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Partition-based Network Equivalent Method for Power System Subsynchronous Oscillation Analysis

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Journal of Modern Power Systems and Clean Energy 2024年第1期12卷 313-320页

作者： Chenxuan Wang weimin zheng Zhen Wang Yangqing Dan Ping Ju the department of Electrical Engineering Zhejiang UniversityHangzhou 310027China the Economic Research Institute of State Grid Zhejiang Electric Power Co. Ltd.Hangzhou 310016China the College of Energy and Electrical Engineering Hohai UniverstiyNanjing 211100China

Given large-scale modern power systems with pow er electronic converters,the numerical simulation with subsyn chronous oscillation(SSO)faces great challenges in engineering practice due to sharply enlarged modeling scale and high com putational *** reduce the modeling scale,network parti tion and equivalent becomes a vital technique in numerical sim *** several methods have been developed for net work equivalent,a generally accepted rule for network parti tion is still *** paper proposes that the system can be partitioned into three parts,i.e.,the internal,the middle,and the external subsystems,in which the internal subsystem consists of all power electronic components,the middle subsys tem includes those selected AC dynamic components with de tailed models,and the remaining components and buses consti tute the external *** external subsystem is further represented by an equivalent RLC network determined by the frequency dependent network equivalent(FDNE)*** the proposed method,the observability index and the electrical distance index are used to identify the interface between the middle and the external *** studies based on a modified Hydro-Quebec system are used to verify the effective ness of the proposed method.

关键词： Electrical distance network equivalent subsyn chronous oscillation observability index

An introduction to Tsinghua Cloud

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science china(Information sciences) 2010年第7期53卷 1481-1486页

作者： zheng weimin1,2.1department of computer science and technology, Tsinghua {2., Beijing 100084,{3. 2.singhua National Laboratory for Information science and technology, Beijing 100084,{3. department of computer {2. and {3. Tsinghua University Beijing China Tsinghua National Laboratory for Information science and technology Beijing China

Cloud computing has become a trend that draws attention from both academia and industry all over the world. This paper unveils details of Tsinghua Cloud, a comprehensive solution for cloud computing developed by Tsing... 详细信息

关键词： cloud computing distributed file system virtual computing environment data sharing

Superconductivity of small metal grains

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science china(Physics,Mechanics & Astronomy) 2005年第4期48卷 431-441页

作者： zheng Renrong1 CHEN Zhiqian2.& ZHU Shunquan1,3.1. department of Physics, Shanghai Normal {2., Shanghai 2.02.4,{3. 2. department of Physics, Southwest Normal {2., Chongqing 400715,{3. 3. department of computer and Electric {13., Shanghai Business School, Shanghai 2.1400,{3. department of Physics Shanghai Normal University Shanghai China department of Physics Southwest Normal University Chongqing China department of computer and Electric {2. Shanghai Business School Shanghai China

The formulas of the energy gap and superconducting critical temperature appropriate for systems with both odd and even number of electrons are derived; the bases of the derivations are BCS theory and energy level statistics. Numerical results qualitatively agree with the experimental phenomena. i.e., the superconductivity of small metallic grains will first enhance then decrease to zero when the grain are getting smaller and smaller. The calculations indicate that the above phenomena happen in the metallic grains belonging to Gaussian Orthogonal Ensemble (GOE) and Gaussian Unitary ensemble (GUE) with zero spin; The superconductivity of small metallic grains in Gaussian Symplectic Ensemble (GSE) will monotonically decrease to zero with the decreasing of the grain size. The analyses suggest that the superconductivity enhancements come from pairing and the balance of the strengths between spin-orbital coupling and external magnetic field. In order to take the latter into account, it is necessary to include the level statistics given by Random Matrix Theory (RMT) in describing small metallic grains.

关键词： size effect, superconductivity enhancements, small metallic grains.

