Typhoons can cause large-area blackouts or partial outages of distribution networks.We define a partial outage state in the distribution network as a gray state and propose a gray-start strategy and two-stage distribu...Typhoons can cause large-area blackouts or partial outages of distribution networks.We define a partial outage state in the distribution network as a gray state and propose a gray-start strategy and two-stage distribution network emergency recovery framework.A phase-space reconstruction and stacked integrated model for predicting wind and photovoltaic generation during typhoon disasters is proposed in the first stage.This provides guidance for second-stage post-disaster emergency recovery scheduling.The emergency recovery scheduling model is established in the second stage,and this model is supported by a thermal power-generating unit,mobile emergency generators,and distributed generators.Distributed generation includes wind power generation,photovoltaics,fuel cells,etc.Simultaneously,we con-sider the gray-start based on the pumped storage unit to be an important first step in the emergency recovery strategy.This model is val-idated on the improved IEEE 33 node system,which utilizes data from the 2022 super typhoon“Muifa”in Zhoushan,Zhejiang,China.Simulations indicate the superiority of a gray start with a pumped storage unit and the proposed emergency recovery strategy.展开更多
Large-scale new energy grid connection leads to the weakening of the system frequency regulation capability,and the system frequency stability is facing unprecedented challenges.In order to solve rapid frequency fluct...Large-scale new energy grid connection leads to the weakening of the system frequency regulation capability,and the system frequency stability is facing unprecedented challenges.In order to solve rapid frequency fluctuation caused by new energy units,this paper proposes a new energy power system frequency regulation strategy with multiple units including the doubly-fed pumped storage unit(DFPSU).Firstly,based on the model predictive control(MPC)theory,the state space equations are established by considering the operating characteristics of the units and the dynamic behavior of the system;secondly,the proportional-differential control link is introduced to minimize the frequency deviation to further optimize the frequency modulation(FM)output of the DFPSU and inhibit the rapid fluctuation of the frequency;lastly,it is verified on theMatlab/Simulink simulation platform,and the results show that the model predictive control with proportional-differential control link can further release the FM potential of the DFPSU,increase the depth of its FM,effectively reduce the frequency deviation of the system and its rate of change,realize the optimization of the active output of the DFPSU and that of other units,and improve the frequency response capability of the system.展开更多
The integration of large-scale renewable energy introduces frequency instability challenges due to inherent intermittency.While doubly-fed pumped storage units(DFPSUs)offer frequency regulation potential in pumping mo...The integration of large-scale renewable energy introduces frequency instability challenges due to inherent intermittency.While doubly-fed pumped storage units(DFPSUs)offer frequency regulation potential in pumping mode,conventional strategies fail to address hydraulic-mechanical coupling dynamics and operational constraints,limiting their effectiveness.This paper presents an innovative primary frequency control strategy for double-fed pumped storage units(DFPSUs)operating in pumpingmode,integrating an adaptive parameter calculation method.This method is constrained by operational speed and power limits,addressing key performance factors.A dynamic model that incorporates the reversible pump-turbine characteristics is developed to translate frequency deviations into coordinated adjustments in speed and power during pumping operations.The research thoroughly analyzes the influence of control parameters on the frequency response dynamics.Additionally,the paper introduces a deep reinforcement learning(DRL)-based optimization framework,which enables real-time tuning of control parameters in response to changing rotor speed and frequency states.This method strategicallymanages the utilization of kinetic energy while ensuring compliance with operational safety constraints.The effectiveness of the proposed strategy is validated through simulation studies conducted on a four-machine,two-area DFPSU system.These studies demonstrate the strategy’s potential for improving frequency regulation performance under a variety of operating conditions,highlighting its effectiveness in optimizing energy storage and frequency control in power grids.展开更多
We present experimental results on kilojoule ultraviolet laser output with 1%spectral broadening.Through stimulated rotational Raman scattering(SRRS)with signal laser injection,we achieve effective spectral broadening...We present experimental results on kilojoule ultraviolet laser output with 1%spectral broadening.Through stimulated rotational Raman scattering(SRRS)with signal laser injection,we achieve effective spectral broadening in short-range propagation,with good retention of the original near-field distribution and time waveform.Theoretical calculations show that 2%bandwidth spectral broadening can be achieved by injecting 20 kW/cm^(2) signal light at 2.2 GW/cm^(2) flux of the pump laser.In addition,high-frequency modulation in the near field can be effectively avoided through replacement of the original random noise signal light by the controllable signal light.The SRRS in the atmospheric environment excited with signal laser injection can provide wide-band light output with controllable beam quality without long-distance propagation,representing an important potential route to realization of broadband laser drivers.展开更多
