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A Full Dynamic Voltage Stability Research Based on Time-domain Simulation
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作者 Yuyao Chen Yanping Zhang +2 位作者 Jian Zhang Yanjun Zhang Lixin Song 《Energy and Power Engineering》 2013年第4期769-773,共5页
The voltage stability is substantially a dynamic stability, but the primary method which is more mature and engineering practical to analyze the stability of voltage is still static analysis. The time-domain simulatio... The voltage stability is substantially a dynamic stability, but the primary method which is more mature and engineering practical to analyze the stability of voltage is still static analysis. The time-domain simulation is an important measure in research of complex power grid. With the development of full dynamic simulation technology, the research of dynamic voltage stability by using full dynamic simulation program which is based on time-domain simulation can be carried out. This paper uses full dynamic simulation program in dynamic voltage stability research, lays special stress on research in how generator over-excitation limiter functioned and influence in dynamic voltage stability research, and raise 2 methods and steps to figure out dynamic stable voltage in both over-excitation counted and not counted. The simulation results of examples indicate the correctness and effectiveness of these methods, and also fully verify the function and influence of generator over-excitation limiter in full dynamic voltage stability research. 展开更多
关键词 dynamic VOLTAGE STABILITY GENERATOR Over-excitation LIMITER time-domain simulation
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Temperature and Pressure Effects on Terahertz Time-Domain Spectroscopy of Crystalline Methedrine by Molecular Dynamics Simulation
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作者 Yu Xin Hassan Yousefi Oderji +3 位作者 Ran Hai Cailong Fu Raja Aljarmouzi Hongbin Ding 《Advances in Molecular Imaging》 2014年第4期58-69,共12页
In this study, the terahertz time-domain spectroscopy (THz-TDS) of crystalline methedrine, which is one of the illegal drugs, is performed using molecular dynamics simulation by the Fourier transform of time derivativ... In this study, the terahertz time-domain spectroscopy (THz-TDS) of crystalline methedrine, which is one of the illegal drugs, is performed using molecular dynamics simulation by the Fourier transform of time derivative auto-correlation functions of the dipole moment. In order to accurately detect the drugs from samples, it is necessary to build a complete database for terahertz spectra under different external conditions from theoretical calculation, which are hardly obtained from the experiments directly. Our results show remarkable consistency with the available experimental data in the frequency range of 10 - 100 cm-1 indicating that the presented method has significant capability to simulate terahertz spectra at various conditions. We investigated the effects of temperature and pressure on THz-TDS by simulating the system at temperature range between 78.4 K and 400 K at pressures up to 100 atm. Results show the spectral features of THz-TDS both in intensity and profile are highly sensitive to the variation of temperature and with a lower magnitude to the variation of pressure. The vanishing, rebuilding and shifting of spectral peaks are due to the complex mechanisms such as the anharmonicity, shifting in the vibration energy levels, formation and destruction of hydrogen-binding and the deformation of the potential energy surface during the environment changing. This improved our understanding for complicated THz-TDS of crystalline methedrine and would be useful for assignment of the practical measurements. 展开更多
关键词 Methedrine MOLECULAR dynamics simulation TERAHERTZ time-domain SPECTROSCOPY
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Splash Zone Dynamic Analysis of A Suspended Semi-Submerged Subsea Module for Irregular Waves
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作者 ZAN Ying-fei GUO Rui-nan +3 位作者 LI Feng LIU Pei-lin HUANG Fu-xiang TIAN Li-feng 《China Ocean Engineering》 SCIE EI CSCD 2023年第2期258-271,共14页
Experimental and numerical studies on the dynamic cable tension of a subsea module during semi-submerged hoisting tests are performed. The experiments are carried out in irregular waves and the time-domain numerical s... Experimental and numerical studies on the dynamic cable tension of a subsea module during semi-submerged hoisting tests are performed. The experiments are carried out in irregular waves and the time-domain numerical simulations are conducted using the software “Simulation of Marine Operations”. The numerical formulation is validated through a comparison with experimental test measurements. The effects of the significant wave height, spectral peak period,and wave direction on the dynamic effect in the main sling and sub-slings are then investigated numerically. The relationship between the wave parameters and the dynamic effect is identified in the time and frequency domains,enabling the allowable sea states to be partially specified. The extreme dynamic effects in all slings under different wave conditions are estimated by using cumulative distribution functions of the Gumbel distribution. The results show that it is reasonable to model a complex subsea module via slender elements and depth-dependent coefficients in simulations of offshore operations. Lowering operations are safer if the wave height is 1 m and the wave period is larger than 8 s because the wave steepness is sufficient for the maximum possible dynamic effect to remain below 0.9. The dynamic tension may decrease when the wave direction is approximately 150°. It is dangerous for subsea modules to encounter lateral waves while entering the water because large overloads and underloads in the extreme dynamic tension may cause snap loads to occur and the slings to become slack. 展开更多
关键词 splash zone subsea module cavity shell time-domain simulation dynamic effect
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Solution and Analysis of Chatter Stability for End Milling in the Time-domain 被引量:32
