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Distributed Secondary Control and Optimal Power Sharing in Microgrids

IEEE/CAA Journal of Automatica Sinica 2015年第3期2卷 304-312页

作者： Gang Chen Ening Feng the Key Laboratory of Dependable Service Computing in Cyber Physical Society of Ministry of Education and the College of Automation Chongqing University

We address the control problem of microgrids and present a fully distributed control system which consists of primary controller, secondary controller, and optimal active power sharing controller. Different from the existing control structure in microgrids, all these controllers are implemented as local controllers at each distributed generator. Thus, the requirement for a central controller is obviated. The performance analysis of the proposed control systems is provided, and the finite-time convergence properties for distributed secondary frequency and voltage controllers are achieved. Moreover, the distributed control system possesses the optimal active power sharing property. In the end, a microgrid test system is investigated to validate the effectiveness of the proposed control strategies. © 2014 Chinese Association of Automation.

关键词： Control system analysis Control systems Distributed parameter control systems Distributed parameter networks Electric power distribution

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Load-redistribution strategy based on time-varying load against cascading failure of complex network

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Chinese Physics B 2015年第7期24卷 371-377页

作者：刘军熊庆宇石欣王楷石为人 School of Automation Chongqing University Key Laboratory of Dependable Service Computing in Cyber Physical Society Ministry of Education School of Software Engineering Chongqing University

Cascading failure can cause great damage to complex networks, so it is of great significance to improve the network robustness against cascading failure. Many previous existing works on load-redistribution strategies require global information, which is not suitable for large scale networks, and some strategies based on local information assume that the load of a node is always its initial load before the network is attacked, and the load of the failure node is redistributed to its neighbors according to their initial load or initial residual capacity. This paper proposes a new load-redistribution strategy based on local information considering an ever-changing load. It redistributes the loads of the failure node to its nearest neighbors according to their current residual capacity, which makes full use of the residual capacity of the network. Experiments are conducted on two typical networks and two real networks, and the experimental results show that the new load-redistribution strategy can reduce the size of cascading failure efficiently.

关键词： load redistribution time-varying load cascading failure complex networks

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Morphable Resistive Memory Optimization for Mobile Virtualization

Morphable Resistive Memory Optimization for Mobile Virtualiz...

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作者： Long, Linbo Liu, Duo Liang, Liang Zhu, Xiao Zhong, Kan Shao, Zili Sha, Edwin Hsing-Mean Key Laboratory of Dependable Service Computing in Cyber Physical Society Ministry of Education Chongqing University Chongqing400044 China College of Computer Science Chongqing University Chongqing400044 China College of Communication Engineering Chongqing University Chongqing400044 China Department of Computing Hong Kong Polytechnic University Kowloon999077 Hong Kong

Virtualization offers significant benefits, such as better isolation and security for mobile systems. However, the limited amount of memory and virtualization's memory-demanding nature make it challenging to virtualize mobile systems efficiently. In this paper, we utilize morphable resistive memories to design a high-performance mobile system with an extensible memory space. With morphable resistive memories, a simple and effective page management technique, Balloonfish, is proposed to convert the memory cell state between multilevel and single-level for achieving a balance between performance and memory space. First, an application-specific page allocation is proposed for managing morphable resistive memories in virtualized mobile systems. Besides, we use a balloon-style algorithm to balance memory allocation among multiple virtual machines. Our evaluation based on the Samsung Exynos 5250 system-on-chip with various real Android applications shows that our system achieves 28.63% performance improvement compared with the baseline scheme. © 1982-2012 IEEE.

关键词： Phase change memory

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A Novel Approach for Short-Term Electric Load Forecasting

A Novel Approach for Short-Term Electric Load Forecasting

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World Congress on Intelligent Control and Automation

作者： Xiaoqin Wu Zhixi Shen Yongduan Song Key Laboratory of Dependable Service Computing in Cyber Physical Society Ministry of Education and School of Automation Chongqing University Chongqing 400044 China

ISBN: (纸本)9781467384155

Rapid and accurate load forecasting is vital for renewable yet highly stochastic power (such as wind and solar power) to be massively utilized in practice. The model-based forecasting algorithms are derived from the specific load models. This paper proposes a new approach for load forecasting in power systems by using trajectory tracking stability theory. And based upon Lyapunov stability theory, the proposed method is essentially model independent and can ensure the prediction error convergence.

关键词： Load forecasting Load modeling Integrated circuits Forecasting Predictive models Trajectory load forecasting Load modeling Prediction models trajectory Integrated circuits Electronic circuits stability theory electric loads forecasting specific load

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Optimizing Data Placement of MapReduce on Ceph-Based Framework under Load-Balancing Constraint

Optimizing Data Placement of MapReduce on Ceph-Based Framewo...

