From the perspective of a community energy operator,a two-stage optimal scheduling model of a community integrated energy system is proposed by integrating information on controllable loads.The day-ahead scheduling an...From the perspective of a community energy operator,a two-stage optimal scheduling model of a community integrated energy system is proposed by integrating information on controllable loads.The day-ahead scheduling analyzes whether various controllable loads participate in the optimization and investigates the impact of their responses on the operating economy of the community integrated energy system(IES)before and after;the intra-day scheduling proposes a two-stage rolling optimization model based on the day-ahead scheduling scheme,taking into account the fluctuation of wind turbine output and load within a short period of time and according to the different response rates of heat and cooling power,and solves the adjusted output of each controllable device.The simulation results show that the optimal scheduling of controllable loads effectively reduces the comprehensive operating costs of community IES;the two-stage optimal scheduling model can meet the energy demand of customers while effectively and timely suppressing the random fluctuations on both sides of the source and load during the intra-day stage,realizing the economic and smooth operation of IES.展开更多
Microseismic(MS)events generated during coal and rock hydraulic fracturing(HF)include wet events caused by fracturing fuid injection,in addition to dry events caused by stress perturbations.The mixture of these two ev...Microseismic(MS)events generated during coal and rock hydraulic fracturing(HF)include wet events caused by fracturing fuid injection,in addition to dry events caused by stress perturbations.The mixture of these two events makes efective fracturing MS events pickup difcult.This study is based on physical experiments of diferent coal and rock HF and uniaxial compression.The diferences of waveform characteristic parameters of various coal and rock ruptures were analyzed using the Hilbert–Huang transform,leading to some useful conclusions.The phase characteristics of the acoustic emission(AE)energy difered signifcantly and responded well to the pumping pressure curve.The AE waveforms of HF exhibit similar energy and frequency distribution characteristics after Empirical mode decomposition.The main frequency bands for coal,sandstone,and shale samples are 100–300 kHz,while the mudstone sample is in the range of 50–150 kHz.The decay ratios for coal,sandstone,shale and mudstone samples are 0.78,0.83,0.67 and 0.85,respectively.When compared to the uniaxial compression test,the main frequency bands of HF were reduced for coal,sandstone and mudstone samples,whereas shale remained essentially unchanged.The duration,instantaneous energy,and total energy of the HF waveform are smaller than those of uniaxial compression,while the decay ratio is greater,especially for the mudstone samples.The waveform characteristic parameters,trained using the multilayer perceptron neural network,can efectively identify HF and uniaxial compression events with an accuracy of 96%.展开更多
As an effective carrier of integrated clean energy,the microgrid has attracted wide attention.The randomness of renewable energies such as wind and solar power output brings a significant cost and impact on the econom...As an effective carrier of integrated clean energy,the microgrid has attracted wide attention.The randomness of renewable energies such as wind and solar power output brings a significant cost and impact on the economics and reliability of microgrids.This paper proposes an optimization scheme based on the distributionally robust optimization(DRO)model for a microgrid considering solar-wind correlation.Firstly,scenarios of wind and solar power output scenarios are generated based on non-parametric kernel density estimation and the Frank-Copula function;then the generated scenario results are reduced by K-means clustering;finally,the probability confidence interval of scenario distribution is constrained by 1-norm and∞-norm.The model is solved by a column-and-constraint generation algorithm.Experimental studies are conducted on a microgrid system in Jiangsu,China and the obtained scheduling solution turned out to be superior under wind and solar power uncertainties,which verifies the effectiveness of the proposed DRO model.展开更多
In the context of the joint operation of China’s intra-provincial markets and inter-provincial trading,how to meet the load demand and energy consumption using inter-provincial renewable energy trading is a key probl...In the context of the joint operation of China’s intra-provincial markets and inter-provincial trading,how to meet the load demand and energy consumption using inter-provincial renewable energy trading is a key problem.The combined operation of intra-provincial and inter-provincial markets provides a new way for provincial power companies to optimize and clear the intra-provincial power market,complete the intra-provincial consumption responsibility weight index,and consume renewable energy across provinces and regions.This paper combines power generation and consumption within the province,uses inter-provincial renewable energy trading tomeet the load demand within the province and completes the index of intra-provincial consumption responsibility weights.The intra-provincial market trading and inter-provincial market clearing are respectively taken as the upper and lower levels of the model.Under the two-level electricity market operation framework,the upper-level model aims to minimize the expected total operating cost within the province considering the carbon emission cost and the weight of the consumption responsibility,while the lower-level model aims to minimize the inter-provincial renewable energy purchasing cost.Finally,the influence of inter-provincial transaction mechanism,risk aversion coefficient,voucher price,and responsibility weight on operating cost is analyzed.Simulation is used to verify that the proposed model can meet the requirements of the provincial load power consumption and the consumption responsibility weight index,and promote the consumption of renewable energy.展开更多
