This paper introduces the implementation and data analysis associated with a state-wide power quality monitoring and analysis system in China. Corporation specifications on power quality monitors as well as on communi...This paper introduces the implementation and data analysis associated with a state-wide power quality monitoring and analysis system in China. Corporation specifications on power quality monitors as well as on communication protocols are formulated for data transmission. Big data platform and related technologies are utilized for data storage and computation. Compliance verification analysis and a power quality performance assessment are conducted, and a visualization tool for result presentation is finally presented.展开更多
Hydrogen can serve as a carrier to store renewable energy in large scale.However,hydrogen storage still remains a challenge in the current stage.It is difficult to meet the technical requirements applying the conventi...Hydrogen can serve as a carrier to store renewable energy in large scale.However,hydrogen storage still remains a challenge in the current stage.It is difficult to meet the technical requirements applying the conventional storage of compressed gaseous hydrogen in high-pressure tanks or the solid-state storage of hydrogen in suitable materials.In the present work,a gaseous and solid-state(G-S)hybrid hydrogen storage system with a low working pressure below 5 MPa for a 10 kW hydrogen energy storage experiment platform is developed and validated.A Ti-Mn type hydrogen storage alloy with an effective hydrogen capacity of 1.7 wt%was prepared for the G-S hybrid hydrogen storage system.The G-S hybrid hydrogen storage tank has a high volumetric hydrogen storage density of 40.07 kg H_(2)m^(-3) and stores hydrogen under pressure below5 MPa.It can readily release enough hydrogen at a temperature as low as-15C when the FC system is not fully activated and hot water is not available.The energy storage efficiency of this G-S hybrid hydrogen storage system is calculated to be 86.4%-95.9%when it is combined with an FC system.This work provides a method on how to design a G-S hydrogen storage system based on practical demands and demonstrates that the G-S hybrid hydrogen storage is a promising method for stationary hydrogen storage application.展开更多
The AC/DC hybrid distribution network is one of the trends in distribution network development, which poses great challenges to the traditional distribution transformer. In this paper, a new topology suitable for AC/D...The AC/DC hybrid distribution network is one of the trends in distribution network development, which poses great challenges to the traditional distribution transformer. In this paper, a new topology suitable for AC/DC hybrid distribution network is put forward according to the demands of power grid, with advantages of accepting DG and DC loads, while clearing DC fault by blocking the clamping double sub-module(CDSM) of input stage. Then, this paper shows the typical structure of AC/DC distribution network that is hand in hand. Based on the new topology, this paper designs the control and modulation strategies of each stage, where the outer loop controller of input stage is emphasized for its twocontrol mode. At last, the rationality of new topology and the validity of control strategies are verified by the steady and dynamic state simulation. At the same time, the simulation results highlight the role of PET in energy regulation.展开更多
The DC electrical resistivity-temperature characteristic is an important property for insulating materials to operate at a high stress level.In order to improve the DC electrical resistivity at elevated temperature in...The DC electrical resistivity-temperature characteristic is an important property for insulating materials to operate at a high stress level.In order to improve the DC electrical resistivity at elevated temperature in a targeted way,a positive temperature coefficient(PTC)material(Ba Ti O3-based compound(BT60))was selected as the filler in this paper,whose electrical resistivity has a PTC effect when the temperature exceeds its Curie temperature.The BT60 was treated with hydrogen peroxide and(3-Aminopropyl)triethoxysilane.Epoxy composites with different loadings of BT60 fillers(0 wt%,0.5 wt%,and 2 wt%of epoxy)were prepared,denoted as EP-0,EP-0.5,and EP-2.It was shown that BT60 was able to maintain the DC breakdown strength when its loading was less than 2 wt%of epoxy.As the temperature exceeds 60°C,BT60 will compensate for the negative temperature coefficient effect of epoxy resin to some extent.The electrical resistivity of EP-2 was improved by 55%compared with that of neat epoxy at 90°C.It was found that the potential barrier at the grain boundary of BT60 and the deep traps in the interface between BT60 and the epoxy resin hinder the migration of carriers and thus increase the electrical resistivity of epoxy composite.展开更多
