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Distributed Photovoltaic Systems Design and Technology Requirements
SANDIA REPORT

SAND2008-0946 P
Unlimited Release
Printed February 2008




Renewable Systems Interconnection Study:

Distributed Photovoltaic Systems Design and Technology
Requirements

Chuck Whitaker, Jeff Newmiller, Michael Ropp, Benn Norris





Prepared by
Sandia National Laboratories
Albuquerque, New Mexico 87185 and Livermore, California 94550

Sandia is a multiprogram laboratory operated by Sandia Corporation,
a Lockheed Martin Company, for the United States Department of Energys
National Nuclear Security Administration under Contract DE-AC04-94AL85000.



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ii
SAND2008-0946 P
Unlimited Release
Printed February 2008


Renewable Systems Interconnection Study:

Distributed Photovoltaic Systems Design and Technology
Requirements





Chuck Whitaker,
Jeff Newmiller
BEW Engineering

Michael Ropp,
Northern Plains Power Technologies

Ben Norris,
Norris Engineering Consulting


Sandia Contract 717448


Abstract
To facilitate more extensive adoption of renewable distributed electric generation, the U.S.
Department of Energy launched the Renewable Systems Interconnection (RSI) study during
the spring of 2007. The study addressed the technical and analytical challenges that must be
addressed to enable high penetration levels of distributed renewable energy technologies.
Interest in PV systems is increasing and the installation of large PV systems or large groups of
PV systems that are interactive with the utility grid is accelerating, so the compatibility of
higher levels of distributed generation needs to be ensured and the grid infrastructure
protected. The variability and nondispatchability of todays PV systems affect the stability of
the utility grid and the economics of the PV and energy distribution systems. Integration
issues need to be addressed from the distributed PV system side and from the utility side.
Advanced inverter, controller, and interconnection technology development must produce
hardware that allows PV to operate safely with the utility and act as a grid resource that
provides benefits to both the grid and the owner.

iii
iv Preface
Now is the time to plan for the integration of significant quantities of distributed renewable
energy into the electricity grid. Concerns about climate change, the adoption of state-level
renewable portfolio standards and incentives, and accelerated cost reductions are driving steep
growth in U.S. renewable energy technologies. The number of distributed solar photovoltaic
(PV) installations, in particular, is growing rapidly. As distributed PV and other renewable
energy technologies mature, they can provide a significant share of our nations electricity
demand. However, as their market share grows, concerns about potential impacts on the
stability and operation of the electricity grid may create barriers to their future expansion.
To facilitate more extensive adoption of renewable distributed electric generation, the U.S.
Department of Energy launched the Renewable Systems Interconnection (RSI) study during
the spring of 2007. This study addresses the technical and analytical challenges that must be
addressed to enable high penetration levels of distributed renewable energy technologies.
Because integration-related issues at the distribution system are likely to emerge first for PV
technology, the RSI study focuses on this area. A key goal of the RSI study is to identify the
research and development needed to build the foundation for a high-penetration renewable
energy future while enhancing the operation of the electricity grid.
The RSI study consists of 15 reports that address a variety of issues related to distributed
systems technology development; advanced distribution systems integration; system-level
tests and demonstrations; technical and market analysis; resource assessment; and codes,
standards, and regulatory implementation. The RSI reports are:
Renewable Systems Interconnection: Executive Summary
Distributed Photovoltaic Systems Design and Technology Requirements
Advanced Grid Planning and Operation
Utility Models, Analysis, and Simulation Tools
Cyber Security Analysis
Power System Planning: Emerging Practices Suitable for Evaluating the Impact of
High-Penetration Photovoltaics
Distribution System Voltage Performance Analysis for High-Penetration
Photovoltaics
Enhanced Reliability of Photovoltaic Systems with Energy Storage and Controls
Transmission System Performance Analysis for High-Penetration Photovoltaics
Solar Resource Assessment
Test and Demonstration Program Definition
Photovoltaics Value Analysis
Photovoltaics Business Models

v

Production Cost Modeling for High Levels of Photovoltaic Penetration
Rooftop Photovoltaics Market Penetration Scenarios.

Addressing grid-integration issues is a necessary prerequisite for the long-term viability of the
distributed renewable energy industry, in general, and the distributed PV industry, in particular.
The RSI study is one step on this path. The Department of Energy is also working with
stakeholders to develop a research and development plan aimed at making this vision a reality.


vi Acknowledgments
The authors wish to acknowledge the extensive contributions of the following people to this
report:
Jovan Bebic, General Electric Global Research Division
Mike Behnke, BEW Engineering
Ward Bower, Sandia National Laboratories
John Bzura, National Grid
Tom Key, Electric Power Research Institute.


vii Acronyms

AC
alternating
current
ADSL
asymmetric
digital
subscriber
line
BPL

broadband over power line
DG
distributed
generation, distributed generator
EMS
energy
management
system
GE
General
Electric
IEC
International
Electro-technical
Committee
IEEE
Institute
of
Electrical and Electronics Engineers
LAN
local
area
network
LTC
load
tap
changing
LV
low
voltage
MPP
maximum power point
MTBF
mean time before failure
MV medium
voltage
NDZ nondetection
zone
NREL National
Renewable Energy Laboratory
OF over
frequency
OV over
voltage
PLCC
power
line
carrier
communications
PV
photovoltaic
RSI
Renewable
Systems
Integration
SEGIS
solar
energy
grid integration system
SFS
Sandia
Frequency
Shift
SVC
static
VAr
compensator
SVR
step
voltage
regulator
SVS
Sandia
Voltage
Shift
UF
under
frequency
UPS
uninterruptible
power
supply
UV
under
voltage
VAr
volt-ampere
reactive
VPCC

point of common coupling voltage
WECC

Western Electricity Coordinating Council





vi