检索结果-南通市图书馆

Phillips-Heffron model for current-controlled power electronic generation unit

在线全文

学校读者我要写书评

暂无评论

Journal of Modern Power Systems and Clean Energy 2018年第3期6卷 582-594页

作者： Shulong TAN hua geng geng YANG Department of Automation Tsinghua University

This paper presents a Phillips-Heffron model for the generation unit with current-controlled(CC) voltage source converter(VSC) as the interface. A concept of current angle is put forward for the CC-VSC, and the relationship between the current angle and the power angle is also quantified. Based on the current angle, a PhillipsHeffron model is established for the generation unit with CC-VSC, considering the dynamic of phase-locked-loop(PLL) in the weak grid. The model demonstrates that small-signal dynamics of the generation unit is similar to that of the traditional synchronous generator(SG) which is characterized by the electromechanical swing *** the dynamics can be depicted by the famous inertia,synchronizing and damping coefficients. Small-signal stability of a CC-VSC-based single machine infinite bus system is analyzed by means of the traditional theory of power system. Based on the relationship between the current angle and the power angle, the Phillips-Heffron model of the CC-VSC is also used in stability analysis of multimachine power system, and parameter optimizations of the CC-VSC are also studied for stability improvement.

关键词： Phillips-Heffron model Voltage source converter Current angle Synchronous generator Small-signal stability

Decoupling Scheme for Virtual Synchronous Generator Controlled Wind Farms Participating in Inertial Response

在线全文

学校读者我要写书评

暂无评论

Journal of Modern Power Systems and Clean Energy 2021年第2期9卷 347-355页

作者： Jiangbei Xi hua geng Xin Zou the Department of Automation Tsinghua UniversityBeijingChina the State Grid Economic and Technological Research Institute Co.Ltd. BeijingChina

In this paper,the dynamic coupling between the wind turbine rotor speed recovery(WTRSR)and inertial response of the conventional virtual synchronous generator(VSG)controlled wind farms(WFs)is *** distinguishing features are ***,the inertial response characteristics of VSG controlled WFs(VSG-WFs)are impaired by the dynamic ***,when the influence of WTRSR is dominant,the inertial response characteristics of VSG-WFs are even worse than the condition under which WFs do not participate in the response of grid ***,this phenomenon cannot be eliminated by only enlarging the inertia parameter of VSG-WFs,because the influence of WTRSR would also increase with the enhancement of inertial response.A decoupling scheme to eliminate the negative influence is then proposed in this *** starting the WTRSR process after inertial response period,the dynamic coupling is eliminated and the inertial response characteristics of WFs are ***,the effectiveness of the analysis and the proposed scheme are verified by simulation results.

关键词： Wind turbine rotor speed recovery(WTRSR) inertial response virtual synchronous generator(VSG) decoupling scheme

Transient stochastic response of quasi integerable Hamiltonian systems

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2013年第4期29卷 602-611页

作者： Zhong-hua Liu Jian-hua geng Wei-Qiu Zhu Department of Civil Engineering Xiamen University Department of Mechanics State Key Laboratory of Fluid Power Transmission and Control Zhejiang University

The approximate transient response of quasi in- tegrable Hamiltonian systems under Gaussian white noise excitations is investigated. First, the averaged It6 equa- tions for independent motion integrals and the associated Fokker-Planck-Kolmogorov （FPK） equation governing the transient probability density of independent motion integrals of the system are derived by applying the stochastic averag- ing method for quasi integrable Hamiltonian systems. Then, approximate solution of the transient probability density of independent motion integrals is obtained by applying the Galerkin method to solve the FPK equation. The approxi- mate transient solution is expressed as a series in terms of properly selected base functions with time-dependent coeffi- cients. The transient probability densities of displacements and velocities can be derived from that of independent mo- tion integrals. Three examples are given to illustrate the ap- plication of the proposed procedure. It is shown that the re- suits for the three examples obtained by using the proposed procedure agree well with those from Monte Carlo simula- tion of the original systems.

