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Missing interpolation model for wind power data based on the improved CEEMDAN method and generative adversarial interpolation network 被引量:3
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作者 Lingyun Zhao Zhuoyu Wang +4 位作者 Tingxi Chen Shuang Lv Chuan Yuan Xiaodong Shen Youbo Liu 《Global Energy Interconnection》 EI CSCD 2023年第5期517-529,共13页
Randomness and fluctuations in wind power output may cause changes in important parameters(e.g.,grid frequency and voltage),which in turn affect the stable operation of a power system.However,owing to external factors... Randomness and fluctuations in wind power output may cause changes in important parameters(e.g.,grid frequency and voltage),which in turn affect the stable operation of a power system.However,owing to external factors(such as weather),there are often various anomalies in wind power data,such as missing numerical values and unreasonable data.This significantly affects the accuracy of wind power generation predictions and operational decisions.Therefore,developing and applying reliable wind power interpolation methods is important for promoting the sustainable development of the wind power industry.In this study,the causes of abnormal data in wind power generation were first analyzed from a practical perspective.Second,an improved complete ensemble empirical mode decomposition with adaptive noise(ICEEMDAN)method with a generative adversarial interpolation network(GAIN)network was proposed to preprocess wind power generation and interpolate missing wind power generation sub-components.Finally,a complete wind power generation time series was reconstructed.Compared to traditional methods,the proposed ICEEMDAN-GAIN combination interpolation model has a higher interpolation accuracy and can effectively reduce the error impact caused by wind power generation sequence fluctuations. 展开更多
关键词 Wind power data repair Complete ensemble empirical mode decomposition with adaptive noise(CEEMDAN) Generative adversarial interpolation network(GAIN)
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Behavioural analysis and dynamic simulation of the debris flow that occurred in Ganluo County(Sichuan, China) on 30 August 2020 被引量:1
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作者 LI Nuo-dong LIU Wei ZHAO Jin-heng 《Journal of Mountain Science》 SCIE CSCD 2022年第6期1495-1508,共14页
On August 30, 2020, a high-intensity storm that dropped 45.4 mm of rain in 5 hours hit the Heixiluo basin and triggered a landslide-generated debris flow event, causing fatalities and damage. The original source of th... On August 30, 2020, a high-intensity storm that dropped 45.4 mm of rain in 5 hours hit the Heixiluo basin and triggered a landslide-generated debris flow event, causing fatalities and damage. The original source of the debris flow was a large slope collapse on a steep hillside. The fallen debris mass was enlarged through sediment entrainment and slope collapse and ultimately buried a bridge at the gully entrance. Approximately 6.9×10;m;of material, including sediments and collapsed slope deposits in the gullies, was entrained, and the maximum erosion depth reached 17 m. A geomorphological analysis was initially performed based on a detailed field investigation to recognize the liquid and solid sources of the debris flow and the areas subjected to deposition and erosion. A map of the erosiondeposition distribution was obtained based on preand post-event DEMs. Using the rainfall estimated by the nearest rain gauge and the solid source estimated by the DEMs, runoff and debris flow propagation was simulated using a liquid-solid two-phase model that considers the effects of runoff and entrainment. The similarity between the estimated and simulated deposition-erosion volumes was satisfactory. The behaviour of debris flows captured in the simulation is broadly in line with the main features of the observed event. 展开更多
关键词 Debris flow Formation analysis Two-phase model Dynamic simulation
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Blockchain-based Distributed Power Market Trading Mechanism
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作者 Dongjun Cui Jinghan He +1 位作者 Guofang Zhang Zihan Hou 《Computers, Materials & Continua》 SCIE EI 2022年第8期2845-2858,共14页
Distributed power market trading has the characteristics of large number of participants,scattered locations,small single trading scale,and point-to-point trading.The traditional centralized power trading model has th... Distributed power market trading has the characteristics of large number of participants,scattered locations,small single trading scale,and point-to-point trading.The traditional centralized power trading model has the problems of large load,low efficiency,high cost,reliance on third parties and unreliable data.With the characteristics of decentralization and nontampering,blockchain can establish a point-to-point trusted trading environment and provide effective solutions to the above problems.Therefore,this paper proposed a distributed power market trading framework based on blockchain.In this framework,the distributed power supply characteristics and trading needs of each participant are analyzed,a complete distributed trading process based on blockchain is designed.In addition,we have studied the key technologies of distributed power market trading.With the goal of power service reputation and maximum revenue of distributed power providers,we have established a matching degree model,a distributed power market trading optimization model,and designed a smart contract-based power market trading optimization strategy and power trading settlement strategy.Finally,we designed experiments to verify the performance of the proposed framework. 展开更多
