling cost. In the configuration planning stage, based on the daily operation cost, the equipment capacity is configured with the lowest equipment investment cost and annual operation cost. Finally, Cplex is used to solve the above two-stage objective functions and obtain the optimal configuration scheme and scheduling results through mutual iteration. The results show that the charging method considering the remaining charge of EVs and carbon trading mechanism can significantly reduce carbon emissions and operating costs of the system. The proposed configuration approach can well realize low-carbon economic operation of the multi-energy coupling IES.

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    Numerical Study of Combustion Characteristics of Methane/Hydrogen Hybrid Fuel of Lean Premixed Swirl
    WANG Xinci, LIU Aiguo, WU Xiaoqu, ZHANG Yunjie
    Journal of Shanghai Jiao Tong University    2024, 58 (8): 1179-1187.   DOI: 10.16183/j.cnki.jsjtu.2022.502
    Abstract241)   HTML14)    PDF(pc) (22873KB)(1175)       Save

    The numerical simulation method is used to study the influence of the mixing ratio of methane/hydrogen mixture on the combustion characteristics and pollutant emission characteristics of the combustor. The results show that due to the action of combustion chemical reaction, there exists a certain difference in the structure of cold and hot flow fields. The flow velocity of the hot flow field increases, and the recirculation zone becomes larger. The hydrogen content has a significant impact on the structure and temperature distribution characteristics of the hot flow field, and a central recirculation zone is formed when the hydrogen content is less than 20%, which can maintain stable combustion. When the hydrogen content is greater than 40%, the central recirculation zone disappears, the external recirculation zone is extended, and the spontaneous combustion and flashback occur to varying degrees. As the inlet air temperature increases, the spontaneous ignition phenomenon becomes more obvious, and the inlet air temperature decreases, the flashback phenomenon becomes more obvious. NOx emissions increase with the increase of hydrogen content, CO emissions decrease with the increase of hydrogen content, and CO is concentrated in the combustion zone of the main combustion stage.

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    Intelligent Global Sensitivity Analysis Based on Deep Learning
    WU Shuchen, QI Zongfeng, LI Jianxun
    Journal of Shanghai Jiao Tong University    2022, 56 (7): 840-849.   DOI: 10.16183/j.cnki.jsjtu.2021.191
    Abstract1287)   HTML52)    PDF(pc) (1418KB)(1111)       Save

    This paper proposes an end-to-end method that combines deep learning and sensitivity analysis, which can perform gradient back propagation calculation sensitivity on the saved weight information while training the model. The structure and activation function of the depth model are specially designed to adapt to the subsequent sensitivity calculation. The experimental results conducted on a Boston house prices dataset, a track information fusion dataset, and the G function show that the proposed method is more accurate than classical methods such as Sobol’ method when the parameter distribution is uneven, and has a stronger robustness. Compared with the traditional neural network method, the accuracy of the proposed method is higher. The experiment proves that the sample parameter sensitivity obtained by the deep learning model can be used to optimize the model output.

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    Cited: CSCD(1)
    Reconstruction of Ship Propeller Wake Field Based on Physics-Informed Neural Networks
    HOU Xianrui, ZHOU Xingyu, HUANG Xiaocheng
    Journal of Shanghai Jiao Tong University    2024, 58 (11): 1654-1664.   DOI: 10.16183/j.cnki.jsjtu.2023.101
    Abstract576)   HTML15)    PDF(pc) (18611KB)(1089)       Save

    Physics-informed neural networks (PINN) are applied to the reconstruction of the ship propeller wake field. First, the principle and basic framework of PINN were introduced. Then, the Burgers equation was selected to verify the feasibility of PINN in solving partial differential equations. After that, the propeller of KVLCC2 in open water is simulated using computational fluid dynamics (CFD) software STAR CCM+, and the flow field information of the KVLCC2 propeller is obtained. Based on the simulated flow field information data, the training sample set was constructed to train PINN. The trained PINN was used to infer the approximate solution of the governing equation at any time and space. Finally, the velocity and pressure distribution obtained by PINN were compared with the velocity and pressure distribution simulated by STAR CCM+. The results validate the reliability of PINN in propeller wake field reconstruction, which can be concluded that PINN can be applied to the reconstruction of the ship propeller wake field.

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    Circulation Control of Airfoil Aerodynamic Force Under Ground Effect of Wavy Wall
    LIU Hao, SUN Jianhong, SUN Zhi, TAO Yang, WANG Dechen, LIU Guangyuan
    Journal of Shanghai Jiao Tong University    2022, 56 (8): 1101-1110.   DOI: 10.16183/j.cnki.jsjtu.2021.384
    Abstract809)   HTML40)    PDF(pc) (3280KB)(1061)       Save

    The interaction of airflow and sea waves seriously affects the flight stability and cruising safety of ground effect vehicles. The influence of different sea states and different angles of attack were analyzed numerically on the aerodynamic characteristics of the airfoil under ground effect of wavy wall. The influence of the constant blowing and periodic blowing methods was further studied on the aerodynamic force of the airfoil under ground effect. The simulation results show that the lift coefficient of the airfoil changes periodically with the wave under the wavy ground wall. The amplitude of the lift coefficient fluctuation is larger with the increasing of wave height and angle of attack, or the decreasing of wavelength. Applying the circulation control method for periodic blowing in the same period as the relative motion of the waves can effectively weaken the fluctuation of the airfoil lift coefficient under wavy sea conditions and improve the flight stability and safety of ground effect vehicles.

