

Improving the Summation Law for Harmonic Current
Emissions of Parallel Operated PV Inverters by Considering Equivalent
Grid Impedance
Hasanali Moghadam, Florian Ackermann and
Sönke Rogalla
2017/04/25

Abstrac
For connection of a PV park to the electricity
network, a precompliance study has to prove that the harmonic emissions
at the point of common coupling (PCC) stays below the limits specified
by the standards or local or national grid codes. An equation defined
in IEC 6140021 [1] is used to estimate the total harmonic current emission
of the park at the PCC prior to installation. The equation uses the harmonic
emission of a single inverter to predict the spectrum of the total current
for a given number of identical inverters connected in parallel at the
PCC.
This paper considers the interaction of parallel operated inverters and
the grid impedance. It proposes an approach based on the so called “equivalent
grid impedance”, to improve the performance of summation law for
evaluation of the current harmonics emissions at the PCC of PV parks.
Improvement of this method would be helpful for power plant constructors.
Published in: Renewable Energy
& Power Quality Journal (RE&PQJ, Nº. 15) 
Pages: 371376 
Date of Publication: 2017/04/25 
ISSN: 2172038X 
Date of Current Version: 
REF: 32517 
Issue Date: April 2017 
DOI:10.24084/repqj15.325 
Publisher: EA4EPQ 
Authors and affiliations
Hasanali Moghadam, Florian Ackermann and Sönke
Rogalla
Department Power Electronics and Grid Technologies. Fraunhofer Institute
for Solar Energy Systems ISE
Freiburg (Germany)
Key word
Grid equivalent impedance, harmonic emissions, point of
common coupling, photovoltaic inverter, summation law
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