IEEE Power & Energy Magazine - March/April 2015 - 42

operating on similar time scales. For example, when several
inverters simultaneously perform volt/var control or other forms
of voltage regulation, unintended interactions may occur among
the inverters and with the existing voltage regulation equipment
on a distribution circuit. As DER penetrations increase, there
will likely be thousands of DERs with active volt/var control
operating on a single distribution circuit. These conditions need
to be thoroughly understood, and standardized methods for controlling system voltage under these conditions must be developed. Since it will be difficult to evaluate thousands of individual
DERs in a laboratory setting, power-HIL (PHIL) testing is being
evaluated to see if it can accurately simulate realistic distribution
feeder conditions and larger-scale deployments of DERs.
For communication-based features, system-level testing
that includes communications hardware, power hardware,
and intelligent controllers can help ensure that all parts interoperate as desired. Ongoing research at the testing laboratories is incorporating real-time simulation of communications
systems (including communication errors) into existing HIL
capabilities. This type of testing is referred to as communications HIL and can be run along with PHIL to simultaneously
simulate both power and communications dynamics. This
will be critical to a full understanding of the impacts of using
various communications and control methods for determining DER operation.
There are a large number of additional areas that will
need to be developed and validated as DER penetration levels increase to fully integrate DERs into the electric power
system. These areas include:
✔✔ development of unified procedures for the design and
validation of DER simulation models
✔✔ simulations of grid functions to determine proper settings for different situations
✔✔ standardization of secure communication for DERs
(currently being developed by the SunSpec Alliance)
✔✔ validation of the draft certification standards coming
from different standards-making organizations (e.g.,
updates to IEEE 1547 and UL 1741)
✔✔ cybersecurity testing
✔✔ building an international consensus on certification
standards to minimize the testing requirements for
DER manufacturers and allow interoperability.
As the DER industry has matured, DERs are now seen as
an important player with respect to maintaining overall system operations and stability. In the coming years, we expect
DER installations to become fully active participants in grid
operations and provide a lot of the same characteristics as
bulk generators. The emergence of smart grid controls for
DERs will make the electric power system more reliable and
more sustainable. Smart grid test labs and the ability to verify new functionality are critical to speeding the deployment
and future success of these technologies.

ieee power & energy magazine

Acknowledgments
NREL's portion of this work was supported by the DOE
under contract number DE-AC36-08-GO28308. NREL
gratefully acknowledges the support of Dan Ton of the
DOE's Office of Electricity Delivery and Energy Reliability
and Alvin Razon, Ranga Pitchumani, and Kevin Lynn of the
DOE's Office of Energy Efficiency and Renewable Energy.
The participation of AIT within ISGAN-SIRFN is funded
as part of the IEA's Research Cooperation program by the
Austrian Ministry for Transport, Innovation, and Technology under contract number FFG 839566.
Sandia National Laboratories is a multiprogram laboratory
managed and operated by Sandia Corporation, a wholly owned
subsidiary of Lockheed Martin Corporation, for the DOE's
National Nuclear Security Administration under contract number DE-AC04-94AL85000. This work was sponsored by the
DOE's Office of International Affairs and Office of Electricity.

For Further Reading
ENTSO-E Network Code for Requirements for Grid Connection Applicable to all Generators, Mar. 8, 2013, ENTSOE AISBL, Brussels, Belgium.
California Public Utilities Commission, "Recommendations for updating the technical requirements for inverters in
distributed energy resources, Smart Inverter Working Group
recommendations," Jan. 2014.
International Electrotechnical Commission, "Communication networks and systems for power utility automation-
Part 90-7: Object models for power converters in distributed
energy resources (DER) systems," Ed. 1.0, IEC Tech. Rep.
IEC 61850-90-7, Feb. 2013.
J. Johnson S. Gonzalez, M. E. Ralph, A. Ellis, and R.
Broderick, "Test protocols for advanced inverter interoperability functions," Sandia Tech. Rep. SAND2013-9880 and
SAND2013-9875, Nov. 2013.
A. Hoke, S. Chakraborty, and T. Basso, "Testing of advanced PV inverters conforming to IEEE Standard 1547-
Amendment 1," in Proc. IEEE Photovoltaic Specialists
Conf. (PVSC), Denver, CO, June 2014, pp. 1014-1021.

Biographies
Roland Bründlinger is with AIT, Vienna, Austria.
Thomas Strasser is with AIT, Vienna, Austria.
Georg Lauss is with AIT, Vienna, Austria.
Andy Hoke is with NREL, Golden, Colorado.
Sudipta Chakraborty is with NREL, Golden, Colorado.
Greg Martin is with NREL, Golden, Colorado.
Benjamin Kroposki is with NREL, Golden, Colorado.
Jay Johnson is with Sandia National Laboratories, Albuquerque, New Mexico.
Erik de Jong is with DNV GL, Arnhem, The Netherlands.
p&e

march/april 2015

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