To enhance energy interaction among low-voltage stations(LVSs)and reduce the line loss of the distribution network,a novel operation mode of the micro-pumped storage system(mPSS)has been proposed based on the common r...To enhance energy interaction among low-voltage stations(LVSs)and reduce the line loss of the distribution network,a novel operation mode of the micro-pumped storage system(mPSS)has been proposed based on the common reservoir.First,some operation modes of mPSS are analyzed,which include the separated reservoir mode(SRM)and common reservoir mode(CRM).Then,based on the SRM,and CRM,an energy mutual assistance control model between LVSs has been built to optimize energy loss.Finally,in the simulation,compared to the model without pumped storage in the LVS,the SRMand CLRMcan decrease the total energy loss by 294.377 and 432.578 kWh,respectively.The configuration of mPSS can improve the utilization rate of the new energy source generation system,and relieve the pressure of transformer capacity in the LVS.Compared with the SRM,the proposed CRM has reduced the total energy loss by 138.201 kWh,increased the new energy consumption by 161.642 kWh,and decreased the line loss by 7.271 kWh.With the efficiency of the mPSS improving,the total energy loss reduction of CRM will be 3.5 times that of SRM.Further,the CRMcan significantly reduce the reservoir capacity construction of mPSS and ismore suitable for scenarios where the capacity configuration of mPSS is limited.展开更多
In the context of the accelerated global transition to green and low-carbon energy,China’s energy structure is undergoing profound changes.As of early 2025,the installed capacity of wind and photovoltaic power in Chi...In the context of the accelerated global transition to green and low-carbon energy,China’s energy structure is undergoing profound changes.As of early 2025,the installed capacity of wind and photovoltaic power in China has exceeded 1.4 billion kilowatts,accounting for 42.9%of the total installed power generation capacity,historically surpassing thermal power as the largest power source.However,the randomness,volatility,and intermittency of renewable energy generation pose unprecedented challenges to the power system’s regulatory capacity.In this context,pumped storage,as the most technically mature and economically advantageous large-scale energy storage method,is experiencing explosive growth,providing strategic opportunities for the transformation and upgrading of manufacturing enterprises.展开更多
With the rapid integration of renewable energy sources,modern power systems are increasingly challenged by heightened volatility and uncertainty.Doubly-fed variable-speed pumped storage units(DFVS-PSUs)have emerged as...With the rapid integration of renewable energy sources,modern power systems are increasingly challenged by heightened volatility and uncertainty.Doubly-fed variable-speed pumped storage units(DFVS-PSUs)have emerged as promising technologies for mitigating grid oscillations and enhancing system flexibility.However,the excitation converters in DFVS-PSUs are prone to significant issues such as elevated common-mode voltage(CMV)and neutral-point voltage(NPV)fluctuations,which can lead to electromagnetic interference and degrade transient performance.To address these challenges,an optimized virtual space vector pulse width modulation(OVSVPWM)strategy is proposed,aiming to suppress CMV and NPV simultaneously through coordinated multi-objective control.Specifically,a dynamic feedback mechanism is introduced to adjust the balancing factor of basic vectors in the synthesized virtual small vector in real-time,achieving autonomous balancing of the NPV.To address the excessive switching actions introduced by the OVSVPWM strategy,a phase duty ratio-based sequence reconstruction method is adopted,which reduces the total number of switching actions to half of the original.A zero-level buffering scheme is employed to reconstruct the single-phase voltage-level output sequence,achieving peak CMV suppression down to udc/6.Simulation results demonstrate that the proposed strategy significantly improves electromagnetic compatibility and operational stability while maintaining high power quality.展开更多
Diode pumped monolithic nonplanar ring laser has been developed, yielding single frequency laser and has the advantages of compactness, reliability and high efficiency. Its principles are given in detail and a monolit...Diode pumped monolithic nonplanar ring laser has been developed, yielding single frequency laser and has the advantages of compactness, reliability and high efficiency. Its principles are given in detail and a monolithic nonplanar ring laser is designed. As a result, a laser of hundreds milliwatts cw single frequency output was built up, placed in a magnetic field and pumped by LD. The optical conversion efficiency was more than 15% and the slope efficiency more than 30%. The laser beam had a good quality, with M 2 about 1 2.展开更多
Numerical simulation is described which estimates the performance of thulium sensitized holmium doped CW fluoride fiber laser at 2.04 μm for both core and cladding pumped. This model takes into account the mechanis...Numerical simulation is described which estimates the performance of thulium sensitized holmium doped CW fluoride fiber laser at 2.04 μm for both core and cladding pumped. This model takes into account the mechanisms of cross relaxation and energy transfer to describe the laser operation. A subroutine program for calculating the absorption rate of cladding pumped scheme is included in the model. The losses of signal and pump light along the fiber have been taken into account. The test of cladding pumped scheme program shows good agreement with the experimental result. The experimental results of core pumping Tm Ho doped fiber laser in fluoride host are compared with the present model, and shows a good agreement with calculations. This model also provides data of the optimum parameters for the configuration of the efficient cladding pumped Tm Ho fluoride laser systems.展开更多
Continuous-wave radiation of 5W at 532 nm was produced with an Nd:YVO_(4)/KTP intracavity&equency-doubled laser end-pumped by a diode-laser-array at pump power of 17.2 W,giving optical conversion efRciency of 29.1...Continuous-wave radiation of 5W at 532 nm was produced with an Nd:YVO_(4)/KTP intracavity&equency-doubled laser end-pumped by a diode-laser-array at pump power of 17.2 W,giving optical conversion efRciency of 29.1%.The output power stability was measured to be better than 1.5%in short term operation.The pump-induced thermal lensing was also measured,showing good agreement with the performance of the laser.展开更多
