Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Solar PV Frequency Control in the U.S. EI and ERCOT Interconnections --
  Case Studies and Recommendations   This paper studied the solar PV frequency control in the U.S. Eastern
Interconnection (EI) and Texas Interconnection (ERCOT) systems. The studied
frequency control approaches include droop frequency control, inertia control,
and droop-inertia-combined frequency control. The control effects of different
frequency controls of PV in the EI and ERCOT are studied using actual high PV
penetration interconnection grid models to provide suggestions to the future
revision of future PV frequency control standards.

2
The categories of this paper are: math
18
The categories of this paper are: econ
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
30
The categories of this paper are: q-alg
6
The categories of this paper are: astro-ph
36
The categories of this paper are: cmp-lg
28
The categories of this paper are: alg-geom
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
22
The categories of this paper are: chao-dyn
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The categories of this paper are: solv-int
27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th