关键词 Blockchain distributed power trading smart contract market trading
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Demand Responsive Market Decision-Makings and Electricity Pricing Scheme Design in Low-Carbon Energy System Environment
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作者 Hongming Yang Qian Yu +2 位作者 Xiao Huang Ben Niu Min Qi 《Energy Engineering》 EI 2021年第2期285-301,共17页
The two-way interaction between smart grid and customers will continuously play an important role in enhan-cing the overall efficiency of the green and low-carbon electric power industry and properly accommodating int... The two-way interaction between smart grid and customers will continuously play an important role in enhan-cing the overall efficiency of the green and low-carbon electric power industry and properly accommodating intermittent renewable energy resources.Thus far,the existing electricity pricing mechanisms hardly match the technical properties of smart grid;neither can they facilitate increasing end users participating in the electri-city market.In this paper,several relevant models and novel methods are proposed for pricing scheme design as well as to achieve optimal decision-makings for market participants,in which the mechanisms behind are com-patible with demand response operation of end users in the smart grid.The electric vehicles and prosumers are jointly considered by complying with the technical constraints and intrinsic economic interests.Based on the demand response of controllable loads,the real-time pricing,rewarding pricing and insurance pricing methods are proposed for the retailers and their bidding decisions for the wholesale market are also presented to increase the penetration level of renewable energy.The proposed demand response oriented electricity pricing scheme can provide some useful operational references on the cooperative operation of controllable loads and renewable energy through the feasible retail and wholesale market pricing methods,and thereby enhancing the development of the low-carbon energy system. 展开更多
关键词 Controllable load demand response low-carbon energy system optimal decision retail pricing renewable energy smart grid wholesale pricing
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A New Principle of Fault Identification of on the Same Tower Based on Traveling Wave Reactive Powers
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作者 Hao Wu Ruikai Ye +2 位作者 Xingxing Dong Kunjian Yu Zhengwei Chang 《Journal of Power and Energy Engineering》 2019年第7期50-70,共21页
In order to improve the reliability of fault identification of the double-circuit transmission lines on the same tower, a new algorithm for fast protection of double-circuit transmission lines on the same tower based ... In order to improve the reliability of fault identification of the double-circuit transmission lines on the same tower, a new algorithm for fast protection of double-circuit transmission lines on the same tower based on the reactive powers of traveling wave is proposed. With the implementation of S-transform, the initial traveling wave reactive powers are calculated and the change characteristics of reactive power under different fault conditions are studied. The protection criterion is constructed by analyzing the ratio of the reactive powers of the same end on double-circuit transmission lines and the ratio of the reactive powers at both ends on the same line. According to the ratio of reactive power on the same side of the line and both ends of the same line, it is possible to identify whether the faults of the double-circuit line of the same tower occurred in or out of the protection zone. A large number of simulation results show that the protection performance is sensitive and reliable, and quick to respond. The criterion is simple and is basically not affected by fault initial angles, fault types, and transitional resistances. 展开更多
关键词 Double-Circuit Transmission Line on the SAME TOWER TRAVELING Wave Reactive Power S-TRANSFORM Fault Identification
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Effects of Transformer DC Bias and the Relationship Between UHVDC Grounding Current and Grounding Resistances 被引量:3
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作者 JIANG Wei WU Guang-ning +3 位作者 XIAO Hua HUANG Zhen Saleh Yahya Muhammed GUAN Lan 《高电压技术》 EI CAS CSCD 北大核心 2008年第12期2530-2535,共6页