CUDA-Zero:a framework for porting shared memory GPU applications to multi-GPUs

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science china(Information sciences) 2012年第3期55卷 663-676页

作者： CHEN DeHao , CHEN WenGuang & zheng weimin {2. of {3. science and technology, Tsinghua university, Beijing 100084, china department of computer {2. and {3. Tsinghua University Beijing China

As the prevalence of general purpose computations on GPU, shared memory programming models were proposed to ease the pain of GPU programming. However, with the demanding needs of more intensive workloads, it’s desirable to port GPU programs to more scalable distributed memory environment, such as multi-GPUs. To achieve this, programs need to be re-written with mixed programming models (e.g. CUDA and message passing). Programmers not only need to work carefully on workload distribution, but also on scheduling mechanisms to ensure the efficiency of the execution. In this paper, we studied the possibilities of automating the process of parallelization to multi-GPUs. Starting from a GPU program written in shared memory model, our framework analyzes the access patterns of arrays in kernel functions to derive the data partition schemes. To acquire the access pattern, we proposed a 3.tiers approach: static analysis, profile based analysis and user annotation. Experiments show that most access patterns can be derived correctly by the first two tiers, which means that zero efforts are needed to port an existing application to distributed memory environment. We use our framework to parallelize several applications, and show that for certain kinds of applications, CUDA-Zero can achieve efficient parallelization in multi-GPU environment.

关键词： CUDA parallelization data access pattern multi-GPU

A user-space file system for on-demand legacy desktop software

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science china(Information sciences) 2011年第6期54卷 1142-1150页

作者： ZHANG YouHui 1,2., SU GeLin 1,2.& zheng {3. 1,{2. department of {3. science and technology, Tsinghua university, Beijing 100084, china 2.Tsinghua National Laboratory for Information science and technology, Tsinghua university, Beijing 100084, china department of computer {2. and {3. Tsinghua University Beijing China Tsinghua National Laboratory for Information science and technology Tsinghua University Beijing China

Some user-level virtualization technologies have been used to convert legacy software (like the existing Windows desktop applications) into the on-demand software without any modification. To give the client a friendly and compatible method to access on-demand legacy software across the Internet, this paper presents a clientend file system for this usage case. It is a Windows user-space file system based on the cloud storage (where the on-demand software is stored), which converts the local file system accesses into remote visits. Quite a few optimizations are adopted and adjusted to suit the file-access-pattern of on-demand software, including the local cache, metadata/data/software prefetch and content-addressable storage (CAS), to decrease the number of remote visits and/or to overlap IO (input/output) operations with software execution. Detailed access-pattern analyses are also presented. This file system has been implemented and tests show that it is practical for much daily-used software-a local cache of limited size can provide up to 80% hit ratio and the corresponding overhead of running-time is about 3.%. Owing to this method, on any compatible and networked computer, a user can use his/her personalized software conveniently although it does not exist on the local host.

关键词： on-demand software software as a service user-space file system cloud storage

Optimizing write operation on replica in data grid

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science china(Information sciences) 2011年第1期54卷 1-11页

作者： XU PengZhi,WU YongWei,HUANG XiaoMeng, YANG GuangWen & zheng weimin {2. of {3. science and technology,Tsinghua university,Beijing 100084,china department of computer {2. and {3. Tsinghua University Beijing China

Replication technique can improve access performance and data availability of data grid systems. So far,most related work on data replication in data grid systems focuses on read-only *** write operations have been widely used in practice,its optimization problem has not been suciently *** this paper,we show that write requests from users can be processed by a nearest site,regardless of the location of latest written *** policy of write nearby instead of write to the latest replica can improve the performance of write operations,while inconsistency is caused between multiple ***,we propose two metadata management algorithms to make sure that users can retrieve up-to-date datasets at any *** extend OptorSim to support the implementation and evaluation of our *** results of simulation show that our scheme achieves performance gains up to 3.3.compared with WriteMaster scheme.

