According to the multi-time-scale characteristics of power generation and demand-side response(DR)resources,as well as the improvement of prediction accuracy along with the approaching operating point,a rolling peak s...According to the multi-time-scale characteristics of power generation and demand-side response(DR)resources,as well as the improvement of prediction accuracy along with the approaching operating point,a rolling peak shaving optimization model consisting of three different time scales has been proposed.The proposed peak shaving optimization model considers not only the generation resources of two different response speeds but also the two different DR resources and determines each unit combination,generation power,and demand response strategy on different time scales so as to participate in the peaking of the power system by taking full advantage of the fast response characteristics of the concentrating solar power(CSP).At the same time,in order to improve the accuracy of the scheduling results,the combination of the day-ahead peak shaving phase with scenario-based stochastic programming can further reduce the influence of wind power prediction errors on scheduling results.The testing results have shown that by optimizing the allocation of scheduling resources in each phase,it can effectively reduce the number of starts and stops of thermal power units and improve the economic efficiency of system operation.The spinning reserve capacity is reduced,and the effectiveness of the peak shaving strategy is verified.展开更多
Improving the ability of innovation and Entrepreneurship of impoverished college students in local colleges and universities could alleviate employment pressure to a certain extent, solve employment difficulties and h...Improving the ability of innovation and Entrepreneurship of impoverished college students in local colleges and universities could alleviate employment pressure to a certain extent, solve employment difficulties and help college students realize their self-worth, which are related to social stability and economic development. By using the methods of questionnaire and individual interviews, this paper investigates some of the students who set up files for poverty alleviation in northwest local colleges and universities, and understand the current situation of innovation and Entrepreneurship of poor college students. It is hoped that the ability of innovation and entrepreneurship can be improved by enhancing the awareness of innovation and entrepreneurship, improving the education system, innovating learning mode, building a practical platform and implementing quality management.展开更多
DC-link capacitors play a vital role in managing ripple voltage and current in converters and various devices.This study focuses on exploring the aging characteristics of DC-link capacitors in alternating humid and th...DC-link capacitors play a vital role in managing ripple voltage and current in converters and various devices.This study focuses on exploring the aging characteristics of DC-link capacitors in alternating humid and thermal environments aligned with the operational conditions in photovoltaic and wind power applications.Adhering to relevant power equipment standards,we designed a 24-h alternating humid and thermal aging environment tailored to the requirements of DC-link capacitors.An aging test platform is established,and 20 widely used metallized polypropylene film capacitors are selected for evaluation.Parameters such as the capacitance,equivalent series resistance(ESR),and phase angle are assessed during aging,as well as the onset time and extent of aging at various intervals.This study focuses on the aging mechanisms,analyzing electrode corrosion,the self-healing process,and dielectric aging.Fitting the aging characteristics enabled us to calculate the lifespan of the capacitor and predict it under different degrees of capacitance decay.The results show that under alternating humid and thermal conditions,capacitance attenuation and ESR increase exhibit exponential nonlinearity,influenced by factors such as the oxidation and self-healing of capacitive metal electrodes,dielectric main-chain fracture,and crystal transformation.This study underscores the pivotal role of encapsulation in determining the aging decay time.展开更多
The development and utilization of large-scale distributed power generation and the increase of impact loads represented by electric locomotives and new energy electric vehicles have brought great challenges to the st...The development and utilization of large-scale distributed power generation and the increase of impact loads represented by electric locomotives and new energy electric vehicles have brought great challenges to the stable operation of the regional power grid.To improve the prediction accuracy of power systems with source-load twoterminal uncertainties,an adaptive cubature Kalman filter algorithm based on improved initial noise covariance matrix Q0 is proposed in this paper.In the algorithm,the Q0 is used to offset the modeling error,and solves the problem of large voltage amplitude and phase fluctuation of the source-load two-terminal uncertain systems.Verification of the proposed method is implemented on the IEEE 30 node system through simulation.The results show that,compared with the traditional methods,the improved adaptive cubature Kalman filter has higher prediction accuracy,which verifies the effectiveness and accuracy of the proposed method in state estimation of the new energy power system with source-load two-terminal uncertainties.展开更多