Recently years,UHVDC transmission system is paid more attention to in the field of China's power system.It takes key part in the China electrical power development stratagem.But,many problems are caused by UHVDC s... Recently years,UHVDC transmission system is paid more attention to in the field of China's power system.It takes key part in the China electrical power development stratagem.But,many problems are caused by UHVDC system,such as DC bias,corrosion of metal underground and so on.DC bias is harm to the transformers nearby UHVDC grounding polar.In this paper,the influences of DC grounding current on transformer are introduced and some suggestions of DC bias solution were provided.And,the relationship between UHVDC Grounding Current and grounding Resistance of Substation was analyzed.Firstly,two-part network circuit was used to equivalent the grounding circuit.Then,an analysis of rules was done between DC bias current and grounding resistance.Finally,the conclusion is given that DC bias current rises fast as DC grounding resistance or AC grounding resistance rises.It drops when resistance of AC transmission line or interaction resistance between DC grounding system and AC grounding system rises.Decreasing AC grounding resistance and DC grounding resistance is important to restrain DC bias current.Increasing resistance of AC transmission line such as adding resistance into transformer neutral-point grounding is a useful way to limit DC bias current. 展开更多
关键词 UHVDC 变压器 直流偏磁 接地电阻
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Influence of UHVDC Monopole Operation on Soil Resistivity 被引量:1
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作者 HUANG Zhen WU Guang-ning +3 位作者 JIANG Wei XIAO Hua ZHOU Li-ren GUAN Lan 《高电压技术》 EI CAS CSCD 北大核心 2009年第3期445-450,共6页
关键词 特高压直流输电系统 电力技术 电流 电阻率 计算方法
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Data-driven Optimal Dynamic Dispatch for Hydro-PV-PHS Integrated Power Systems Using Deep Reinforcement Learning Approach 被引量:3
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作者 Jingxian Yang Jichun Liu +2 位作者 Yue Xiang Shuai Zhang Junyong Liu 《CSEE Journal of Power and Energy Systems》 SCIE EI CSCD 2023年第3期846-858,共13页
To utilize electricity in a clean and integrated manner,a zero-carbon hydro-photovoltaic(PV)-pumped hydro storage(PHS)integrated power system is studied,considering the uncertainties of PV and load demand.It is a chal... To utilize electricity in a clean and integrated manner,a zero-carbon hydro-photovoltaic(PV)-pumped hydro storage(PHS)integrated power system is studied,considering the uncertainties of PV and load demand.It is a challenge for operators to develop a dynamic dispatch mechanism for such a system,and traditional dispatch methods are difficult to adapt to random changes in the actual environment.Therefore,this study proposes a real-time dynamic dispatch strategy considering economic operation and complementary regulatory ability.First,the dynamic dispatch of a hydro-PV-PHS integrated power system is presented as a multi-objective optimization problem and the weight factor between different goals is effectively calculated using information entropy.Afterwards,the dispatch model is converted into the Markov decision process,where the dynamic dispatch decision is formulated as a reinforcement learning framework.Then,a deep deterministic policy gradient(DDPG)is deployed towards the online decision for dispatch in continuous action spaces.Finally,a case study is applied to evaluate the performance of the proposed method based on a real hydroPV-PHS integrated power system in China.Simulations show that the system agent reduces the power volatility of supply by 26.7%after hydropower regulating and further relieves power fluctuation at the point of common coupling(PCC)to the upperlevel grid by 3.28%after PHS participation.The comparison results verify the effectiveness of the proposed method. 展开更多
关键词 DDPG dynamic economic dispatch hydro-PVPHS integrated power system information entropy UNCERTAINTIES
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Two-stage distributionally robust optimization-based coordinated scheduling of integrated energy system with electricity-hydrogen hybrid energy storage 被引量:6
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作者 Yibin Qiu Qi Li +4 位作者 Yuxuan Ai Weirong Chen Mohamed Benbouzid Shukui Liu Fei Gao 《Protection and Control of Modern Power Systems》 SCIE EI 2023年第2期278-291,共14页
A coordinated scheduling model based on two-stage distributionally robust optimization(TSDRO)is proposed for integrated energy systems(IESs)with electricity-hydrogen hybrid energy storage.The scheduling problem of the... A coordinated scheduling model based on two-stage distributionally robust optimization(TSDRO)is proposed for integrated energy systems(IESs)with electricity-hydrogen hybrid energy storage.The scheduling problem of the IES is divided into two stages in the TSDRO-based coordinated scheduling model.The first stage addresses the day-ahead optimal scheduling problem of the IES under deterministic forecasting information,while the sec-ond stage uses a distributionally robust optimization method to determine the intraday rescheduling problem under high-order uncertainties,building upon the results of the first stage.The scheduling model also considers col-laboration among the electricity,thermal,and