The effect of phosphorus passivation on 4H-SiC（0001） silicon （Si） dangling bonds is investigated using ab initio atomistic thermodynamic calculations. Phosphorus passivation commences with chemisorption of phospho...The effect of phosphorus passivation on 4H-SiC（0001） silicon （Si） dangling bonds is investigated using ab initio atomistic thermodynamic calculations. Phosphorus passivation commences with chemisorption of phosphorus atoms at high-symmetry coordinated sites. To determine the most stable structure during the passivation process of phosphorus, a surface phase diagram of phosphorus adsorption on SiC （0001） surface is constructed over a coverage range of 1/9-1 monolayer （ML）. The calculated results indicate that the 1/3 ML configuration is most energetically favorable in a reasonable environment. At this coverage, the total electron density of states demonstrates that phosphorus may effectively reduce the interface state density near the conduction band by removing 4H-SiC （0001） Si dangling bonds. It provides an atomic level insight into how phosphorus is able to reduce the near interface traps.展开更多
Firstly, relevant stress properties of millisecond level breaking process and microsecond level commutation process of hybrid HVDC circuit breaker are studied in detail on the basis of the analysis for the application...Firstly, relevant stress properties of millisecond level breaking process and microsecond level commutation process of hybrid HVDC circuit breaker are studied in detail on the basis of the analysis for the application environment and topological structure and operating principles of hybrid circuit breakers, and key stress parameters in transient state process of two time dimensions are extracted. The established digital simulation circuit for PSCAD/EMTDC device-level operation of the circuit breaker has verified the stress properties of millisecond level breaking process and microsecond level commutation process. Then, equivalent test method, circuits and parameters based on LC power supply are proposed on the basis of stress extraction. Finally, the results of implemented breaking tests for complete 200 kV circuit breaker, 100 kV and 50 kV circuit breaker units, as well as single power electronic module have verified the accuracy of the simulation circuit and mathematical analysis. The result of this paper can be a guide to electrical structure and test system design of hybrid HVDC circuit breaker.展开更多
Effect of triangle structure defects in a 180-μm-thick as-grown n-type 4H-SiC homoepitaxial layer on the carrier lifetime is quantitatively analyzed, which is grown by a horizontal hot-wall chemical vapor deposition ...Effect of triangle structure defects in a 180-μm-thick as-grown n-type 4H-SiC homoepitaxial layer on the carrier lifetime is quantitatively analyzed, which is grown by a horizontal hot-wall chemical vapor deposition reactor.By microwave photoconductivity decay lifetime measurements and photoluminescence measurements, the results show that the average carrier lifetime of as-grown epilayer across the whole wafer is 2.59μs, while it is no more than 1.34μs near a triangle defect（TD）. The scanning transmission electron microscope results show that the triangle structure defects have originated from 3C-SiC polytype and various types of as-grown stacking faults.Compared with the as-grown stacking faults, the 3C-SiC polytype has a great impact on the lifetime. The reduction of TD is essential to increasing the carrier lifetime of the as-grown thick epilayer.展开更多
The dependence on portable devices and electrical vehicles has triggered the awareness on the energy storage systems with ever-growing energy density.Lithium metal batteries(LMBs)has revived and attracted considerable...The dependence on portable devices and electrical vehicles has triggered the awareness on the energy storage systems with ever-growing energy density.Lithium metal batteries(LMBs)has revived and attracted considerable attention due to its high volumetric(2046 m Ah cm-3),gravimetric specific capacity(3862 m Ah g^(-1))and the lowest reduction potential(-3.04 V vs.SHE.).However,during the electrochemical process of lithium anode,the growth of lithium dendrite constitutes the biggest stumbling block on the road to LMBs application.The undesirable dendrite not only limit the Coulombic efficiency(CE)of LMBs,but also cause thermal runaway and other safety issues due to short-circuits.Understanding