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Control Strategy Optimization of Voltage Source Converter Connected to Various Types of AC Systems

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Journal of Modern Power Systems and Clean Energy 2021年第1期9卷 77-84页

作者： Zehong Liu senior member Xianshan Guo State Grid Corporation of China Beijing 100031China

Connecting the voltage source converters(VSCs) to various types of AC systems results in different operation characteristics and core problems associated with traditional control strategies. Therefore, it is necessary to optimize the control strategies of the VSCs according to the types of AC *** the VSCs connected to islanded renewable power plants, a voltage/frequency(V/f) droop control strategy is proposed to damp fluctuations of AC voltage and frequency in the island,which is vital for bipolar VSC control. In addition, a multibranch impedance equivalent method for renewable power plants is proposed, with which large-scale renewable power plants can be modeled accurately in the frequency domain to prevent wide-band oscillation. For the VSCs connected to strong AC systems, smart AC voltage and coordinated frequency transient control strategies are proposed, which can improve AC system transient stability. For the VSCs connected to weak AC systems, the relationship between the system stability and strength is analyzed, and then the control strategy of inner-loop control parameter optimization and outer-loop power limiting(if necessary) is proposed to improve the stability of the allied system. The proposed strategies are verified by both software simulation and field commissioning.

关键词： Control strategy optimization islanded renewable power plants stability voltage source converter(VSC) AC system

Interactive Fault Localization Using Test Information

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Journal of Computer Science & Technology 2009年第5期24卷 962-974页

作者：郝丹张路 senior member 谢涛梅宏孙家骕 Key Laboratory of High Confidence Software Technologies Ministry of Education Institute of Software School of Electronics Engineering and Computer Science Peking University Beijing 100871 China Department of Computer Science North Carolina State University Raleigh NC 27695 U.S.A.

Debugging is a time-consuming task in software development. Although various automated approaches have been proposed, they are not effective enough. On the other hand, in manual debugging, developers have difficulty in choosing breakpoints. To address these problems and help developers locate faults effectively, we propose an interactive fault-localization framework, combining the benefits of automated approaches and manual debugging. Before the fault is found, this framework continuously recommends checking points based on statements＇ suspicions, which are calculated according to the execution information of test cases and the feedback information from the developer at earlier checking points. Then we propose a naive approach, which is an initial implementation of this framework. However, with this naive approach or manual debugging, developers＇ wrong estimation of whether the faulty statement is executed before the checking point （breakpoint） may make the debugging process fail. So we propose another robust approach based on this framework, handling cases where developers make mistakes during the fault-localization process. We performed two experimental studies and the results show that the two interactive approaches are quite effective compared with existing fault-localization approaches. Moreover, the robust approach can help developers find faults when they make wrong estimation at some checking points.

关键词： debugging fault localization interactive approach

基于分裂-叠加结构的部分功率主动调控型准单级直流变换方法

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电源学报 2024年第2期22卷 98-105页

作者：侍良东程钰杰杨帆吴红飞南京航空航天大学自动化学院南京211106 南京电子器件研究所南京211106 南京邮电大学自动化学院南京210023

针对“直流变压器级联PWM变换器”两级式架构中各级变换器均需处理全部负载功率、多级变换效率低的问题,提出了基于分裂-叠加架构的部分功率主动调控型准单级直流变换方法。通过将直流变压器输出分裂为两个端口,使得其中一个端口的功率... 详细信息

针对“直流变压器级联PWM变换器”两级式架构中各级变换器均需处理全部负载功率、多级变换效率低的问题,提出了基于分裂-叠加架构的部分功率主动调控型准单级直流变换方法。通过将直流变压器输出分裂为两个端口,使得其中一个端口的功率无需经后级PWM变换器处理而直接传输至负载,等效实现了准单级功率变换,且有效降低了PWM变换器的功率容量和损耗,提高了系统效率。详细分析了分裂-叠加式架构的原理和电路实现方法,深入研究了系统输出电压调节的原理和特性。以其中一个电路为例,详细分析了工作原理、电压调节特性和关键参数设计方法,并通过实验结果验证了所提方案的有效性和正确性。

关键词：双输出直流变压器分裂-叠加结构准单级直流变换

Assisting Visually Impaired People to Acquire Targets on a Large Wall-Mounted Display

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Journal of Computer Science & Technology 2014年第5期29卷 825-836页

作者： Kibum Kim member ACM IEEE 任向实 senior member Center for Human Computer Interaction Kochi University of Technology Kochi 782-8502 Japan