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International Conference on Parallel and Distributed Systems (ICPADS)

作者： Edwin H.-M. Sha Yutong Liang Weiwen Jiang Xianzhang Chen Qingfeng Zhuge College of Computer Science Chongqing University Chongqing China Key Laboratory of Dependable Service Computing in Cyber Physical Society Ministry of Education Chongqing

ISBN: (纸本)9781509053827

Ceph has been widely used as a distributed object store and file system due to its high availability, reliability and scalability. Strategies of data placements in Ceph composed of heterogeneous clusters can greatly affect the system performance and load balancing. For a given application, it is critical to find the optimal data placement in Ceph, such that the completion time of the application can be minimized under the load-balancing constraint. This paper presents a novel Ceph-based framework that integrally considers the load balancing and the heterogeneities, including the computational capacity and the network bandwidth. The presented framework is suitable for the applications based on the principle of moving computation rather than data across clusters, such as MapReduce. According to the Ceph-based framework and the properties of MapReduce, we formulate the Mixed Integer Linear Programming (MILP) to obtain the optimal data placement. However, because of the large computational complexity of MILP, we devise an efficient algorithm to obtain the near-optimal solutions. The experimental results show that the proposed algorithm can achieve up to 25.6% improvement on system performance, compared with the original strategy implemented in Ceph.

关键词： Performance evaluation Load management Clustering algorithms Distributed databases Bandwidth Partitioning algorithms Reliability

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Yet Another Robot Application?

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IEEE ROBOTICS & AUTOMATION MAGAZINE 2016年第2期23卷 12-+页

作者： Salvini, Pericle Korsah, Ayorkor Nourbakhsh, Illah Department of Computer Architecture and Automation Computer Science Faculty Complutense University of Madrid c∖José García Santesmases s∖n Madrid Spain Key Laboratory of Dependable Service Computing in the Cyber Physical Society of the Ministry of Education Chongqing University and the College of Automation Chongqing University Chongqing China School of Automation Chongqing University Chongqing China Department of Electrical Engineering and Computer Science Northwestern University Evanston IL School of Electrical and Electronic Engineering Nanyang Technological University Singapore

The articles in this special section is to find out what lies beyond the fascination toward robots that we have inherited from popular culture, the pleasure of learning with robots derived from the gamification of learning, and the strong appeal for robotics technologies given by its aura of innovation. Are there authentic ways in which robotics can improve education, and what affordances does robotics, in particular, provide for such educational transformation? Indeed, one of the biggest gray areas of educational robotics concerns the lack of empirical evidence on the educational (pedagogical as well as psychological) effectiveness of robots that is related to both the lack of standardized evaluation criteria and the methodological difficulties in conducting sound scientific tests.

关键词： Special issues and sections Robots Computer applications Technology forecasting Engineering education STEM Education Programming

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Distributed multi-agent optimization subject to nonidentical constraints and communication delays

Distributed multi-agent optimization subject to nonidentical...

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作者： Lin, Peng Ren, Wei Song, Yongduan School of Electronic and Information Engineering Xi'An Jiaotong University China State Key Laboratory of Networking and Switching Technology Beijing University of Posts and Telecommunications Beijing China Department of Electrical and Computer Engineering University of California Riverside United States Key Laboratory of Dependable Service Computing Cyber Physical Society Ministry of Education Chongqing University China School of Automation Chongqing University China

In this paper, we study a distributed optimization problem using a subgradient projection algorithm for multi-agent systems subject to nonidentical constraints and communication delays under local communication. Here the agents capable of communicating with their local neighbors are constrained to remain in possibly different closed convex sets and optimize a global objective function composed of a sum of local objective functions, each of which is known to only one agent. First, we consider the case of fixed graphs and show that distributed optimization might not be achieved on general strongly connected directed graphs. Instead, the agents optimize a weighted sum of the local objective functions. Then we consider the case of switching graphs and show that distributed optimization can be achieved when the adjacency matrices are doubly stochastic and the union of the directed graphs is strongly connected among each time interval of a certain bounded length. Furthermore, we consider the case of communication delays, where the delays are mutually independent. It is shown that the distributed optimization problem can be solved by introducing additional delays to the subgradient projection algorithm and the communication delays can be arbitrarily bounded. Finally, numerical examples are included to show the obtained theoretical results. © 2015 Elsevier Ltd. All rights reserved.

关键词： Multi agent systems

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FLIC: Fast, Lightweight Checkpointing for Mobile Virtualization using NVRAM

FLIC: Fast, Lightweight Checkpointing for Mobile Virtualizat...