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    Cited: CSCD(3)
    A Wind-Solar-Electric Vehicles Coordination Scheduling Method for High Proportion New Energy Grid-Connected Scenarios
    LI Linyan, HAN Shuang, QIAO Yanhui, LI Li, LIU Yongqian, YAN Jie, LIU Haidong
    Journal of Shanghai Jiao Tong University    2022, 56 (5): 554-563.   DOI: 10.16183/j.cnki.jsjtu.2022.040
    Abstract1082)   HTML400)    PDF(pc) (1648KB)(1043)       Save

    Wind-solar-electric vehicles coordinated optimization scheduling can effectively reduce the adverse effects of multiple uncertainties of wind-solar output and disorderly charging of electric vehicles on the power system. Most of the existing optimization scheduling models take the minimum equivalent load fluctuation as the optimization objective, which, only considering the overall fluctuation of equivalent load, cannot measure the matching degree of output-load, and do not consider the difference of output in different output scenarios. Therefore, a wind-solar-electric vehicles coordination scheduling method for high proportion new energy grid-connected scenarios is proposed. First, the disordered charging model of electric vehicles by Monte Carlo simulation is constructed. Then, a wind-solar output typical day classification model using Gap statistical and K-means++ is constructed based on the forecasting data of wind and solar power. Finally, taking the minimum equivalent load variance and load tracking coefficient as the double optimization objectives, a wind-solar-electric vehicles coordination optimization scheduling model is established, and the NSGA-II algorithm is used to solve it. The results demonstrate that the proposed model can effectively improve the matching degree of wind-solar output and load, and reduce the fluctuation of equivalent load, so as to reduce the adverse effects of multiple uncertainties of wind-solar output and disorderly charging of electric vehicles on the power system.

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    Cited: CSCD(9)
    Mechanism of Forced Subsynchronous Oscillation of Large-Scale Photovoltaic Power Generation Grid-Connected System with Series Compensation Tranmmission Lines
    LIN Yong, KANG Jiale, YU Hao, CHEN Honglin, YANG Yanji, CHEN Wuhui
    Journal of Shanghai Jiao Tong University    2022, 56 (9): 1118-1127.   DOI: 10.16183/j.cnki.jsjtu.2021.415
    Abstract889)   HTML135)    PDF(pc) (1463KB)(1003)       Save

    There exists the subsynchronous oscillation (SSO) instability risk in large-scale photovoltaic(PV) grid-connected systems with series compensation, which is generally explained by the negative damped oscillation theory. In this paper, the inter-photovoltaic harmonics due to maximum power point tracking (MPPT) control are used as the disturbance source and the large-scale PV grid-connected system with series compensation as the forced system. The forced oscillation theory is used to reveal the SSO mechanism of PV power generation based on the interaction between the perturbed MPPT and the series compensation grid-connected system, and verified in the PSCAD/EMTDC simulation platform. The results show that the perturbed MPPT-based PV inverter outputs interharmonic currents to the system due to the modulation coupling on the AC-DC side, which may lead to serious forced SSO problems when the interharmonic frequency is close to the frequency of inherent weakly damped mode of the system, causing a shock to the system stability. The simulation results verify the correctness of the proposed theory.

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    Cited: CSCD(6)
    Ultra-Short-Term Load Forecasting of Electric Vehicle Charging Stations Based on Ensemble Learning
    LI Hengjie, ZHU Jianghao, FU Xiaofei, FANG Chen, LIANG Daming, ZHOU Yun
    Journal of Shanghai Jiao Tong University    2022, 56 (8): 1004-1013.   DOI: 10.16183/j.cnki.jsjtu.2021.486
    Abstract1405)   HTML399)    PDF(pc) (3182KB)(978)       Save

    Accurate electric vehicle load forecasting is the basis for maintaining the safe and economical operation of charging stations, and for supporting the planning and decision-making of new and expanded charging infrastructure. In order to improve the accuracy of the ultra-short-term load forecasting of charging stations, an ultra-short-term load forecasting method based on ensemble learning is proposed. First, aimed at the prediction accuracy and the response speed, the light gradient boosting machine (LightGBM) framework is utilized to build several basic regressors. Next, the basic regressors are integrated by using the adaptive boosting (Adaboost) method. Finally, by using hyperparameter adjustment and optimization, a dual-system for ultra-short-term load forecasting of charging stations named energy ensemble boosting-light gradient boosting machine (EEB-LGBM) is generated. The analysis of the numerical examples shows that the proposed model has a higher accuracy than the back propagation neural network (BPNN), convolutional neural networks-long short term memory (CNN-LSTM), autoregressive integrated moving average (ARIMA), and other load forecasting methods, which can greatly reduce the training time and the computing power requirements of the training platform.