Aiming at the current limit value of six steady-state energy indexes, the current radar method is used for reference. A method of comprehensive evaluation of power quality based on improved radar method is proposed, w...Aiming at the current limit value of six steady-state energy indexes, the current radar method is used for reference. A method of comprehensive evaluation of power quality based on improved radar method is proposed, which improves the power quality index Type radar pattern to represent the steady-state indicator. Each of the main indicators corresponds to a partial ring, and the angle of the annular portion is mainly affected by the size of the weight. Compared with the previous radar map method to maintain the independence of the indicators and a single indicator of the binding data assessment. The method has the advantages of good feasibility.展开更多
This paper studies the mixed radial-angular integrability of parametric Marcinkiewicz integrals along"polynomial curves".Under the assumption that the kernels satisfy certain rather weak size conditions on t...This paper studies the mixed radial-angular integrability of parametric Marcinkiewicz integrals along"polynomial curves".Under the assumption that the kernels satisfy certain rather weak size conditions on the unit sphere with radial roughness,the authors prove that such operators are bounded on the mixed radial-angular spaces.Meanwhile,corresponding vector-valued versions are also obtained.展开更多
Frequency is an important indicator for the oper-ation of microgrids.However,the randomness and uncertainty of renewable energy and load variability may lead to frequency undulation.So,a robust load frequency control(...Frequency is an important indicator for the oper-ation of microgrids.However,the randomness and uncertainty of renewable energy and load variability may lead to frequency undulation.So,a robust load frequency control(LFC)is pro-posed for isolated wind-diesel microgrids considering time delay and parameter uncertainty.The control strategy can suppress frequency fuctuation and optimize frequency dynamic response.First,the double compensation loop,including feedforward control and integral sliding mode control(SMC),is devised to provide anti-disturbance compensation for the diesel generator system and ameliorate the frequency stability of independent microgrids.Secondly,a dynamic fuzzy controller,composed of wind speed and load demand,is designed to provide real-time response reference power for doubly fed induction generator systems(DFIGs),which can promote the effective participation of a wind turbine system for frequency regulation.Then,the proportional differential(PD)parameters of a dynamic fuzzy controller and the frequency adjustment compensation of DFIGs can be obtained by using a particle swarm optimization(PSO)algorithm.Thirdly,load demand is an important index of the robust dynamic load frequency control method;the radial basis function(RBF)neural network observer(NNO)based on the LFC model is presented to obtain more accurate load deviations and improve the control precision of LFC.The performance of the proposed LFC method is tested under different operation cases.Index Terms-Load frequency control,microgrid,neural network observer,sliding mode,time delay and parameter uncertainty.展开更多
Red phosphor,with longer wavelength,is highly desirable for full-spectrum WLEDs.Targeted deep red phosphors(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)were designed from the initial model of SrLiAl_(3)N_(4):Eu^(2+)by structural ...Red phosphor,with longer wavelength,is highly desirable for full-spectrum WLEDs.Targeted deep red phosphors(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)were designed from the initial model of SrLiAl_(3)N_(4):Eu^(2+)by structural modification.The correlations among structural evolution,crystal-field environment,and luminescence properties were elucidated.Replacing Sr^(2+)with Gd^(3+)in(Sr,Gd)LiAl_(3)N_(4):Eu^(2+)leads to the enhanced crystal field splitting,larger Stokes shift,and increased structural polyhedron distortion differences,consequently resulting in spectral red-shift and broadening.For further spectral tuning,Mg,with lower electronegativity,was also introduced to modify the local crystal structure,consequently resulting in a further red-shift towards 675 nm and enhanced photoluminescence intensity in(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+).What’s more,w-LEDs were fabricated by using blue LED chip,blue,green,red and deep red((Sr,Gd)Li(Al,Mg)_(3)N_(4):Eu^(2+))phosphors whose color rendering index were Ra 96.0 and R997.7.All above results demonstrate that the partial replacements of Sr^(2+)by Gd^(3+)and Al^(3+)by Mg^(2+)are effective methods for spectral modulation and(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)phosphors are suitable for highquality full-spectrum WLEDs.展开更多
A series of high phase purity blue light excitable yellow-emitting La_(3-x)Si_6 N_(11):xCe^(3+) phosphors were synthesized by the high temperature solid state reactions method. The structure and luminescent properties...A series of high phase purity blue light excitable yellow-emitting La_(3-x)Si_6 N_(11):xCe^(3+) phosphors were synthesized by the high temperature solid state reactions method. The structure and luminescent properties were investigated. The phase structure was studied by means of X-ray diffraction, structures refinements and energy dispersive X-ray spectroscopy. The phosphors effectively excited by the light of450 nm and show intense yellow emission at 535 nm with FWHM of 115 nm corresponding to the5 d →~2 F_(5/2) and 5 d →~2 F_(7/2) transitions of Ce^(3+). In addition,the optimized La_(2.86)Si_6 N_(11):0.14 Ce^(3+) exhibits a weak thermal quenching, which remains 98.2% of the initial emission intensity when heated to 200 ℃,the thermal quenching properties exhibit a modest decline when the temperature returned to room temperature. The above results indicate that La_3 Si_6 N_(11):Ce^(3+) can be regarded as a high promising phosphor for applications in high power white-light LED.展开更多
A novel white-light emitting single-phase phosphor La_3 Si_6 N_(11):Dy^(3+),exhibiting two emission peaks centering at 475 and 575 nm, was prepared via conventional solid-state reactions. The structure and morphology ...A novel white-light emitting single-phase phosphor La_3 Si_6 N_(11):Dy^(3+),exhibiting two emission peaks centering at 475 and 575 nm, was prepared via conventional solid-state reactions. The structure and morphology of La_3 Si_6 N_(11):Dy^(3+)/Tb^(3+) were investigated by X-ray diffraction(XRD) and scanning electron microscopy(SEM). The emission colors can be tuned from white to yellow-green through increasing the Tb^(3+) concentration in La_3 Si_6 N_(11):Dy^(3+),Tb^(3+), The mechanism of energy transfer(ET) from Dy^(3+) to Tb^(3+) is confirmed according to the excitation,emission spectra and decay lifetimes curve. The temperaturedependent luminescence measurements of La_(2.83)Si_6 N_(11):0.1 Dy^(3+),0.07 Tb^(3+) were also performed, and a good thermal stability is shown, suggesting superior properties for the application as white lightemitting diodes(w-LEDs) phosphor.展开更多