gas networks,focusing on economic operation and carbon emissions.The flexibility of these networks and the energy gradient utilization of hydrogen units during operation are also incor-porated into the model.To improve computational efficiency,the nonlinear formulations in the TSDRO-based coordinated scheduling model are properly linearized to obtain a Mixed-Integer Linear Programming model.The Column-Constraint Generation(C&CG)algorithm is then employed to decompose the scheduling model into a mas-ter problem and subproblems.Through the iterative solution of the master problem and subproblems,an efficient analysis of the coordinated scheduling model is achieved.Finally,the effectiveness of the proposed TSDRO-based coordinated scheduling model is verified through case studies.The simulation results demonstrate that the proposed TSDRO-based coordinated scheduling model can effectively accomplish the optimal scheduling task while consider-ing the uncertainty and flexibility of the system.Compared with traditional methods,the proposed TSDRO-based coordinated scheduling model can better balance conservativeness and robustness. 展开更多
关键词 Two-stage distributionally robust optimization Optimal scheduling Integrated energy systems HYDROGEN UNCERTAINTY
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Research on On-Line Coordinated Control Strategy to Improve the Voltage Vulnerability after Disturbance
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作者 Qun-Ying Liu Qi-Fang Liu +1 位作者 Deng Liu Yong-Feng Liao 《Journal of Electronic Science and Technology》 CAS 2014年第1期1-6,共6页
The on-line coordinated control strategy among multi-voltage controls is important to keep voltage security in post-fault systems. Based on the wide area measuring information, the energy function, which can qualify t... The on-line coordinated control strategy among multi-voltage controls is important to keep voltage security in post-fault systems. Based on the wide area measuring information, the energy function, which can qualify the impacts of the different control actions on voltage of different nodes, is proposed. And then, considering the impacts of different control actions on the node voltage being treated as a weight matrix, the energy margin is used as the objective function and the reactive power margin is innovatively used as the constraint to regulate the control actions globally according to the weight values. At last, the objective functions are solved to get the optimal global coordinated control strategies. The proposed method is identified in an IEEE-30 Bus system and the simulation results show that it effectively improves the voltage stability. 展开更多
关键词 Index Terms---Coordinated controls energy margin reactive power margin voltage vulnerability.
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Research on the Prevention and Control Methods for Forest Disasters in China's Forestry Ecological Environment Construction
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作者 Yanrong CAI Xueqing ZHAO Qiuyu LAI 《Agricultural Biotechnology》 CAS 2022年第4期148-160,共13页
With the development of economy,China has gradually begun to pay attention to the protection of the natural environment.Under the concept of"lucid waters and lush mountains are invaluable assets",importance ... With the development of economy,China has gradually begun to pay attention to the protection of the natural environment.Under the concept of"lucid waters and lush mountains are invaluable assets",importance has been attached to the development of forestry economy.The protection of forest resources and the prevention and control of disasters are important contents and necessary components in the construction of China's forestry ecological environment.Through the analysis and research on the types of forest disasters(forest fires,biological disasters,meteorological disasters,geological disasters,deforestation)and disaster-causing factors,some basic countermeasures were put forward with the aim to enhance the production capacity of forest resources,improve the ecological environment of forest resources and prevent forest resource disasters. 展开更多
关键词 Lucid waters and lush mountains Invaluable assets Forest disasters Disaster prevention and mitigation Basic countermeasures
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Non-intrusive Load Monitoring Based on Graph Total Variation for Residential Appliances
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作者 Xiaoyang Ma Diwen Zheng +3 位作者 Xiaoyong Deng Ying Wang Dawei Deng Wei Li 《Journal of Modern Power Systems and Clean Energy》 SCIE EI CSCD 2024年第3期947-957,共11页