Large displays have become ubiquitous in our everyday lives, but these displays are designed for sighted *** paper addresses the need for visually impaired people to access targets on large wall-mounted displays. We developed an assistive interface which exploits mid-air gesture input and haptic feedback, and examined its potential for pointing and steering tasks in human computer interaction（HCI）. In two experiments, blind and blindfolded users performed target acquisition tasks using mid-air gestures and two different kinds of feedback（i.e., haptic feedback and audio feedback）. Our results show that participants perform faster in Fitts＇ law pointing tasks using the haptic feedback interface rather than the audio feedback interface. Furthermore, a regression analysis between movement time（MT） and the index of difficulty（ID）demonstrates that the Fitts＇ law model and the steering law model are both effective for the evaluation of assistive interfaces for the blind. Our work and findings will serve as an initial step to assist visually impaired people to easily access required information on large public displays using haptic interfaces.

关键词： haptic I/O auditory(non-speech) feedback interaction style human computer interaction visually impaired people

Parallel LDPC Decoding on GPUs Using a Stream-Based Computing Approach

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Journal of Computer Science & Technology 2009年第5期24卷 913-924页

作者： Gabriel Falcao Student member Shinichi Yamagiwa Vitor Silva Leonel Sousa senior member Department of Electrical and Computer Engineering University of Coimbra Instituto de Telecomunicacoes PoloⅡUniversidade de Coimbra 3030-290 Coimbra Portugal INESC-ID Technical University of Lisbon Rua Alves Redol n.9 1000-029 Lisboa Portugal Department of Electrical and Computer Engineering IST Technical University of Lisbon Rua Alves Redol n.9 1000-029 Lisboa Portugal

Low-Density Parity-Check （LDPC） codes are powerful error correcting codes adopted by recent communication standards. LDPC decoders are based on belief propagation algorithms, which make use of a Tanner graph and very intensive message-passing computation, and usually require hardware-based dedicated solutions. With the exponential increase of the computational power of commodity graphics processing units （GPUs）, new opportunities have arisen to develop general purpose processing on GPUs. This paper proposes the use of GPUs for implementing flexible and programmable LDPC decoders. A new stream-based approach is proposed, based on compact data structures to represent the Tanner graph. It is shown that such a challenging application for stream-based computing, because of irregular memory access patterns, memory bandwidth and recursive flow control constraints, can be efficiently implemented on GPUs. The proposal was experimentally evaluated by programming LDPC decoders on GPUs using the Caravela platform, a generic interface tool for managing the kernels＇ execution regardless of the GPU manufacturer and operating system. Moreover, to relatively assess the obtained results, we have also implemented LDPC decoders on general purpose processors with Streaming Single Instruction Multiple Data （SIMD） Extensions. Experimental results show that the solution proposed here efficiently decodes several codewords simultaneously, reducing the processing time by one order of magnitude.

关键词： data-parallel computing graphics processing unit (GPU) Caravela low-density parity-check (LDPC) code error correcting code

ROAD+:Route Optimization with Additional Destination-Information and Its Mobility Management in Mobile Networks

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Journal of Computer Science & Technology 2010年第2期25卷 298-312页

作者： Moonseong Kim Matt W. Mutka member, ACM senior member Jeonghoon Park Hyunseung Choo Department of Computer Science and Engineering Michigan State University East Lansing MI 48824 U.S.A. Digital Media and Communication Business Samsung Electronics Korea School of Information and Communication Engineering Sungkyunkwan University 440-746 Korea

In the NEtwork MObility （NEMO） environment, mobile networks can form a nested structure. In nested mobile networks that use the NEMO Basic Support （NBS） protocol, pinball routing problems occur because packets are routed to all the home agents of the mobile routers using nested tunneling. In addition, the nodes in the same mobile networks can communicate with each other regardless of Internet connectivity. However, the nodes in some mobile networks that are based on NBS cannot communicate when the network is disconnected from the Internet. In this paper, we propose a route optimization scheme to solve these problems. We introduce a new IPv6 routing header named ＂destination-information header＂（DH）, which uses DH instead of routing header type 2 to optimize the route in the nested mobile network. The proposed scheme shows at least 30% better performance than ROTIO and similar performance improvement as DBU in inter-route optimization. With respect to intra-route optimization, the proposed scheme always uses the optimal routing path. In addition, the handover mechanism in ROAD＋ outperforms existing schemes and is less sensitive to network size than other existing schemes.

