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Multi-Period Resilient Model for VSC-Based AC-DC HDS Considering Public-Safety Power Shutoff to Mitigate Wildfires

CSEE Journal of Power and Energy Systems 2024年第2期10卷 821-833页

作者： Zekai Wang Tao Ding Xiaosheng Zhang Chenggang Mu Pengwei Du Fangxing Li School of Electrical Engineering Xi'an Jiaotong UniversityXi'an 710049China Electric Reliability Council of Texas AustinTX76574 USA Department of Electrical Engineering and Computer science The University of TennesseeKnoxville(UTK)TN37996USA

This paper proposes a voltage source converter (VSC) -based AC-DC hybrid distribution system (HDS) resilient model to mitigate power outages caused by wildfires. Before a wildfire happens, the public-safety power shutoff (PSPS) strategy is applied to actively cut some vulnerable lines which may easily cause wildfires, and reinforce some lines that are connected to critical loads. To mitigate load shedding caused by active line disconnection in the PSPS strategy, network reconfiguration is applied before the wildfire occurrence. During the restoration period, repair crews (RCs) repair faulted lines, and network reconfiguration is also taken into consideration in the recovery strategy to pick up critical loads. Since there exists possible errors in the wildfire prediction, several different scenarios of wildfire occurrence have been taken into consideration, leading to the proposition of a stochastic multi-period resilient model for the VSC-based AC-DC HDS. To accelerate the computational performance, a progressive hedging algorithm has been applied to solve the stochastic model which can be written as a mixed-integer linear program. The proposed model is verified on a 106-bus AC-DC HDS under wildfire conditions, and the result shows the proposed model not only can improve the system resilience but also accelerate computational speed.

关键词： AC-DC hybrid distribution system restoration network reconfiguration progressive hedging public safety power shutoffs strategy resilience

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Design of a Bio-inspired,Two-winged,Flapping-wing Micro Air Vehicle with High-lift Performance

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Journal of Bionic Engineering 2024年第3期21卷 1191-1207页

作者： Kai Hu Huichao Deng Shengjie Xiao Gongyu Yang Yuhong Sun Space Robot Laboratory The School of Mechanical EngineeringBeihang UniversityBeijing100191China

In this paper,we present the development of our latest flapping-wing micro air vehicle(FW-MAV),named Explobird,which features two wings with a wingspan of 195 mm and weighs a mere 25.2 g,enabling it to accomplish vertical take-off and hover *** devised a novel gear-based mechanism for the flapping system to achieve high lift capability and reliability and conducted extensive testing and analysis on the wings to optimise power matching and lift *** Explobird can deliver a peak lift-to-weight ratio of 1.472 and an endurance time of 259 s during hover flight powered by a single-cell LiPo *** the inherent instability of the prototype,we discuss the derivatives of its longitudinal system,underscoring the importance of feedback control,position of the centre of gravity,and increased *** demonstrate the effect of damping enhancement on stability,we also designed a passive stable ***,the vehicle is actively stabilised in roll by adjusting the wing root bars and in pitch through high-authority tail control,whereas yaw is passively *** a series of flight tests,we successfully demonstrate that our prototype can perform vertical take-off and hover flight under wireless *** promising results position the Explobird as a robust vehicle with high lift capability,paving the way towards the use of FW-MAVs for carrying load equipment in multiple tasks.

关键词： Flapping wing Biologically inspired robots Mechanical design Flight dynamics Damping enhancement

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Bubble nucleation in the two-flavor quark-meson model

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Chinese Physics C 2024年第5期48卷 92-106页

作者：汪俊荣余紫琬毛鸿 School of Physics Hangzhou Normal UniversityHangzhou 311121China

We investigate the dynamics of a first-order quark-hadron transition via homogeneous thermal nucleation in the two-flavor quark-meson *** contribution of the fermionic vacuum loop in the effective thermodynamics potential and phase diagram,together with the location of the critical endpoint(CEP),is obtained in the temperature and chemical potential *** weak and strong first-order phase transitions,by taking the temperature as a variable,the critical bubble profiles,evolutions of the surface tension,and saddle-point action in the presence of a nucleation bubble are numerically calculated in detail when fixing the chemical potentials atμ=306 MeV andμ=309 *** results show that the system could be trapped in the metastable state for a long time as long as the temperature is between the metastable region characterized by the up and low spinodal ***,the surface tension at criticality will rise to approximately 4 MeV/fm2 when the chemical potential is very *** a small surface tension value would favor a mixed phase in the cores of compact stars and may have an important implication in astrophysics.

