IEEE Power & Energy Magazine - March/April 2015 - 49

not, delays in the closed loop or deteri0.2
oration of the waveform content due to
CaWave SMA
bandwidth limitation of the I/O cards
CbWave SMA
may be introduced.
0.1
CbWave SMA
Examples of current and voltage
measurements from selected 12-kV
0
fault tests performed on commercial PV
inverters with a PHIL test setup are given
-0.1
in Figures 7-9. The results clearly show
the transient behavior of PV inverter
currents in response to three-phase and
-0.2
(a)
single-phase faults applied at 12 kV.
Using this approach, one is able to fully
S1) PV12
S1) PV10
S1) PV11
represent and evaluate the protection and
0.4
control aspects of the PV inverters without any simplification.
0.2
PHIL testing that utilizes the approach described above is cost-effective
0
and provides precise performance eval-0.2
uation results in situations such as:
✔✔ general certification testing of
-0.4
smart inverters and power electronic equipment
-0.6
✔✔ multiple inverter testing for high
0.07991 0.15371
0.2275
0.3013
0.37509 0.44888 0.52268
penetrations of DER and PV
(b)
inverter clusters
✔✔ integrated testing of device-level figure 9. PV inverter currents and voltages for a line-to-ground fault at 12 kV,
and/or plant-level control and oper- about 2 mi away from the POI, with a delta high-side transformer on DUT.
ation through communications and
utility practices. Advanced testing methods, such as PHIL using
remote operator commands
✔✔ microgrid control and protection scheme tests and evalu- a real-time simulation test setup, can help accurately characterize the dynamic behavior of PV inverters as they interact with
ation of islanding capability
✔✔ testing volt/var management schemes with power elec- the distribution grid.
tronic apparatus and DERs.

Summary
Utility control and generation dispatching are integral parts of
enabling high penetrations of PVs on distribution systems. The
control and communication features of smart inverters will provide utilities with additional flexibility and the capabilities to
introduce new mitigation solutions to properly utilize distribution assets and accommodate increases in renewable resources.
Smart inverter capabilities are, however, in an early stage of
development and require investigation, evaluation, and testing to
characterize the features offered and determine exactly how they
respond to system events such as voltage variations, faults, and
islanding. In addition, inverter features and requirements need to
be customized to match utilities' interconnection requirements,
as well as existing or planned distribution system automation
and operational aspects. Although the aim is to achieve standard
control and communication features, many aspects of deploying controls, optimizing schemes and settings, and integrating
inverters into utility communication architectures will be utility-specific for now. These processes will require coordination
with existing infrastructure if they are to accommodate specific
march/april 2015

For Further Reading

T. Chang, F. Katiraei, and C. Sun, "Accidental islanding of distribution systems with multiple distributed generation units of
various technologies," presented at the Joined CIGRE-EPRI
Conf., Grid of the Future, Boston, MA, Oct. 20-22, 2013.
T. Basso. (2014, Dec.). IEEE 1547 and 2030 Standards
for Distributed Energy Resources Interconnection and Interoperability with the Electricity Grid. Tech. Rep. NREL/
TP-5D00-63157. [Online]. Available: http://www.nrel.gov/
docs/fy15osti/63157.pdf
F. Katiraei, J. Holbach, and T. Chang, "Fault current contribution of solar PV inverters," presented at the Western Protective Relay Conf., Washington State University, Oct. 2012.

Biographies
Farid Katiraei is with Quanta Technology, Toronto, Canada.
Chase Sun is with Pacific Gas and Electric, Boston,
Massachusetts.
Babak Enayati is with National Grid USA, San Francisco,
California.
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http://www.nrel.gov/

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - March/April 2015