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Transient Stability Analysis of co.verter-based Islanded Microgrids Based on Iterative Equal Area Criterion co.sidering Reactive power Loop Dynamics and Varying Damping

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Journal of Modern power Systems and Clean energy 2024年第4期12卷 1170-1182页

作者： Xilin Li Jingyi Zhang Zhen Tian Xiaoming Zha Wei Wang Meng Huang Chong Shao Hubei Key Laboratory of power Equipment&System Security for Integrated energy School of Electrical Engineering and AutomationWuhan UniversityWuhanChina NARI Technology co. Ltd.NanjingChina State Grid Gansu electric power co.pany LanzhouChina

With the rapid increase in the installed capacity of renewable energy in modern power systems,the stable operation of power systems with co.siderable power electronic equipment requires further *** co.verter-based islanded mi-crogrid(CIM)systems equipped with grid-following(GFL)and grid-forming(GFM)voltage-source co.verters(VSCs),it is chal-lenging to maintain stability due to the mutual co.pling effects between different VSCs and the loss of voltage and frequency sup-port from the power *** previous studies,quantitative transient stability analysis was primarily used to assess the active power loop of ***,frequency and voltage dy-namics are found to be strongly co.pled,which strongly affects the estimation result of stability *** addition,the vary-ing damping terms have not been fully *** bridge these gaps,this paper investigates the transient stability of CIM co.sid-ering reactive power loop dynamics and varying ***,an accuracy-enhanced nonlinear model of the CIM is derived based on the effects of reactive power loop and post-disturbance frequency jump *** these effects will elimi-nates the risk of *** reactive power loop dynamics make the model co.fficients be no longer co.stant and thus vary with the power *** evaluate quantitatively the effects of re-active power loop and varying damping on the transient stability of CIM,an iterative criterion based on the equal area criterion theory is *** addition,the effects of parameters on the stable boundary of power system are analyzed,and the dynamic interaction mechanisms are *** and experiment results verify the merits of the proposed method.

关键词： Transient stability co.verter iterative criterion reactive power loop post-disturbance frequency jump

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Characteristic stress and strain precursor information for fine-grained granite during failure process under triaxial loading and unloading co.ditions

Rock Mechanics Bulletin

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Rock Mechanics Bulletin 2024年第1期3卷 105-114页

作者： Zhen Peng Xing Su Yuda Chen Jianqiang Xia Diyuan Li School of Resources and Safety engineering Central South UniversityChangsha410083China china energy engineering group Guangdong electric power Design Institute co. Ltd.Guangzhou510663China

The unloading effect by excavation may cause irreversible and severe damage to the surrounding rock masses in underground *** this paper,both co.ventional triaxial co.pression(CTC)tests and triaxial unloading co.fining pressure(TUCP)tests were co.ducted on fine-grained granite to study its triaxial co.pression failure processes due to *** on the crack volumetric strain(CVS)method,the crack axial strain(CAS)method and crack radial area strain(CRAS)method were proposed to identify the failure precursor information(including stress thresholds and axial strain at the initiation point of crack co.nectivity stage)during the rock failure *** results of the CTC tests show that the stable crack development stressσsd,unstable crack development stressσusd,and crack co.nectivity stressσct identified by the CAS method are 6%,74%–84%,and 86%–97%of the peak stress,*** the TUCP cases,as the co.fining pressure increases,the stress thresholds,axial pressure at failure and axial strain at the start of the crack co.nectivity stage increase,while the time ratio of the crack co.nectivity stage to the entire unloading stage *** indicates that fine-grained granite is prone to generate more cracks and leads to fail suddenly under high co.fining ***,this new method demonstrates that the point at which the derivative of the radial crack area strain transitions from stable to a sudden increase or decrease is defined as the precursor point of rock *** results of axial strain at the starting point of the crack co.nectivity stage are very close to those predicted by the AE method,withβ1 no more than 11%.

关键词： co.ventional triaxial co.pression test Triaxial unloading co.fining pressure test Stress thresholds Volumetric strain Aco.stic emission

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New Hybrid CHP System Integrating Solar energy and Exhaust Heat Thermochemical Synergistic co.version with Dual-Source energy Storage

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Journal of Thermal Science 2024年第3期33卷 970-984页

作者： QIN Yuanlong LIU Taixiu LI Peijing ZHAO Kai JIAO Fan PEI Gang LIU Qibin Department of Thermal Science and energy engineering University of Science and Technology of ChinaHefei230027China Institute of engineering Thermophysics Chinese Academy of SciencesBeijing100190China University of Chinese Academy of Sciences Beijing100049China School of energy Power and Mechanical EngineeringNorth China Electric Power UniversityBeijing102206China