关键词： quark-meson model nucleation false vacuum decay surface tension first-order phase transition

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Stress Concentration Effect in Interface Between Conductor and Epoxy Resin in Coaxial Components of Power Equipment

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CSEE Journal of Power and Energy Systems 2024年第1期10卷 412-420页

作者： Chuang Wang Kang Lei Qing Sun Hui Li Jiawei Zhang Lang Zhao Zongren Peng School of Electrical Engineering Xi’an University of TechnologyXi’an 710054China Xi’an Power Supply Company State Grid Shaanxi Electric Power CompanyXi’an 710032China State Key Laboratory of Electrical Insulation and Power Equipment Xi’an Jiaotong UniversityXi’an 710049China

The spacer used in gas insulated switchgear(GIS)plays a vital role in its safe *** mismatch of mechanical properties between conductor and insulating material in spacers results in stress concentration at the interface between *** a hydrostatic test,mechanical damages are often initiated from the *** this paper,the stress between aluminum conductors and epoxy resin is studied by using a simplified coaxial structure *** measurement system and finite element simulation are used to explore the generation of stress and strain during curing and *** real-time measurement of strain at the interface shows that the residual strain in the entire process is primarily generated during the cooling ***,the temperature and stress/strain distribution at the interface during the cooling stage are further studied,and combined with experiments and *** consistency between the finite element simulation and the experimental measurement results verifies the validity of the simulation method *** results show that the maximum of the first principal stress generated during the cooling stage of the production process is concentrated on the upper and lower edges of the interface which is critical to the impact of the production quality of the spacer.

关键词： Epoxy resin GIS interface stress/strain distribution

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Accurate Distinction of Weak and Strong AC Grids for Emerging Hierarchical-Infeed LCC-UHVDC Systems

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 772-777页

作者： Hao Xiao Xianzhong Duan Yi Zhang Department of Electrical and Computer Engineering University of ManitobaWinnipeg R3T 2N2ManitobaCanada State Key Laboratory of Advanced Electromagnetic Engineering and Technology Hubei Electric Power Security and High Efficiency Key LaboratorySchool of Electrical and Electronic EngineeringHuazhong University of Science and TechnologyWuhan 430074HubeiChina RTDS Technologies Inc. Winnipeg R3T 2E1ManitobaCanada

Distinction of weak and strong AC grids for emerging hierarchical-infeed LCC-UHVDC systems is important for planning and operation departments. However, accuracy of earlier distinction methods is limited as they were developed by empirical reasoning without rigorous theoretical analysis. Hence in this letter, hierarchical-infeed interactive effective short-circuit ratio (HIESCR) index is first used for strength evaluation of HIDC systems with complex inter-inverter interactions considered. Boundary HIESCR (BHIESCR) is also introduced in the proposed distinction method of weak and strong AC grids. That is, weak (or strong) AC grids are, respectively, identified when HIESCR is less (or greater) than BHIESCR. Second, it is shown BHIESCR remains almost unchanged as 3.0 versus various system parameters and rated operation variables based on rigorous theoretical analysis. This salient feature makes the proposed method more accurate than earlier methods. Finally, the proposed method is validated by simulations based on the PSCAD/EMTDC program.

关键词： Hierarchical-Infeedinteractive effective short-circuit ratio hierarchical-infeed LCC-UHVDC systems inter-inverter interactions strong AC grids weak AC grids

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Low-Frequency Stability Analysis of Power Electronic Traction Transformer Based Train-Network System

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CSEE Journal of Power and Energy Systems 2024年第4期10卷 1608-1617页

作者： Yi Hong Yang Li Zhikang Shuai Hanyu Yang College of Electrical and Information Engineering Hunan University and the Advanced Energy Technology Center of State Grid Shanghai Energy Interconnection Research Institute Co.Ltd.Shanghai 201203China College of Electrical and Information Engineering Hunan UniversityChangsha 410082China College of Electrical Engineering and Controal science in Nanjing Tech University Nanjing 211816China

Power electronic traction transformers(PETTs)will be increasingly applied to locomotives in the future for their small volume and light ***,similar to conventional trains,PETTs behave as constant power loads and may cause low-frequency oscillation(LFO)to the train-network *** solve this issue,a mathematical model of the PETT is firstly proposed and verified based on the extended describing function(EDF)method in this *** the proposed model,the LLC converter is simplified to an equivalent circuit consisting of a capacitor and a resistor in *** is further demonstrated that the model can apply to various LLC converters with different topologies and ***,when the parameter differences between cells are not obvious,the PETT can be simplified to a single-phase rectifier(i.e.,conventional train)by equivalent *** on the model of PETT,the system low-frequency stability and influential factors are analyzed by using the generalized Nyquist ***,the correctness and accuracy of theoretical analyses are validated by off-line and hardware-in-the-loop simulation results.

