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IEEE/CAA Journal of Automatica Sinica 2024年第3期11卷 569-580页

作者： Zhuwu Shao Yujuan Wang Zeqiang Li Yongduan Song the state key laboratory of power transmission equipment&system security and new technology and the School of AutomationChongqing UniversityChongqing 400044China IEEE

This work proposes an event-triggered adaptive control approach for a class of uncertain nonlinear systems under irregular constraints.Unlike the constraints considered in most existing papers,here the external irregular constraints are considered and a constraints switching mechanism(CSM)is introduced to circumvent the difficulties arising from irregular output constraints.Based on the CSM,a new class of generalized barrier functions are constructed,which allows the control results to be independent of the maximum and minimum values(MMVs)of constraints and thus extends the existing results.Finally,we proposed a novel dynamic constraint-driven event-triggered strategy(DCDETS),under which the stress on signal transmission is reduced greatly and no constraints are violated by making a dynamic trade-off among system state,external constraints,and inter-execution intervals.It is proved that the system output is driven to close to the reference trajectory and the semi-global stability is guaranteed under the proposed control scheme,regardless of the external irregular output constraints.Simulation also verifies the effectiveness and benefits of the proposed method.

关键词： Adaptive control dynamic constraint-driven event-triggered control irregular output constraints nonlinear strict-feed-back systems

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Multi-area Frequency-constrained Unit Commitment for power systems with High Penetration of Renewable Energy Sources and Induction Machine Load

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Journal of Modern power systems and Clean Energy 2024年第3期12卷 754-766页

作者： Leibao Wang Hui Fan Jifeng Liang Longxun Xu Tiecheng Li Peng Luo Bo Hu Kaigui Xie the state Grid Hebei Electric power Research Institute state key laboratory of power transmission equipment & system security and new technology Chongqing University

The increasing penetration of renewable energy sources(RESs) brings great challenges to the frequency security of power systems. The traditional frequency-constrained unit commitment(FCUC) analyzes frequency by simplifying the average system frequency and ignoring numerous induction machines(IMs) in load, which may underestimate the risk and increase the operational cost. In this paper, we consider a multiarea frequency response(MAFR) model to capture the frequency dynamics in the unit scheduling problem, in which regional frequency security and the inertia of IM load are modeled with high-dimension differential algebraic equations. A multi-area FCUC(MFCUC) is formulated as mixed-integer nonlinear programming(MINLP) on the basis of the MAFR model. Then, we develop a multi-direction decomposition algorithm to solve the MFCUC efficiently. The original MINLP is decomposed into a master problem and subproblems. The subproblems check the nonlinear frequency dynamics and generate linear optimization cuts for the master problem to improve the frequency security in its optimal solution. Case studies on the modified IEEE 39-bus system and IEEE 118-bus system show a great reduction in operational costs. Moreover, simulation results verify the ability of the proposed MAFR model to reflect regional frequency security and the available inertia of IMs in unit scheduling.

关键词： security Frequency response Load modeling Indexes Costs Sensitivity power system dynamics

security-constrained transmission Maintenance Optimization Considering Generation and Operational Risk Costs

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Journal of Modern power systems and Clean Energy 2024年第3期12卷 767-781页

作者： Dan Xu Zhi Cai Qian Cheng Guodong Huang Jingyang Zhou Junjie Tang Beijing key laboratory of Research and system Evaluation of power Dispatching Automation technology China Electric Power Research Institute state key laboratory of power transmission equipment & system security and new technology Chongqing University

With the large-scale integration of renewable energy, the traditional maintenance arrangement during the load valley period cannot satisfy the transmission demand of renewable energy generation. Simultaneously, in a market-oriented operation mode, the power dispatching control center aims to reduce the overall power purchase cost while ensuring the security of the power system. Therefore, a security-constrained transmission maintenance optimization model considering generation and operational risk costs is proposed herein. This model is built on double-layer optimization framework, where the upper-layer model is used for maintenance and generation planning, and the lowerlayer model is primarily used to address the operational security risk arising from the random prediction error and N-1 transmission failure. Correspondingly, a generation-maintenance iterative algorithm based on a defined cost feedback is included to increase solution efficiency. Generation cost is determined using long-term security-constrained unit commitment, and the operational risk cost is obtained using a double-layer N-1 risk assessment model. An electrical correlation coupling coefficient is proposed for the solution process to avoid maintenance of associated equipment simultaneously, thereby improving model convergence efficiency. The IEEE 118-bus system is used as a test case for illustration, and test results suggest that the proposed model and algorithm can reduce the total cost of transmission maintenance and system operation while effectively improving the solution efficiency of the joint optimization model.

