IEEE Power & Energy Magazine - March/April 2015 - 69

The present study is focused on modeling, measuring,
and mitigating the impacts of high-penetration PV integration
on the distribution system.
voltage's being lower and higher, respectively, than standard
service voltages. For this study, type 0 sag and swell events
correspond to voltages between 0.88 and 0.98 per unit (pu)
and 1.05 and 1.10 pu, respectively. Further analysis on voltage
deviations (not to be confused with voltage sags and swells)
represent second-over-second voltage deviations and again are
sorted into categories based on the magnitude of the voltage
deviations. Type 0 events correspond to second-over-second
voltage deviations larger than 1% pu but less than 2.5% pu, type 1
events to those between 2.5% pu and 4% pu, and type 2 events
to those greater than 4% pu.
It is important to note that while voltage deviations are
numerous, they do not necessarily mean that the voltage is
deviating outside the range of acceptable service voltages,
as in the case of voltage sags and swells; they are simply a
measurement of near-instantaneous voltage change, not magnitude. Both of these analyses, voltage sag/swell and voltage deviation, are completed for the calculated primary-side
voltage of the distribution transformer for which the DMU
was installed, which is compensated based on the measured
load current supplied to the customers connected to the transformer. Voltage sags and swells are a partial indication of the
power quality impacts the interconnected high-penetration
PV systems may be causing. The determination of the number of voltage deviation events is meant to be a proxy for
general voltage variability caused primarily by the variability of the nearby PV systems. Over this particular month of
observed operation, which coincided with high levels of PV
generation, there were no observed voltage sags and only 19
voltage swells that resulted in a primary voltage between 1.05
and 1.10 pu (event type 0). There were a large number of
second-over-second voltage deviations of small magnitude,
but there was only one second-over-second voltage deviation
greater than 2.5% pu.

Mitigating the Impacts of PV Integration
The field demonstration of using advanced PV inverter functionality to mitigate some of the distribution system-level
impacts of high-penetration PVs has been one of the major
goals of this project from its inception. Without the active
mitigation of PV impacts, integration on individual distribution circuits and the distribution system as a whole will be
unnecessarily limited. Also, more traditional methods of mitigating the impacts related to PV integration, such as installing heavier conductors to reduce voltage rise at a PV system
point of interconnection, are not the only possible mitigation
methods-and mitigation measures that are equally or more
march/april 2015

effective are likely to be more economical. Under this project, one field demonstration has already been completed; two
more are scheduled for completion in early 2015.
The 1.5-MW PV system on the Fontana, California, study
circuit shown in Figure 1(a) consists of three 500-kVA PV
inverters capable of operating at off-unity power factor settings.
Using the results from the model-based PV impact mitigation
studies, a two-week-long field demonstration was planned for
the last week in September 2013 and the first week of October
2013. The operating power factor set point for the three inverters was adjusted to a power factor of 0.95 at the start of the
demonstration period. Figure 5 shows the measured real and
reactive power output from the 1.5-MW PV system and the
calculated power factor for two days during the demonstration period. One day is representative of clear weather conditions, and the other was a particularly variable weather day. As
can be determined from the figure, the PV inverters and the
1.5-MW PV system as a whole were capable of operating with
a fixed off-unity power factor under both sets of conditions. As
the power factor control is implemented locally within the PV
inverters themselves, the effective bandwidth of power factor
control is higher than the speed at which power developed by
the PV panels changes due to local weather conditions.