This paper presents the cw output characteristics of Nd^(3+):KGd(WO_(4))_(2)(KGW)laser crystal with different NcP+concentration grown in our laboratory.The laser output at 1.067 μm of KGW crystal(3×3×6 mm)w...This paper presents the cw output characteristics of Nd^(3+):KGd(WO_(4))_(2)(KGW)laser crystal with different NcP+concentration grown in our laboratory.The laser output at 1.067 μm of KGW crystal(3×3×6 mm)was obtained to be 68.9 mW and the slope efficiency reached 28.8%when pumped by laser diode of power 305 mW at 807 nm.展开更多
Magnetocardiography(MCG)measurement is important for investigating the cardiac biological activities.Traditionally,the extremely weak MCG signal was detected by using superconducting quantum interference devices(SQUID...Magnetocardiography(MCG)measurement is important for investigating the cardiac biological activities.Traditionally,the extremely weak MCG signal was detected by using superconducting quantum interference devices(SQUIDs).As a room-temperature magnetic-field sensor,optically pumped magnetometer(OPM)has shown to have comparable sensitivity to that of SQUIDs,which is very suitable for biomagnetic measurements.In this paper,a synthetic gradiometer was constructed by using two OPMs under spin-exchange relaxation-free(SERF)conditions within a moderate magnetically shielded room(MSR).The magnetic noise of the OPM was measured to less than 70 fT/Hz1/2.Under a baseline of 100 mm,noise cancellation of about 30 dB was achieved.MCG was successfully measured with a signal to noise ratio(SNR)of about 37 dB.The synthetic gradiometer technique was very effective to suppress the residual environmental fields,demonstrating the OPM gradiometer technique for highly cost-effective biomagnetic measurements.展开更多
During Jan.1995 to Dec.1996, monthly investigations on the zoobenthic communities of West Lake, samples were collected from six sampling stations. A total of 26 species of macrozoobenthos were identified. The seasonal...During Jan.1995 to Dec.1996, monthly investigations on the zoobenthic communities of West Lake, samples were collected from six sampling stations. A total of 26 species of macrozoobenthos were identified. The seasonal changes in density and biomass of zoobenthos in this lake were analyzed. The annual mean densities were 980～2751 ind/m\+2 and mean biomass was 19.69-122.80 g/m\+2. The densities in winter and early spring were higher than those in summer and autumn. Comparative study of theprevious data (1982 to 1983) collected by the authors, showed that the succession of zoobenthic communities, dominated by \%Procludius choreus\% in density and \%Bellamya purificata\% in biomass, had been occurred in Xiaonan sub\|lake after Qiantang River water was drawn into it; and that the species and biomass of zoobenthos were then increased and the density was decreased. In other sub\|lakes, the dominant species were \%Limnodrilus hoffmeisteri\% and \%Tokunagayusurika akamusi \%in density and \%Branchiura sowerbyi\% and \%Tokunagayusurika akamusi \%in biomass. The water quality was bad in these sub\|lakes because these dominant species are indicators of eutrophication. According to the Margalef index and Goodnight index, West Lake is still an eutrophic lake. Only the water quality of Xiaonan sub\|lake was improved after water drawn from the Qiantang River was introduced into it.展开更多
Seawater pumped storage systems have bright prospect for energy storage in the coming years.The operational conditions of seawater pumped storage system are complex and harsh,where metal materials suff er from severe ...Seawater pumped storage systems have bright prospect for energy storage in the coming years.The operational conditions of seawater pumped storage system are complex and harsh,where metal materials suff er from severe general and local corrosion.The corrosion behavior of Q235B carbon steel in simulated seawater pumped storage system under operational conditions was studied by potentiodynamic polarization,cyclic potentiodynamic polarization,and scanning electron microscope(SEM).The results confi rm that the working pressure aff ected the corrosion resistance of Q235B carbon steel during the whole immersion period.The pressure promoted the electrochemical reaction of corrosion process and the corrosion rate increased with pressure at the initial immersion period.However,the stable rust layer formed after longtime immersion at diff erent pressures increased the corrosion resistance of carbon steel,and decreased the corrosion degree of carbon steel.Meanwhile,the working pressure aff ected the pitting corrosion behavior of Q235B carbon steel during the whole immersion period.The pitting corrosion potential was more negative and the tendency of pitting corrosion was higher at 4 MPa during the whole immersion period.However,pressure also accelerated the formation rate of protective rust layer on the steel surface.Q235B carbon steel has higher susceptibility to pitting corrosion at 4 MPa in the static seawater.展开更多
As water scarcity is becoming a growing threat to human development, finding effective solutions has become an urgent need. To make better use of water resources, seawater desalination and storage systems using renewa...As water scarcity is becoming a growing threat to human development, finding effective solutions has become an urgent need. To make better use of water resources, seawater desalination and storage systems using renewable energy sources(RES) are designed and implemented around the world. In this paper, an optimal capacity planning method for RES-pumped storage-seawater desalination(RES-PS-D) system is introduced. The configuration of the RES-PS-D system is clarified first, after which a cost-benefit analysis is performed using all cost and benefit components. A function for determining maximum economic benefits of the RES-PS-D system is then established, and the constraints are proposed based on various limitations. The mixed-integer linear programming algorithm is applied to solve the optimal function. A case study is introduced to validate the feasibility and effectiveness of the method. The conclusion shows that the strategy is suitable for solving the configuration optimization problem, and finally both merits and defects of the method are discussed.展开更多