关键词： Extended describing function method impedance model low-frequency oscillation power electronic traction transformer train-network system

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Transient Stability Analysis and Design of VSGs with Different DC-Link Voltage Controllers

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 593-604页

作者： Chao Shen Wei Gu Wanxing Sheng Keyan Liu School of Electrical Engineering Southeast UniversityNanjingChina Power Distribution Research Department China Electric Power Research InstituteBeijing 100192China

Virtual synchronous control has been widely studied for the advantages of emulating inertia for voltage source converters (VSCs). A constant dc-link voltage is usually assumed in existing literature to estimate transient stability of virtual synchronous generators (VSGs). However, actual power supply in the dc-side of VSGs is limited and different dc-link voltage controllers are needed to achieve power balance between DC side and AC side. Addition of dc-link voltage controller has great influence on transient behavior of VSGs, which has not been investigated by previous research. To fill this gap, this paper gives insights into the effect of dc-link voltage dynamics on transient stability of VSGs. First, two typical kinds of VSGs with dc-link voltage controllers are introduced. Then, mathematical models considering dc-link dynamics are established and the effect of dc-link voltage controllers on transient synchronization stability of VSGs is revealed through equal area criterion (EAC). It is found that dc-link voltage controller would reduce stability margin of VSGs and design-oriented transient stability analysis is carried out quantitively using critical clearing time (CCT). Finally, simulation results are given to validate correctness of theoretical analysis.

关键词： DC-link voltage dynamics equal area criterion(eac) transient synchronization stability virtual synchronous generator(VSG)

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An Improved Method for Approximating the Infinite-Horizon Value Function of the Discrete-Time Switched LQR Problem

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Journal of Systems science & Complexity 2024年第1期37卷 22-39页

作者： HOU Tan LI Yuanlong LIN Zongli Department of Automation Shanghai Jiao Tong UniversityShanghai 200240China Key Laboratory of System Control and Information Processing Ministry of Education of ChinaShanghai 200240China Shanghai Engineering Research Center of Intelligent Control and Management Shanghai 200240China Charles L.Brown Department of Electrical and Computer Engineering University of VirginiaCharlottesvilleVA 22904-4743USA

This paper considers the problem of approximating the infinite-horizon value function of the discrete-time switched LQR *** particular,the authors propose a new value iteration method to generate a sequence of monotonically decreasing functions that converges exponentially to the value *** method facilitates us to use coarse approximations resulting from faster but less accurate algorithms for further value iteration,and thus,the proposed approach is capable of achieving a better approximation for a given computation time compared with the existing *** numerical examples are presented in this paper to illustrate the effectiveness of the proposed method.

关键词： Optimal control switched linear systems switched LQR problem.

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Defect Detection in c-Si Photovoltaic Modules via Transient Thermography and Deconvolution Optimization

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Chinese Journal of Electrical Engineering 2024年第1期10卷 3-11页

作者： Zekai Shen Hanqi Dai Hongwei Mei Yanxin Tu Liming Wang State Grid Hangzhou Power Supply Company State Grid Zhejiang Electric Power Co.Ltd.Hangzhou 310000China Huairou Power Supply Branch State Grid Beijing Electric Power Co.Ltd.Beijing 101400China Tsinghua Shenzhen International Graduate School Tsinghua UniversityShenzhen 518055China

Defects may occur in photovoltaic(PV)modules during production and long-term use,thereby threatening the safe operation of PV power *** thermography is a promising defect detection technology;however,its detection is limited by transverse thermal *** phenomenon is particularly noteworthy in the panel glasses of PV modules.A dynamic thermography testing method via transient thermography and Wiener filtering deconvolution optimization is *** on the time-varying characteristics of the point spread function,the selection rules of the first-order difference image for deconvolution are *** with a broken grid and artificial cracks were tested to validate the performance of the optimization *** with the feature images generated by traditional methods,the proposed method significantly improved the visual *** defect size detection can be realized by combining the deconvolution optimization method with adaptive threshold *** the same batch of PV products,the detection error could be controlled to within 10%.

关键词： Photovoltaic module transient thermography point spread function deconvolution optimization quantitative detection

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A Survey on Model Predictive Control of DFIGs in Wind Energy Conversion Systems

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CSEE Journal of Power and Energy Systems 2024年第3期10卷 1085-1104页

作者： Shuo Yan Junyu Chen Minghao Wang Yongheng Yang Jose M.Rodriguez STEM College RMIT UniversityMelbourneAustralia Hong Kong Polytechnic University Hong KongChina State Key Laboratory of Internet of Things for Smart City(UM) Department of Electrical and Computer EngineeringUniversity of MacaoMacaoChina College of Electrical Engineering Zhejiang UniversityHangzhou 310027China Universidad San Sebastin Campus BellavistaSantiago de ChileCLSantiago de Chile 000000Chile IEEE

This paper presents a comprehensive study on the model predictive control(MPC)of doubly fed induction generators(DFIG)in wind energy conversion systems(WECS);in particular the MPC of the rotor side *** general principle of prevalent MPC strategies is discussed to introduce the theoretical framework in the first ***,mainstream and high-performance MPC methods of DFIGs have been identified as model predictive current control(MPCC),model predictive torque control(MPTC),and model predictive power control(MPPC).Starting from analyzing dynamic models,these MPC strategies are investigated in terms of operating principles and technical *** paper further investigates implementation of MPC strategies in unbalanced *** on the quantitative and qualitative analysis of several case studies,performance of various MPC schemes is compared and their special features are *** for designing MPC strategies of DFIGs in WECS are provided.

关键词： Doubly fed induction generator(DFIG) model predictive control(MPC) wind energy

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