关键词： Maintenance engineering Costs Optimization power systems Renewable energy sources power grids Load modeling

Analysis of SF6 decomposed products by fibre-enhanced Raman spectroscopy for gas-insulated switchgear diagnosis

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High Voltage 2024年第1期9卷 206-216页

作者： Jianxin Wang Weigen Chen Pinyi Wang Fu Wan Zhixian Zhang Shoufei Gao Yingying Wang School of Electrical Engineering Chongqing UniversityChongqingChina state key laboratory of power transmission equipment&system security and new technology Chongqing UniversityChongqingChina Institute of Photonics technology Jinan UniversityGuangzhouChina

Sulphur hexafluoride(SF6)decomposed products analysis is highly critical in the earlystage fault diagnosis of gas-insulated switchgear(GIS).Spectrum technology outperforms traditional methods on non-invasiveness,no sample preparation,and no consumption.Here,the authors present an improved fibre-enhanced Raman spectroscopy(FERS)as a comprehensive analytical tool to detect a suite of SF_(6)decomposed products(SO_(2)F_(2),SOF_(2),SO_(2),H_(2)S,CF_(4),OCS,CO_(2),and CO).The FERS approach is combined with two iris diaphragms for spatial filtering and a rear-end reflector for additional Raman signal enhancement.Limits of detection down to 1×10^(−6)–8×10^(−6)are achieved for different SF6 decompositions,and quantification of an undefined multigas,sampled from an 800 kV GIS in service,is realised utilising SF6 as the internal standard gas and with a maximum error of 5.5%.The GIS is diagnosed according to the results and confirmed by an on-site check.The authors foresee that this technique will provide a route for trace gas analysis in the power industry.

关键词： SF6 diagnosis fibre

Evaluation of lightning-induced overvoltage on a 10 kV distribution line based on electromagnetic return-stroke model using finite-difference time-domain

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High Voltage 2024年第2期9卷 356-366页

作者： Pan Duan Lianfang Zhang Xiaogang Huang Jian Sun Yue Qi Qing Yang School of Automation Chongqing University of Posts and TelecommunicationsChongqingChina Chongqing power Co Tongnan BurChongqingChina China Southern power Grid Science Research Institute GuangzhouChina state key laboratory of power transmission equipment&system security and new technology Chongqing UniversityChongqingChina

Accurate simulation of lightning-induced overvoltage for overhead distribution lines is helpful to prevent lightning trip accidents.An electromagnetic return-stroke model was used to represent lightning and then a 3D finite-difference time-domain(FDTD)method was adopted to simulate the lightning-induced overvoltage on a distribution line without a field-line coupling model.How lightning-induced overvoltage behave for different ground conductivity and varying distance between the distribution line and the lightning channel was analysed.The results showed that the overvoltage waveforms at the centre point of the line corresponding to lightning strikes on the lossy ground and an ideal ground(σ=∞)were similar;however,the peak amplitudes of the waveform were affected by soil conductivity at a close distance.The relationship between magnitude of the overvoltage and distance can be described by a second-order exponential decay equation.Finally,the overvoltage calculated using the proposed model was compared with those obtained based on Agrawal's model and measurements made using the newly developed intelligent insulator on site.From these comparisons,it could be concluded that the FDTD method with the electromagnetic return-stroke model produces reasonably accurate results of the attenuated oscillation waveform,which can better reproduce the overvoltage on operational distribution lines.

关键词： lightning distribution return

Novel sandwich structured glass fiber Cloth/Poly(ethylene oxide)-MXene composite electrolyte

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Nano Materials Science 2024年第1期6卷 60-67页

作者： Yu-Qin Mao Guang-He Dong Wei-Bin Zhu Yuan-Qing Li Pei Huang Shao-Yun Fu College of Aerospace Engineering Chongqing UniversityChongqing400044China state key laboratory of power transmission equipment and system security and new technology Chongqing UniversityChongqing400044China