Non-intrusive load monitoring is a technique for monitoring the operating conditions of electrical appliances by collecting the aggregated electrical information at the household power inlet.Despite several studies on... Non-intrusive load monitoring is a technique for monitoring the operating conditions of electrical appliances by collecting the aggregated electrical information at the household power inlet.Despite several studies on the mining of unique load characteristics,few studies have extensively considered the high computational burden and sample training.Based on lowfrequency sampling data,a non-intrusive load monitoring algorithm utilizing the graph total variation(GTV)is proposed in this study.The algorithm can effectively depict the load state without the need for prior training.First,the combined Kmeans clustering algorithm and graph signals are used to build concise and accurate graph structures as load models.The GTV representing the internal structure of the graph signal is introduced as the optimization model and solved using the augmented Lagrangian iterative algorithm.The introduction of the difference operator reduces the computing cost and addresses the inaccurate reconstruction of the graph signal.With low-frequency sampling data,the algorithm only requires a little prior data and no training,thereby reducing the computing cost.Experiments conducted using the reference energy disaggregation dataset and almanac of minutely power dataset demonstrated the stable superiority of the algorithm and its low computational burden. 展开更多
关键词 Non-intrusive load monitoring graph total variation augmented Lagrangian function smart grid
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Butler matrix enabled multi-beam optical phased array for two-dimensional beam-steering and ranging
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作者 ZUOYU ZHOU WEIHAN XU +6 位作者 CHUXIN LIU RUIYANG XU CHEN ZHU XINHANG LI LIANGJUN LU JIANPING CHEN LINJIE ZHOU 《Photonics Research》 SCIE EI CAS CSCD 2024年第5期912-920,共9页
Based on the wavelength transparency of the Butler matrix(BM)beamforming network,we demonstrate a multibeam optical phased array(MOPA)with an emitting aperture composed of grating couplers at a 1.55μm pitch for wavel... Based on the wavelength transparency of the Butler matrix(BM)beamforming network,we demonstrate a multibeam optical phased array(MOPA)with an emitting aperture composed of grating couplers at a 1.55μm pitch for wavelength-assisted two-dimensional beam-steering.The device is capable of simultaneous multi-beam operation in a field of view(FOV)of 60°×8°in the phased-array scanning axis and the wavelength-tuning scanning axis,respectively.The typical beam divergence is about 4°on both axes.Using multiple linearly chirped lasers,multibeam frequency-modulated continuous wave(FMCW)ranging is realized with an average ranging error of 4 cm.A C-shaped target is imaged for proof-of-concept 2D scanning and ranging. 展开更多
关键词 OPTICAL tuning BEAM
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Improving thermal stability of LiNbO_(3)based electro-optical electric field sensor by depositing a TiO_(2)film
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作者 She Wang Hai Wang +2 位作者 Chanxiao Li Chijie Zhuang Rong Zeng 《High Voltage》 SCIE EI 2022年第5期840-846,共7页
Electro-optic electric field sensors based on LiNbO3 are widely used for the measurement of electric fields or transient voltages.However,the working bias of the sensor is influenced by the temperature due to the ther... Electro-optic electric field sensors based on LiNbO3 are widely used for the measurement of electric fields or transient voltages.However,the working bias of the sensor is influenced by the temperature due to the thermo-optic effect of LiNbO_(3).An athermal electrooptic electric field sensor was demonstrated by coating a thin layer of TiO_(2)film which has a negative thermo-optic coefficient,on the common-path interferometer based sensor to compensate LiNbO_(3)'s positive thermo-optic coefficient.Both calculation and experimental studies were conducted.The experimental results reasonably agree well with the calculated values,and the results show the sensor coated with a 640 nm thick TiO_(2)film has a much smaller temperature dependence of 0.011°/℃compared to the initial value of 0.1°/℃. 展开更多
关键词 FILM FIELD stability
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Fast Solution Method for the Large-scale Unit Commitment Problem with Long-term Storage
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作者 Bo Li Chunjie Qin +4 位作者 Ruotao Yu Wei Dai Mengjun Shen Ziming Ma Jianxiao Wang 《Chinese Journal of Electrical Engineering》 EI CSCD 2023年第3期39-49,共11页
Long-term storage(LTS)can provide various services to address seasonal fluctuations in variable renewable energy by reducing energy curtailment.However,long-term unit commitment(UC)with LTS involves mixed-integer prog... Long-term storage(LTS)can provide various services to address seasonal fluctuations in variable renewable energy by reducing energy curtailment.However,long-term unit commitment(UC)with LTS involves mixed-integer programming with large-scale coupling constraints between consecutive intervals(state-of-charge(SOC)constraint of LTS,ramping rate,and minimum up/down time constraints of thermal units),resulting in a significant computational burden.Herein,an iterative-based fast solution method is proposed to solve the long-term UC with LTS.First,the UC with coupling constraints is split into several sub problems that can be solved in parallel.Second,the solutions of the sub problems are adjusted to obtain a feasible solution that satisfies the coupling constraints.Third,a decoupling method for long-term time-series coupling constraints is proposed to determine the global optimization of the SOC of the LTS.The price-arbitrage model of the LTS determines the SOC boundary of the LTS for each sub problem.Finally,the sub problem with the SOC boundary of the LTS is iteratively solved independently.The proposed method was verified using a modified IEEE 24-bus system.The results showed that the computation time of the unit combination problem can be reduced by 97.8%,with a relative error of 3.62%. 展开更多
