At present,smart substations use the IEC61850 standard based on the architectural framework of three layers and two networks to realize information digitization and advanced applications.Although the smart substation ...At present,smart substations use the IEC61850 standard based on the architectural framework of three layers and two networks to realize information digitization and advanced applications.Although the smart substation offers many improvements in design,equipment manufacturing,and construction,the intelligent devices used in smart substations are costly,and are also difficult to maintain since they are dispersed within a single unit.Functionality optimization and device integration,thus,have become important issues in smart substation development.This paper presents an integrated solution and implementation process for a smart substation system.In the process layer,an integrated intelligence component is developed that functions both as an intelligent terminal and a merging unit.In the bay layer,an integrated station-area protection measurement and control master device is designed to achieve such functions as protection,monitoring,control,fault recorder,and power quality monitoring.Finally,in the station control layer,an integrated information platform is established to bring together various system functions and to promote interactive sharing.Integration technology improves the economy and practicality of the smart substation,especially in a distribution power grid.展开更多
Iron(Fe)is an important element for the terrestrial and marine ecosystems through its biogeochemical cycling on the Earth’s surface.China has a long rice cultivation history,with extensive rice distribution across ma...Iron(Fe)is an important element for the terrestrial and marine ecosystems through its biogeochemical cycling on the Earth’s surface.China has a long rice cultivation history,with extensive rice distribution across many types of paddy soils.Paddy soils are the largest anthropogenic wetlands on earth with critical roles in ecosystem functions.The periodic artificial submergence and drainage during paddy soil evolution result in significant changes in soil moisture regime and redox conditions from the natural soils,which facilitate the increase of Fe solubility and mobilization.However,there is a lack of systematic assessment on the magnitude of the migration and loss amount of Fe from paddy soils.In order to quantify the Fe loss and assess the dynamic evolution of Fe in the soils after rice cultivation,seven paddy soil chronosequences derived from different landscapes(bog,plain,terrace)and parent materials(acidic,neutral,calcareous)with cultivation history from 0 to 2,000 yr were studied.Results showed that the rates and trajectories of Fe evolution showed distinct patterns among the studied seven paddy soil chronosequences.However,net losses of Fe from 1 m soil depth occurred at all studied paddy soil chronosequences regardless of the original landscapes and parent materials.Fe in the paddy soils derived from the calcareous lacustrine sediments in the bog area showed a slight accumulation during the initial stage(50 yr)of paddy cultivation,with a loss rate of0.026 kg m^(-2)yr^(-1) during the 50-to 500-yr time period.For the paddy soils developed on the calcareous marine sediments in the plain area,Fe evolution was dominated by the internal movement in soil profiles through coupled reducing-eluviation reactions in the surface horizons and oxidation-illuviation in the subsurface horizons within 1,000 yr of paddy cultivation,with an averaged net loss rate of 0.029 kg m^(-2)yr^(-1) during the 1,000-to 2,000-yr time period of rice cultivation.In contrast,Fe in the paddy soils derived from the acidic and neutral parent materials in the plain and terraced upland areas was rapidly lost during the initial stage of paddy cultivation,with a maximum loss rate of 1.106 kg m^(-2)yr^(-1),while the Fe loss rate decreased gradually with increasing paddy cultivation age.Soil pH,CaCO_(3),and organic matter contents of the original soils,the length of time of paddy cultivation,landscape types and positions,and changes in soil moisture regime and redox condition induced by artificial submergence and drainage were the main factors controlling the rates and trajectories of Fe loss during paddy soils evolution.The amount of Fe loss caused by rice cultivation at the national scale was estimated based on the data collected from this study and the literature.The Fe loss fluxes of paddy soils in China were about 46.4–195.7 Tg yr^(-1),and the amounts of Fe losses from paddy fields nationwide were about 5,121.5–9,412.2 Tg.Quantifying Fe loss from paddy fields is important to scientifically assess the impact of paddy cultivation on the Fe biogeochemical cycle.展开更多