The insulating paper of the transformer is affected by many factors during the operation,meanwhile,the surface texture of the paper is easy to change.To explore the relationship between the aging state and surface tex...The insulating paper of the transformer is affected by many factors during the operation,meanwhile,the surface texture of the paper is easy to change.To explore the relationship between the aging state and surface texture change of insulating paper,firstly,the thermal aging experiment of insulating paper is carried out,and the insulating paper samples with different aging times are obtained.After then,the images of the aged insulating paper samples are collected and pre-processed.The pre-processing effect is verified by constructing and calculating the gray surface of the sample.Secondly,the texture features of the insulating paper image are extracted by box dimension and multifractal spectrum.Based on that,the extreme learning machine(ELM)is taken as the classification tool with texture features and aging time as the input and output,to train the algorithm and construct the corresponding relationship between the texture feature and the aging time.After then,the insulating paper with unknown aging time is predicted with a trained ELMalgorithm.The numerical test results show that the texture features extracted from the fractal dimension of the micro image can effectively characterize the aging state of insulating paper,the average accuracy can reach 91.6%.It proves that the fractal dimension theory can be utilized for assessing the aging state of insulating paper for onsite applications.展开更多
With the growing demand for precise voltage adjustment and reactive regulation,the frequent operation of on-load tap changers(OLTCs)in oil-immersed systems has led to increased erosion of switch contacts by arcs durin...With the growing demand for precise voltage adjustment and reactive regulation,the frequent operation of on-load tap changers(OLTCs)in oil-immersed systems has led to increased erosion of switch contacts by arcs during the switching process.This erosion causes significant wear on the contacts,thereby reducing their lifespan.Therefore,the present study aims to investigate the behavior and mechanism of arc erosion on contact surfaces in oil-immersed OLTCs.To achieve this,a self-designed friction and wear test device for OLTC contacts was utilized to conduct experiments at various sliding speeds and contact pressures.Additionally,finite element analysis was employed to validate the experimental results regarding the influence of sliding speed on arc energy.The surface morphology of the contacts was observed using an optical microscope.The findings revealed that as the sliding speed increased,the arc energy,arc initiation rate,and contact resistance initially exhibited an upward trend,then decreased,and eventually increased again.The minimum values were observed at a sliding speed of 90 mm/s.Moreover,the arc energy,arc initiation rate,and contact resistance decreased gradually as the contact pressure increased.After reaching a contact pressure of 1.5 N,the variation in the arc energy stabilized.At lower contact pressures,arc erosion dominated the wear on the contact surface.However,at higher contact pressures,the wear transitioned from predominantly arc erosion to a combination of mechanical wear and arc erosion.In summary,experimental and analytical investigations provided insights into the effects of sliding speed and contact pressure on the behavior of arc erosion,contact resistance,and surface damage of OLTC contacts in oil-immersed systems.展开更多
Due to unique photo-physical characteristics,rare earth(RE)complexes play important roles in many fields,for example,telecommunications,life science,and organic light-emitting diodes(OLEDs).Especially,thanks to narrow...Due to unique photo-physical characteristics,rare earth(RE)complexes play important roles in many fields,for example,telecommunications,life science,and organic light-emitting diodes(OLEDs).Especially,thanks to narrow emission bandwidth and 100%theoretical internal quantum efficiency(IQE),the study of RE complexes in the electroluminescence field has been a hot research topic in recent 30 years.As a leading technology in solid-state light source fields,OLEDs have attracted great interest from academic researchers and commercial endeavors.In the last decades,OLED-based products have trickled into the commercial market and developed quickly into portable display devices.Here,we briefly introduce the luminescent characteristics and electroluminescent(EL)study of RE complexes in material synthesis and device design.Moreover,we emphatically reveal the innovative application of RE complexes as sensitizers in OLEDs.Through experimental validation,the application of RE complexes as sensitizers can realize the complementary advantages of RE complexes and transition metal complexes,leading to significantly improved performances of OLEDs.The application of RE complexes as sensitizers provides a new strategy for designing and developing novel high performances OLEDs.展开更多