Broadband near-infrared phosphors are highly desirable for food testing.Targeted Ca_(2)LuHf_(2)Al_(3)O_(12):Cr^(3+)(CLHA:Cr^(3+)) and Ca_(2)LuHf_(2)Al_(3)O_(12):Ce^(3+),Cr^(3+)(CLHA:Ce^(3+),Cr^(^(3+))) phosphors were ...Broadband near-infrared phosphors are highly desirable for food testing.Targeted Ca_(2)LuHf_(2)Al_(3)O_(12):Cr^(3+)(CLHA:Cr^(3+)) and Ca_(2)LuHf_(2)Al_(3)O_(12):Ce^(3+),Cr^(3+)(CLHA:Ce^(3+),Cr^(^(3+))) phosphors were synthesized by the conventional high-temperature solid state reaction.The CLHA:Cr^(3+)phosphor,with a good thermal stability,shows a red shift owing to radiation reabsorption and non-radiative transition with increasing Cr^(3+)content.For co-doped sample,the emission intensity of Cr^(3+)can be enhanced by three times due to the energy transfer from Ce^(3+)to Cr^(3+),which can be evidenced by a significant overlap between the PLE of Cr^(3+)single-doped phosphor and the PL of Ce^(3+)single-doped phosphor.In addition,the mechanism of energy transfer is identified as a quadrupole-quadrupole interaction according to decay Lifetime and Dexter’s energy transfer formula.The broadband NIR emission peaked at 775 nm of CLHA:Cr^(3+),Ce^(3+)phosphor shows a bright prospect in nondestructive quality-control analysis systems for food.展开更多
Wide color gamut(WCG) backlight for liquid crystal display(LCD) utilizing white light-emitting diodes(LED) has attracted considerable attention for their high efficiency and color reduction.In this review,recent devel...Wide color gamut(WCG) backlight for liquid crystal display(LCD) utilizing white light-emitting diodes(LED) has attracted considerable attention for their high efficiency and color reduction.In this review,recent developments in crystal structure,luminescence and applications of phosphors for wide color gamut LED backlight are introduced.As novel red phosphors,Mn4+activate fluoride and aluminate phosphors are advanced in quantum efficiency,thermal quenching and color saturation for their characteristic spectrum with broad excitation band and linear emission.The crystal structure and fluorescence properties of Mn4+doped fluosilicate,fluorogermanate,fluotitanate,as well as Sr4 Al14O25,CaAl12O19 and BaMgAl10O17 phosphors are discussed in detail.A serial of narrow-band red-emitting Eu2+,Eu3+and Pr3+-doped nitride silicates and molybdate phosphors are also introduced.Rare-earth-doped oxynitride and silicate green-emitting phosphors have attracted more and more attention because of the wide excitation,narrow emission,high quenching temperature,high quantum efficiency,such as β-sialon:Eu2+,Ba3Si6O12N2:Eu2+,MSi2O2N2:Eu2+(M=Ca,Sr,Ba),y-AlON:Mn2+and Ca3Sc2Si3O12:Ce3+.All above phosphors demonstrate their adaptability in wide color gamut LCD display.Especially for Mn4+doped fluosilicate red phosphor and β-sialon:Eu2+green phosphor.To achieve an ultra-high color gamut in white LED backlight and against the OLED,innovative narrow-band-emission red and green phosphor materials with independent intellectual property rights are continuously pursed.展开更多
Eu^(2+) activated BaSi_2 O_2 N_2 oxynitride bluish-green phosphor was synthesized adopting conventional high-temperature solid-state reaction method, in which BaF_2, Na_2 CO_3 and NH_4 Cl were used as the fluxes.The p...Eu^(2+) activated BaSi_2 O_2 N_2 oxynitride bluish-green phosphor was synthesized adopting conventional high-temperature solid-state reaction method, in which BaF_2, Na_2 CO_3 and NH_4 Cl were used as the fluxes.The phase formation, size distribution and microscopic morphology were characterized to investigate the influence of adding fluxes on photo luminescence properties. The results indicate that with the addition of BaF_2 flux, the particle morphology becomes regular and size distribution narrows and the phase purity of BaSi_2 O_2 N_2:Eu^(2+) phosphor can be improved effectively. The photoluminescence intensity of BaSi_2 O_2 N_2:Eu^(2+) phosphor with BaF_2 as flux gets enhanced obviously, which is much higher than that of Na_2 CO_3, NH_4 Cl and without flux. The optimum content of BaF2 flux is 4 wt%, and the maximum photoluminescence intensity of the BaSi_2 O_2 N_2:Eu^(2+) phosphor prepared with BaF_2 flux rises to 141%,meanwhile, the phosphors with BaF_2 flux exhibits low thermal quenching. The results indicate that the BaSi_2 O_2 N_2:Eu^(2+) is sort of promising bluish-green phosphor for application in full-spectra LED.展开更多
Y_3 Al_5 O_(12):Ce3+ is the most famous phosphor material due to its excellent photolumincent properties.Here,through first-principles calculation,the effect of carbon interstitial defects on Y_3 Al_5 O_(12):Ce3+phosp...Y_3 Al_5 O_(12):Ce3+ is the most famous phosphor material due to its excellent photolumincent properties.Here,through first-principles calculation,the effect of carbon interstitial defects on Y_3 Al_5 O_(12):Ce3+phosphor was investigated. It is found that the carbon interstitials tend to occupy the next-nearest sites of Ce^(3+) ion in Y_3 Al_5 O_(12):Ce3+ lattice. Specially,these interstitial defects can shorten the Ce3+-O^(2-) bond length, leading to a larger crystal field splitting of 5 d orbital of the Ce^(3+) atom and bigger 5 d centroid shift.These two factors cause the emission spectrum of Y_3 Al_5 O_(12)(C):Ce^(3+) red shift compared with that of Y_3 Al_5 O_(12):Ce3+. Moreover, with our comparison experiment, we find that the Y_3 Al_5 O_(12)(C):Ce3+ has an obvious red shift compared with that of Y_3 Al_5 O_(12):Ce^(3+) system,which is in accord with our first principles calculation. Our work systematically investigates the impact of the carbon interstitial defect on Y_3 Al_5 O_(12):Ce^(3+),and provides a new route to tune the emission spectrum in Y_3 Al_5 O_(12):Ce^(3+).展开更多