We demonstrate a high-power single-frequency diode-side pumped Nd:YAG laser at 1064 nm.A bow-tie ring cavity configuration comprising two plane and two curved mirrors with two-rod birefringence compensation is employe...We demonstrate a high-power single-frequency diode-side pumped Nd:YAG laser at 1064 nm.A bow-tie ring cavity configuration comprising two plane and two curved mirrors with two-rod birefringence compensation is employed.The influence of length Lx between two curved mirrors on output power and beam quality is investigated theoretically and experimentally while the separation of the flat mirrors is set to be 656 mm and the fold angle is 10°.When the pump powers are 358,343 and 329 W at 808 nm,the maximal output powers of 31.9,26 and 14.1 W are obtained with beam quality factors M2=1.41,1.12 and 1.20 for Lx=205,215 and 230 mm,respectively.展开更多
Mechanically pumped two-phase loop(MPTL)which is a prominent two-phase heat transfer technology presents a promising prospect in thermal control for space payload.However,transient behavior of MPTL caused by phase-cha...Mechanically pumped two-phase loop(MPTL)which is a prominent two-phase heat transfer technology presents a promising prospect in thermal control for space payload.However,transient behavior of MPTL caused by phase-change and heat sources load-on/off in simulated space environment is rarely reported.In the present study,one MPTL setup was designed and constructed,and experimentally studied.Particularly,a novel two-phase thermally-controlled accumulator integrated with passive cooling measure and three capillary structures was designed as the temperature-control device.Dynamic behavior of the start-up,temperature control,and temperature adjustment were monitored;meanwhile,thermodynamic behavior within the proposed accumulator,the operating behavior as well as the heat and mass transfer behavior between the main loop and the accumulator were revealed.The results show that the fluid management function of the capillary structures for the novel accumulator is verified.The working point of the MPTL system can be adjusted by changing the temperature control point of the accumulator and it is little influenced by external heat flux and heat sources on/off.Pressure-drop oscillations which are manifested as fluctuations of temperature and pressure can be observed after phase changing due to the compressible volume within the accumulator and the negative-slope portion of the internal pressure.展开更多
In this work,we presented the measurements and calculations for the optimal pump conditions and their effects on thermal lens,fracture limit and laser efficiencies of end pumped Tm-doped yttrium aluminum perovskite(Tm...In this work,we presented the measurements and calculations for the optimal pump conditions and their effects on thermal lens,fracture limit and laser efficiencies of end pumped Tm-doped yttrium aluminum perovskite(Tm:YAP)laser rod pumped at 1064 nm.The results showed that the measured overall efficiency of produced laser at~1.98μm is enhanced from 3.9%to 6.9%when the pump spot diameter is reduced from 390μm to 210μm.The maximum output power and oscillation threshold are also enhanced with reduced pump spot size.The maximum thermal stress and focal length of thermally induced lens are also addressed.展开更多
Every year in China,a significant number of mines are closed or abandoned.The pumped hydroelectric storage(PHS)and geothermal utilization are vital means to efficiently repurpose resources in abandoned mine.In this wo...Every year in China,a significant number of mines are closed or abandoned.The pumped hydroelectric storage(PHS)and geothermal utilization are vital means to efficiently repurpose resources in abandoned mine.In this work,the development potentials of the PHS and geothermal utilization systems were evaluated.Considering the geological conditions and meteorological data available of Jiahe abandoned mine,a simple evaluation model for PHS and geothermal utilization was established.The average efficiency of the PHS system exceeds 70%and the regulatable energy of a unit volume is over 1.53 kW·h/m^(3).The PHS system achieves optimal performance when the wind/solar power ratio reaches 0.6 and 0.3 in daily and year scale,respectively.In the geothermal utilization system,the outlet temperature and heat production are significantly affected by the injection flow rate.The heat production performance is more stable at lower rate flow,and the proportion of heat production is higher in the initial stage at greater flow rate.As the operating time increases,the proportion of heat production gradually decreases.The cyclic heat storage status has obvious advantages in heat generation and cooling.Furthermore,the energy-saving and emission reduction benefits of PHS and geothermal utilization systems were calculated.展开更多
In this paper, according to the temperature and strain distribution obtained by considering the Gaussian pump profile and dependence of physical properties on temperature, we derive an analytical model for refractive ...In this paper, according to the temperature and strain distribution obtained by considering the Gaussian pump profile and dependence of physical properties on temperature, we derive an analytical model for refractive index variations of the diode side-pumped Nd：YAG laser rod. Then we evaluate this model by numerical solution and our maximum relative errors are 5% and 10% for variations caused by thermo–optical and thermo–mechanical effects; respectively. Finally, we present an analytical model for calculating the focal length of the thermal lens and spherical aberration. This model is evaluated by experimental results.展开更多
基金supported in part by the National Nat-ural Science Foundation of China(52177110)Key Pro-gram of the National Natural Science Foundation of China(U22B20106,U2142206)+2 种基金Shenzhen Science and Technology Program(JCYJ20210324131409026)the Science and Technology Project of the State Grid Corpo-ration of China(5200-202319382A-2-3-XG)State Grid Zhejiang Elctric Power Co.,Ltd.Science and Tech-nology Project(B311DS24001A).
