Download Style E 36 by 48 - University of Nevada, Las Vegas

Local Load Power Factor Correction by GridInteractive PV Inverters
†
Peng ,Yahia
†
Baghzouz ,
‡
Haddad
Wenxin
Salim
(†)University of Nevada, Las Vegas (USA), (‡)University of Skikda, Skikda (Algeria)
Introduction
(b)
PSCAD Model of PV System with VAR Generation Capability.
PV systems are characterized as
intermittent power sources, dependent on
the fluctuating sunlight. In addition,
conventional PV systems currently operate
at unity power factor, regardless of the local
reactive power needs.
PV inverter technology has the potential
to provide significant added value by
integrating advanced control functions that
can provide beneficial grid support such as
a source of reactive power
Reactive Power Generation &
VAR Control Methodologies
The reactive power of the PV inverter can
be controlled such that the inverter does not
exceed its kVA rating. The figure below
shows the Power Generation Duration Curve
(PGDC) of a 2.5 kW PV system and the
corresponding reactive power availability.
VAR production is made possible by
advancing the generated current waveform
with respect to the utility voltage waveform
by some angle.
To improve the operating power factor of
the feeder, two cases are considered:
• Case A - the inverters supply all their
reactive power capacity during the
daylight hours.
• Case B - the inverters operate at
constant power factor of 70.7%, then
switch to Case A when they reach their
VAR generation capability.
Simulated PV Inverter Active and
Reactive Power Generation
The solar irradiance is assumed to drop
by 20% every second starting from the peak
value, and the inverter rating is 2.5 kVA.
Case A
Case B
Impact of PV Penetration on Local
Feeder Load Characteristics
PV systems that operate at unity power
factor lead to lower power factor during the
daylight hours as show in the figure below
(10% PV penetration), thus lower distribution
system operating efficiency.
Case A
Conclusions
Case B
In distribution feeders with significant PV
penetration, VAR generation from inverters
may be needed during some parts of the day
to restore the operating power factor. Simple
local VAR control using either constant kVA or
constant power factor control is shown to
provide satisfactory results.
VAR generation by a PV inverter, however,
will slightly reduce the efficiency of the overall
PV system during daylight (due to higher
current generation).