A series of non-rare earth Mn^(4+)-activated strontium aluminate phosphors Sr_(4)Al_(14)O_(25):Mn^(4+)co-doped with Sc^(3+)ions were successfully synthesized by a high-temperature solid-state reaction method.XRD resul...A series of non-rare earth Mn^(4+)-activated strontium aluminate phosphors Sr_(4)Al_(14)O_(25):Mn^(4+)co-doped with Sc^(3+)ions were successfully synthesized by a high-temperature solid-state reaction method.XRD result reveals that there is no introduction of additional phase but expansion of lattice with incorporation of Sc34 ions.Excitation and emission spectrum measurement shows that the synthesized phosphors can be efficiently excited by near-ultraviolet and blue light,and a deep red emission centered at 652 nm with a narrow full width at half maximum(FWHM)can be obtained,which is attributed to the transition^(2)E→^(4)A_(2)of Mn^(4+)ions.In addition,the crystal field strength parameter(Dq)and Racah parameters(B,C)and energies of states were calculated based on experimental data.Moreover,the luminous intensity of Sr_(4)Al_(14-x)SCxO_(25):Mn^(4+)is enhanced and increased by 60%compared with Mn^(4+)single incorporated sample at x=0.06.A phenomenon of redshift is observed in the excitation spectrum and discussed systematically.Finally,the mechanism of the positive effects with Sc^(3+)ions incorporated into lattice is discussed in detail.All the results suggest that the Sr_(4)Al_(13.94)Sc_(0.06)O_(25):Mn^(4+)phosphor will become one of the great candidates for backlight of LCD.展开更多
To improve the stability of a wind-diesel hybrid microgrid,a frequency control strategy is designed by using the hybrid energy storage system and the adjustable diesel generator with load frequency control(LFC).The ob...To improve the stability of a wind-diesel hybrid microgrid,a frequency control strategy is designed by using the hybrid energy storage system and the adjustable diesel generator with load frequency control(LFC).The objective of frequency control is to quickly respond to the disturbed system to reduce system frequency deviation and restore stability.By evaluating the area control error,the disturbance state of the system can be divided into four different areas by a corresponding control strategy for precise adjustments.For the diesel generator,an adaptive sliding mode(SM)algorithm is used to design LFC that can participate in frequency modulation.The frequency coordination con-trol strategy proposed in this paper can realize the partition adjustment according to different resources,and ensure frequency stability.The proposed control strategy is verified by RTDS simulations in multiple scenarios.展开更多
Magnetic harmonic gears with high gear ratios exhibit high torque densities.However,the revolution and rotation of the eccentric rotor makes the magnetic field analysis complex.In this study,an analytical model of mag...Magnetic harmonic gears with high gear ratios exhibit high torque densities.However,the revolution and rotation of the eccentric rotor makes the magnetic field analysis complex.In this study,an analytical model of magnetic fields for magnetic harmonic gears is developed by using the fractional linear transformation method.The transformation formula is accurate in theory and suitable for the analysis of magnetic fields with large eccentricity.The rotor eccentricity region in the z-plane is mapped onto a uniform region in the w-plane.The magnetic field solutions are obtained by modulating the magnetic field distributions without rotor eccentricity with the relative permeance function derived from the effect of rotor eccentricity.The torque of magnetic harmonic gears is calculated from the radial and tangential components of the air-gap magnetic fields.Results of the finite element method and prototype test confirm the validity of the analytical prediction.展开更多
In order to obtain near-infrared phosphor pumped by blue chip with high luminous efficiency, a novel near-infrared phosphor Ce^(3+)/Er^(3+) doped La_3Si_6N_(11) was designed and firstly prepared via conventional solid...In order to obtain near-infrared phosphor pumped by blue chip with high luminous efficiency, a novel near-infrared phosphor Ce^(3+)/Er^(3+) doped La_3Si_6N_(11) was designed and firstly prepared via conventional solid-state reactions. The structure and morphology of Ce^(3+)/Er^(3+) doped La_3Si_6N_(11) were investigated by X-ray diffraction(XRD) and scanning electron microscopy(SEM). Compared with Er^(3+) doped La_3Si_6N_(11),the emission intensity of the Ce^(3+), Er^(3+) co-doped phosphor can be increased more than 5 times.Meanwhile, the mechanism of energy transfer from Ce^(3+) to Er^(3+) is confirmed according to the excitation,emission spectra and decay lifetimes curve. Above results suggest that La_3 Si_6 N_(11):Ce^(3+),Er^(3+) is a promising near-infrared phosphor for blue pumped LEDs(light-emitting diodes).展开更多
A broadband blue-emitting Sr_(1-x)Ca_(x)Lu_(2)O_(4):Ce^(3+)(x=0-0.2) phospho rs were synthesized,which can be used for near-UV pumped white light-emitting diodes(w-LEDs).The crystal structures,photoluminescence pro pe...A broadband blue-emitting Sr_(1-x)Ca_(x)Lu_(2)O_(4):Ce^(3+)(x=0-0.2) phospho rs were synthesized,which can be used for near-UV pumped white light-emitting diodes(w-LEDs).The crystal structures,photoluminescence pro perties,external quantum efficiency,the rmal stability and application perfo rmance of Sr_(1-x)Ca_(x)Lu_(2)O_(4):Ce^(3+),by partially substituting Sr^(2+) with Ca^(2+)(x=0-0.2),were studied by various analytical techniques.When the Ca/Sr ratio of Sr_(1-x)Ca_(x)Lu_(2)O_(4):Ce^(3+) gradually increases,the emission peak of Sr_(1-x)Ca_(x)Lu_(2)O_(4):Ce^(3+) red-shiftes from 459 to 465 nm,corrected external quantum efficiency increases from 31.8% to 42.9%,and the thermal stability is also improved.The mechanism of the changes of the photoluminescence emission and excitation spectra,external quantum efficiency and thermal stability properties was also investigated in detail.In addition,a w-LED was fabricated by using SrLu_(2)O_(4):Ce^(3+)(blue),β-sialon:Eu^(2+)(green) and(Sr,Ca)AlSiN_(3):Eu^(2+)(red) phosphors combined with a 405 nm near-UV LED chip,and its color rendering index(CRI) reaches 96.0.When Sr_(0.8)Ca_(0.2)Lu_(2)O_(4):Ce^(3+) is applied as blue phosphor to substitute SrLu_(2)O_(4):Ce^(3+),the obtained w-LED devices have high luminous efficiency,and CRI greater than 95.0.These re sults show that the Sr_(1-x)Ca_(x)Lu_(2)O_(4):Ce^(3+) can be potential blue phosphors for n-UV pumped high CRI w-LEDs application.展开更多
基金supported in part by the National Natural Science Foundation of China(51977127)Shanghai Municipal Science and Technology Commission(19020500800)“Shuguang Program”(20SG52)Shanghai Education Development Foundation and Shanghai Municipal Education Commission.