For the efficient use of solar and fuels and to improve the supply-demand matching performance in co.bined heat and power(CHP)systems,this paper proposes a hybrid solar/methanol energy system integrating solar/exhaust thermochemical and thermal energy *** proposed system includes parabolic trough solar co.lectors(PTSC),a thermochemical reactor,an internal co.bustion engine(ICE),and hybrid storage of thermal and chemical energy,which uses solar energy and methanol fuel as input and outputs power and *** methanol thermochemical deco.position reaction,mid-and-low temperature solar heat and exhaust heat are upgraded to chemical energy for efficient power *** thermal energy storage(TES)stores surplus thermal energy,acting as a backup source to produce heat without emitting co.(2).Due to the energy storage,time-varying solar energy can be used steadily and efficiently;co.siderable supply-demand mismatches can be avoided,and the operational flexibility is *** the design co.dition,the overall energy efficiency,exergy efficiency,and net solar-to-electric efficiency achieve 72.09%,37.65%,and 24.63%,*** fuel saving rate(FSR)and the co.(2) emission reduction(ER_(co.(2)))achieve 32.97%and 25.33%,*** research findings provide a promising approach for the efficient and flexible use of solar energy and fuels for co.bined heat and power.

关键词： hybrid energy system solar thermochemical exhaust heat energy storage operational flexibility

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An Algorithm for Short-Circuit Current Interval in Distribution Networks with Inverter Type Distributed Generation Based on Affine Arithmetic

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energy engineering 2024年第7期121卷 1903-1920页

作者： Yan Zhang Bowen Du Benren Pan GuannanWang Guoqiang Xie Tong Jiang electric power Research Institute State Grid Jiangxi Electric Power Co.Ltd.Nanchang330096China School of electrical and Electronic engineering North China Electric Power UniversityBeijing102206China

During faults in a distribution network,the output power of a distributed generation(DG)may be ***,the output currents of distributed power sources are also affected by the output power,resulting in uncertainties in the calculation of the short-circuit current at the time of a ***,the impacts of such uncertainties around short-circuit currents will increase with the increase of distributed power ***,it is very important to develop a method for calculating the short-circuit current while co.sidering the uncertainties in a distribution *** this study,an affine arithmetic algorithm for calculating short-circuit current intervals in distribution networks with distributed power sources while co.sidering power fluctuations is *** proposed algorithm includes two *** the first stage,normal operations are co.sidered to establish a co.servative interval affine optimization model of injection currents in distributed power *** by the fluctuation range of distributed generation power at the moment of fault occurrence,the model can then be used to solve for the fluctuation range of injected current amplitudes in distributed power *** seco.d stage is implemented after a malfunction *** this stage,an affine optimization model is first *** model is developed to characterizes the short-circuit current interval of a transmission line,and is co.strained by the fluctuation range of the injected current amplitude of DG during normal ***,the range of the short-circuit current amplitudes of distribution network lines after a short-circuit fault occurs is *** algorithm proposed in this article obtains an interval range co.taining accurate results through interval *** with traditional point value calculation methods,interval calculation methods can provide more reliable analysis and calculation *** range of short-circuit current amplitude ob

关键词： Short circuit calculation inverter type distributed power supplies affine arithmetic distribution network

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Numerical Simulation Study on Influence of Equation of State on Internal Flow Field and Performance of S-co.(2)co.pressor

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Journal of Thermal Science 2024年第3期33卷 888-898页

作者： ZHANG Lei YANG Zhenyu SUN Enhui ZHANG Qian AN Guangyao YUAN Wei Hebei Key Laboratory of Low Carbon and High Efficiency power Generation Technology North China Electric Power UniversityBaoding071003China School of energy Power&Mechanical EngineeringNorth China Electric Power UniversityBaoding071028China

The low power co.sumption of the near-critical co.pressor is the key factor for the high efficiency of supercritical co.(2)Brayton *** the numerical simulation of the co.pressor,the rapid changes in the thermophysical properties of the co.(2)near the critical point make it difficult to capture the co.densation *** paper investigates the influence of fluid physical properties on the co.densation ***,the differences in the physical properties of co.(2)in the SRK EOS(equation of state),PR EOS,and SW EOS are ***,the simulation of nozzles and co.pressors were carried out and *** show that the co.densation positions predicted by the three EOSs are basically the *** with SW EOS,the disparities between the maximum co.densation mass fraction predicted by the PR and SRK EOSs is5.7%and 11.5%,and that of total pressure ratio is 0.3%and 3.8%,*** results show that PR EOS can be co.sidered for numerical simulation in engineering *** its physical property calculation results are closer to the actual physical properties while the physical properties change more gently,it has co.siderable accuracy and numerical stability.

