14,516 research outputs found
Distributed Contingency Analysis over Wide Area Network among Dispatch Centers
Traditionally, a regional dispatch center uses the equivalent method to deal
with external grids, which fails to reflect the interactions among regions.
This paper proposes a distributed N-1 contingency analysis (DCA) solution,
where dispatch centers join a coordinated computation using their private data
and computing resources. A distributed screening method is presented to
determine the Critical Contingency Set (DCCS) in DCA. Then, the distributed
power flow is formulated as a set of boundary equations, which is solved by a
Jacobi-Free Newton-GMRES (JFNG) method. During solving the distributed power
flow, only boundary conditions are exchanged. Acceleration techniques are also
introduced, including reusing preconditioners and optimal resource scheduling
during parallel processing of multiple contingencies. The proposed method is
implemented on a real EMS platform, where tests using the Southwest Regional
Grid of China are carried out to validate its feasibility.Comment: 5 pages, 6 figures, 2017 IEEE PES General Meetin
Energy-Efficient Flow Scheduling and Routing with Hard Deadlines in Data Center Networks
The power consumption of enormous network devices in data centers has emerged
as a big concern to data center operators. Despite many
traffic-engineering-based solutions, very little attention has been paid on
performance-guaranteed energy saving schemes. In this paper, we propose a novel
energy-saving model for data center networks by scheduling and routing
"deadline-constrained flows" where the transmission of every flow has to be
accomplished before a rigorous deadline, being the most critical requirement in
production data center networks. Based on speed scaling and power-down energy
saving strategies for network devices, we aim to explore the most energy
efficient way of scheduling and routing flows on the network, as well as
determining the transmission speed for every flow. We consider two general
versions of the problem. For the version of only flow scheduling where routes
of flows are pre-given, we show that it can be solved polynomially and we
develop an optimal combinatorial algorithm for it. For the version of joint
flow scheduling and routing, we prove that it is strongly NP-hard and cannot
have a Fully Polynomial-Time Approximation Scheme (FPTAS) unless P=NP. Based on
a relaxation and randomized rounding technique, we provide an efficient
approximation algorithm which can guarantee a provable performance ratio with
respect to a polynomial of the total number of flows.Comment: 11 pages, accepted by ICDCS'1
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