IEEE Power & Energy Magazine - March/April 2015 - 63

and protection. Planning engineers-who are often also the engineers that address PV interconnection
requests-may need to determine whether the interconnection of a new PV system will adversely impact
the automatic voltage regulation devices on the interconnected distribution circuit. Distribution operations engineers may be concerned about the possible restrictions that a certain utility-scale PV system
imposes on distribution circuit reconfiguration options, and protection engineers may find it challenging
to adjust recloser settings when the PV system desensitizes the recloser pickup to faults at the end of the
distribution circuit.
This article describes some of the research efforts and results from a five-year project focused on
developing new guidelines, best practices, and "rules of thumb" for the integration of utility-scale
PV systems into the distribution system. The project has included the extensive modeling, measurement, and mitigation-through the use of advanced PV inverter functionality-of three circuits
within the service territory of Southern California Edison (SCE) that had large amounts of utilityscale PVs interconnected to them. While much of the work has focused on these three SCE circuits,
the overall results of the project have been expanded so as to relate to any utility through the inclusion of model case studies of circuits with alternate voltage regulation equipment and strategies.
Although the penultimate result of this project is the publication of a PV grid-integration handbook
specifically for use by distribution engineers (which will be
completed in early 2015), a preliminary review of the project's results provides a look at how future utility-scale PV
systems will be integrated more easily and with less impact
on the distribution system.

Measuring and
Mitigating Solar PV
Impacts in Southern
California Using
Power Factors
Other than One

Modeling PV Grid-Integration Scenarios
to Determine Impact and Develop
Mitigation Strategies

In 2010, SCE received approval from the California Public
Utility Commission to install a total of 250 MW of distribution-connected, utility-scale PV systems, with a portion of
those systems being directly owned by SCE. This approval
of SCE's Solar Photovoltaic Program (SPVP)-see "SCE's
SPVP: Deploying 200-Plus MW of Distribution-Connected
PV" for a summary-resulted in the immediate build-out
of a number of PV systems that produced high-penetration
PV integration scenarios (a PV system is typically considered to have a "high penetration" of integrated PVs when the ratio of the PV system's capacity to the peak loading of the interconnected circuit
exceeds approximately 15%) on multiple distribution circuits in SCE's service territory. Three distribution circuits experiencing the impacts of high-penetration PV integration were selected for detailed
modeling and analysis. In this article, these circuits are referred to as the "SCE study circuits" and are
denoted by their localities: Fontana, Porterville, and Palmdale, California.
Figure 1 shows the types of PV systems interconnected to the SCE study circuits. The Fontana, California, study circuit was the first PV system installation completed under the SPVP. During the course of
the project, the PV system shown in Figure 1(a) was first expanded from 2 MW to a total of 3 MW of generating capacity; later a 1.5-MW system was added on a warehouse rooftop nearby, resulting in a total of
4.5 MW of PVs currently installed on the circuit. This circuit serves a commercial warehouse district and
a shopping mall. Figure 1(b) shows the 5-MW ground-mounted, fixed-tilt PV system that interconnects to
the Porterville, California, study circuit. This circuit serves rural and agricultural loads in the San Joaquin
Valley. The third circuit studied is located near Palmdale, California, and is representative of a very lightly
loaded rural circuit with an interconnected, utility-scale, 3-MW PV system.
These three circuits were extensively modeled, using fully validated circuit models, and analyzed
to determine the distribution system-level impacts resulting from the integration of high penetrations
of PVs on the circuits. The impacts studied included:
✔ voltage violations (overvoltage) and variations (flicker)
✔ automatic voltage regulation equipment operation
✔ component and line current overloads
✔ reverse power flows

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

IEEE Power & Energy Magazine - March/April 2015 - Cover1
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IEEE Power & Energy Magazine - March/April 2015 - Cover3
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