Recently,poly(ethylene oxide)(PEO)-based solid polymer electrolytes have been attracting great attention,and efforts are currently underway to develop PEO-based composite electrolytes for next generation high performance all-solid-state lithium metal batteries.In this article,a novel sandwich structured solid-state PEO composite electrolyte is developed for high performance all-solid-state lithium metal batteries.The PEO-based composite electrolyte is fabricated by hot-pressing PEO,LiTFSI and Ti_(3)C_(2)T_(x) MXene nanosheets into glass fiber cloth(GFC).The as-prepared GFC@PEO-MXene electrolyte shows high mechanical properties,good electrochemical stability,and high lithium-ion migration number,which indicates an obvious synergistic effect from the microscale GFC and the nanoscale MXene.Such as,the GFC@PEO-1 wt%MXene electrolyte shows a high tensile strength of 43.43 MPa and an impressive Young's modulus of 496 MPa,which are increased by 1205%and 6048%over those of PEO.Meanwhile,the ionic conductivity of GFC@PEO-1 wt%MXene at 60℃ reaches 5.01×10^(-2) S m^(-1),which is increased by around 200%compared with that of GFC@PEO electrolyte.In addition,the Li/Li symmetric battery based on GFC@PEO-1 wt%MXene electrolyte shows an excellent cycling stability over 800 h(0.3 mA cm^(-2),0.3 mAh cm^(-2)),which is obviously longer than that based on PEO and GFC@PEO electrolytes due to the better compatibility of GFC@PEO-1 wt%MXene electrolyte with Li anode.Furthermore,the solid-state Li/LiFePO_(4) battery with GFC@PEO-1 wt%MXene as electrolyte demonstrates a high capacity of 110.2–166.1 mAh g^(-1) in a wide temperature range of 25–60C,and an excellent capacity retention rate.The developed sandwich structured GFC@PEO-1 wt%MXene electrolyte with the excellent overall performance is promising for next generation high performance all-solid-state lithium metal batteries.

关键词： Solid polymer electrolyte Ti_(3)C_(2)T_(x)MXene Poly(ethylene oxide) Glass fiber cloth All-solid-state Li metal Battery

power Flow Model for Medium-voltage Distribution systems Considering Measurement and Structure Characteristics

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Journal of Modern power systems and Clean Energy 2024年第2期12卷 571-583页

作者： Zhengmei Lu Wei Yan Dezhi Huang Junjie Tang Ferdinanda Ponci Antonello Monti state key laboratory of power transmission equipment&system security and new technology Chongqing UniversityChongqing 400044China state Grid Zhejiang Yiwu power Supply Company State Grid Zhejiang Electric Power CompanyYiwu 322001China Institute for Automation of Complex power systems of the E.ON Energy Research Center at RWTH Aachen University Aachen52074Germany Digital Energy Fraunhofer FIT Aachen52072Germany IEEE

Medium-voltage distribution systems(MVDSs)mainly consist of a feeder head,lines,distribution transformers,and the equivalent load or power supply interfaced with the distribution transformers.The information of such load or power supply can be measured via the three-wattmeter method(THM)and the two-wattmeter method(TWM).The measurements can be used to perform the control of the power supply and simulate the characteristics of the load,so the models of the load and the power supply need to consider the measurement characteristics.Existing research works on three-phase power flow(PF)just consider the measurement characteristics of THM.Hence,the PF equation of the bus measured via TWM is firstly built.Based on conventional measurements,an accurate and general model of the grounded and ungrounded slack bus is proposed.Furthermore,the influence arising from the connection type and angle shift of distribution transformers on the admittance matrix is considered,and thus a general three-phase transformer model is summarized,which is applicable for all the transformers mentioned herein.Finally,newton's method is adopted to solve the PF calculation,and the performance of the proposed PF model is demonstrated through designed tests.

关键词： Medium-voltage distribution system three-phase power flow calculation measurement characteristic slack bus modeling distribution transformer

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Pricing Binary Variables of system-wide Constraints for power system Optimization

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CSEE Journal of power and Energy systems 2024年第3期10卷 1131-1144页

作者： Jiaxun Li Wei Lin Zhifang Yang Mikhail Davidson state key laboratory of power transmission equipment and system security and new technology College of Electrical EngineeringChongqing UniversityChongqing 400030China Department of Electrical Engineering The Hong Kong Polytechnic UniversityHong Kong SAR 999077China Faculty of Computational Mathematics and Cybernetics Moscow State UniversityMoscow 119991Russia IEEE