As indispensable strategic materials for high-tech industries,rare earth elements and yttrium(REY)have become particularly important in recent years,raising the demand of developing new approaches for reclamation of R...As indispensable strategic materials for high-tech industries,rare earth elements and yttrium(REY)have become particularly important in recent years,raising the demand of developing new approaches for reclamation of REY from REY-rich materials such as coal combustion products(CCPs).In this study,five coal-fired power plants(CFPPs)in Guizhou of southwest China were selected for investigating REY concentrations of solid samples,atmospheric emissions,and recovery potentials.REY concentrations of feed fuels are higher in this study(147.2-468.6 mg/kg)than what have been reported previously for coals in China and the world.REY atmospheric emissions are extremely low(38.70-180.11 mg REY/t coal).REY are enriched in bottom ash and fly ash,with average of 658±296 mg/kg and maximum of 1257 mg/kg from the five CFPPs.Relative enrichment factors(REF)of REY in bottom ash and fly ash compared with the feed fuel are 0.86-1.02 and 0.91-1.04,respectively.REY concentrations in desulfurized gypsum are very low(6-17 mg/kg),and that is mostly inherited from limestone.Critical REY(Nd,Eu,Tb,Dy,Y,and Er)in bottom/fly ash account for 34%-39%of the total REY and the outlook coefficients(Cout1)are in the range of 0.89-1.11.This study indicates a promising prospect to reclaim REY from REYrich CCPs(bottom and fly ash)in CFPPs in Guizhou,especially in the central-north Guizhou,although such practices require further technology advancement.展开更多
In this paper,an improved active stabilization strategy of the interface converters in microgrid applications is proposed on the basis of the passivity-based stability criterion(PBSC).As a critical part of AC and DC h...In this paper,an improved active stabilization strategy of the interface converters in microgrid applications is proposed on the basis of the passivity-based stability criterion(PBSC).As a critical part of AC and DC hybrid microgrids,the DC microgrid is taken as an example.In particular,a stabilization method with a proportional-integral(PI)controller and firstorder high-pass filter(HPF)is proposed to meet the passivity requirements of the overall control diagram with respect to the output voltage.Meanwhile,an output current feedback control loop is introduced to ensure the output impedance passivity.Moreover,a small-signal model of the parallel interface converter system is established to comprehensively study the influence of control parameters on the passivity of the converters.Based on the active stabilization method proposed in this study,by manipulating the control diagram of each interface converter,the passivity and stability of the DC microgrids with variable configuration can be guaranteed.Therefore,a generic and simplified design approach is realized.A simulation model with three interface converters is implemented in MATLAB/Simulink,and the effectiveness of the proposed passivity-based active stabilization algorithm is verified by using this simulation model.展开更多
基金supported in part by the research program of State Grid Corporation of China under Grant PD71-15-036.
文摘At present,smart substations use the IEC61850 standard based on the architectural framework of three layers and two networks to realize information digitization and advanced applications.Although the smart substation offers many improvements in design,equipment manufacturing,and construction,the intelligent devices used in smart substations are costly,and are also difficult to maintain since they are dispersed within a single unit.Functionality optimization and device integration,thus,have become important issues in smart substation development.This paper presents an integrated solution and implementation process for a smart substation system.In the process layer,an integrated intelligence component is developed that functions both as an intelligent terminal and a merging unit.In the bay layer,an integrated station-area protection measurement and control master device is designed to achieve such functions as protection,monitoring,control,fault recorder,and power quality monitoring.Finally,in the station control layer,an integrated information platform is established to bring together various system functions and to promote interactive sharing.Integration technology improves the economy and practicality of the smart substation,especially in a distribution power grid.
基金supported by the National Natural Science Foundation of China(Grant Nos.41967001&41401238)State Key Laboratory of Soil and Sustainable Agriculture,Institute of Soil Science,Chinese Academy of Sciences(Grant No.Y20160001)Science and Technology Project of Guizhou Province(Grant No.Qian Ke He[2017]1209)。
文摘Iron(Fe)is an important element for the terrestrial and marine ecosystems through its biogeochemical cycling on the Earth’s surface.China has a long rice cultivation history,with extensive rice distribution across many types of paddy soils.Paddy soils are the largest anthropogenic wetlands on earth with critical roles in ecosystem functions.The periodic artificial submergence and drainage during paddy soil evolution result in significant changes in soil moisture regime and redox conditions from the natural soils,which facilitate the increase of Fe solubility and mobilization.However,there is a lack of systematic assessment on the magnitude of the migration and loss amount of Fe from paddy soils.In order to quantify the Fe loss and assess the dynamic evolution of Fe in the soils after rice cultivation,seven paddy soil chronosequences derived from different landscapes(bog,plain,terrace)and parent materials(acidic,neutral,calcareous)with cultivation history from 0 to 2,000 yr were studied.Results showed that the rates and trajectories of Fe evolution showed distinct patterns among the studied seven paddy soil chronosequences.However,net