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作者 李忠群 刘强 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2008年第2期169-178,共10页
In this paper, the instantaneous undeformed chip thickness is modeled to include the dynamic modulation caused by the tool vibration while the dynamic regenerative effects are taken into account. The numerical method ... In this paper, the instantaneous undeformed chip thickness is modeled to include the dynamic modulation caused by the tool vibration while the dynamic regenerative effects are taken into account. The numerical method is used to solve the differential equations goveming the dynamics of the milling system. Several chatter detection criteria are applied synthetically to the simulated signals and the stability diagram is obtained in time-domain. The simulation results in time-domain show a good agreement with the analytical prediction, which is validated by the cutting experiments. By simulating the chatter stability lobes in the time-domain and analyzing the influences of different spindle speeds on the vibration amplitudes of the tool under a Fixed chip-load condition, conclusions could be drawn as follows: In rough milling, higher machining efficiency can be achieved by selecting a spindle speed corresponding to the axial depth of cut in accordance with the simulated chatter stability lobes, and in Fmish milling, lower surface roughness can be achieved by selecting a spindle speed well beyond the resonant frequency of machining system. 展开更多
关键词 high-speed milling chatter stability lobe dynamic cutting force time-domain simulation cutting parameter optimization
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计及频率静特性的低频减载方案的研究 被引量:10
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作者 刘少华 王超 +2 位作者 安军 王铮 周凌 《电力系统保护与控制》 EI CSCD 北大核心 2011年第9期140-144,共5页
针对目前电网制定的低频减载方案中忽略了频率静特性而导致的负荷过切现象进行了研究,提出了一种计及频率静特性的改进减载方案。该方案充分考虑了减载后系统频率调节系数增大,自身吸收的功率也下降的特点,将低频减载各级切除的负荷量减... 针对目前电网制定的低频减载方案中忽略了频率静特性而导致的负荷过切现象进行了研究,提出了一种计及频率静特性的改进减载方案。该方案充分考虑了减载后系统频率调节系数增大,自身吸收的功率也下降的特点,将低频减载各级切除的负荷量减少10%。对方案的原理进行了详细的介绍,并采用多机系统进行了时域动态仿真(TDDS)。仿真结果表明该方案可以有效地抑制现有低频减载各级动作后造成的负荷过切现象。 展开更多
关键词 电力系统 低频减载 系统频率调节系数 时域动态仿真 优化
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Improved State-space Modelling for Microgrids Without Virtual Resistances
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作者 Paranagamage S.A.Peiris Shaahin Filizadeh Dharshana Muthumuni 《Journal of Modern Power Systems and Clean Energy》 SCIE EI CSCD 2024年第2期584-596,共13页
Power converters and their interfacing networks are often treated as modular state-space blocks for small-signal stability studies in microgrids;they are interconnected by matching the input and output states of the n... Power converters and their interfacing networks are often treated as modular state-space blocks for small-signal stability studies in microgrids;they are interconnected by matching the input and output states of the network and converters.Virtual resistors have been widely used in existing models to generate a voltage for state-space models of the network that require voltage inputs.This paper accurately quantifies the adverse impacts of adding the virtual resistance and proposes an alternative method for network modelling that eliminates the requirement of the virtual resistor when interfacing converters with microgrids.The proposed nonlinear method allows initialization,time-domain simulations of the nonlinear model,and linearization and eigenvalue generation.A numerically linearized small-signal model is used to generate eigenvalues and is compared with the eigenvalues generated using the existing modelling method with virtual resistances.Deficiencies of the existing method and improvements offered by the proposed modelling method are clearly quantified.Electromagnetic transient(EMT)simulations using detailed switching models are used for validation of the proposed modelling method. 展开更多
关键词 Low-voltage converter state-space modelling dynamic phasor time-domain simulation eigenvalue analysis
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Information Entropy Based Prioritization Strategy for Data-driven Transient Stability Batch Assessment 被引量:1
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作者 Rong Yan Zhaoyu Wang +2 位作者 Yuxuan Yuan Guangchao Geng Quanyuan Jiang 《CSEE Journal of Power and Energy Systems》 SCIE CSCD 2021年第3期443-455,共13页
Transient stability batch assessment(TSBA)is es-sential for dynamic security check in both power system planning and day-ahead dispatch.It is also a necessary technique to generate sufficient training data for data-dr... Transient stability batch assessment(TSBA)is es-sential for dynamic security check in both power system planning and day-ahead dispatch.It is also a necessary technique to generate sufficient training data for data-driven online transient stability assessment(TSA).However,most existing work suffers from various problems including high computational burden,low model adaptability,and low performance robustness.Therefore,it is still a significant challenge in modern power systems,with numerous scenarios(e.g.,operating conditions and"N-k"contin-gencies)to be assessed at the same time.The purpose of this work is to construct a data-driven method to early terminate time-domain simulation(TDS)and dynamically schedule TSBA task queue a prior,in order to reduce computational burden without compromising accuracy.To achieve this goal,a time-adaptive cas-caded convolutional neural networks(CNNs)model is developed to predict stability and early terminate TDS.Additionally,an information entropy based prioritization strategy is designed to distinguish informative samples,dynamically schedule TSBA task queue and timely update model,thus further reducing simulation time.Case study in IEEE 39-bus system validates the effectiveness of the proposed method. 展开更多
关键词 Cascaded convolutional neural networks(CNNs) dynamic task queue information entropy based prioritization strategy time-domain simulation(TDS) transient stability batch assessment(TSBA)
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