关键词： supercritical carbon dioxide equation of state centrifugal co.pressor numerical simulation co.densation

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Optimal Scheduling of Regional Integrated energy Systems co.sidering Hybrid Demand Response

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CSEE Journal of power and energy Systems 2024年第3期10卷 1208-1219页

作者： Ganyun Lyu Bin Cao Dexiang Jia Nan Wang Jun Li Guangyu Chen Department of electrical engineering Nanjing Institute of TechnologyNanjing 211167China State Grid energy Research Institute co. LTDBeijing 102209China State Grid Integrated energy Service group co. LTDBeijing 100032China IEEE CSEE

Flexible load can optimize the load curve,which is an important means to promote renewable energy *** peculiarities of electricity,heat,co.ling and gas loads are analyzed in this paper,co.sidering the fuzzy degree of human perception for water temperature,and the characteristic model of hot water load is *** the fuzzy degree of human perception of ambient temperature,the characteristic model of co.ling load is established by using PMV and PPD ***,co.sidering four co.binations of cut load,translatable load,transferable load and alternative load,and co.sidering the co.pling relationship of co.posite parts,different response models of load are established *** the minimum co.t of the system,including operation and co.pensation co.ts as the objective function,the optimization scheduling model of the regional integrated energy system is established,and the Gurobi solver is used for simulation analysis to solve the optimal output and load response curve of each piece of *** results show that the load curve can be optimized,the flexible regulation ability of the regional integrated energy system can be enhanced,the energy loss of the system can be reduced,and the wind power co.sumption ability of the system can be increased by co.sidering the integrated demand response.

关键词： Alternative load day ahead optimal scheduling integrated demand response PMV and PPD index regional integrated energy system

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Experimental investigation of spectral evolution in flash radiation by hypervelocity impact on aluminum plates

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Defence Technology（防务技术） 2024年第7期37卷 96-110页

作者： Xing Chen Yonggang Lu Zhiwen Li Zhonghua Cui Institute of Systems engineering China Academy of Engineering PhysicsMianyang 621900SichuanChina Chongqing Qianwei Technology group co. LtdChongqing 401121China

In this study,a series of hypervelocity impact tests were carried out based on a two-stage light gas gun,and the sequence spectrum and radiation evolution data of the impact products under different impact co.ditions were *** diameter of the projectile is 3-5 mm,the impact velocity is 3.13-6.58 km/s,and the chamber pressure is 0.56-990 *** spectrum of ejected debris cloud in the 250-310 nm band were obtained using a transient spectral measurement system and a multi-channel radiometer measurement *** test results reveal that the flash radiation intensity increases as a power function with the kinetic energy of the ***,the peak value of the line spectrum decreases as the chamber vacuum degree increases,while the radiation width gradually *** line spectrum in the spectral characterization curve co.responds to the ejected debris clouds splitting phase,which does not produce significant line spectrum during material fragmentation and is dominated by the co.tinuum spectrum produced by blackbody *** will appear one or three characteristic peaks in the flash radiation time curve,the first and seco.d peaks co.respond to the penetration phase and the third peak co.responds to the expansion phase of the ejected debris clouds on the time scale,the first and seco.d peaks are more sensitive to the chamber vacuum degree,and when the pressure is higher than 99 Pa,the first and seco.d characteristic peaks will *** radiant heat attenuation of the flash under different impact co.ditions is significantly different,the attenuation exponent has a power function relationship with the impact velocity and the chamber vacuum degree,while the attenuation exponent has a linear relationship with the diameter of the projectile,the specific expression of the attenuation exponent is obtained by *** findings from this research can serve as a valuable reference for remote diagnostic technologies based on flash radiation characte

关键词： Hypervelocity impact Flash radiation Evolution Spectral characteristics Damage evaluation

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Performance Enhancement of Parabolic Trough co.lector by Using Homogenizer and Spiral

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Journal of Thermal Science 2024年第2期33卷 658-674页

作者： LI Peijing LIU Taixiu QIN Yuanlong ZHENG Zhimei ZHAO Kai LIU Qibin School of energy Powerand Mechanical EngineeringNorth China Electric Power UniversityBeijing102206China Institute of engineering Thermophysics Chinese Academy of SciencesBeijing100190China University of Chinese Academy of Science Beijing100049China Department of Thermal Science and energy engineering University of Science and Technology of ChinaHefei230027China Research Institute of Science and Technology of china Three Gorges group co.poration Beijing100038China

In co.ventional parabolic trough co.lectors(PTCs),sunlight is co.centrated at the bottom of the absorber tube,resulting in a significant circumferential temperature gradient across the absorber tube,heat loss and thermal deformation,which affects the safety and thermal performance of *** this study,a new receiver with homogenizer and spiral(RHS) is proposed,achieving the optical and thermal synergy to ameliorate the thermal deformation of the absorber tube and enhance thermal efficiency.A plane structure homogenizer is designed to improve uniformity of the co.centrated solar flux of absorber tube through seco.d *** co.bination with the spiral,it improves the optical-thermal efficiency of the PTC by enhancing heat exchange between the fluid and the backlight side of the absorber *** performance of the co.lector is numerically studied by building a three-dimensional co.pled light-thermal-structure *** results show that the thermal deformation of the RHS is reduced by more than 96% and the optical-thermal efficiency is improved by 1.2%-0.63% co.pared with co.ventional receivers(CRs) under the same inlet temperature *** proposed receiver is validated to be effective in reducing thermal deformation and improving optical-thermal efficiency.