文摘From the perspective of a community energy operator,a two-stage optimal scheduling model of a community integrated energy system is proposed by integrating information on controllable loads.The day-ahead scheduling analyzes whether various controllable loads participate in the optimization and investigates the impact of their responses on the operating economy of the community integrated energy system(IES)before and after;the intra-day scheduling proposes a two-stage rolling optimization model based on the day-ahead scheduling scheme,taking into account the fluctuation of wind turbine output and load within a short period of time and according to the different response rates of heat and cooling power,and solves the adjusted output of each controllable device.The simulation results show that the optimal scheduling of controllable loads effectively reduces the comprehensive operating costs of community IES;the two-stage optimal scheduling model can meet the energy demand of customers while effectively and timely suppressing the random fluctuations on both sides of the source and load during the intra-day stage,realizing the economic and smooth operation of IES.
基金supported by the National Natural Science Foundation of China(52074049)Chongqing Natural Science Foundation(cstc2021jcyj-msxmX0764)the Independent Research fund of The State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines(Anhui University of Science and Technology)(SKLMRDPC19KF07).
文摘Microseismic(MS)events generated during coal and rock hydraulic fracturing(HF)include wet events caused by fracturing fuid injection,in addition to dry events caused by stress perturbations.The mixture of these two events makes efective fracturing MS events pickup difcult.This study is based on physical experiments of diferent coal and rock HF and uniaxial compression.The diferences of waveform characteristic parameters of various coal and rock ruptures were analyzed using the Hilbert–Huang transform,leading to some useful conclusions.The phase characteristics of the acoustic emission(AE)energy difered signifcantly and responded well to the pumping pressure curve.The AE waveforms of HF exhibit similar energy and frequency distribution characteristics after Empirical mode decomposition.The main frequency bands for coal,sandstone,and shale samples are 100–300 kHz,while the mudstone sample is in the range of 50–150 kHz.The decay ratios for coal,sandstone,shale and mudstone samples are 0.78,0.83,0.67 and 0.85,respectively.When compared to the uniaxial compression test,the main frequency bands of HF were reduced for coal,sandstone and mudstone samples,whereas shale remained essentially unchanged.The duration,instantaneous energy,and total energy of the HF waveform are smaller than those of uniaxial compression,while the decay ratio is greater,especially for the mudstone samples.The waveform characteristic parameters,trained using the multilayer perceptron neural network,can efectively identify HF and uniaxial compression events with an accuracy of 96%.
基金supported in part by the National Natural Science Foundation of China(51977127)in part by the ShanghaiMunicipal Science and in part by the Technology Commission(19020500800)“Shuguang Program”(20SG52)Shanghai Education Development Foundation and Shanghai Municipal Education Commission.
文摘As an effective carrier of integrated clean energy,the microgrid has attracted wide attention.The randomness of renewable energies such as wind and solar power output brings a significant cost and impact on the economics and reliability of microgrids.This paper proposes an optimization scheme based on the distributionally robust optimization(DRO)model for a microgrid considering solar-wind correlation.Firstly,scenarios of wind and solar power output scenarios are generated based on non-parametric kernel density estimation and the Frank-Copula function;then the generated scenario results are reduced by K-means clustering;finally,the probability confidence interval of scenario distribution is constrained by 1-norm and∞-norm.The model is solved by a column-and-constraint generation algorithm.Experimental studies are conducted on a microgrid system in Jiangsu,China and the obtained scheduling solution turned out to be superior under wind and solar power uncertainties,which verifies the effectiveness of the proposed DRO model.
基金supported by National Natural Science Foundation of China (51977127)Shanghai Municipal Science and Technology Commission (19020500800)“Shuguang Program” (20SG52)Shanghai Education Development Foundation and Shanghai Municipal Education Commission.
文摘In the context of the joint operation of China’s intra-provincial markets and inter-provincial trading,how to meet the load demand and energy consumption using inter-provincial renewable energy trading is a key problem.The combined operation of intra-provincial and inter-provincial markets provides a new way for provincial power companies to optimize and clear the intra-provincial power market,complete the intra-provincial consumption responsibility weight index,and consume renewable energy across provinces and regions.This paper combines power generation and consumption within the province,uses inter-provincial renewable energy trading tomeet the load demand within the province and completes the index of intra-provincial consumption responsibility weights.The intra-provincial market trading and inter-provincial market clearing are respectively taken as the upper and lower levels of the model.Under the two-level electricity market operation framework,the upper-level model aims to minimize the expected total operating cost within the province considering the carbon emission cost and the weight of the consumption responsibility,while the lower-level model aims to minimize the inter-provincial renewable energy purchasing cost.Finally,the influence of inter-provincial transaction mechanism,risk aversion coefficient,voucher price,and responsibility weight on operating cost is analyzed.Simulation is used to verify that the proposed model can meet the requirements of the provincial load power consumption and the consumption responsibility weight index,and promote the consumption of renewable energy.