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    Cited: CSCD(6)
    Real-Time Calculation of Carbon Emissions in County-Level Administrative Regions Based on ‘Energy Brain’
    CHEN Yun, SHEN Hao, WANG Jiayu, ZHAO Wenkai, PAN Zhijun, WANG Xiaohui, XIAO Yinjing
    Journal of Shanghai Jiao Tong University    2022, 56 (9): 1111-1117.   DOI: 10.16183/j.cnki.jsjtu.2021.364
    Abstract1229)   HTML785)    PDF(pc) (851KB)(972)       Save

    Existing calculation methods of carbon emission cannot well meet the needs of gradual refinement and real-time of carbon emission regions. In order to ensure the real-time and accuracy of carbon emissions responsibility allocation, a real-time calculation method of carbon emissions in urban regions is proposed. The improved K-means clustering algorithm is used to cluster and combine the operating periods and operating scenarios of the urban area energy load,so as to obtain the typical carbon emission characteristics. The regional unit electricity carbon emission is proposed as a carbon emission indicator, the operating period and scenario are classified, and the unit electricity carbon emission and the total carbon emission of urban regions for each cluster are calculated. The proposed algorithm is verified based on part of the historical data of energy consumption in the energy brain of a certain region in eastern China. The results show that the clustering method and carbon emission indicators can effectively calculate the total carbon emission of urban regions in real-time.

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    A Novel Prediction Model for Fatigue Strength
    DUAN Hongyan, TANG Guoxin, SHENG Jie, CAO Mengjie, PEI Lei, TIAN Hongwei
    Journal of Shanghai Jiao Tong University    2022, 56 (6): 801-808.   DOI: 10.16183/j.cnki.jsjtu.2021.051
    Abstract1313)   HTML127)    PDF(pc) (1208KB)(966)       Save

    Fatigue failure is one of the most important reasons for the failure of engineering application components. However, due to the high cost of fatigue experiments, it is necessary to use mechanical properties to predict fatigue strength. Based on the true stress-strain curves, a novel model for fatigue strength prediction is established and is used to calculate the fatigue strength. The strength predicted is compared with that calculated by the staircase method and the Basquin equation. The results show that the model could obtain the fatigue strength of the materials only by using tensile strength and work-hardening strength, and it is suitable for other steels, which greatly saves costs and increases accuracy.

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    Cited: CSCD(2)
    Numerical Simulation and Flow Pattern Evolution of Gas-Liquid Two-Phase Flow Passing Through a 90° Pipe Bend Based on CFD
    WANG Zhiwei, HE Yanping, LI Mingzhi, QIU Ming, HUANG Chao, LIU Yadong
    Journal of Shanghai Jiao Tong University    2022, 56 (9): 1159-1167.   DOI: 10.16183/j.cnki.jsjtu.2021.185
    Abstract1099)   HTML47)    PDF(pc) (11131KB)(961)       Save

    In order to investigate the evolution characteristics of gas-liquid two-phase flow passing through a 90° pipe bend, the volume of fluid (VOF) multiphase flow model and the Realizable k-ε turbulence model are used to conduct numerical simulations. The evolution of velocity, pressure distribution, gas void fraction, and flow pattern passing through a 90° pipe bend is studied in detail. The results show that different gas-liquid two-phase flow patterns will produce different degrees of secondary flow phenomenon after passing through the 90° pipe bend, and the tangential velocity presents a bimodal distribution, which eventually dissipates into a unimodal distribution in the horizontal pipe. The pressure on the outer wall of the pipe bend increases as the inlet velocity increases. The change of gas void fraction is related to the transformation of the flow pattern, the bubbly flow evolves into a slender slug flow in the horizontal pipe after passing through the 90° pipe bend, and the gas void fraction will decrease. The slug flow, the churn flow, and the annular flow evolve into the stratified-wave flow in the horizontal pipe after passing through the pipe bend, and the variation of the gas void fraction is relatively low. The research results can provide certain theoretical support for the design and development of gas-liquid two-phase flow conveying elbows and the prediction of induced stress.

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    Cited: CSCD(1)
    An Admittance Reshaping Strategy of Three-Phase LCL Grid-Connected Inverter Based on Modified Passive Control
    WANG Han, ZHANG Jianwen, SHI Gang, ZHU Miao, CAI Xu
    Journal of Shanghai Jiao Tong University    2023, 57 (9): 1105-1113.   DOI: 10.16183/j.cnki.jsjtu.2022.120
    Abstract469)   HTML36)    PDF(pc) (3313KB)(944)       Save

    The passivity-based control (PBC) based on energy function has been studied for grid-connected converters to achieve a better performance. However, traditional PBC method relies on the accurate mathematical model of grid-connected inverter. In previous studies on PBC, the effect of digital control delay is rarely considered and the stability under grid impedance uncertainties is not discussed, especially in the capacitive grid or complex weak grid. To address these issues, this paper proposes an improved PBC method to reshape the output admittance for LCL-filtered grid-connected inverters. The system passive region is expanded up to the Nyquist frequency by adding a capacitor current feedback loop which can achieve active damping control of LCL resonant frequency under the wide range of grid impedance changes. The parameter design method is also presented for the proposed PBC control. To verify the correctness of the theoretical analysis, both simulation and experiments are conducted on a 3 kW grid-connected inverter prototype.