关键词： NEtwork MObility (NEMO) route optimization (RO) NEMO basic support (NBS) pinball routing problem mobile network nested mobile network

Global-to-Local Approach to Rigorously Developing Distributed System with Exception Handling

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Journal of Computer Science & Technology 2009年第2期24卷 238-249页

作者：蔡超裘宗燕 senior member, member, CCF, IEEE 杨红丽赵翔鹏 LMAM and Department of Informatics School of Mathematical Science Peking University Beijing 100871 China College of Computer Sciences Beijing University of Technology Beijing 100124 China

Cooperative distributed system covers a wide range of applications such as the systems for industrial controlling and business-to-business trading, which are usually safety-critical. Coordinated exception handling （CEH） refers to exception handling in the cooperative distributed systems, where exceptions raised on a peer should be dealt with by all relevant peers in a consistent manner. Some CEH algorithms have been proposed. A crucial problem in using these algorithms is how to develop the peers which are guaranteed coherent in both normal execution and exceptional execution. Straightforward testing or model checking is very expensive. In this paper, we propose an effective way to rigorously develop the systems with correct CEH behavior. Firstly, we formalize the CEH algorithm by proposing a Peer Process Language to precisely describe the distributed systems and their operational semantics. Then we dig out a set of syntactic conditions, and prove its sufficiency for system coherence. Finally~ we propose a global-to-local approach, including a language describing the distributed systems from a global perspective and a projection algorithm, for developing the systems. Given a well-formed global description, a set of peers can be generated automatically. We prove the system composed of these peers satisfies the conditions, that is, it is always coherent and correct for CEH.

关键词： distributed system exception handling fault tolerant formal methods

Designing Motion Gesture Interfaces in Mobile Phones for Blind People

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Journal of Computer Science & Technology 2014年第5期29卷 812-824页

作者： Nem Khan Dim 任向实 senior member ACM IEEE School of Information Kochi University of Technology Kochi 782-8502 Japan

Despite the existence of advanced functions in smartphones, most blind people are still using old-fashioned phones with familiar layouts and dependence on tactile buttons. Smartphones support accessibility features including vibration, speech and sound feedback, and screen readers. However, these features are only intended to provide feedback to user commands or input. It is still a challenge for blind people to discover functions on the screen and to input the commands. Although voice commands are supported in smartphones, these commands are difficult for a system to recognize in noisy environments. At the same time, smartphones are integrated with sophisticated motion sensors, and motion gestures with device tilt have been gaining attention for eyes-free input. We believe that these motion gesture interactions offer more efficient access to smartphone functions for blind people. However, most blind people are not smartphone users and they are aware of neither the affordances available in smartphones nor the potential for interaction through motion gestures. To investigate the most usable gestures for blind people, we conducted a user-defined study with 13 blind participants. Using the gesture set and design heuristics from the user study, we implemented motion gesture based interfaces with speech and vibration feedback for browsing phone books and making a call. We then conducted a second study to investigate the usability of the motion gesture interface and user experiences using the system. The findings indicated that motion gesture interfaces are more efficient than traditional button interfaces. Through the study results, we provided implications for designing smartphone interfaces.

关键词： design motion gesture user-defined study

CCNoC:Cache-Coherent Network on Chip for Chip Multiprocessors

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Journal of Computer Science & Technology 2010年第2期25卷 257-266页

作者：王惊雷薛一波 member, CCF, IEEE 王海霞李崇民汪东升 senior member,CCF Department of Computer Science and Technology Tsinghua University Beijing 100084 China Tsinghua National Laboratory of Information Science and Technology Beijing 100084 China

As the number of cores in chip multiprocessors （CMPs） increases, cache coherence protocol has become a key issue in integration of chip multiprocessors. Supporting cache coherence protocol in large chip multiprocessors still faces three hurdles： design complexity, performance and scalability. This paper proposes Cache Coherent Network on Chip （CCNoC）, a scheme that decouples cache coherency maintenance from processors and shared L2 caches and implements it completely in network on chip to free up processors and shared L2 caches from the chore of maintaining coherency, thereby reduces design complexity of CMPs. In this way, CCNoC also improves the performance of cache coherence protocol through reducing directory access latency and enhances scalability by avoiding massive directories overhead in shared L2 caches. In CCNoC, coherence state caches and active directory caches are implemented in the network interface components of network on chip to maintain cache coherence states for blocks in L1 caches and manage directory information for recently accessed blocks in L2 caches respectively. CCNoC provides a scalable CMP framework to tackle cache coherency which is the foundation of CMP. This paper evaluates the performance of CCNoC. Experimental results show that for a 16-core system, CCNoC improves performance by 3% on average over the conventional chip multiprocessor and by 10% at best, while reduces storage overhead by 1.8% and saves directory storage by 88%, showing good scalability.

关键词： chip multiprocessor network on chip cache coherence protocol