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Inexact convex relaxations for AC optimal power flow: Towards AC feasibility

Journal Article · · Electric Power Systems Research
 [1];  [1];  [2]
  1. Technical Univ of Denmark, Lyngby (Denmark)
  2. Georgia Inst. of Technology, Atlanta, GA (United States); Argonne National Lab. (ANL), Lemont, IL (United States)
Convex relaxations of AC optimal power flow (AC-OPF) problems have attracted significant interest as in several instances they provably yield the global optimum to the original non-convex problem. If, however, the relaxation is inexact, the obtained solution is not AC-feasible. The quality of the obtained solution is essential for several practical applications of AC-OPF, but detailed analyses are lacking in existing literature. Here, this paper aims to cover this gap. We provide an in-depth investigation of the solution characteristics when convex relaxations are inexact, we assess the most promising AC feasibility recovery methods for large-scale systems, and we propose two new metrics that lead to a better understanding of the quality of the identified solutions. We perform a comprehensive assessment on 96 different test cases, ranging from 14 to 3120 buses, and we show the following: (i) Despite an optimality gap of less than 1%, several test cases still exhibit substantial distances to both AC feasibility and local optimality and the newly proposed metrics characterize these deviations. (ii) Penalization methods fail to recover an AC-feasible solution in 15 out of 45 test cases. (iii) The computational benefits of warm-starting non-convex solvers have significant variation, but a computational speedup exists in over 75% of cases.
Research Organization:
Argonne National Laboratory (ANL), Argonne, IL (United States)
Sponsoring Organization:
USDOE Office of Electricity (OE)
Grant/Contract Number:
AC02-06CH11357
OSTI ID:
1829268
Alternate ID(s):
OSTI ID: 1634274
Journal Information:
Electric Power Systems Research, Journal Name: Electric Power Systems Research Vol. 187; ISSN 0378-7796
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

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