With the trend of multiple energies or flexible demand in power systems,binary variables appear in systemwide constraints,which are the foundation of marginal pricing currently in markets.An appropriate pricing method incentivizes compliance of market participants;otherwise,compliance can be incentivized by paying discriminatory uplift payments which jeopardize transparency of markets.This paper proposes two theorems to examine whether the binary variables brought by multiple energies and flexible demand will impact compliance under marginal pricing.The first theorem shows sufficient conditions with which marginal pricing with fixed binary variables incentivizes compliance,while the second theorem shows sufficient conditions to require uplift payments.To improve transparency by reducing uplift payments under cases which fall into the second theorem,this paper further proposes a pricing method by combining 1)designed constraints to price binary variables in system-wide constraints,and 2)convex hull pricing to price binary variables in private constraints.Effectiveness of the proposed theorems and pricing method is verified in an electricity-gas case(consisting of the IEEE 30-bus system and the NGS 10-node system)and the IEEE 118-bus test system.

关键词： Binary variables impact analysis pricing under non-convexities

Improved Proximal Policy Optimization Algorithm for Sequential security-constrained Optimal power Flow Based on Expert Knowledge and Safety Layer

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Journal of Modern power systems and Clean Energy 2024年第3期12卷 742-753页

作者： Yanbo Chen Qintao Du Honghai Liu Liangcheng Cheng Muhammad Shahzad Younis state key laboratory of Alternate Electrical power system with Renewable Energy Sources and School of Electrical & Electronic Engineering North China Electric Power University School of Engineering Xining University key laboratory of Smart Operation of new Energy power system Ministry of Education Qinghai University China Electric power Research Institute National University of Sciences and technology

In recent years, reinforcement learning(RL) has emerged as a solution for model-free dynamic programming problem that cannot be effectively solved by traditional optimization methods. It has gradually been applied in the fields such as economic dispatch of power systems due to its strong selflearning and self-optimizing capabilities. However, existing economic scheduling methods based on RL ignore security risks that the agent may bring during exploration, which poses a risk of issuing instructions that threaten the safe operation of power system. Therefore, we propose an improved proximal policy optimization algorithm for sequential security-constrained optimal power flow(SCOPF) based on expert knowledge and safety layer to determine active power dispatch strategy, voltage optimization scheme of the units, and charging/discharging dispatch of energy storage systems. The expert experience is introduced to improve the ability to enforce constraints such as power balance in training process while guiding agent to effectively improve the utilization rate of renewable energy. Additionally, to avoid line overload, we add a safety layer at the end of the policy network by introducing transmission constraints to avoid dangerous actions and tackle sequential SCOPF problem. Simulation results on an improved IEEE 118-bus system verify the effectiveness of the proposed algorithm.

关键词： Renewable energy sources Safety power systems Optimization power grids Energy storage Training

A Compact UHF Antenna Based on Hilbert Fractal Elements and a Serpentine Arrangement for Detecting Partial Discharg

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Energy Engineering 2024年第5期121卷 1127-1141页

作者： Xiang Lin Jian Fang Ming Zhang Kuang Yin Yan Tian Yingfei Guo Qianggang Wang Guangzhou power Supply Bureau of Guangdong power Grid Co. Ltd.China Southern Power GridGuangzhou510620China state key laboratory of power transmission equipment technology School of Electrical EngineeringChongqing UniversityChongqing400044China

Efforts to protect electric power systems from faults have commonly relied on the use of ultra-high frequency(UHF)antennas for detecting partial discharge(PD)as a common precursor to faults.However,the effectiveness of existing UHF antennas suffers from a number of challenges such as limited bandwidth,relatively large physical size,and low detection sensitivity.The present study addresses these issues by proposing a compact microstrip patch antenna with fixed dimensions of 100 mm×100 mm×1.6 mm.The results of computations yield an optimized antenna design consisting of 2nd-order Hilbert fractal units positioned within a four-layer serpentine arrangement with a fractal unit connection distance of 3.0 mm.Specifically,the optimized antenna design achieves a detection bandwidth for which the voltage standing wave ratio is less than 2 that is approximately 97.3%of the UHF frequency range(0.3–3 GHz).Finally,a prototype antenna is fabricated using standard printed circuit board technology,and the results of experiments demonstrate that the proposed antenna is capable of detecting PD signals at a distance of 8 m from the discharge source.

关键词： power system fault partial discharge UHF antenna fractal antenna micro-strip antenna