文摘Typhoons can cause large-area blackouts or partial outages of distribution networks.We define a partial outage state in the distribution network as a gray state and propose a gray-start strategy and two-stage distribution network emergency recovery framework.A phase-space reconstruction and stacked integrated model for predicting wind and photovoltaic generation during typhoon disasters is proposed in the first stage.This provides guidance for second-stage post-disaster emergency recovery scheduling.The emergency recovery scheduling model is established in the second stage,and this model is supported by a thermal power-generating unit,mobile emergency generators,and distributed generators.Distributed generation includes wind power generation,photovoltaics,fuel cells,etc.Simultaneously,we con-sider the gray-start based on the pumped storage unit to be an important first step in the emergency recovery strategy.This model is val-idated on the improved IEEE 33 node system,which utilizes data from the 2022 super typhoon“Muifa”in Zhoushan,Zhejiang,China.Simulations indicate the superiority of a gray start with a pumped storage unit and the proposed emergency recovery strategy.
基金supported by the National Natural Science Foundation of China(Project No.52377082)the Scientific Research Program of Jilin Provincial Department of Education(Project No.JJKH20230123KJ).
文摘Large-scale new energy grid connection leads to the weakening of the system frequency regulation capability,and the system frequency stability is facing unprecedented challenges.In order to solve rapid frequency fluctuation caused by new energy units,this paper proposes a new energy power system frequency regulation strategy with multiple units including the doubly-fed pumped storage unit(DFPSU).Firstly,based on the model predictive control(MPC)theory,the state space equations are established by considering the operating characteristics of the units and the dynamic behavior of the system;secondly,the proportional-differential control link is introduced to minimize the frequency deviation to further optimize the frequency modulation(FM)output of the DFPSU and inhibit the rapid fluctuation of the frequency;lastly,it is verified on theMatlab/Simulink simulation platform,and the results show that the model predictive control with proportional-differential control link can further release the FM potential of the DFPSU,increase the depth of its FM,effectively reduce the frequency deviation of the system and its rate of change,realize the optimization of the active output of the DFPSU and that of other units,and improve the frequency response capability of the system.
文摘The integration of large-scale renewable energy introduces frequency instability challenges due to inherent intermittency.While doubly-fed pumped storage units(DFPSUs)offer frequency regulation potential in pumping mode,conventional strategies fail to address hydraulic-mechanical coupling dynamics and operational constraints,limiting their effectiveness.This paper presents an innovative primary frequency control strategy for double-fed pumped storage units(DFPSUs)operating in pumpingmode,integrating an adaptive parameter calculation method.This method is constrained by operational speed and power limits,addressing key performance factors.A dynamic model that incorporates the reversible pump-turbine characteristics is developed to translate frequency deviations into coordinated adjustments in speed and power during pumping operations.The research thoroughly analyzes the influence of control parameters on the frequency response dynamics.Additionally,the paper introduces a deep reinforcement learning(DRL)-based optimization framework,which enables real-time tuning of control parameters in response to changing rotor speed and frequency states.This method strategicallymanages the utilization of kinetic energy while ensuring compliance with operational safety constraints.The effectiveness of the proposed strategy is validated through simulation studies conducted on a four-machine,two-area DFPSU system.These studies demonstrate the strategy’s potential for improving frequency regulation performance under a variety of operating conditions,highlighting its effectiveness in optimizing energy storage and frequency control in power grids.
基金supported by the Presidential Foundation of CAEP(Grant No.YZJJZL2023116)the National Nature Science Foundation of China(Grant No.12275249)the Youth Talent Fund of the Laser Fusion Research Center,CAEP(Grant Nos.RCFCZ7-2024-2 and RCFPD4-2020-4).