Conclusions
The present study is focused on modeling, measuring, and mitigating the impacts of high-penetration PV integration on the
distribution system. The impacts of utility-scale PV systems
of 500 kW to 5 MW have been extensively modeled using
validated circuit models. Research-grade data acquisition systems have been installed on three study circuits to measure
and observe the impacts of the interconnected PV systems.
An initial field demonstration of the ability of utility-scale PV
systems to operate at an off-unity power factor has been completed. From these and other project activities not included in
this article, the following insights into some of the potential
PV impacts and ways to mitigate them have been gained:
✔✔ SCE engineers successfully interconnected more than
200 MW of PVs on their distribution system without
the need for extensive distribution system upgrades.
Many of the interconnected circuits have reached PV
penetration limits, however, that cannot be exceeded
without significant system upgrades or other mitigation measures.
✔✔ Utility-scale PV integration on the distribution system
is often limited primarily by the amount of voltage
rise expected at the point of interconnection. There
ieee power & energy magazine

69



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

IEEE Power & Energy Magazine - March/April 2015 - Cover1
IEEE Power & Energy Magazine - March/April 2015 - Cover2
IEEE Power & Energy Magazine - March/April 2015 - 1
IEEE Power & Energy Magazine - March/April 2015 - 2
IEEE Power & Energy Magazine - March/April 2015 - 3
IEEE Power & Energy Magazine - March/April 2015 - 4
IEEE Power & Energy Magazine - March/April 2015 - 5
IEEE Power & Energy Magazine - March/April 2015 - 6
IEEE Power & Energy Magazine - March/April 2015 - 7
IEEE Power & Energy Magazine - March/April 2015 - 8
IEEE Power & Energy Magazine - March/April 2015 - 9
IEEE Power & Energy Magazine - March/April 2015 - 10
IEEE Power & Energy Magazine - March/April 2015 - 11
IEEE Power & Energy Magazine - March/April 2015 - 12
IEEE Power & Energy Magazine - March/April 2015 - 13
IEEE Power & Energy Magazine - March/April 2015 - 14
IEEE Power & Energy Magazine - March/April 2015 - 15
IEEE Power & Energy Magazine - March/April 2015 - 16
IEEE Power & Energy Magazine - March/April 2015 - 17
IEEE Power & Energy Magazine - March/April 2015 - 18
IEEE Power & Energy Magazine - March/April 2015 - 19
IEEE Power & Energy Magazine - March/April 2015 - 20
IEEE Power & Energy Magazine - March/April 2015 - 21
IEEE Power & Energy Magazine - March/April 2015 - 22
IEEE Power & Energy Magazine - March/April 2015 - 23
IEEE Power & Energy Magazine - March/April 2015 - 24
IEEE Power & Energy Magazine - March/April 2015 - 25
IEEE Power & Energy Magazine - March/April 2015 - 26
IEEE Power & Energy Magazine - March/April 2015 - 27
IEEE Power & Energy Magazine - March/April 2015 - 28
IEEE Power & Energy Magazine - March/April 2015 - 29
IEEE Power & Energy Magazine - March/April 2015 - 30
IEEE Power & Energy Magazine - March/April 2015 - 31
IEEE Power & Energy Magazine - March/April 2015 - 32
IEEE Power & Energy Magazine - March/April 2015 - 33
IEEE Power & Energy Magazine - March/April 2015 - 34
IEEE Power & Energy Magazine - March/April 2015 - 35
IEEE Power & Energy Magazine - March/April 2015 - 36
IEEE Power & Energy Magazine - March/April 2015 - 37
IEEE Power & Energy Magazine - March/April 2015 - 38
IEEE Power & Energy Magazine - March/April 2015 - 39
IEEE Power & Energy Magazine - March/April 2015 - 40
IEEE Power & Energy Magazine - March/April 2015 - 41
IEEE Power & Energy Magazine - March/April 2015 - 42
IEEE Power & Energy Magazine - March/April 2015 - 43
IEEE Power & Energy Magazine - March/April 2015 - 44
IEEE Power & Energy Magazine - March/April 2015 - 45
IEEE Power & Energy Magazine - March/April 2015 - 46
IEEE Power & Energy Magazine - March/April 2015 - 47
IEEE Power & Energy Magazine - March/April 2015 - 48
IEEE Power & Energy Magazine - March/April 2015 - 49
IEEE Power & Energy Magazine - March/April 2015 - 50
IEEE Power & Energy Magazine - March/April 2015 - 51
IEEE Power & Energy Magazine - March/April 2015 - 52
IEEE Power & Energy Magazine - March/April 2015 - 53
IEEE Power & Energy Magazine - March/April 2015 - 54
IEEE Power & Energy Magazine - March/April 2015 - 55
IEEE Power & Energy Magazine - March/April 2015 - 56
IEEE Power & Energy Magazine - March/April 2015 - 57
IEEE Power & Energy Magazine - March/April 2015 - 58
IEEE Power & Energy Magazine - March/April 2015 - 59