关键词： Transient response ~ Stochastic averagingmethod ~ Galerkin method ~ Quasi integrable Hamiltoniansystem

Analysis and Control of Frequency Stability in Low-Inertia Power Systems: A Review

在线全文

学校读者我要写书评

暂无评论

IEEE/CAA Journal of Automatica Sinica 2024年第12期11卷 2363-2383页

作者： Changjun He hua geng Kaushik Rajashekara Ambrish Chandra the Department of Automation Tsinghua University and also with Beijing National Research Center for Information Science and Technology Tsinghua University IEEE the University of Houston the Department of Electrical Engineering Ecole de Technologie Superieure University of Quebec

Power electronic-interfaced renewable energy sources(RES) exhibit lower inertia compared to traditional synchronous generators. The large-scale integration of RES has led to a significant reduction in system inertia, posing significant challenges for maintaining frequency stability in future power systems. This issue has garnered considerable attention in recent years. However, the existing research has not yet achieved a comprehensive understanding of system inertia and frequency stability in the context of low-inertia systems. To this end, this paper provides a comprehensive review of the definition, modeling,analysis, evaluation, and control for frequency stability. It commences with an exploration of inertia and frequency characteristics in low-inertia systems, followed by a novel definition of frequency stability. A summary of frequency stability modeling,analysis, and evaluation methods is then provided, along with their respective applicability in various scenarios. Additionally,the two critical factors of frequency control—energy sources at the system level and control strategies at the device level —are examined. Finally, an outlook on future research in low-inertia power systems is discussed.

关键词： Frequency control frequency stability definition low inertia power system with high penetration of renewable energy sources

Modeling framework of voltage-source converters based on equivalence with synchronous generator

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Modern Power Systems and Clean Energy 2018年第6期6卷 1291-1305页

作者： Shulong TAN hua geng geng YANG huai WANG Frede BLAABJERG Department of Automation Tsinghua University Department of Energy Technology Aalborg University

Along with the increasing penetration of distributed generation with voltage-source converters(VSCs),there are extensive concerns over the potential virtual rotor angle stability, which is characterized by oscillations of power and frequency during the dynamic process of synchronization in the grid. Several control strategies have been developed for VSCs to emulate rotating inertia as well as damping of oscillations. This paper classifies these strategies and provides a small-signal modeling framework including all kinds of VSCs in different applications for virtual rotor angle stability. A unified perspective based on the famous Phillips–Heffron model is established for various VSCs. Thus, the concepts of equivalent inertia and the synchronizing and damping coefficients in different VSCs are highlighted, based on the similarities with the synchronous generator(SG) system in both physical mechanisms and mathematical models. It revealed the potentiality of various VSCs to achieve equivalence with the SG. This study helps promote the unity of VSCs and traditional SGs in both theories and methods for analyzing the dynamic behavior and enhancing the stability. Finally,future research needs and new perspectives are addressed.

关键词： Voltage-source converter(VSC) Synchronous generator Virtual rotor angle stability Inertia Synchronizing Damping

Reflection-based traveltime and waveform inversion with second-order optimization

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2022年第4期19卷 1582-1591页

作者： Teng-Fei Wang Jiu-Bing Cheng Jian-hua geng State Key Laboratory of Marine Geology Tongji UniversityShanghai200092China School of Ocean and Earth Science Tongji UniversityShanghai200092China