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    Cited: CSCD(1)
    A Dual-System Reinforcement Learning Method for Flexible Job Shop Dynamic Scheduling
    LIU Yahui, SHEN Xingwang, GU Xinghai, PENG Tao, BAO Jinsong, ZHANG Dan
    Journal of Shanghai Jiao Tong University    2022, 56 (9): 1262-1275.   DOI: 10.16183/j.cnki.jsjtu.2021.215
    Abstract1209)   HTML75)    PDF(pc) (4009KB)(936)       Save

    In the production process of aerospace structural parts, there coexist batch production tasks and research and development (R&D) tasks. Personalized small-batch R&D and production tasks lead to frequent emergency insertion orders. In order to ensure that the task is completed on schedule and to solve the flexible job shop dynamic scheduling problem, this paper takes minimization of equipment average load and total completion time as optimization goals, and proposes a dual-loop deep Q network (DL-DQN) method driven by a perception-cognition dual system. Based on the knowledge graph, the perception system realizes the representation of workshop knowledge and the generation of multi-dimensional information matrix. The cognitive system abstracts the scheduling process into two stages: resource allocation agent and process sequencing agent, corresponding to two optimization goals respectively. The workshop status matrix is designed to describe the problems and constraints. In scheduling decision, action instructions are introduced step by step. Finally, the reward function is designed to realize the evaluation of resource allocation decision and process sequence decision. Application of the proposed method in the aerospace shell processing of an aerospace institute and comparative analysis of different algorithms verify the superiority of the proposed method.

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    Cited: CSCD(3)
    An LC Inverter Based on Novel Dual-Loop Control
    LI Shuang, SHI Jianqiang
    Journal of Shanghai Jiao Tong University    2022, 56 (9): 1139-1147.   DOI: 10.16183/j.cnki.jsjtu.2021.275
    Abstract1086)   HTML133)    PDF(pc) (1553KB)(932)       Save

    To improve the voltage tracking and anti-disturbance performance of the LC inverter, a novel voltage-current dual-loop control strategy is proposed. First, the voltage loop is tuned to first-order inertia link by zero-pole cancellation based on virtual resistance, which restrains the overshoot during voltage tracking. Next, the hypo-time-optimal current-loop is adopted to enhance the response speed of the current loop, which suppresses the sudden change of transient voltage. Finally, the cause of overshoot during the voltage recovery period is analyzed and the overshoot is eliminated by the adaptive integrator initial value, which modifies the voltage waveform distortion under loading disturbance. Based on the traditional double-loop control, the voltage loop and the current loop are improved respectively by the proposed novel control strategy, which overcomes the shortcomings of step response and anti-load disturbance performance. The feasibility and effectiveness of this method are validated through simulations on MATLAB/Simulink.

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    Inertial Control Strategy for Wind Farm with Distributed Energy Storage System Based on Model Predictive Control
    SHEN Yangwu, SONG Xingrong, LUO Ziren, SHEN Feifan, HUANG Sheng
    Journal of Shanghai Jiao Tong University    2022, 56 (10): 1285-1293.   DOI: 10.16183/j.cnki.jsjtu.2022.134
    Abstract1117)   HTML1101)    PDF(pc) (1641KB)(928)       Save

    Distributed energy storage (DES) wind turbine is an effective means to solve the problem of system frequency stability caused by large-scale wind power connection. In this paper, an inertial control method for DES wind farms based on model predictive control (MPC) is proposed.First, the linearized prediction model of the DES wind farm is established. Then, on this basis, in combination with the control framework of MPC, an optimization model and strategy of MPC inertial control are proposed considering the cost of energy storage loss and the balanced change of wind turbine rotor speed,in order to achieve the balanced change of wind turbine rotor speed during inertia control. The simulation results show that the proposed control strategy can effectively coordinate the active power output of the wind power generation unit and the energy storage system unit in the DES wind turbine, reduce the cost of charging and discharging loss of the energy storage system, and ensure that the rotational speed of all wind turbines in the wind farm tends to be average during the inertial control period, avoiding the problem of wind turbines exiting frequency regulation due to excessive reduction of the rotational speed of wind turbines. The inertial control strategy of the DES wind farm is beneficial to improve the frequency stability of the power grid, which is of great significance to ensure the safe operation of the power grid.

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    Cited: CSCD(4)
    Radar Signal Recognition Based on Dual Channel Convolutional Neural Network
    QUAN Daying, CHEN Yun, TANG Zeyu, LI Shitong, WANG Xiaofeng, JIN Xiaoping
    Journal of Shanghai Jiao Tong University    2022, 56 (7): 877-885.   DOI: 10.16183/j.cnki.jsjtu.2021.209
    Abstract1095)   HTML29)    PDF(pc) (4098KB)(928)       Save

    In order to solve the problems of difficult feature extraction and low recognition rate of radar signal at low signal-to-noise ratios, a dual channel convolutional neural network model based on Choi-Williams distribution (CWD) and multisynchrosqueezing transform (MSST) is proposed, which obtains two-dimensional time-frequency images by CWD and MSST time-frequency analyses on radar signals. Respectively, the time-frequency images are preprocessed and sequencely fed to a dual channel convolutional neural network for deep feature extraction. Finally, the features acquired by the two channels are fused, and the radar signal is classified and recognized through the convolutional neural network classifier. The simulation results show that when the signal-to-noise ratio is -10 dB, the overall recognition accuracy can reach above 96%, which is excellent at low signal-to-noise ratios.

