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Branch flow model: Relaxations and convexification

Farivar, Masoud and Low, Steven (2014) Branch flow model: Relaxations and convexification. In: 2014 IEEE PES T&D Conference and Exposition. IEEE , Piscataway, NJ. ISBN 978-1-4799-3656-4.

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We propose a branch flow model for the analysis and optimization of mesh as well as radial networks. The model leads to a new approach to solving optimal power flow (OPF) that consists of two relaxation steps. The first step eliminates the voltage and current angles and the second step approximates the resulting problem by a conic program that can be solved efficiently. For radial networks, we prove that both relaxation steps are always exact, provided there are no upper bounds on loads. For mesh networks, the conic relaxation is always exact but the angle relaxation may not be exact, and we provide a simple way to determine if a relaxed solution is globally optimal. We propose convexification of mesh networks using phase shifters so that OPF for the convexified network can always be solved efficiently for an optimal solution. We prove that convexification requires phase shifters only outside a spanning tree of the network and their placement depends only on network topology, not on power flows, generation, loads, or operating constraints. Part I introduces our branch flow model, explains the two relaxation steps, and proves the conditions for exact relaxation. Part II describes convexification of mesh networks, and presents simulation results.

Item Type:Book Section
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Low, Steven0000-0001-6476-3048
Additional Information:© 2014 IEEE.
Record Number:CaltechAUTHORS:20170124-173857414
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:73684
Deposited By: Kristin Buxton
Deposited On:26 Jan 2017 00:29
Last Modified:11 Nov 2021 05:20

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