Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: hynet: An Optimal Power Flow Framework for Hybrid AC/DC Power Systems   High-voltage direct current (HVDC) systems are increasingly incorporated into
today's AC power grids, necessitating optimal power flow (OPF) tools for the
analysis, planning, and operation of such hybrid systems. To this end, we
introduce hynet, a Python-based open-source OPF framework for hybrid AC/DC
grids with point-to-point and radial multi-terminal HVDC systems. hynet's
design promotes ease of use and extensibility, which is supported by the
particular mathematical model and software design presented in this paper. The
system model features a unified representation of AC and DC subgrids as well as
a concise and flexible converter model, which enable the compact description of
a hybrid AC/DC power system and its OPF problem. To support convex relaxation
based OPF solution techniques, a state space relaxation is introduced to obtain
a unified OPF formulation that is analogous to the OPF of AC power systems.
This enables the direct generalization of relaxation-related results for AC
grids to hybrid AC/DC grids, which is shown for the semidefinite and
second-order cone relaxation as well as associated results on exactness and
locational marginal prices. Finally, hynet's object-oriented software design is
discussed, which provides extensibility via inheritance and standard design
patterns, and its robust and competitive performance is illustrated with case
studies.

20
The categories of this paper are: acc-phys
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The categories of this paper are: econ
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess
27
The categories of this paper are: comp-gas
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
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The categories of this paper are: chem-ph
23
The categories of this paper are: solv-int
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The categories of this paper are: adap-org
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The categories of this paper are: alg-geom
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-ex