the mechanisms of lithium nucleation and dendrite growth provides insights to solve these problems.Herein,we summarize the electrochemical models that inherently describe the lithium nucleation and dendrite growth,such as the thermodynamic,electrodeposition kinetics,internal stress,and interface transmission models.Essential parameters of temperature,current density,internal stress and interfacial Li+flux are focused.To improve the LMBs performance,state-of-the-art optimization procedures have been developed and systematically illustrated with the intrinsic regulation principles for better lithium anode stability,including electrolyte optimization,artificial interface layers,threedimensional hosts,external field,etc.Towards practical applications of LMBs,the current development of pouch cell LMBs have been further introduced with different assembly systems and fading mechanism.However,challenges and obstacles still exist for the development of LMBs,such as in-depth understanding and in-situ observation of dendrite growth,the surface protection under extreme condition and the self-healing of solid electrolyte interface.展开更多
In response to the underutilization of energy and insufficient flexible operation capability of rural energy supply systems in China,this study proposes an optimal dispatch approach for a rural multi-energy supply sys...In response to the underutilization of energy and insufficient flexible operation capability of rural energy supply systems in China,this study proposes an optimal dispatch approach for a rural multi-energy supply system(RMESS)considering virtual energy storage(VES).First,to enable the flexible utilization of rural biomass resources and the thermal inertia of residential building envelopes,this study constructed VES-I and VES-II models that describe electrical-thermal and electrical-gas coupling from an electrical viewpoint.Subsequently,an RMESS model encompassing these two types of VES was formulated.This model delineates the intricate interplay of multi-energy components within the RMESS framework and facilitates the precise assessment of the adjustable potential for optimizing RMESS operations.Based on the above models,a day-ahead optimal dispatch model for an RMESS considering a VES is proposed to achieve optimal economic performance while ensuring efficient energy allocation.Comparative simulations validated the effectiveness of the VES modeling and the day-ahead optimal dispatch approach for the RMESS.展开更多
基金supported by the State Grid Science and Technology Project (GEIRI-DL-71-17-002)
文摘This paper introduces the implementation and data analysis associated with a state-wide power quality monitoring and analysis system in China. Corporation specifications on power quality monitors as well as on communication protocols are formulated for data transmission. Big data platform and related technologies are utilized for data storage and computation. Compliance verification analysis and a power quality performance assessment are conducted, and a visualization tool for result presentation is finally presented.
基金supported by State Grid Corporation of China(No.SGRIDGKJ[2016]123)Education Department of Guangxi Zhuang Autonomous Region(No.2019KY0021)the Natural Science Foundation of Guangxi Province(2019GXNSFBA185004,2018GXNSFAA281308,2019GXNSFAA245050)。
文摘Hydrogen can serve as a carrier to store renewable energy in large scale.However,hydrogen storage still remains a challenge in the current stage.It is difficult to meet the technical requirements applying the conventional storage of compressed gaseous hydrogen in high-pressure tanks or the solid-state storage of hydrogen in suitable materials.In the present work,a gaseous and solid-state(G-S)hybrid hydrogen storage system with a low working pressure below 5 MPa for a 10 kW hydrogen energy storage experiment platform is developed and validated.A Ti-Mn type hydrogen storage alloy with an effective hydrogen capacity of 1.7 wt%was prepared for the G-S hybrid hydrogen storage system.The G-S hybrid hydrogen storage tank has a high volumetric hydrogen storage density of 40.07 kg H_(2)m^(-3) and stores hydrogen under pressure below5 MPa.It can readily release enough hydrogen at a temperature as low as-15C when the FC system is not fully activated and hot water is not available.The energy storage efficiency of this G-S hybrid hydrogen storage system is calculated to be 86.4%-95.9%when it is combined with an FC system.This work provides a method on how to design a G-S hydrogen storage system based on practical demands and demonstrates that the G-S hybrid hydrogen storage is a promising method for stationary hydrogen storage application.