Composited cable terminals are critical for reliable power delivery of traditional and traction power supply systems.During its operation,the cable terminal continually undergoes complex circumstances where humidity,t...Composited cable terminals are critical for reliable power delivery of traditional and traction power supply systems.During its operation,the cable terminal continually undergoes complex circumstances where humidity,temperature,field strength,mechanical stress and other factors continuously change at different levels.In extreme cases,defects or even failures may occur in the cable terminals,leading to catastrophic accidents.This makes the condition monitoring and defect detection of composited cable terminals become an imperative need for the power industry.The“state-of-the-art”technology of cable terminal condition assessment is focussed and a systematic review of the current research progress of cable terminal condition assessment from the operation circumstances to failure mechanisms is provided.It covers both online/offline condition monitoring methods and defects detection approaches.In addition,challenges and future research directions for cable terminal condition assessment are also addressed.It is concluded that the non-destructive and non-intrusive methods like terahertz imaging and ultrasonic testing,and multi-source information fusion methods as well as the digital twin technology have been gaining popularity for cable terminal defect inspection.It is expected the presented work can provide a global field of vision for further advancement of both scholars and industrial engineers in this field.展开更多
An accurate extraction of vibration signal characteristics of an on-load tap changer(OLTC)during contact switching can effectively help detect its abnormal state.Therefore,an improved fuzzy C-means clustering method f...An accurate extraction of vibration signal characteristics of an on-load tap changer(OLTC)during contact switching can effectively help detect its abnormal state.Therefore,an improved fuzzy C-means clustering method for abnormal state detection of the OLTC contact is proposed.First,the wavelet packet and singular spectrum analysis are used to denoise the vibration signal generated by the moving and static contacts of the OLTC.Then,the Hilbert-Huang transform that is optimized by the ensemble empirical mode decomposition(EEMD)is used to decompose the vibration signal and extract the boundary spectrum features.Finally,the gray wolf algorithm-based fuzzy C-means clustering is used to denoise the signal and determine the abnormal states of the OLTC contact.An analysis of the experimental data shows that the proposed secondary denoising method has a better denoising effect compared to the single denoising method.The EEMD can improve the modal aliasing effect,and the improved fuzzy C-means clustering can effectively identify the abnormal state of the OLTC contacts.The analysis results of field measured data further verify the effectiveness of the proposed method and provide a reference for the abnormal state detection of the OLTC.展开更多
基金support of the projects Youth Science Foundation of Gansu Province(Source-Grid-Load Multi-Time Interval Optimization Scheduling Method Considering Wind-PV-CSP Combined DC Transmission,No.22JR11RA148)Youth Science Foundation of Lanzhou Jiaotong University(Research on Coordinated Dispatching Control Strategy of High Proportion New Energy Transmission Power System with CSP Power Generation,No.2020011).
文摘According to the multi-time-scale characteristics of power generation and demand-side response(DR)resources,as well as the improvement of prediction accuracy along with the approaching operating point,a rolling peak shaving optimization model consisting of three different time scales has been proposed.The proposed peak shaving optimization model considers not only the generation resources of two different response speeds but also the two different DR resources and determines each unit combination,generation power,and demand response strategy on different time scales so as to participate in the peaking of the power system by taking full advantage of the fast response characteristics of the concentrating solar power(CSP).At the same time,in order to improve the accuracy of the scheduling results,the combination of the day-ahead peak shaving phase with scenario-based stochastic programming can further reduce the influence of wind power prediction errors on scheduling results.The testing results have shown that by optimizing the allocation of scheduling resources in each phase,it can effectively reduce the number of starts and stops of thermal power units and improve the economic efficiency of system operation.The spinning reserve capacity is reduced,and the effectiveness of the peak shaving strategy is verified.
文摘Improving the ability of innovation and Entrepreneurship of impoverished college students in local colleges and universities could alleviate employment pressure to a certain extent, solve employment difficulties and help college students realize their self-worth, which are related to social stability and economic development. By using the methods of questionnaire and individual interviews, this paper investigates some of the students who set up files for poverty alleviation in northwest local colleges and universities, and understand the current situation of innovation and Entrepreneurship of poor college students. It is hoped that the ability of innovation and entrepreneurship can be improved by enhancing the awareness of innovation and entrepreneurship, improving the education system, innovating learning mode, building a practical platform and implementing quality management.
基金Supported by the Opening Project of State Key Laboratory of Large Electric Drive System and Equipment Technology(SKLLDJ022020004).