文摘Aiming at the current limit value of six steady-state energy indexes, the current radar method is used for reference. A method of comprehensive evaluation of power quality based on improved radar method is proposed, which improves the power quality index Type radar pattern to represent the steady-state indicator. Each of the main indicators corresponds to a partial ring, and the angle of the annular portion is mainly affected by the size of the weight. Compared with the previous radar map method to maintain the independence of the indicators and a single indicator of the binding data assessment. The method has the advantages of good feasibility.
基金supported by the NSFC(11771358,11701333,11871101)。
文摘This paper studies the mixed radial-angular integrability of parametric Marcinkiewicz integrals along"polynomial curves".Under the assumption that the kernels satisfy certain rather weak size conditions on the unit sphere with radial roughness,the authors prove that such operators are bounded on the mixed radial-angular spaces.Meanwhile,corresponding vector-valued versions are also obtained.
基金supported in the National Key Research and Development of China(No.2018YFB1503001)Shanghai Municipal Natural Science Foundation(No.22ZR1425500).
文摘Frequency is an important indicator for the oper-ation of microgrids.However,the randomness and uncertainty of renewable energy and load variability may lead to frequency undulation.So,a robust load frequency control(LFC)is pro-posed for isolated wind-diesel microgrids considering time delay and parameter uncertainty.The control strategy can suppress frequency fuctuation and optimize frequency dynamic response.First,the double compensation loop,including feedforward control and integral sliding mode control(SMC),is devised to provide anti-disturbance compensation for the diesel generator system and ameliorate the frequency stability of independent microgrids.Secondly,a dynamic fuzzy controller,composed of wind speed and load demand,is designed to provide real-time response reference power for doubly fed induction generator systems(DFIGs),which can promote the effective participation of a wind turbine system for frequency regulation.Then,the proportional differential(PD)parameters of a dynamic fuzzy controller and the frequency adjustment compensation of DFIGs can be obtained by using a particle swarm optimization(PSO)algorithm.Thirdly,load demand is an important index of the robust dynamic load frequency control method;the radial basis function(RBF)neural network observer(NNO)based on the LFC model is presented to obtain more accurate load deviations and improve the control precision of LFC.The performance of the proposed LFC method is tested under different operation cases.Index Terms-Load frequency control,microgrid,neural network observer,sliding mode,time delay and parameter uncertainty.
基金supported by the National Key Research and Development Program of China(2021YFB3500402)。
文摘Red phosphor,with longer wavelength,is highly desirable for full-spectrum WLEDs.Targeted deep red phosphors(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)were designed from the initial model of SrLiAl_(3)N_(4):Eu^(2+)by structural modification.The correlations among structural evolution,crystal-field environment,and luminescence properties were elucidated.Replacing Sr^(2+)with Gd^(3+)in(Sr,Gd)LiAl_(3)N_(4):Eu^(2+)leads to the enhanced crystal field splitting,larger Stokes shift,and increased structural polyhedron distortion differences,consequently resulting in spectral red-shift and broadening.For further spectral tuning,Mg,with lower electronegativity,was also introduced to modify the local crystal structure,consequently resulting in a further red-shift towards 675 nm and enhanced photoluminescence intensity in(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+).What’s more,w-LEDs were fabricated by using blue LED chip,blue,green,red and deep red((Sr,Gd)Li(Al,Mg)_(3)N_(4):Eu^(2+))phosphors whose color rendering index were Ra 96.0 and R997.7.All above results demonstrate that the partial replacements of Sr^(2+)by Gd^(3+)and Al^(3+)by Mg^(2+)are effective methods for spectral modulation and(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)phosphors are suitable for highquality full-spectrum WLEDs.
基金Project supported by the National Basic Research Program of China(2014CB643801)
文摘A series of high phase purity blue light excitable yellow-emitting La_(3-x)Si_6 N_(11):xCe^(3+) phosphors were synthesized by the high temperature solid state reactions method. The structure and luminescent properties were investigated. The phase structure was studied by means of X-ray diffraction, structures refinements and energy dispersive X-ray spectroscopy. The phosphors effectively excited by the light of450 nm and show intense yellow emission at 535 nm with FWHM of 115 nm corresponding to the5 d →~2 F_(5/2) and 5 d →~2 F_(7/2) transitions of Ce^(3+). In addition,the optimized La_(2.86)Si_6 N_(11):0.14 Ce^(3+) exhibits a weak thermal quenching, which remains 98.2% of the initial emission intensity when heated to 200 ℃,the thermal quenching properties exhibit a modest decline when the temperature returned to room temperature. The above results indicate that La_3 Si_6 N_(11):Ce^(3+) can be regarded as a high promising phosphor for applications in high power white-light LED.
基金supported by the National Key Research and Development Plan(2017YFB0404300,2017YFB0404301)
文摘A novel white-light emitting single-phase phosphor La_3 Si_6 N_(11):Dy^(3+),exhibiting two emission peaks centering at 475 and 575 nm, was prepared via conventional solid-state reactions. The structure and morphology of La_3 Si_6 N_(11):Dy^(3+)/Tb^(3+) were investigated by X-ray diffraction(XRD) and scanning electron microscopy(SEM). The emission colors can be tuned from white to yellow-green through increasing the Tb^(3+) concentration in La_3 Si_6 N_(11):Dy^(3+),Tb^(3+), The mechanism of energy transfer(ET) from Dy^(3+) to Tb^(3+) is confirmed according to the excitation,emission spectra and decay lifetimes curve. The temperaturedependent luminescence measurements of La_(2.83)Si_6 N_(11):0.1 Dy^(3+),0.07 Tb^(3+) were also performed, and a good thermal stability is shown, suggesting superior properties for the application as white lightemitting diodes(w-LEDs) phosphor.