基金supported by National Key Research and Development Program of China (2016YFB0900500,2017YFB0903100)the State Grid Science and Technology Project (SGRI-DL-F1-51-011)
文摘The AC/DC hybrid distribution network is one of the trends in distribution network development, which poses great challenges to the traditional distribution transformer. In this paper, a new topology suitable for AC/DC hybrid distribution network is put forward according to the demands of power grid, with advantages of accepting DG and DC loads, while clearing DC fault by blocking the clamping double sub-module(CDSM) of input stage. Then, this paper shows the typical structure of AC/DC distribution network that is hand in hand. Based on the new topology, this paper designs the control and modulation strategies of each stage, where the outer loop controller of input stage is emphasized for its twocontrol mode. At last, the rationality of new topology and the validity of control strategies are verified by the steady and dynamic state simulation. At the same time, the simulation results highlight the role of PET in energy regulation.
基金support from National Natural Science Foundation of China(No.51977186)the China Postdoctoral Science Foundation(No.2019M650029)+3 种基金the Young Elite Scientists Sponsorship Program by CAST(No.2018QNRC001)the National Key R&D Program of China(No.2017YFB0902704)the State Key Development Program of Basic Research of China(973 Program)(No.2014CB239501)the Science and Technology Project of the State Grid Corp.of China(No.52110418001Y).
文摘The DC electrical resistivity-temperature characteristic is an important property for insulating materials to operate at a high stress level.In order to improve the DC electrical resistivity at elevated temperature in a targeted way,a positive temperature coefficient(PTC)material(Ba Ti O3-based compound(BT60))was selected as the filler in this paper,whose electrical resistivity has a PTC effect when the temperature exceeds its Curie temperature.The BT60 was treated with hydrogen peroxide and(3-Aminopropyl)triethoxysilane.Epoxy composites with different loadings of BT60 fillers(0 wt%,0.5 wt%,and 2 wt%of epoxy)were prepared,denoted as EP-0,EP-0.5,and EP-2.It was shown that BT60 was able to maintain the DC breakdown strength when its loading was less than 2 wt%of epoxy.As the temperature exceeds 60°C,BT60 will compensate for the negative temperature coefficient effect of epoxy resin to some extent.The electrical resistivity of EP-2 was improved by 55%compared with that of neat epoxy at 90°C.It was found that the potential barrier at the grain boundary of BT60 and the deep traps in the interface between BT60 and the epoxy resin hinder the migration of carriers and thus increase the electrical resistivity of epoxy composite.
基金Project supported by the National High Technology Research and Development Program of China(Grant No.2014AA052401)the National Natural Science Foundation of China(Grant No.61474013)the National Grid Science&Technology Project,China(Grant No.5455DW150006)
文摘The effect of phosphorus passivation on 4H-SiC（0001） silicon （Si） dangling bonds is investigated using ab initio atomistic thermodynamic calculations. Phosphorus passivation commences with chemisorption of phosphorus atoms at high-symmetry coordinated sites. To determine the most stable structure during the passivation process of phosphorus, a surface phase diagram of phosphorus adsorption on SiC （0001） surface is constructed over a coverage range of 1/9-1 monolayer （ML）. The calculated results indicate that the 1/3 ML configuration is most energetically favorable in a reasonable environment. At this coverage, the total electron density of states demonstrates that phosphorus may effectively reduce the interface state density near the conduction band by removing 4H-SiC （0001） Si dangling bonds. It provides an atomic level insight into how phosphorus is able to reduce the near interface traps.
基金supported by SGCC Scientific and Technological Project(52110116004W)
文摘Firstly, relevant stress properties of millisecond level breaking process and microsecond level commutation process of hybrid HVDC circuit breaker are studied in detail on the basis of the analysis for the application environment and topological structure and operating principles of hybrid circuit breakers, and key stress parameters in transient state process of two time dimensions are extracted. The established digital simulation circuit for PSCAD/EMTDC device-level operation of the circuit breaker has verified the stress properties of millisecond level breaking process and microsecond level commutation process. Then, equivalent test method, circuits and parameters based on LC power supply are proposed on the basis of stress extraction. Finally, the results of implemented breaking tests for complete 200 kV circuit breaker, 100 kV and 50 kV circuit breaker units, as well as single power electronic module have verified the accuracy of the simulation circuit and mathematical analysis. The result of this paper can be a guide to electrical structure and test system design of hybrid HVDC circuit breaker.