Reflection-based inversion that aims to reconstruct the low-to-intermediate wavenumbers of the subsurface model, can be a complementary to refraction-data-driven full-waveform inversion(FWI), especially for the deep target area where diving waves cannot be acquired at the surface. Nevertheless, as a typical nonlinear inverse problem, reflection waveform inversion may easily suffer from the cycleskipping issue and have a slow convergence rate, if gradient-based first-order optimization methods are used. To improve the accuracy and convergence rate, we introduce the Hessian operator into reflection traveltime inversion(RTI) and reflection waveform inversion(RWI) in the framework of second-order optimization. A practical two-stage workflow is proposed to build the velocity model, in which Gauss-Newton RTI is first applied to mitigate the cycle-skipping problem and then Gauss-Newton RWI is employed to enhance the model resolution. To make the Gauss-Newton iterations more efficiently and robustly for large-scale applications, we introduce proper preconditioning for the Hessian matrix and design appropriate strategies to reduce the computational costs. The example of a real dataset from East China Sea demonstrates that the cascaded Hessian-based RTI and RWI have good potential to improve velocity model building and seismic imaging, especially for the deep targets.

关键词： Reflection waveform inversion Reflection traveltime inversion Gauss-Newton Hessian

From electronic excited state theory to the property predictions of organic optoelectronic materials

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2013年第9期56卷 1277-1284页

作者： ShuaI ZhiGang XU Wei PENG Qian geng hua MOE Key Laboratory of Organic Optoelectronics and Molecular Engineering Department of ChemistryTsinghua University Key Laboratory of Organic Solids Beijing National Laboratory for Molecular ScienceInstitute of ChemistryChinese Academy of Sciences

We introduce here a work package for a National Natural Science Foundation of China Major Project. We propose to develop computational methodology starting from the theory of electronic excitation processes to predicting the opto-electronic property for organic materials, in close collaborations with experiments. Through developing methods for the electron dynamics, considering superexchange electronic couplings, spin-orbit coupling elements between excited states, electron-phonon relaxation, intermolecular Coulomb and exchange terms we combine the statistical physics approaches including dynamic Monte Carlo, Boltzmann transport equation and Boltzmann statistics to predict the macroscopic properties of opto-electronic materials such as light-emitting efficiency, charge mobility, and exciton diffusion length. Experimental synthesis and characterization of D-A type ambipolar transport material as well as novel carbon based material will provide a test ground for the verification of theory.

关键词： electron dynamics methods statistical physics approaches light-emitting efficiency charge mobility exciton diffusion

Suspension of Australian National Electricity Market in 2022 Necessitates Mechanism Evolution Ensuring Power Supply Security

在线全文

学校读者我要写书评

暂无评论

Journal of Modern Power Systems and Clean Energy 2023年第2期11卷 674-679页

作者： Zhenfei Tan hua geng Xiaoyuan Xu Sijie Chen Zheng Yan Key Laboratory of Control of Power Transmission and Conversion Ministry of Educationand Shanghai Non-Carbon Energy Conversion and Utilization InstituteShanghai Jiao Tong UniversityShanghai 200240China

The National Electricity Market(NEM)in Australia was suspended during June 15-23,2022,with a primary attribution to the lack of available generation *** incident is noteworthy because it was the first market suspension in NEM’s history and took place in a major energy exporting *** this letter,we review the outline and impacts of the *** the perspectives of market regulation,electricity supply,and electricity demand,we identify three underlying causes of the market suspension and offer four recommendations for the market mechanism evolution to ensure power supply security.

关键词： Electricity market administered pricing power system security energy crisis demand response

Gallai's Conjecture on Path Decompositions

在线全文

学校读者我要写书评

暂无评论

Journal of the Operations Research Society of China 2023年第3期11卷 439-449页

作者： geng-hua Fan Jian-Feng Hou Chui-Xiang Zhou Center for Discrete Mathematics Fuzhou UniversityFuzhou350003FujianChina

Gallai's conjecture asserts that every connected graph on n vertices can be decomposed into at most n+1/2 *** E-subgraph of a graph G,denoted by G_(e),is the subgraph induced by the vertices of even degree in G.A triangle pair is a graph consisting of two triangles with exactly one vertex in *** this paper,it is proved that Gallai's conjecture is true for graphs G in which G_(e)contains no triangle pair and each block of G_(e)has maximum degree at most 3.

关键词： Gallai's conjecture Path Triangle Decomposition