关键词： replication data grid simulation access latency

A　Nonprecedence－based　Query　Schedule　Algorithm　on　Heterogeneous　Multiprocessor　System

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Journal of Systems Engineering and Electronics 1995年第3期6卷 63-69页

作者： He Jun bang Dingxing & zheng weimin({2. of {3. science & technology,Tsinghua university, Beijing, 100084, china) department of computer {2. & {3. Tsinghua University Beijing 100084 China

There has been a number of algorithms designed to handle intra-query or inter-query scheduling in multiprocessor-based parallel database system. They all have the assumption that the processorsare identical. But in some cases, such as shared nothing environment, this assumption would not be fullyvalid. In this paper we devise and evaluate a scheduling algorithm ELLIST to handle nonprecedence-basedheterogeneous malleable scheduling problem. It uses LLIST-NM as subroutine that handles nonmalleablescheduling without precedence and assuming the processors are identical. Even though the problem we considered is NP-hard in the strong sense, the schedule generated by our algorithm is seen experimentally toachieve results that are close to optimum when there are enough tasks to be scheduled.

关键词： Heterogeneous malleable scheduling Makespan Affinity

Predicting the behavior of large scale P2. systems by parallel discrete event simulation

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science china(Information sciences) 2010年第6期53卷 1109-1121页

作者： zheng weimin1,YU HongLiang1,SHI GuangYu2.& CHEN Jian2.1department of computer science and technology,Tsinghua {2.,Beijing 100084,{3. 2.uawei Technologies Co.,Ltd,Shenzhen 51812.,{3. department of computer {2. and {3. Tsinghua University Beijing China Huawei Technologies Co. Ltd Shenzhen China

P2. systems are becoming the dominator of *** systems are typically composed of thousands to millions of physical computers,which make it difficult to predict their behaviors without a large scale distributed system *** paper is an attempt to predict the behavior of large scale P2. systems by building a novel parallel simulator:AegeanSim,which provides parallel discrete event simulation of such systems on high performance server *** abstract the execution of P2. applications with a specific event model,and parallel the simulation of events in a cluster,thus expanding the simulation scale and boosting the simulation process dramatically.A 1-stage synchronization method is proposed to improve the *** event callback interface is designed to implement their application logic easily while keeping the simulator *** use AegeanSim to predict the behavior of a typical P2. system:*** comparing the simulation behavior of BT with that of related BT studies and verifying its efficiency,scalability and accuracy,we make predictions about the behavior of BT system assuming they are assaulted by different man-made system *** reasonable results are found:(1) Tracker isolation can hardly work because of its short attacking time window.(2. Limiting the bandwidth of BT may be an efficient way to control it.

关键词： P2. simulation parallel

A computer simulation of nucleation and growth of thin films

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science china(Physics,Mechanics & Astronomy) 2004年第4期47卷 442-451页

作者： zheng Xiaoping1,ZHANG Peifeng2.HE Deyan2.LIU Jun2. MA Jiantai3.1. Key Laboratory of Opto-Electronic technology and Intelligent Control, Ministry of Education, Lanzhou Jiaotong {2., Lanzhou 73.070,{3. 2. School of Physical science and technology, Lanzhou {2., Lanzhou 73.000,{3. 3. School of Chemistry and Chemistry Engineering, Lanzhou {2., Lanzhou 73.000,{3. Key Laboratory of Opto-Electronic technology and Intelligent Control Ministry of Education Lanzhou Jiaotong University Lanzhou China School of Physical science and technology Lanzhou University Lanzhou China School of Chemistry and Chemistry Engineering Lanzhou University Lanzhou China

A three-dimensional kinetic Monte Carlo technique has been developed for simulating the nucleation and growth of thin films. This model involves incident atom attachment, surface diffusion of the atoms on the growing surface and atom detachment from the growing surface. It takes some new effects into account, such as a significant improvement in calculation of activation energy for the atom diffusion, which renders the model more reasonable. In addition three optimum temperatures and the consistency of their dependence on deposition rate have been found out; the dependence of the surface roughness and relative density on the deposition rate has been discussed; and the approximation of freezing neighbour atoms and periodic boundary conditions has been applied.

关键词： Monte Carlo, thin film, nucleation, surface roughness, relative density.