文摘We present experimental results on kilojoule ultraviolet laser output with 1%spectral broadening.Through stimulated rotational Raman scattering(SRRS)with signal laser injection,we achieve effective spectral broadening in short-range propagation,with good retention of the original near-field distribution and time waveform.Theoretical calculations show that 2%bandwidth spectral broadening can be achieved by injecting 20 kW/cm^(2) signal light at 2.2 GW/cm^(2) flux of the pump laser.In addition,high-frequency modulation in the near field can be effectively avoided through replacement of the original random noise signal light by the controllable signal light.The SRRS in the atmospheric environment excited with signal laser injection can provide wide-band light output with controllable beam quality without long-distance propagation,representing an important potential route to realization of broadband laser drivers.
基金sponsored by the State Grid Corporation of China Technology Project(Research on Key Technologies and Equipment Development of Micro Pumped Storage for Distributed New Energy Consumption in Distribution Networks,5400-202324196A-1-1-ZN).
文摘To enhance energy interaction among low-voltage stations(LVSs)and reduce the line loss of the distribution network,a novel operation mode of the micro-pumped storage system(mPSS)has been proposed based on the common reservoir.First,some operation modes of mPSS are analyzed,which include the separated reservoir mode(SRM)and common reservoir mode(CRM).Then,based on the SRM,and CRM,an energy mutual assistance control model between LVSs has been built to optimize energy loss.Finally,in the simulation,compared to the model without pumped storage in the LVS,the SRMand CLRMcan decrease the total energy loss by 294.377 and 432.578 kWh,respectively.The configuration of mPSS can improve the utilization rate of the new energy source generation system,and relieve the pressure of transformer capacity in the LVS.Compared with the SRM,the proposed CRM has reduced the total energy loss by 138.201 kWh,increased the new energy consumption by 161.642 kWh,and decreased the line loss by 7.271 kWh.With the efficiency of the mPSS improving,the total energy loss reduction of CRM will be 3.5 times that of SRM.Further,the CRMcan significantly reduce the reservoir capacity construction of mPSS and ismore suitable for scenarios where the capacity configuration of mPSS is limited.
文摘In the context of the accelerated global transition to green and low-carbon energy,China’s energy structure is undergoing profound changes.As of early 2025,the installed capacity of wind and photovoltaic power in China has exceeded 1.4 billion kilowatts,accounting for 42.9%of the total installed power generation capacity,historically surpassing thermal power as the largest power source.However,the randomness,volatility,and intermittency of renewable energy generation pose unprecedented challenges to the power system’s regulatory capacity.In this context,pumped storage,as the most technically mature and economically advantageous large-scale energy storage method,is experiencing explosive growth,providing strategic opportunities for the transformation and upgrading of manufacturing enterprises.
文摘With the rapid integration of renewable energy sources,modern power systems are increasingly challenged by heightened volatility and uncertainty.Doubly-fed variable-speed pumped storage units(DFVS-PSUs)have emerged as promising technologies for mitigating grid oscillations and enhancing system flexibility.However,the excitation converters in DFVS-PSUs are prone to significant issues such as elevated common-mode voltage(CMV)and neutral-point voltage(NPV)fluctuations,which can lead to electromagnetic interference and degrade transient performance.To address these challenges,an optimized virtual space vector pulse width modulation(OVSVPWM)strategy is proposed,aiming to suppress CMV and NPV simultaneously through coordinated multi-objective control.Specifically,a dynamic feedback mechanism is introduced to adjust the balancing factor of basic vectors in the synthesized virtual small vector in real-time,achieving autonomous balancing of the NPV.To address the excessive switching actions introduced by the OVSVPWM strategy,a phase duty ratio-based sequence reconstruction method is adopted,which reduces the total number of switching actions to half of the original.A zero-level buffering scheme is employed to reconstruct the single-phase voltage-level output sequence,achieving peak CMV suppression down to udc/6.Simulation results demonstrate that the proposed strategy significantly improves electromagnetic compatibility and operational stability while maintaining high power quality.
基金Fundfor Research on Doctoral Programs in Institutions of Higher Learning
文摘Diode pumped monolithic nonplanar ring laser has been developed, yielding single frequency laser and has the advantages of compactness, reliability and high efficiency. Its principles are given in detail and a monolithic nonplanar ring laser is designed. As a result, a laser of hundreds milliwatts cw single frequency output was built up, placed in a magnetic field and pumped by LD. The optical conversion efficiency was more than 15% and the slope efficiency more than 30%. The laser beam had a good quality, with M 2 about 1 2.
文摘Numerical simulation is described which estimates the performance of thulium sensitized holmium doped CW fluoride fiber laser at 2.04 μm for both core and cladding pumped. This model takes into account the mechanisms of cross relaxation and energy transfer to describe the laser operation. A subroutine program for calculating the absorption rate of cladding pumped scheme is included in the model. The losses of signal and pump light along the fiber have been taken into account. The test of cladding pumped scheme program shows good agreement with the experimental result. The experimental results of core pumping Tm Ho doped fiber laser in fluoride host are compared with the present model, and shows a good agreement with calculations. This model also provides data of the optimum parameters for the configuration of the efficient cladding pumped Tm Ho fluoride laser systems.