关键词 Constraint splitting long-term storage mix-integer programming unit commitment
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Multi-stage sizing approach for development of utility-scale BESS considering dynamic growth of distributed photovoltaic connection 被引量:7
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作者 Zao TANG Youbo LIU +3 位作者 Junyong LIU Ran LI Lili WEN Guofang ZHANG 《Journal of Modern Power Systems and Clean Energy》 SCIE EI 2016年第4期554-565,共12页
The battery energy storage system(BESS)is regarded as one of the most promising address operational challenges caused by distributed generations.This paper proposes a novel multi-stage sizing model for utility-scale B... The battery energy storage system(BESS)is regarded as one of the most promising address operational challenges caused by distributed generations.This paper proposes a novel multi-stage sizing model for utility-scale BESS,to optimize the BESS development strategies for distribution networks with increasing penetration levels and growth patterns of dispersed photovoltaic(PV)panels.Particularly,an integrated model is established in order to accommodate dispersed PVs in short-term operation scale while facilitating appropriate profits in long-term planning scale.Clusterwise reduction is adopted to extract the most representative operating scenarios with PVs and BESS integration,which is able to decrease the computing complexity caused by scenario redundancy.The numerical studies on IEEE 69-bus distribution system verify the feasibility of the proposed multi-stage sizing approach for the utility-scale BESS. 展开更多
关键词 Multi-stage sizing BESS Growth pattern Long-time planning Short-term scheduling
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Scenario-based analysis and probability assessment of sub-synchronous oscillation caused by wind farms with direct-driven wind generators 被引量:4
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作者 Zhi AN Chen SHEN +3 位作者 Zetian ZHENG Feng LIU Xiaoqing CHANG Wei WEI 《Journal of Modern Power Systems and Clean Energy》 SCIE EI CSCD 2019年第2期243-253,共11页
Recently, explanations of the sub-synchronous oscillation(SSO) caused by wind farms based on directdriven wind generators(DDWGs) have been published in the literatures, in which the controller parameters of DDWGs and ... Recently, explanations of the sub-synchronous oscillation(SSO) caused by wind farms based on directdriven wind generators(DDWGs) have been published in the literatures, in which the controller parameters of DDWGs and the system equivalent parameters play an important role. However, more than one set of parameters can cause weakly damped sub-synchronous modes. The most vulnerable and highly possible scenario is still unknown. To find scenarios that have potential oscillation risks, this paper proposes a small disturbance model of wind farms with DDWGs connected to the grid using a state-space modeling technique. Taguchi’s orthogonal array testing is introduced to generate different scenarios.Multiple scenarios with different parameter settings that may lead to SSOs are found. A probabilistic analysis method based on the Gaussian mixture model is employed to evaluate the consistency of these scenarios with the actual accidents. Electromagnetic transient simulations are performed to verify the findings. 展开更多
关键词 Direct-driven wind GENERATOR Subsynchronous OSCILLATION Probabilistic assessment RANDOMNESS
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Measurement-based solution for low frequency oscillation analysis 被引量:4
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作者 Chen SHEN Zhi AN +2 位作者 Xianzhong DAI Wei WEI Lijie DING 《Journal of Modern Power Systems and Clean Energy》 SCIE EI 2016年第3期406-413,共8页
This paper presents a measurement-based solution for low frequency oscillation(LFO) analysis in both real time monitoring and off-line case study. An online LFO property discrimination method is developed first,which ... This paper presents a measurement-based solution for low frequency oscillation(LFO) analysis in both real time monitoring and off-line case study. An online LFO property discrimination method is developed first,which alternately uses empirical mode decomposition(EMD)/Hilbert transform(HT) and square calculation to process the measurement data. The method magnifies the variation trend of oscillating variables to accurately discriminate the property of the oscillation. Subsequently, an oscillation source locating method for the forced oscillation(FO) and a strongly correlated generator identification method for the weak damping oscillation(WDO) are proposed. Finally, numerical study results on a test system of the isolated Changdu grid in Tibet validate the proposed methods. 展开更多