文摘DC-link capacitors play a vital role in managing ripple voltage and current in converters and various devices.This study focuses on exploring the aging characteristics of DC-link capacitors in alternating humid and thermal environments aligned with the operational conditions in photovoltaic and wind power applications.Adhering to relevant power equipment standards,we designed a 24-h alternating humid and thermal aging environment tailored to the requirements of DC-link capacitors.An aging test platform is established,and 20 widely used metallized polypropylene film capacitors are selected for evaluation.Parameters such as the capacitance,equivalent series resistance(ESR),and phase angle are assessed during aging,as well as the onset time and extent of aging at various intervals.This study focuses on the aging mechanisms,analyzing electrode corrosion,the self-healing process,and dielectric aging.Fitting the aging characteristics enabled us to calculate the lifespan of the capacitor and predict it under different degrees of capacitance decay.The results show that under alternating humid and thermal conditions,capacitance attenuation and ESR increase exhibit exponential nonlinearity,influenced by factors such as the oxidation and self-healing of capacitive metal electrodes,dielectric main-chain fracture,and crystal transformation.This study underscores the pivotal role of encapsulation in determining the aging decay time.
基金supported by the Tianyou Youth Talent Lift Program of Lanzhou Jiaotong University,the Nature Science Foundation of Gansu(No.21JR1RA255)the Gansu University Innovation Fund Project(Nos.2020A-036 and 2021B-111).
文摘The development and utilization of large-scale distributed power generation and the increase of impact loads represented by electric locomotives and new energy electric vehicles have brought great challenges to the stable operation of the regional power grid.To improve the prediction accuracy of power systems with source-load twoterminal uncertainties,an adaptive cubature Kalman filter algorithm based on improved initial noise covariance matrix Q0 is proposed in this paper.In the algorithm,the Q0 is used to offset the modeling error,and solves the problem of large voltage amplitude and phase fluctuation of the source-load two-terminal uncertain systems.Verification of the proposed method is implemented on the IEEE 30 node system through simulation.The results show that,compared with the traditional methods,the improved adaptive cubature Kalman filter has higher prediction accuracy,which verifies the effectiveness and accuracy of the proposed method in state estimation of the new energy power system with source-load two-terminal uncertainties.
基金This work was supported by the Tianyou Youth Talent Lift Program of Lanzhou Jiaotong University,the Youth Science Foundation of Lanzhou Jiaotong University(No.2019029)the University Innovation Fund Project of Gansu Provincial Department of Education(No.2020A-036)the Young Doctor Foundation of JYT.GANSU.GOV.CN(No.2021QB-060).
文摘The insulating paper of the transformer is affected by many factors during the operation,meanwhile,the surface texture of the paper is easy to change.To explore the relationship between the aging state and surface texture change of insulating paper,firstly,the thermal aging experiment of insulating paper is carried out,and the insulating paper samples with different aging times are obtained.After then,the images of the aged insulating paper samples are collected and pre-processed.The pre-processing effect is verified by constructing and calculating the gray surface of the sample.Secondly,the texture features of the insulating paper image are extracted by box dimension and multifractal spectrum.Based on that,the extreme learning machine(ELM)is taken as the classification tool with texture features and aging time as the input and output,to train the algorithm and construct the corresponding relationship between the texture feature and the aging time.After then,the insulating paper with unknown aging time is predicted with a trained ELMalgorithm.The numerical test results show that the texture features extracted from the fractal dimension of the micro image can effectively characterize the aging state of insulating paper,the average accuracy can reach 91.6%.It proves that the fractal dimension theory can be utilized for assessing the aging state of insulating paper for onsite applications.