losses of Fe from 1 m soil depth occurred at all studied paddy soil chronosequences regardless of the original landscapes and parent materials.Fe in the paddy soils derived from the calcareous lacustrine sediments in the bog area showed a slight accumulation during the initial stage(50 yr)of paddy cultivation,with a loss rate of0.026 kg m^(-2)yr^(-1) during the 50-to 500-yr time period.For the paddy soils developed on the calcareous marine sediments in the plain area,Fe evolution was dominated by the internal movement in soil profiles through coupled reducing-eluviation reactions in the surface horizons and oxidation-illuviation in the subsurface horizons within 1,000 yr of paddy cultivation,with an averaged net loss rate of 0.029 kg m^(-2)yr^(-1) during the 1,000-to 2,000-yr time period of rice cultivation.In contrast,Fe in the paddy soils derived from the acidic and neutral parent materials in the plain and terraced upland areas was rapidly lost during the initial stage of paddy cultivation,with a maximum loss rate of 1.106 kg m^(-2)yr^(-1),while the Fe loss rate decreased gradually with increasing paddy cultivation age.Soil pH,CaCO_(3),and organic matter contents of the original soils,the length of time of paddy cultivation,landscape types and positions,and changes in soil moisture regime and redox condition induced by artificial submergence and drainage were the main factors controlling the rates and trajectories of Fe loss during paddy soils evolution.The amount of Fe loss caused by rice cultivation at the national scale was estimated based on the data collected from this study and the literature.The Fe loss fluxes of paddy soils in China were about 46.4–195.7 Tg yr^(-1),and the amounts of Fe losses from paddy fields nationwide were about 5,121.5–9,412.2 Tg.Quantifying Fe loss from paddy fields is important to scientifically assess the impact of paddy cultivation on the Fe biogeochemical cycle.
基金Project supported by the K.C.Wong Education FoundationNational Natural Science Foundation of China(U1612442)+3 种基金Key Grant for Creative Research Groups of Guizhou Provincial Education Department(Qian-Jiao-He KY Zi2016047)Young Scientific Talents Growth Project of Guizhou Provincial Education Department(Qian-Jiao-He KY Zi 2016252)Doctoralof Zunyi Normal University(Zun-Shi BS 201815)Science and Technology Project of Guizhou Provincial Science and Technology Department(Qian-Ke-He-Ping-Tai-RenCai 20175727-07)。
文摘As indispensable strategic materials for high-tech industries,rare earth elements and yttrium(REY)have become particularly important in recent years,raising the demand of developing new approaches for reclamation of REY from REY-rich materials such as coal combustion products(CCPs).In this study,five coal-fired power plants(CFPPs)in Guizhou of southwest China were selected for investigating REY concentrations of solid samples,atmospheric emissions,and recovery potentials.REY concentrations of feed fuels are higher in this study(147.2-468.6 mg/kg)than what have been reported previously for coals in China and the world.REY atmospheric emissions are extremely low(38.70-180.11 mg REY/t coal).REY are enriched in bottom ash and fly ash,with average of 658±296 mg/kg and maximum of 1257 mg/kg from the five CFPPs.Relative enrichment factors(REF)of REY in bottom ash and fly ash compared with the feed fuel are 0.86-1.02 and 0.91-1.04,respectively.REY concentrations in desulfurized gypsum are very low(6-17 mg/kg),and that is mostly inherited from limestone.Critical REY(Nd,Eu,Tb,Dy,Y,and Er)in bottom/fly ash account for 34%-39%of the total REY and the outlook coefficients(Cout1)are in the range of 0.89-1.11.This study indicates a promising prospect to reclaim REY from REYrich CCPs(bottom and fly ash)in CFPPs in Guizhou,especially in the central-north Guizhou,although such practices require further technology advancement.
基金This work was supported in part by the National Natural Science Foundation of China(Nos.51137003,61233008 and 51520105011)and in part by the Special Project of International Scientific and Technological Cooperation of China(No.2015DFR70850).
文摘In this paper,an improved active stabilization strategy of the interface converters in microgrid applications is proposed on the basis of the passivity-based stability criterion(PBSC).As a critical part of AC and DC hybrid microgrids,the DC microgrid is taken as an example.In particular,a stabilization method with a proportional-integral(PI)controller and firstorder high-pass filter(HPF)is proposed to meet the passivity requirements of the overall control diagram with respect to the output voltage.Meanwhile,an output current feedback control loop is introduced to ensure the output impedance passivity.Moreover,a small-signal model of the parallel interface converter system is established to comprehensively study the influence of control parameters on the passivity of the converters.Based on the active stabilization method proposed in this study,by manipulating the control diagram of each interface converter,the passivity and stability of the DC microgrids with variable configuration can be guaranteed.Therefore,a generic and simplified design approach is realized.A simulation model with three interface converters is implemented in MATLAB/Simulink,and the effectiveness of the proposed passivity-based active stabilization algorithm is verified by using this simulation model.