关键词 Low frequency oscillation Oscillation property discrimination Oscillation source location Strongly correlated generator identification
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Longer conserved alpine forests ecosystem exhibits higher stability to climate change on the Tibetan Plateau 被引量:1
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作者 Jian Li Nan Cong +8 位作者 Jiaxing Zu Yuqin Xin Ke Huang Quan Zhou Yaojie Liu Lin Zhou Li Wang Yang Liu Ge Zhang 《Journal of Plant Ecology》 SCIE CSCD 2019年第4期645-652,共8页
Aims Vegetation dynamics are simultaneously regulated by climate change and anthropogenic activities.Since the 1980s,climate has been warming on the Tibetan Plateau(TP)at a rate higher than North Hemisphere average.An... Aims Vegetation dynamics are simultaneously regulated by climate change and anthropogenic activities.Since the 1980s,climate has been warming on the Tibetan Plateau(TP)at a rate higher than North Hemisphere average.Anthropogenic activities,including grazing,farming,and urbanization,are also influencing the alpine ecosystem on the TP.Especially,an ensemble of large engineering projects,such as power transported from west to east by State Grid,has been in operation on the TP.While studies disentangling effects of climate and anthropogenic activities interference are still lacking for the forest ecosystems on the TP.The overarching objectives of this study were to separate effects of natural climates and human interferences on forest ecosystem dynamics on the TP.Methods We compared vegetation activities of two typical natural reserves(Gongbu natural reserve,GNR,and Yarlung zangbo river grand canyon natural reserve,YNR)and their surroundings in southeastern Tibet(outside of the natural reserves,ONR)using long-term satel-lite normalized difference vegetation index(NDVI)dataset.Linear regression and partial correlation analyses were constructed for the relationship between vegetation activity and climates to evaluate the distinct climate effects on the two natural reserves.Important Findings The two natural reserves were established at different time,which were related to anthropogenic activities impact durations.The results showed that the annual mean NDVI fluctuated between 0.5 and 0.6 in the relatively longer reserved YNR,which was re-markably higher than those in other regions(with NDVI lower than 0.45).The vegetation vigor in the YNR showed neither a sig-nificant temporal trend nor significant relationship with climate.Nevertheless,vegetation vigor exhibited a significant increasing trend during the last three decades(0.012/decade)at the GNR.The inter-decadal analysis turned out positive relationships between vegetation vigor and annual temperature since late 1990s until early 2000s when the GNR was officially established.This study underlined the importance of considering human interference duration when assessing the relationships between vegetation dy-namics and climates. 展开更多
关键词 climate change human interference natural reserves vegetation activity Southeastern Tibet
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Torsion Failure Analysis of Galvanized Steel Wires for Transmission and Distribution Lines Based on ANSYS Numerical Simulation
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作者 WANG Man ZHANG Xiaomin +1 位作者 LONG Peng JIANG Yu 《Journal of Shanghai Jiaotong university(Science)》 EI 2019年第5期632-639,共8页
This study provides a detailed failure analysis of galvanized steel wires(3 mm in diameter) for a 35 k V transmission and distribution line, which was carried out by combining the conventional material analysis method... This study provides a detailed failure analysis of galvanized steel wires(3 mm in diameter) for a 35 k V transmission and distribution line, which was carried out by combining the conventional material analysis methods with the finite element method(FEM). It is found that the failed material had good plasticity(5% in elongation),and under the soft torsion loading condition(0.75 in stress state soft coefficient), the ductile fracture should occur on the material. Additionally, the theoretical number of torsions calculated by the FEM was 26.2 times, while the actual number of torsions achieved by the test was only 2.2 times and the local fracture surface exhibited brittle fracture characteristics. The results showed that the local torsion brittle fracture of the material with good plasticity was caused by triaxial stress in the torsion condition, which led to the formation of cavity in the pulling stress area in the material’s center, and the finite element calculation results indicated that the stress state soft coefficient at the cavity was distributed between 0.31 and 0.38, and the stress concentration at the cavity was more than twice the normal value. Besides, the Widmanstatten structure formed as the improper hot working process is the corresponding structural reason. 展开更多
关键词 galvanized steel wire torsion brittle fracture triaxial stress state cavity rupture finite element method(FEM)
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