基金Supported by the National Advanced Materials Commit tee of the"863 Program"under Grant No.863-715-001-0030.
文摘Continuous-wave radiation of 5W at 532 nm was produced with an Nd:YVO_(4)/KTP intracavity&equency-doubled laser end-pumped by a diode-laser-array at pump power of 17.2 W,giving optical conversion efRciency of 29.1%.The output power stability was measured to be better than 1.5%in short term operation.The pump-induced thermal lensing was also measured,showing good agreement with the performance of the laser.
基金Supported by the National Natural Science Foundation of ChinaFujian Provincial Natural Science Foundation.
文摘This paper presents the cw output characteristics of Nd^(3+):KGd(WO_(4))_(2)(KGW)laser crystal with different NcP+concentration grown in our laboratory.The laser output at 1.067 μm of KGW crystal(3×3×6 mm)was obtained to be 68.9 mW and the slope efficiency reached 28.8%when pumped by laser diode of power 305 mW at 807 nm.
基金Project supported by the National Natural Science Foundation of China(Grant No.61701486)。
文摘Magnetocardiography(MCG)measurement is important for investigating the cardiac biological activities.Traditionally,the extremely weak MCG signal was detected by using superconducting quantum interference devices(SQUIDs).As a room-temperature magnetic-field sensor,optically pumped magnetometer(OPM)has shown to have comparable sensitivity to that of SQUIDs,which is very suitable for biomagnetic measurements.In this paper,a synthetic gradiometer was constructed by using two OPMs under spin-exchange relaxation-free(SERF)conditions within a moderate magnetically shielded room(MSR).The magnetic noise of the OPM was measured to less than 70 fT/Hz1/2.Under a baseline of 100 mm,noise cancellation of about 30 dB was achieved.MCG was successfully measured with a signal to noise ratio(SNR)of about 37 dB.The synthetic gradiometer technique was very effective to suppress the residual environmental fields,demonstrating the OPM gradiometer technique for highly cost-effective biomagnetic measurements.
文摘During Jan.1995 to Dec.1996, monthly investigations on the zoobenthic communities of West Lake, samples were collected from six sampling stations. A total of 26 species of macrozoobenthos were identified. The seasonal changes in density and biomass of zoobenthos in this lake were analyzed. The annual mean densities were 980～2751 ind/m\+2 and mean biomass was 19.69-122.80 g/m\+2. The densities in winter and early spring were higher than those in summer and autumn. Comparative study of theprevious data (1982 to 1983) collected by the authors, showed that the succession of zoobenthic communities, dominated by \%Procludius choreus\% in density and \%Bellamya purificata\% in biomass, had been occurred in Xiaonan sub\|lake after Qiantang River water was drawn into it; and that the species and biomass of zoobenthos were then increased and the density was decreased. In other sub\|lakes, the dominant species were \%Limnodrilus hoffmeisteri\% and \%Tokunagayusurika akamusi \%in density and \%Branchiura sowerbyi\% and \%Tokunagayusurika akamusi \%in biomass. The water quality was bad in these sub\|lakes because these dominant species are indicators of eutrophication. According to the Margalef index and Goodnight index, West Lake is still an eutrophic lake. Only the water quality of Xiaonan sub\|lake was improved after water drawn from the Qiantang River was introduced into it.
基金Supported by the National Key R&D Program of China(Nos.2017YFB0903700,2017YFB0903702)。
文摘Seawater pumped storage systems have bright prospect for energy storage in the coming years.The operational conditions of seawater pumped storage system are complex and harsh,where metal materials suff er from severe general and local corrosion.The corrosion behavior of Q235B carbon steel in simulated seawater pumped storage system under operational conditions was studied by potentiodynamic polarization,cyclic potentiodynamic polarization,and scanning electron microscope(SEM).The results confi rm that the working pressure aff ected the corrosion resistance of Q235B carbon steel during the whole immersion period.The pressure promoted the electrochemical reaction of corrosion process and the corrosion rate increased with pressure at the initial immersion period.However,the stable rust layer formed after longtime immersion at diff erent pressures increased the corrosion resistance of carbon steel,and decreased the corrosion degree of carbon steel.Meanwhile,the working pressure aff ected the pitting corrosion behavior of Q235B carbon steel during the whole immersion period.The pitting corrosion potential was more negative and the tendency of pitting corrosion was higher at 4 MPa during the whole immersion period.However,pressure also accelerated the formation rate of protective rust layer on the steel surface.Q235B carbon steel has higher susceptibility to pitting corrosion at 4 MPa in the static seawater.
基金supported by the National Natural Science Foundation of China (No.61703081)the Natural Science Foundation of Liaoning Province (No.20170520113)the State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources (No.LAPS19005)
文摘As water scarcity is becoming a growing threat to human development, finding effective solutions has become an urgent need. To make better use of water resources, seawater desalination and storage systems using renewable energy sources(RES) are designed and implemented around the world. In this paper, an optimal capacity planning method for RES-pumped storage-seawater desalination(RES-PS-D) system is introduced. The configuration of the RES-PS-D system is clarified first, after which a cost-benefit analysis is performed using all cost and benefit components. A function for determining maximum economic benefits of the RES-PS-D system is then established, and the constraints are proposed based on various limitations. The mixed-integer linear programming algorithm is applied to solve the optimal function. A case study is introduced to validate the feasibility and effectiveness of the method. The conclusion shows that the strategy is suitable for solving the configuration optimization problem, and finally both merits and defects of the method are discussed.