IEEE Power & Energy Magazine - March/April 2015 - 60
IEEE Power & Energy Magazine - March/April 2015 - 61
IEEE Power & Energy Magazine - March/April 2015 - 62
IEEE Power & Energy Magazine - March/April 2015 - 63
IEEE Power & Energy Magazine - March/April 2015 - 64
IEEE Power & Energy Magazine - March/April 2015 - 65
IEEE Power & Energy Magazine - March/April 2015 - 66
IEEE Power & Energy Magazine - March/April 2015 - 67
IEEE Power & Energy Magazine - March/April 2015 - 68
IEEE Power & Energy Magazine - March/April 2015 - 69
IEEE Power & Energy Magazine - March/April 2015 - 70
IEEE Power & Energy Magazine - March/April 2015 - 71
IEEE Power & Energy Magazine - March/April 2015 - 72
IEEE Power & Energy Magazine - March/April 2015 - 73
IEEE Power & Energy Magazine - March/April 2015 - 74
IEEE Power & Energy Magazine - March/April 2015 - 75
IEEE Power & Energy Magazine - March/April 2015 - 76
IEEE Power & Energy Magazine - March/April 2015 - 77
IEEE Power & Energy Magazine - March/April 2015 - 78
IEEE Power & Energy Magazine - March/April 2015 - 79
IEEE Power & Energy Magazine - March/April 2015 - 80
IEEE Power & Energy Magazine - March/April 2015 - 81
IEEE Power & Energy Magazine - March/April 2015 - 82
IEEE Power & Energy Magazine - March/April 2015 - 83
IEEE Power & Energy Magazine - March/April 2015 - 84
IEEE Power & Energy Magazine - March/April 2015 - 85
IEEE Power & Energy Magazine - March/April 2015 - 86
IEEE Power & Energy Magazine - March/April 2015 - 87
IEEE Power & Energy Magazine - March/April 2015 - 88
IEEE Power & Energy Magazine - March/April 2015 - 89
IEEE Power & Energy Magazine - March/April 2015 - 90
IEEE Power & Energy Magazine - March/April 2015 - 91
IEEE Power & Energy Magazine - March/April 2015 - 92
IEEE Power & Energy Magazine - March/April 2015 - 93
IEEE Power & Energy Magazine - March/April 2015 - 94
IEEE Power & Energy Magazine - March/April 2015 - 95
IEEE Power & Energy Magazine - March/April 2015 - 96
IEEE Power & Energy Magazine - March/April 2015 - Cover3
IEEE Power & Energy Magazine - March/April 2015 - Cover4
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091020
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070820
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050620
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030420
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010220
https://www.nxtbook.com/nxtbooks/pes/powerenergy_111219
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091019
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070819
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050619
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030419
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010219
https://www.nxtbook.com/nxtbooks/pes/powerenergy_111218
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091018
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070818
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050618
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030418
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010218
https://www.nxtbook.com/nxtbooks/pes/powerenergy_111217
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091017
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070817
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050617
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030417
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010217
https://www.nxtbook.com/nxtbooks/pes/powerenergy_111216
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091016
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070816
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050616
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030416
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010216
https://www.nxtbook.com/nxtbooks/ieee/powerenergy_010216
https://www.nxtbook.com/nxtbooks/pes/powerenergy_111215
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091015
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070815
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050615
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030415
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010215
https://www.nxtbook.com/nxtbooks/pes/powerenergy_111214
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091014
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070814
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050614
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030414
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010214
https://www.nxtbookmedia.com