基金Supported by the National Key Research and Development Program of China under Grant No 2016YFB0400500
文摘Effect of triangle structure defects in a 180-μm-thick as-grown n-type 4H-SiC homoepitaxial layer on the carrier lifetime is quantitatively analyzed, which is grown by a horizontal hot-wall chemical vapor deposition reactor.By microwave photoconductivity decay lifetime measurements and photoluminescence measurements, the results show that the average carrier lifetime of as-grown epilayer across the whole wafer is 2.59μs, while it is no more than 1.34μs near a triangle defect（TD）. The scanning transmission electron microscope results show that the triangle structure defects have originated from 3C-SiC polytype and various types of as-grown stacking faults.Compared with the as-grown stacking faults, the 3C-SiC polytype has a great impact on the lifetime. The reduction of TD is essential to increasing the carrier lifetime of the as-grown thick epilayer.
基金supported by the National Natural Science Foundation of China(51804290,22075025)the Beijing Natural Science Foundation(L182023)+1 种基金the Science and Technology Project of Global Energy Interconnection Research Institute Co.Ltd.(SGGR0000WLJS1900858)the Beijing Institute of Technology Research Fund Program for Young Scholars(2019CX04092)。
文摘The dependence on portable devices and electrical vehicles has triggered the awareness on the energy storage systems with ever-growing energy density.Lithium metal batteries(LMBs)has revived and attracted considerable attention due to its high volumetric(2046 m Ah cm-3),gravimetric specific capacity(3862 m Ah g^(-1))and the lowest reduction potential(-3.04 V vs.SHE.).However,during the electrochemical process of lithium anode,the growth of lithium dendrite constitutes the biggest stumbling block on the road to LMBs application.The undesirable dendrite not only limit the Coulombic efficiency(CE)of LMBs,but also cause thermal runaway and other safety issues due to short-circuits.Understanding the mechanisms of lithium nucleation and dendrite growth provides insights to solve these problems.Herein,we summarize the electrochemical models that inherently describe the lithium nucleation and dendrite growth,such as the thermodynamic,electrodeposition kinetics,internal stress,and interface transmission models.Essential parameters of temperature,current density,internal stress and interfacial Li+flux are focused.To improve the LMBs performance,state-of-the-art optimization procedures have been developed and systematically illustrated with the intrinsic regulation principles for better lithium anode stability,including electrolyte optimization,artificial interface layers,threedimensional hosts,external field,etc.Towards practical applications of LMBs,the current development of pouch cell LMBs have been further introduced with different assembly systems and fading mechanism.However,challenges and obstacles still exist for the development of LMBs,such as in-depth understanding and in-situ observation of dendrite growth,the surface protection under extreme condition and the self-healing of solid electrolyte interface.
基金supported by Science and Technology Project of SGCC(5108-202218280A-2-375-XG)。
文摘In response to the underutilization of energy and insufficient flexible operation capability of rural energy supply systems in China,this study proposes an optimal dispatch approach for a rural multi-energy supply system(RMESS)considering virtual energy storage(VES).First,to enable the flexible utilization of rural biomass resources and the thermal inertia of residential building envelopes,this study constructed VES-I and VES-II models that describe electrical-thermal and electrical-gas coupling from an electrical viewpoint.Subsequently,an RMESS model encompassing these two types of VES was formulated.This model delineates the intricate interplay of multi-energy components within the RMESS framework and facilitates the precise assessment of the adjustable potential for optimizing RMESS operations.Based on the above models,a day-ahead optimal dispatch model for an RMESS considering a VES is proposed to achieve optimal economic performance while ensuring efficient energy allocation.Comparative simulations validated the effectiveness of the VES modeling and the day-ahead optimal dispatch approach for the RMESS.