关键词： parabolic trough co.lector homogenizer thermal deformation spiral

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Detection of Nonlinear Behavior Induced by Hard Limiting in Voltage Source co.verters in Wind Farms Based on Higher-order Spectral Analysis

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Journal of Modern power Systems and Clean energy 2024年第2期12卷 630-645页

作者： Zetian Zheng Shaowei Huang Qiangsheng Bu Chen Shen Jun Yan State Key Laboratory of power Systems Department of Electrical EngineeringTsinghua UniversityBeijing 100084China State Grid Jiangsu electric power co. Ltd.Research InstituteNanjingChina

In recent years, sub-synchronous oscillation accidents caused by wind power integration have received extensive attention. The reco.ded co.stant-amplitude waveforms can be induced by either linear or nonlinear oscillation mechanisms. Hence, the nonlinear behavior needs to be distinguished prior to choosing the analysis method. Since the 1960s, the higher-order statistics(HOS) theory has beco.e a powerful tool for the detection of nonlinear behavior(DNB) in production quality co.trol wherein it has mainly been applied to mechanical co.dition monitoring and fault diagnosis. This study focuses on the hard limiters of the voltage source co.verter(VSC) co.trol systems in the wind farms and attempts to detect the nonlinear behavior caused by bi-or uni-lateral saturation hard limiting using the HOS analysis. First, the co.ventional describing function is extended to obtain the detailed frequency domain information on the bi-and uni-lateral saturation hard limiting. Furthermore, the bi-and tri-spectra are introduced as the HOS, which are extended into bi-and tri-co.erence spectra to eliminate the effects of the linear parts on the harmonic characteristics of hard limiting in the VSC co.trol system, respectively. The effectiveness of the HOS in the DNB and the classification of the hard-limiting types is proven, and its detailed derivation and estimation procedure is presented. Finally, the quadratic and cubic phase co.pling in the signals is illustrated, and the performance of the proposed method is evaluated and discussed.

关键词： Bi-co.erence spectrum detection of nonlinear behavior hard limiting higher-order statistics tri-co.erence spectrum voltage source co.verter wind farms.

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Effects of co.Firing Biomass and Pulverized co.l on NO Reduction in Cement Precalciner

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Journal of Thermal Science 2024年第2期33卷 751-760页

作者： LI Pengpeng REN Qiangqiang LYU Qinggang WANG Mingyue School of energy power and Mechanical engineering North China Electric Power UniversityBeijing102206China Institute of engineering Thermophysics Chinese Academy of SciencesBeijing100190China University of Chinese Academy of Sciences Beijing100049China

With increased awareness of the large-scale co.(2) emissions from the cement industry,there has been growing focus on greenhouse gas reduction *** all these strategies,fuel substitution using biomass fuel is extensively used to achieve co.(2) zero-emission in cement *** to the avoidable high-temperature-generated thermal nitrogen oxides during cement production,research on the impact of biomass application on nitrogen oxide emissions shall be carried *** types of biomass fuel and bituminous co.l were used to investigate the NO reduction characteristics under different O_(2) co.centrations on experimental *** was found that the change in oxygen co.centration from 9% to 1% increased the reaction time in the reactor from 555 s to 1425 s,which means the increase in oxygen co.centration can lead to shorter reaction time,and co.respondingly,the existing time of nitric oxide in the flue gas is also shortened,but the peak value of nitric oxide rises,during the process of O_(2) co.centration changing from 1% to 9%,the peak NO co.centration in the flue gas increased from 5.4×10^(-5) to 1.05×10^(-4).An increase in O_(2) co.centration greatly reduces the total reduction of NO and the minimum change in NO *** peak NO co.centration during the co.bustion process of co.n stalk is 4.56×10^(-4),which is approximately 7 times higher than that of co.l,and it is caused by the high amount of N in co.n *** addition of raw meal has an inhibitory effect on the reduction of NO:after adding raw meal,the effective reduction time of NO by fuel decreased by about 20%,but adding raw meal raises co.(2) co.centration of fuel gas in the early stage of reaction.

关键词： cement precalciner biomass fuel co.l NO reduction co.firing

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