基金by the National Basic Research Program of China under Grant No 2010CB630706the National High Technology Research and Development Program+1 种基金the National Natural Science Foundation of Chinathe Knowledge Innovation Program of Chinese Academy of Sciences。
文摘We demonstrate a high-power single-frequency diode-side pumped Nd:YAG laser at 1064 nm.A bow-tie ring cavity configuration comprising two plane and two curved mirrors with two-rod birefringence compensation is employed.The influence of length Lx between two curved mirrors on output power and beam quality is investigated theoretically and experimentally while the separation of the flat mirrors is set to be 656 mm and the fold angle is 10°.When the pump powers are 358,343 and 329 W at 808 nm,the maximal output powers of 31.9,26 and 14.1 W are obtained with beam quality factors M2=1.41,1.12 and 1.20 for Lx=205,215 and 230 mm,respectively.
基金supported by the National Natural Science Foundation of China(No.51806010)Shanghai Sailing Program,China(No.18YF1409100).
文摘Mechanically pumped two-phase loop(MPTL)which is a prominent two-phase heat transfer technology presents a promising prospect in thermal control for space payload.However,transient behavior of MPTL caused by phase-change and heat sources load-on/off in simulated space environment is rarely reported.In the present study,one MPTL setup was designed and constructed,and experimentally studied.Particularly,a novel two-phase thermally-controlled accumulator integrated with passive cooling measure and three capillary structures was designed as the temperature-control device.Dynamic behavior of the start-up,temperature control,and temperature adjustment were monitored;meanwhile,thermodynamic behavior within the proposed accumulator,the operating behavior as well as the heat and mass transfer behavior between the main loop and the accumulator were revealed.The results show that the fluid management function of the capillary structures for the novel accumulator is verified.The working point of the MPTL system can be adjusted by changing the temperature control point of the accumulator and it is little influenced by external heat flux and heat sources on/off.Pressure-drop oscillations which are manifested as fluctuations of temperature and pressure can be observed after phase changing due to the compressible volume within the accumulator and the negative-slope portion of the internal pressure.
基金supported by the Taif University Researchers Supporting Project(No.TURSP-2020/25),Taif University,Taif,Saudi Arabia。
文摘In this work,we presented the measurements and calculations for the optimal pump conditions and their effects on thermal lens,fracture limit and laser efficiencies of end pumped Tm-doped yttrium aluminum perovskite(Tm:YAP)laser rod pumped at 1064 nm.The results showed that the measured overall efficiency of produced laser at~1.98μm is enhanced from 3.9%to 6.9%when the pump spot diameter is reduced from 390μm to 210μm.The maximum output power and oscillation threshold are also enhanced with reduced pump spot size.The maximum thermal stress and focal length of thermally induced lens are also addressed.
基金Project(8212033)supported by the Natural Science Foundation of Beijing,ChinaProject(BBJ2023051)supported by the Fundamental Research Funds of China University of Mining and Technology-BeijingProject(SKLGDUEK202221)supported by the Innovation Fund Research Project,China。
文摘Every year in China,a significant number of mines are closed or abandoned.The pumped hydroelectric storage(PHS)and geothermal utilization are vital means to efficiently repurpose resources in abandoned mine.In this work,the development potentials of the PHS and geothermal utilization systems were evaluated.Considering the geological conditions and meteorological data available of Jiahe abandoned mine,a simple evaluation model for PHS and geothermal utilization was established.The average efficiency of the PHS system exceeds 70%and the regulatable energy of a unit volume is over 1.53 kW·h/m^(3).The PHS system achieves optimal performance when the wind/solar power ratio reaches 0.6 and 0.3 in daily and year scale,respectively.In the geothermal utilization system,the outlet temperature and heat production are significantly affected by the injection flow rate.The heat production performance is more stable at lower rate flow,and the proportion of heat production is higher in the initial stage at greater flow rate.As the operating time increases,the proportion of heat production gradually decreases.The cyclic heat storage status has obvious advantages in heat generation and cooling.Furthermore,the energy-saving and emission reduction benefits of PHS and geothermal utilization systems were calculated.
文摘In this paper, according to the temperature and strain distribution obtained by considering the Gaussian pump profile and dependence of physical properties on temperature, we derive an analytical model for refractive index variations of the diode side-pumped Nd：YAG laser rod. Then we evaluate this model by numerical solution and our maximum relative errors are 5% and 10% for variations caused by thermo–optical and thermo–mechanical effects; respectively. Finally, we present an analytical model for calculating the focal length of the thermal lens and spherical aberration. This model is evaluated by experimental results.