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    Cited: CSCD(2)
    Unmanned Aerial Vehicle Path Planning Algorithm Based on Improved Informed RRT* in Complex Environment
    LIU Wenqian, SHAN Liang, ZHANG Weilong, LIU Chenglin, MA Qiang
    Journal of Shanghai Jiao Tong University    2024, 58 (4): 511-524.   DOI: 10.16183/j.cnki.jsjtu.2022.442
    Abstract1149)   HTML28)    PDF(pc) (11075KB)(917)       Save

    To address the problems of long planning time, redundant planning path, and even planning failure caused by local constraints in narrow spaces in the rapid exploring random trees (RRT) algorithm when unmanned aerial vehicle is planning a path in a complex environment, an improved Informed RRT* algorithm is proposed. First, the artificial potential field (APF) method is used to make the sampling points move to the target point in the way of potential field descending, which improves the purpose and directionality of RRT tree expansion. Considering the complexity of the global environment during tree expansion, an adaptive step size is introduced to accelerate the expansion speed of the RRT tree in an unobstructed environment. Then, relevant constraints are added in the process of random tree expansion to ensure the feasibility of the generated paths. After the first reachable path is found, variable elliptic or ellipsoidal sampling domain is used to limit the selection of sampling points and the expansion range of adaptive step size, so as to accelerate the convergence of the algorithm to the asymptotic optimization. Finally, the original algorithm and the improved algorithm are compared in two-dimensional and three-dimensional complex environment. The simulation results show that the improved algorithm can find a better reachable path with a small number of iterations, lock the elliptic or ellipsoidal sampling domain faster and leave more time for path optimization. The improved algorithm performs better in path planning.

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    Cited: CSCD(2)
    A Transformer-Based Diffusion Model for All-in-One Weather-Degraded Image Restoration
    QIN Jing, WEN Yuanbo, GAO Tao, LIU Yao
    Journal of Shanghai Jiao Tong University    2024, 58 (10): 1606-1617.   DOI: 10.16183/j.cnki.jsjtu.2023.043
    Abstract789)   HTML12)    PDF(pc) (62692KB)(915)       Save

    Image restoration under adverse weather conditions is of great significance for the subsequent advanced computer vision tasks. However, most existing image restoration algorithms only remove single weather degradation, and few studies has been conducted on all-in-one weather-degraded image restoration. The denoising diffusion probability model is combined with Vision Transformer to propose a Transformer-based diffusion model for all-in-one weather-degraded image restoration. First, the weather-degraded image is utilized as the condition to guide the reverse sampling of diffusion model and generate corresponding clean background image. Then, the subspace transposed Transformer for noise estimation (NE-STT) is proposed, which utilizes the degraded image and the noisy state to estimate noise distribution, including the subspace transposed self-attention (STSA) mechanism and a dual grouped gated feed-forward network (DGGFFN). The STSA adopts subspace transformation coefficient to effectively capture global long-range dependencies while significantly reducing computational burden. The DGGFFN employs the dual grouped gated mechanism to enhance the nonlinear characterization ability of feed-forward network. The experimental results show that in comparison with the recently developed algorithms, such as All-in-One and TransWeather, the method proposed obtains a performance gain of 3.68 and 3.08 dB in average peak signal-to-noise ratio while 2.93% and 3.13% in average structural similarity on 5 weather-degraded datasets.

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    Real-Time Detection of Insulator Drop String Based on UAV Aerial Photography
    LI Dengpan, REN Xiaoming, YAN Nannan
    Journal of Shanghai Jiao Tong University    2022, 56 (8): 994-1003.   DOI: 10.16183/j.cnki.jsjtu.2021.416
    Abstract953)   HTML399)    PDF(pc) (28565KB)(897)       Save

    It is of great significance for unmanned aerial vehicle(UAV) to replace manual inspection of power insulators. Aimed at the problem of limited computing power and storage resources of the UAV, an improved real-time target detection algorithm suitable for insulator drop string failure detection is proposed. Based on the YOLOv5s detection network, first, the PANet networks in neck are replaced with bi-directional feature pyramid network(BiFPN) to improve the feature fusion ability. Next, DIoU is used to optimize the loss function to optimize the model. The channel pruning and fine tuning of the γ coefficient generally improve the accuracy, speed, and deployment ability of the detection network. Finally, the image is enhanced at the network output to improve the availability of the algorithm. The proposed algorithm is tested under a specially expanded insulator fault data set. The results show that compared with the original YOLOv5s algorithm, the average accuracy of the proposed algorithm is improved by 3.91%, the detection speed is improved by 25.6%, and the model volume is reduced by 59.1%.

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    Cited: CSCD(2)
    Differentiated Allocation Model of Renewable Energy Green Certificates for New-Type Power System
    ZHANG Shuo, LI Wei, LI Yingzi, LIU Qiang, ZENG Ming
    Journal of Shanghai Jiao Tong University    2022, 56 (12): 1561-1571.   DOI: 10.16183/j.cnki.jsjtu.2022.150
    Abstract1591)   HTML818)    PDF(pc) (1436KB)(891)       Save

    In order to achieve China’s “30·60” decarbonization goal, the green and low-carbon transformation of the energy system is the fundamental support; the construction of new-type power system is the key step, and the green certificate is the important voucher to reflect the green value of renewable energy. Currently, the distribution mechanism of green certificates in China is oversimplified, which neither effectively measures the variability of green values generated by different types of renewable energy, nor balances the coordinated development of renewable energy. Therefore, to differentiate the exchange mechanism of green certificates by different types of renewable energy power in this paper, an evaluation index system is established, which describes the difference between green certificates, considering the comprehensive value of renewable energy, and an evaluation model is built with the criteria importance by using the intercriteria correlation (CRITIC) method, the entropy weight method, and the technique for order preference by similarity to an ideal solution (TOPSIS) method. Under the development scenario of peaking carbon emissions before 2030, the impact of the differentiated distribution model on the green incomes of centralized photovoltaic distributed photovoltaic power, onshore wind power, and offshore wind power is analyzed. Moreover, the development plan of renewable energy is modified in consideration of the effect of the differentiated distribution model, and policy suggestions on green certificates are proposed accordingly. The results show that the differentiated distribution model of green certificates is practical to provide corresponding decision-making support to the construction and improvement of green certificates trading mechanism in China.

