IEEE Power Electronics Magazine - June 2015 - 10

Letter to the Editor

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their views on issues pertaining to
IEEE Power Electronics Magazine
and the power electronics profession. Letters may be edited for publication. Please e-mail all letters
to the editor-in-chief, bindra1@
verizon.net.

In Defense of Photovoltaic
Inverters

T

he article "Power Electronics
at the Grid Edge" by Deepak
Divan, Rohit Moghe, and Anish
Prasai in the December 2014 issue of
IEEE Power Electronics Magazine [1]
was able to demonstrate the ability of
various means to stabilize the voltage
at the edge of the power grid. It was
pointed out that distributed shunt var
injection devices do the job in the
most cost-effective way.
I agree with the authors that var
injection is the most effective way to
manage the problem of voltage stabilization. But I do not agree with their
statement in the second paragraph
that photovoltaic (PV) inverters cannot stabilize voltage.
To prove their statement, they
refer to IEEE Standard 1547.2-2008,
April 2009. In 2014, a new version,
IEEE Standard 1547a-2014, became
valid. Regarding this standard, var
Digital Object Identifier 10.1109/MPEL.2015.2420051
Date of publication: 24 June 2015

10

IEEE POWER ELECTRONICS MAGAZINE

injection with a PV inverter is perIEEE Power Energy Mag., vol. 11, no. 2, pp.
mitted. And it makes a lot of sense
55-64, Mar./ Apr. 2013.
to use the abilities that the new ver[3] D. Mende, J. Schwarz, S. Schmidt, D. Premm,
sion of the standard established. The
V. Sakschewski, M. Pfalzgraf, H. Homeyer, J.
authors of [1] identified that some of
Schmiesing, and J. Brantl, "Reactive power conthe voltage deviations at the edge of
trol of PV plants to increase the grid hosting
the grid are caused by the integration
capacity," in Proc. 28th European Photovoltaic
of renewable resources. That is true,
Solar Energy Conf. Exhibition, pp. 4225-4230,
but due to the fact that renewable re2013.
sources are normally coupled to the
grid via inverters, it seems to be reaAuthors' Reply
sonable to use the same inverter to
We would like to thank the reader for
control the voltage via var injection.
raising the very valid point that PV inNumerous studverters could potenies (see [2] and [3])
tially self-compensate
underlined the abilfor the volatility that
Distributed shunt
ity to stabilize the
comes about due to
var injection devices
grid with the varsolar intermittency. In
do the job in the most
injection capability
light of the recently
cost-effective way.
of PV inverters. It
published 2014 amendis a cost-effective,
ment to IEEE Stanproven, and clever
dard 1547-2003, PV inconcept because one device covers
verters are finally approved to provide
two tasks. Therefore, it is important
var compensation. However, there are
that the use of the new standard
still technical and economical challengis deployed as much as possible to
es that need to be overcome.
decrease the overall costs of renewConsidering the recommendaable sources.
tions of the California Smart Inverter
Andreas Falk
Working Group, one sees that a Q-V
SMA Solar Technology AG
droop plus dead-band profile is used
Niestetal, Germany
to control the var injection of the local PV inverter, covering over 60% of
the allowed voltage band [1]. While
References
this approach can solve the voltage
[1] D. Divan, R. Moghe, and A. Prasai, "Power
compliance issue, it can also defeat
electronics at the grid edge," IEEE Power Electhe broader objective of volt-var contron. Mag., vol. 1, no. 4, pp. 16--22, Dec. 2014.
trol (VVC) that the utility is pursuing
[2] J. von Appen, M. Braun, T. Stetz, K. Diwold,
and investing heavily in. Second, PV
and D. Geibel, "Time in the sun, The challenge of
inverters may not be located ideally,
high PV penetration in the German electric grid,"

 June 2015



Table of Contents for the Digital Edition of IEEE Power Electronics Magazine - June 2015

IEEE Power Electronics Magazine - June 2015 - Cover1
IEEE Power Electronics Magazine - June 2015 - Cover2
IEEE Power Electronics Magazine - June 2015 - 1
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IEEE Power Electronics Magazine - June 2015 - Cover3
IEEE Power Electronics Magazine - June 2015 - Cover4
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