基金Project supported by the National Key Research and Development Program of China(2016YFB400605)。
文摘Broadband near-infrared phosphors are highly desirable for food testing.Targeted Ca_(2)LuHf_(2)Al_(3)O_(12):Cr^(3+)(CLHA:Cr^(3+)) and Ca_(2)LuHf_(2)Al_(3)O_(12):Ce^(3+),Cr^(3+)(CLHA:Ce^(3+),Cr^(^(3+))) phosphors were synthesized by the conventional high-temperature solid state reaction.The CLHA:Cr^(3+)phosphor,with a good thermal stability,shows a red shift owing to radiation reabsorption and non-radiative transition with increasing Cr^(3+)content.For co-doped sample,the emission intensity of Cr^(3+)can be enhanced by three times due to the energy transfer from Ce^(3+)to Cr^(3+),which can be evidenced by a significant overlap between the PLE of Cr^(3+)single-doped phosphor and the PL of Ce^(3+)single-doped phosphor.In addition,the mechanism of energy transfer is identified as a quadrupole-quadrupole interaction according to decay Lifetime and Dexter’s energy transfer formula.The broadband NIR emission peaked at 775 nm of CLHA:Cr^(3+),Ce^(3+)phosphor shows a bright prospect in nondestructive quality-control analysis systems for food.
基金Project supported by National Key Research and Development Program(2017YFB0404301)
文摘Wide color gamut(WCG) backlight for liquid crystal display(LCD) utilizing white light-emitting diodes(LED) has attracted considerable attention for their high efficiency and color reduction.In this review,recent developments in crystal structure,luminescence and applications of phosphors for wide color gamut LED backlight are introduced.As novel red phosphors,Mn4+activate fluoride and aluminate phosphors are advanced in quantum efficiency,thermal quenching and color saturation for their characteristic spectrum with broad excitation band and linear emission.The crystal structure and fluorescence properties of Mn4+doped fluosilicate,fluorogermanate,fluotitanate,as well as Sr4 Al14O25,CaAl12O19 and BaMgAl10O17 phosphors are discussed in detail.A serial of narrow-band red-emitting Eu2+,Eu3+and Pr3+-doped nitride silicates and molybdate phosphors are also introduced.Rare-earth-doped oxynitride and silicate green-emitting phosphors have attracted more and more attention because of the wide excitation,narrow emission,high quenching temperature,high quantum efficiency,such as β-sialon:Eu2+,Ba3Si6O12N2:Eu2+,MSi2O2N2:Eu2+(M=Ca,Sr,Ba),y-AlON:Mn2+and Ca3Sc2Si3O12:Ce3+.All above phosphors demonstrate their adaptability in wide color gamut LCD display.Especially for Mn4+doped fluosilicate red phosphor and β-sialon:Eu2+green phosphor.To achieve an ultra-high color gamut in white LED backlight and against the OLED,innovative narrow-band-emission red and green phosphor materials with independent intellectual property rights are continuously pursed.
基金Project supported by the National Key Research and Development Program of China(2016YFB0701003)
文摘Eu^(2+) activated BaSi_2 O_2 N_2 oxynitride bluish-green phosphor was synthesized adopting conventional high-temperature solid-state reaction method, in which BaF_2, Na_2 CO_3 and NH_4 Cl were used as the fluxes.The phase formation, size distribution and microscopic morphology were characterized to investigate the influence of adding fluxes on photo luminescence properties. The results indicate that with the addition of BaF_2 flux, the particle morphology becomes regular and size distribution narrows and the phase purity of BaSi_2 O_2 N_2:Eu^(2+) phosphor can be improved effectively. The photoluminescence intensity of BaSi_2 O_2 N_2:Eu^(2+) phosphor with BaF_2 as flux gets enhanced obviously, which is much higher than that of Na_2 CO_3, NH_4 Cl and without flux. The optimum content of BaF2 flux is 4 wt%, and the maximum photoluminescence intensity of the BaSi_2 O_2 N_2:Eu^(2+) phosphor prepared with BaF_2 flux rises to 141%,meanwhile, the phosphors with BaF_2 flux exhibits low thermal quenching. The results indicate that the BaSi_2 O_2 N_2:Eu^(2+) is sort of promising bluish-green phosphor for application in full-spectra LED.
基金Project supported by the National Basic Research Program of China(2014CB643801)
文摘Y_3 Al_5 O_(12):Ce3+ is the most famous phosphor material due to its excellent photolumincent properties.Here,through first-principles calculation,the effect of carbon interstitial defects on Y_3 Al_5 O_(12):Ce3+phosphor was investigated. It is found that the carbon interstitials tend to occupy the next-nearest sites of Ce^(3+) ion in Y_3 Al_5 O_(12):Ce3+ lattice. Specially,these interstitial defects can shorten the Ce3+-O^(2-) bond length, leading to a larger crystal field splitting of 5 d orbital of the Ce^(3+) atom and bigger 5 d centroid shift.These two factors cause the emission spectrum of Y_3 Al_5 O_(12)(C):Ce^(3+) red shift compared with that of Y_3 Al_5 O_(12):Ce3+. Moreover, with our comparison experiment, we find that the Y_3 Al_5 O_(12)(C):Ce3+ has an obvious red shift compared with that of Y_3 Al_5 O_(12):Ce^(3+) system,which is in accord with our first principles calculation. Our work systematically investigates the impact of the carbon interstitial defect on Y_3 Al_5 O_(12):Ce^(3+),and provides a new route to tune the emission spectrum in Y_3 Al_5 O_(12):Ce^(3+).
基金Project supported by the National Key Research and Development Program of China(2017YFB0404301)the Team of Excellent Talent Development Project of Xicheng District,Beijing.