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    Cited: CSCD(5)
    Voltage and Frequency Suppression of Intentional Islanding Restoration Process for Distribution System with Multi-Generations
    CHEN Chun, GAO Jing, CAO Yijia, WANG Weiyu, ZHAO Long
    Journal of Shanghai Jiao Tong University    2022, 56 (5): 543-553.   DOI: 10.16183/j.cnki.jsjtu.2021.418
    Abstract994)   HTML1032)    PDF(pc) (4975KB)(872)       Save

    Intentional islanding restoration of distribution systems with multi-generations is of great importance to ensure the power supply of critical loads under extreme conditions, which is beneficial to improve the reliability of distribution systems. There are transient voltage and frequency fluctuations in the process of intentional islanding restoration, when the loads and distributed generations are gradually connected to the grid. The safety and stability of the intentional islanding are affected by the fluctuations, and networking process may fail in serious cases. Hence, the rapid power response of the energy storage system is utilized to suppress voltage and frequency fluctuations. A fluctuation suppression model based on energy storage system control is established, where a voltage and current double-loop feed-forward disturbance compensation control system is designed. A vector control method for energy storage system with improved dual-loop control is proposed, which solves the problems of traditional V/f control voltage offset and excessive voltage fluctuation. MATLAB/Simulink is used to build simulation models in different control modes in accordance with the black-start principle. The simulation results show that the improved double-loop control based on the vector method has a stronger anti-interference ability and significantly improved the islanding black-start self-organizing networking process. Voltage and frequency fluctuations are reduced, and the dynamic response performance of the system is improved.

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    Cited: CSCD(4)
    Optimal Planning of Power Systems with Flexible Resources for High Penetrated Renewable Energy Accommodation
    GUO Yongtao, XIANG Yue, LIU Junyong
    Journal of Shanghai Jiao Tong University    2023, 57 (9): 1146-1155.   DOI: 10.16183/j.cnki.jsjtu.2022.269
    Abstract334)   HTML12)    PDF(pc) (2433KB)(869)       Save

    High penetrated renewable energy has brought great challenges to the flexibility of the power system due to its volatility and intermittency. To improve the capacity of renewable energy accommodation, the flexibility reformation of thermal power units, the construction of gas-fired units, and the electrical energy storage installation are considered as effective solutions. Thus, an optimization model for power system planning scheme considering multi-type flexible resources with their different output characteristics is established. The simulation results on a modified IEEE 24-bus power system and 12-node natural gas system demonstrate the effectiveness of the proposed model. In addition, the applicability of different flexible resource planning schemes is comprehensively evaluated from the perspectives of economy, accommodation capacity, and carbon reduction, so as to meet the different planning goals.

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    Aerodynamic Drag Characteristics of Ultra-Low Orbit Satellites
    WANG Xiaoliang, YAO Xiaosong, GAO Shuang, LIU Guohua
    Journal of Shanghai Jiao Tong University    2022, 56 (8): 1089-1100.   DOI: 10.16183/j.cnki.jsjtu.2021.014
    Abstract910)   HTML27)    PDF(pc) (7210KB)(845)       Save

    Taking the 180~300 km ultra-low orbit satellite as the research object, the aerodynamic drag characteristics of the typical shapes were studied by using the direct simulation Monte Carlo (DSMC) method in the free molecular flow simulation method, which can accurately simulate the three-dimensional complex shapes. By comparing the theoretical drag coefficients of spheres and plates at different velocity rates and the aerodynamic experimental data of 70° bluff body shapes at different velocity rates with the DSMC calculation results, the adaptability of the three-dimensional DSMC method to shape and mesh is verified. The drag characteristics of several typical satellite shapes were calculated and compared, and the pressure difference drag, shear drag, total drag and dimensionless drag coefficients with altitude and shape were obtained. The optimized design of the shape of the ultra-low orbit satellite can reduce the drag by about 10%, which can effectively improve its on-orbit operation characteristics and reduce the design requirements of the own related systems of the satellite.

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    Cited: CSCD(2)
    Review of Single Blade Installation and Docking Technology of Large Offshore Wind Turbine
    XIE Sihong, ZHAO Yongsheng, XU Yiqing, HE Yanping, HAN Zhaolong, XU Yuwang
    Journal of Shanghai Jiao Tong University    2023, 57 (6): 631-641.   DOI: 10.16183/j.cnki.jsjtu.2022.237
    Abstract833)   HTML367)    PDF(pc) (14702KB)(840)       Save

    In recent years, offshore wind turbines show the trend of large-scale development, the installation area of which has been expanding to the deep and far-reaching ocean. However, due to the harsh environmental conditions in the far-reaching ocean region, the traditional rotor-lifting method is facing many limitations. In contrast, the single blade installation technology has significant advantages in installation efficiency and safety, and has gradually become a new research hotspot. Based on the characteristics and difficulties of the offshore single blade installation technology, this paper investigates and summarizes the lifting equipment and key technologies involved in single blade installation section, including blade yokes, the single blade installation dynamic simulation model, and the active control technology. Among them, the research and development of novel single blade installation equipment and methods with active control technology are essential for large-scale offshore wind turbine installation in the far-reaching ocean region. Additionally, based on the development trend and prospect of offshore blade installation and the docking technology, it introduces some technical ideas, including single blade yoke with dynamic positioning function, and double hoop blade vertical installation auxiliary device, which are expected to solve the installation problem of large-scale offshore wind turbines.