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Design, Automation & Test in Europe Conference & Exhibition

作者： Kan Zhong Duo Liu Liang Liang Linbo Long Yi Lin Zili Shao Key Lab. of Dependable Service Computing in Cyber Physical Society (Chongqing Univ.) Ministry of Education China

ISBN: (纸本)9781467392280

Checkpointing is a key enabler of hibernation, live migration and fault-tolerance for virtual machines (VMs) in mobile devices. However, checkpointing a VM is usually heavyweight: the VM's entire memory needs to be dumped to storage, which induces a significant amount of (slow) I/O operations, degrading system performance and user experience. In this paper, we propose FLIC, a fast and lightweight checkpointing machinery for virtualized mobile devices by taking advantages of recent byte-addressable, non-volatile memory (NVRAM). Instead of saving the VM's entire memory to storage, we store its working set pages in NVRAM, avoiding accessing slow flash memory (compared to server-grade SSDs). To cope with the energy constraint of mobile systems, we further deduplicate VM snapshots, reducing the VM's image size and saving storage space. Experimental results based on an Exynos 5250 SoC show that our approach can effectively improve the performance of checkpointing in mobile virutalization and save energy.

关键词： VMs NVRAM SSDs

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Fully distributed flocking with a moving leader for Lagrange networks with parametric uncertainties

Fully distributed flocking with a moving leader for Lagrange...

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作者： Ghapani, Sheida Mei, Jie Ren, Wei Song, Yongduan Department of Electrical and Computer Engineering University of California Riverside United States School of Mechanical Engineering and Automation Harbin Institute of Technology Shenzhen Graduate School Shenzhen China Key Laboratory of Dependable Service Computing Cyber Physical Society Ministry of Education Chongqing University China School of Automation Chongqing University China

This paper addresses the leader-follower flocking problem with a moving leader for networked Lagrange systems with parametric uncertainties under a proximity graph. Here a group of followers move cohesively with the moving leader to maintain connectivity and avoid collisions for all time and also eventually achieve velocity matching. In the proximity graph, the neighbor relationship is defined according to the relative distance between each pair of agents. Each follower is able to obtain information from only the neighbors in its proximity, involving only local interaction. We consider two cases: (i) the leader moves with a constant velocity, and (ii) the leader moves with a varying velocity. In the first case, a distributed continuous adaptive control algorithm accounting for unknown parameters is proposed in combination with a distributed continuous estimator for each follower. In the second case, a distributed discontinuous adaptive control algorithm and estimator are proposed. Then the algorithm is extended to be fully distributed with the introduction of gain adaptation laws. In all proposed algorithms, only one-hop neighbors' information (e.g., the relative position and velocity measurements between the neighbors and the absolute position and velocity measurements) is required, and flocking is achieved as long as the connectivity and collision avoidance are ensured at the initial time and the control gains are designed properly. Numerical simulations are presented to illustrate the theoretical results. © 2016 Elsevier Ltd. All rights reserved.

关键词： Multi agent systems

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Energy-Efficient In-Memory Paging for Smartphones

Energy-Efficient In-Memory Paging for Smartphones

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作者： Zhong, Kan Liu, Duo Liang, Liang Zhu, Xiao Long, Linbo Wang, Yi Sha, Edwin Hsing-Mean College of Computer Science Chongqing University Chongqing400044 China Key Laboratory of Dependable Service Computing in Cyber Physical Society Chongqing University Ministry of Education Chongqing400044 China College of Communication Engineering Chongqing University Chongqing400044 China College of Computer Science and Software Engineering Shenzhen University Shenzhen518060 China

Smartphones are becoming increasingly energy-hungry to support feature-rich applications, posing a lot of pressure on battery lifetime and making energy consumption a non-negligible issue. In particular, dynamic random access memory (DRAM)-based main memory subsystem is a major contributor to the energy consumption of mobile devices. In this paper, we propose direct read (DR). Swap, an energy-efficient in-memory paging design to reduce energy consumption in smartphones. In DR. Swap, we adopt emerging energy-efficient nonvolatile memory (NVM) and use it as the swap area. Utilizing NVMs byte-addressability, we propose DR which guarantees zero memory copy for read-only requests when accessing a page in swap area. To better understand the energy consumption of swapping, we build an energy model to analyze the energy consumption of different paging architectures. We evaluate DR. Swap based on the Google Nexus 5 smartphone, experimental results show that our technique can reduce more than 50% energy consumption compared to DRAM backed swapping. © 2015 IEEE.

关键词： Smartphones

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