文摘With the growing demand for precise voltage adjustment and reactive regulation,the frequent operation of on-load tap changers(OLTCs)in oil-immersed systems has led to increased erosion of switch contacts by arcs during the switching process.This erosion causes significant wear on the contacts,thereby reducing their lifespan.Therefore,the present study aims to investigate the behavior and mechanism of arc erosion on contact surfaces in oil-immersed OLTCs.To achieve this,a self-designed friction and wear test device for OLTC contacts was utilized to conduct experiments at various sliding speeds and contact pressures.Additionally,finite element analysis was employed to validate the experimental results regarding the influence of sliding speed on arc energy.The surface morphology of the contacts was observed using an optical microscope.The findings revealed that as the sliding speed increased,the arc energy,arc initiation rate,and contact resistance initially exhibited an upward trend,then decreased,and eventually increased again.The minimum values were observed at a sliding speed of 90 mm/s.Moreover,the arc energy,arc initiation rate,and contact resistance decreased gradually as the contact pressure increased.After reaching a contact pressure of 1.5 N,the variation in the arc energy stabilized.At lower contact pressures,arc erosion dominated the wear on the contact surface.However,at higher contact pressures,the wear transitioned from predominantly arc erosion to a combination of mechanical wear and arc erosion.In summary,experimental and analytical investigations provided insights into the effects of sliding speed and contact pressure on the behavior of arc erosion,contact resistance,and surface damage of OLTC contacts in oil-immersed systems.
基金fnanced by the National Natural Science Foundation of China(Grant No.62174160)Research Equipment Development Project of Chrdese Academy of Sciences(YJKYYQ20200005).
文摘Due to unique photo-physical characteristics,rare earth(RE)complexes play important roles in many fields,for example,telecommunications,life science,and organic light-emitting diodes(OLEDs).Especially,thanks to narrow emission bandwidth and 100%theoretical internal quantum efficiency(IQE),the study of RE complexes in the electroluminescence field has been a hot research topic in recent 30 years.As a leading technology in solid-state light source fields,OLEDs have attracted great interest from academic researchers and commercial endeavors.In the last decades,OLED-based products have trickled into the commercial market and developed quickly into portable display devices.Here,we briefly introduce the luminescent characteristics and electroluminescent(EL)study of RE complexes in material synthesis and device design.Moreover,we emphatically reveal the innovative application of RE complexes as sensitizers in OLEDs.Through experimental validation,the application of RE complexes as sensitizers can realize the complementary advantages of RE complexes and transition metal complexes,leading to significantly improved performances of OLEDs.The application of RE complexes as sensitizers provides a new strategy for designing and developing novel high performances OLEDs.
基金National Natural Science Foundation of China,Grant/Award Number:52167018。
文摘Composited cable terminals are critical for reliable power delivery of traditional and traction power supply systems.During its operation,the cable terminal continually undergoes complex circumstances where humidity,temperature,field strength,mechanical stress and other factors continuously change at different levels.In extreme cases,defects or even failures may occur in the cable terminals,leading to catastrophic accidents.This makes the condition monitoring and defect detection of composited cable terminals become an imperative need for the power industry.The“state-of-the-art”technology of cable terminal condition assessment is focussed and a systematic review of the current research progress of cable terminal condition assessment from the operation circumstances to failure mechanisms is provided.It covers both online/offline condition monitoring methods and defects detection approaches.In addition,challenges and future research directions for cable terminal condition assessment are also addressed.It is concluded that the non-destructive and non-intrusive methods like terahertz imaging and ultrasonic testing,and multi-source information fusion methods as well as the digital twin technology have been gaining popularity for cable terminal defect inspection.It is expected the presented work can provide a global field of vision for further advancement of both scholars and industrial engineers in this field.
文摘An accurate extraction of vibration signal characteristics of an on-load tap changer(OLTC)during contact switching can effectively help detect its abnormal state.Therefore,an improved fuzzy C-means clustering method for abnormal state detection of the OLTC contact is proposed.First,the wavelet packet and singular spectrum analysis are used to denoise the vibration signal generated by the moving and static contacts of the OLTC.Then,the Hilbert-Huang transform that is optimized by the ensemble empirical mode decomposition(EEMD)is used to decompose the vibration signal and extract the boundary spectrum features.Finally,the gray wolf algorithm-based fuzzy C-means clustering is used to denoise the signal and determine the abnormal states of the OLTC contact.An analysis of the experimental data shows that the proposed secondary denoising method has a better denoising effect compared to the single denoising method.The EEMD can improve the modal aliasing effect,and the improved fuzzy C-means clustering can effectively identify the abnormal state of the OLTC contacts.The analysis results of field measured data further verify the effectiveness of the proposed method and provide a reference for the abnormal state detection of the OLTC.