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    Cited: CSCD(1)
    Design and Realization of Continuum Manipulator Based on Coupling of Double Parallel Mechanism
    WU Guanlun, SHI Guanglin
    Journal of Shanghai Jiao Tong University    2022, 56 (6): 809-817.   DOI: 10.16183/j.cnki.jsjtu.2021.060
    Abstract1052)   HTML48)    PDF(pc) (14846KB)(838)       Save

    A 5-degree-of-freedom continuum manipulator is designed and implemented to improve the flexible positioning ability of the continuum mechanism in applications such as interactivity operations, light object grabbing, and human-machine collaboration. In the design process, by introducing a two-segment constant curvature model, the distribution of degrees of freedom on the mechanism is explained geometrically by the method of twist. Coupling two stretchable parallel modules in series, a two-segment structure is formed for curving and each segment has two degrees of freedom in bending and one degree of freedom in stretching, thereby giving 5 degrees of freedom to the end-effector. Concentrating on the dynamic performance of the manipulator, an electromechanical system platform is built as a prototype. The experiments show that the structure realizes the control of the end-effector during large deformation of the manipulator, and is able to achieve extreme pose in 2 s with an approximation positioning error of 2% of the nominal arm length.

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    Off-Axis Tensile Test and Numerical Simulation of Unidirectional Thermoplastic Composite Laminates
    ZHANG Jian, CHEN Xiuhua, CHEN Yong, FANG Yin
    Journal of Shanghai Jiao Tong University    2023, 57 (2): 201-212.   DOI: 10.16183/j.cnki.jsjtu.2021.352
    Abstract649)   HTML104)    PDF(pc) (13908KB)(835)       Save

    As a high-performance thermoplastic composite material, AS4/PEEK has been widely used in aerospace, military, automotive, and other fields. After conducting the off-axial tensile test of unidirectional AS4/PEEK laminates with different angles, the relevant stress-strain curves and tensile strengths, as well as fracture plane angles are obtained. In simulation, a 3D elastic-plastic model where the parameters are determined by trust-region reflective algorithm is used to describe the nonlinear mechanical behavior of AS4/PEEK laminates. In combination with the LaRC05 criterion and the crack zone theory, a user material subroutine VUMAT based on Abaqus is developed and applied to the numerical simulation of off-axis tensile test. The numerical results show that the 3D elastic-plastic damage constitutive model can accurately simulate the plastic effect of AS4/PEEK laminates and the tensile strength predicted by the numerical method agrees well with those from the test. The proposed 3D elastic-plastic damage model provides an accurate and effective method for the comprehensive analysis of plastic deformation and damage of thermoplastic composites.

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    “Window Effect” and Protective Measures of Exogenous Pulsed Electromagnetic Field on Implantable Cardiac Pacemaker
    LU Wu, DING Ranran, ZHAO Wenbin, HUANG Dong, WANG Zheming
    Journal of Shanghai Jiao Tong University    2022, 56 (11): 1518-1531.   DOI: 10.16183/j.cnki.jsjtu.2021.326
    Abstract1087)   HTML15)    PDF(pc) (24935KB)(825)       Save

    The electromagnetic interference (EMI) from pulsed electromagnetic field (PEMF) on pacemakers is unignorable in modern power grids and healthcare environments, but there is limited study on the interaction mechanisms and protective measures. In this paper, an in-vitro human chest model for pacemaker implantation is made by using pork tissues immersed in 0.9% sodium chloride solution. The effect of PEMFs generated by the switching actions of common electrical equipment and low-frequency medical equipment on pacemakers is simulated by using fast-front current sources. The pulse forming line theory is employed for analyzing the waveform compression of PEMFs in human thoracic cavity. Further, the parameterized bio-electromagnetic transient model of pacemaker in combination with biological tissues is established in finite element software. The results show that pacemaker malfunctions including pacing inhibition and P pulmonale occur under PEMF. The “Window effect” in subcutaneous pouch under PEMF is found by changing the winding of pacemaker leads in the pouch. Based on the research finding, a protective strategy by using composite materials to shield the window area is proposed. The theoretical feasibility of this protective measure is confirmed by simulation, where the intensity of pacemaker EMI could be reduced by 80 dB when the composite materials shielding is used. Finally, a safe distance is developed for pacemaker wearers in electrical and medical environments.