文摘A series of non-rare earth Mn^(4+)-activated strontium aluminate phosphors Sr_(4)Al_(14)O_(25):Mn^(4+)co-doped with Sc^(3+)ions were successfully synthesized by a high-temperature solid-state reaction method.XRD result reveals that there is no introduction of additional phase but expansion of lattice with incorporation of Sc34 ions.Excitation and emission spectrum measurement shows that the synthesized phosphors can be efficiently excited by near-ultraviolet and blue light,and a deep red emission centered at 652 nm with a narrow full width at half maximum(FWHM)can be obtained,which is attributed to the transition^(2)E→^(4)A_(2)of Mn^(4+)ions.In addition,the crystal field strength parameter(Dq)and Racah parameters(B,C)and energies of states were calculated based on experimental data.Moreover,the luminous intensity of Sr_(4)Al_(14-x)SCxO_(25):Mn^(4+)is enhanced and increased by 60%compared with Mn^(4+)single incorporated sample at x=0.06.A phenomenon of redshift is observed in the excitation spectrum and discussed systematically.Finally,the mechanism of the positive effects with Sc^(3+)ions incorporated into lattice is discussed in detail.All the results suggest that the Sr_(4)Al_(13.94)Sc_(0.06)O_(25):Mn^(4+)phosphor will become one of the great candidates for backlight of LCD.
基金supported in part by the National Natural Science Foundation of China (no.61873159)Shanghai Municipal Natural Science Foundation (22ZR1425500).
文摘To improve the stability of a wind-diesel hybrid microgrid,a frequency control strategy is designed by using the hybrid energy storage system and the adjustable diesel generator with load frequency control(LFC).The objective of frequency control is to quickly respond to the disturbed system to reduce system frequency deviation and restore stability.By evaluating the area control error,the disturbance state of the system can be divided into four different areas by a corresponding control strategy for precise adjustments.For the diesel generator,an adaptive sliding mode(SM)algorithm is used to design LFC that can participate in frequency modulation.The frequency coordination con-trol strategy proposed in this paper can realize the partition adjustment according to different resources,and ensure frequency stability.The proposed control strategy is verified by RTDS simulations in multiple scenarios.
文摘Magnetic harmonic gears with high gear ratios exhibit high torque densities.However,the revolution and rotation of the eccentric rotor makes the magnetic field analysis complex.In this study,an analytical model of magnetic fields for magnetic harmonic gears is developed by using the fractional linear transformation method.The transformation formula is accurate in theory and suitable for the analysis of magnetic fields with large eccentricity.The rotor eccentricity region in the z-plane is mapped onto a uniform region in the w-plane.The magnetic field solutions are obtained by modulating the magnetic field distributions without rotor eccentricity with the relative permeance function derived from the effect of rotor eccentricity.The torque of magnetic harmonic gears is calculated from the radial and tangential components of the air-gap magnetic fields.Results of the finite element method and prototype test confirm the validity of the analytical prediction.
基金Project supported by Key Strategic Advanced Electronic Materials Department of the Ministry of Science and Technology,(2017YFB0404300,2017YFB0404301)
文摘In order to obtain near-infrared phosphor pumped by blue chip with high luminous efficiency, a novel near-infrared phosphor Ce^(3+)/Er^(3+) doped La_3Si_6N_(11) was designed and firstly prepared via conventional solid-state reactions. The structure and morphology of Ce^(3+)/Er^(3+) doped La_3Si_6N_(11) were investigated by X-ray diffraction(XRD) and scanning electron microscopy(SEM). Compared with Er^(3+) doped La_3Si_6N_(11),the emission intensity of the Ce^(3+), Er^(3+) co-doped phosphor can be increased more than 5 times.Meanwhile, the mechanism of energy transfer from Ce^(3+) to Er^(3+) is confirmed according to the excitation,emission spectra and decay lifetimes curve. Above results suggest that La_3 Si_6 N_(11):Ce^(3+),Er^(3+) is a promising near-infrared phosphor for blue pumped LEDs(light-emitting diodes).
基金Project supported by the National Key Research and Development Program of China(2017YFB0404301)。
文摘A broadband blue-emitting Sr_(1-x)Ca_(x)Lu_(2)O_(4):Ce^(3+)(x=0-0.2) phospho rs were synthesized,which can be used for near-UV pumped white light-emitting diodes(w-LEDs).The crystal structures,photoluminescence pro perties,external quantum efficiency,the rmal stability and application perfo rmance of Sr_(1-x)Ca_(x)Lu_(2)O_(4):Ce^(3+),by partially substituting Sr^(2+) with Ca^(2+)(x=0-0.2),were studied by various analytical techniques.When the Ca/Sr ratio of Sr_(1-x)Ca_(x)Lu_(2)O_(4):Ce^(3+) gradually increases,the emission peak of Sr_(1-x)Ca_(x)Lu_(2)O_(4):Ce^(3+) red-shiftes from 459 to 465 nm,corrected external quantum efficiency increases from 31.8% to 42.9%,and the thermal stability is also improved.The mechanism of the changes of the photoluminescence emission and excitation spectra,external quantum efficiency and thermal stability properties was also investigated in detail.In addition,a w-LED was fabricated by using SrLu_(2)O_(4):Ce^(3+)(blue),β-sialon:Eu^(2+)(green) and(Sr,Ca)AlSiN_(3):Eu^(2+)(red) phosphors combined with a 405 nm near-UV LED chip,and its color rendering index(CRI) reaches 96.0.When Sr_(0.8)Ca_(0.2)Lu_(2)O_(4):Ce^(3+) is applied as blue phosphor to substitute SrLu_(2)O_(4):Ce^(3+),the obtained w-LED devices have high luminous efficiency,and CRI greater than 95.0.These re sults show that the Sr_(1-x)Ca_(x)Lu_(2)O_(4):Ce^(3+) can be potential blue phosphors for n-UV pumped high CRI w-LEDs application.