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    Cryogenic Minimal Quantity Lubrication Assisted Cutting Process for Polyimide Materials
    CAO Zheng, LEI Xuelin, ZHANG Hang, CAI Xiaojiang
    Journal of Shanghai Jiao Tong University    2022, 56 (6): 784-793.   DOI: 10.16183/j.cnki.jsjtu.2021.173
    Abstract986)   HTML22)    PDF(pc) (21845KB)(820)       Save

    The cutting performance of the porous polyimide material assisted by cold air trace lubrication was investigated, and the influence law of cutting process parameters on the cutting effect (cutting force, surface finish quality, and oil content) of the porous material was explored. The results show that compared with dry cutting and low-temperature cold air cutting, the cutting temperature and the machined surface roughness of cold air micro-lubrication cutting are the lowest, and the damage to the porous runner is the smallest. The depth of cut and the feed volume are the factors that have the greatest influence on milling force and surface roughness, respectively. Defects such as chip burrs and tears are the main factors that lead to the increase in surface roughness. The existence of drawing, micro-crack, stacking, and tiny debris on the workpiece surface are the main causes for the decrease in the oil content and oil delivery rate of the material. The optimal machining parameters of the porous polyimide material in the orthogonal experiment with the aid of cold air trace lubrication are vc=(100±2) mm/min, fz=(0.3±0.01) mm/r, ap=(0.8±0.1) mm (vc is the cutting speed, fz is the feeding rate, and ap is the cutting depth). With the assist of the cryogenic minimal quantity lubrication technology, the low damage processing, high oil content, and high oil delivery rate of cage products can be obtained.

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    Experiment on Wedge-Shaped Latticework Channel Cooling Applied in Aero Engine Gas Turbine Blade Trailing Edge
    XIAO Kehua, LUO Jiahao, RAO Yu
    Journal of Shanghai Jiao Tong University    2022, 56 (8): 1034-1042.   DOI: 10.16183/j.cnki.jsjtu.2021.162
    Abstract922)   HTML33)    PDF(pc) (20093KB)(820)       Save

    In order to study the flow and heat transfer performance of wedge-shaped latticework channels in the turbine blade trailing edge, this paper conducted an experimental study by employing the transient liquid crystal (TLC) technique to investigate the local heat transfer characteristics of the upper and lower main surfaces and applying the pressure scanning valve to mesure the pressure loss of the channels at different Reynolds numbers. The experiment shows that there is a significant difference between the upper and lower main surfaces under the turning flow configuration condition at the trailing edge section. The average Nusselt number of the lower main surface is over 30% higher than that of the upper main surface. In heat transfer coefficient, the wedge-shaped latticework channel is over 46% higher than that of the needle rib channel. There is a strong mass exchange at the interface between the upper and lower channels of the latticework channel. The intermittent high heat transfer areas on the upper and lower main surfaces are corresponding to the interface. As the inlet Reynolds number increases, the channel pressure drop increases rapidly. The pressure drop of the wedge-shaped latticework channel is 5 to 7 times that of the needle ribs, but the heat transfer area of latticework channel is 107.4% higher than the needle ribs channel, and the overall thermal performance of the wedge-shaped latticework channel is still approximately 66% higher than that of the needle ribs channel.

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    Cited: CSCD(1)
    Aggregation Modelling of Grid-Forming Renewable Power Plant for Frequency and Voltage Dynamic Analysis
    GE Chenchen, CHEN Junru, XU Sen, CHANG Xiqiang, MAO Shanxiang, ZHU Rongwu
    Journal of Shanghai Jiao Tong University    2024, 58 (10): 1544-1553.   DOI: 10.16183/j.cnki.jsjtu.2023.061
    Abstract407)   HTML6)    PDF(pc) (2974KB)(819)       Save

    Renewable power plant based on the grid-forming converter has a similar performance with the traditional thermal power plant on the function of active support for the frequency and voltage in the power system. An aggregation model is proposed for the frequency and voltage stability analysis of new power system, the overall operation characteristics of the plant are analyzed, and a method for identifying and selecting the parameters of the aggregation model is proposed. The proposed aggregation model can accurately reflect the dynamic process of the interaction between the renewable power plant and the grid, and ensure a quick simulation rate. In comparison with the electromagnetic transient model for grid-forming renewable power plant, the effectiveness of the proposed aggregation model is verified in MATLAB/Simulink. The accuracy and rapidity of the proposed aggregation model is verified in the frequency and voltage stability simulation analysis of power system based on the case study in the IEEE 39 bus system.

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    Frequency Control Strategy for Interconnected Power Systems with Time Delay Considering Optimal Energy Storage Regulation
    FU Yang, DING Zhiyin, MI Yang
    Journal of Shanghai Jiao Tong University    2022, 56 (9): 1128-1138.   DOI: 10.16183/j.cnki.jsjtu.2022.145
    Abstract964)   HTML130)    PDF(pc) (3139KB)(815)       Save

    Aimed at the problem of large frequency deviation caused by the source load uncertainty and the communication delay in the interconnected power system, a frequency control strategy for interconnected power systems with time-delay considering energy storage regulation is proposed. An interconnected power grid model with time delay which includes a steam turbine generator, a wind turbine generator, and energy storage equipment is established. According to the area control error (ACE), the energy storage device coordinates the steam turbine generator to participate in the frequency control, and the modified particle swarm optimization (MPSO) algorithm is used to optimize the proportional integral derivative (PID) load frequency controller to realize the secondary frequency adjustment, which improves the frequency stability of the load frequency control (LFC) system in a certain time-delay interval. A fractional order PID (FOPID) controller is designed for the energy storage device to adjust the output power and smooth the source load fluctuation. The frequency control performance of the energy storage system is improved to further control the frequency deviation of the interconnected power system. Different working conditions are compared and analyzed on the MATLAB/Simulink platform to verify the effectiveness of the proposed frequency control strategy.

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