IEEE Electrification - June 2019 - 56

23
29
24
22
37
31
33
35
26
27
34
28
21
25
38
30
36
32
20

Peak
Demand Increase (%)

160
140
120
100
80
60
40
20
0
Feeder IDs
Feeder Limit

Uncontrolled EVs

Controlled EVs

Figure 13. The peak-demand increase for 19 residential feeders with
uncontrolled EVs (blue) and controlled EVs (orange). Red dots mark
the maximum increase possible with the existing grid infrastructure.

(as indicated by the red dots in Figure 13). Practically
speaking, some local grid reinforcement will be necessary
to ensure adequate capacity margin.
Reinforcing the grid with storage systems is also a way
to address the problem. This measure provides local support and also accommodates more use of renewable energy. PG&E is implementing stationary storage with 567-MW
capacity approved across four projects, including a 10-MW
aggregation of behind-the-meter batteries located at customer sites and connected to the distribution grid. Utilities
are also demonstrating DER management systems for
optimizing the use of such flexible resources.

Path Forward for EV Adoption
EVs are leading consumers to demand less gasoline and
more electricity. As they charge from the distribution
grid primarily at residential locations, uncontrolled EV
charging will likely increase peak demand, potentially
leading to a degradation in the reliability and quality of
the power supply. As shown in this study, with one EV
per household, 60% of residential feeders might need
some grid reinforcement. Traditionally, reinforcing the
grid has implied investment in new lines, transformers,
and capacitor banks to cover predictable loads. However,
this might prove costly when planning for the potential
worst-case scenario with synchronized EV charging.
Reinforcing the grid should be coupled with some sort of
EV demand management program. With perfect knowledge and control of EV charging parameters, peak
demand could be contained to an approximately 8%
average increase, as opposed to a 64% increase in the
uncontrolled case.
Large utilities in California are now able to encourage off-peak charging by providing EV customers with
electricity price signals through static TOU rates. On
average, shifting 28% of EVs to off-peak charging with
TOU rates would limit the peak-demand increase to
existing feeder capacity margins for most residential
feeders. Although static TOU rates have been successful, some concerns exist regarding their ability to

I E E E E l e c t r i f i cati o n M agaz ine / J UN E 2019

provide adequate incentives in more dynamic systems,
as well as the risks they bring to creating new peak
demands at the beginning of lower-priced off-peak
periods. In this context, new static TOU rate designs
need to be developed that enable demand management systems and coexist with options that accommodate greater flexibility.
As the spread of solar PVs and fast-charging EVs
makes power systems less predictable, forms of dynamic
pricing have been suggested to align real-time distribution grid conditions with economic incentives. While
some control strategies and business models exist at the
transmission-grid level, distribution grids are in the very
early stages of adopting dynamic pricing. The path forward for high EV penetration includes a combination of
innovations in TOU rate designs, long-term load forecasting to plan grid reinforcement, and a DER management
system with local dynamic price signals to optimize the
grid for EVs and other DERs.

For Further Reading
A. Allison and M. Whited, "Electric vehicles are not crashing
the grid: Lessons from California Synapse," Synapse Energy
Economics, Nov. 2017. [Online]. Available: http://www.synapseenergy.com/sites/default/files/EVs-Not-Crashing-Grid17-025_0.pdf
K. Knezovic, M. Marinelli, A. Zecchino, P. B. Andersen, and
C. Traeholt, "Supporting involvement of electric vehicles in
distribution grids: Lowering the barriers for a proactive integration energy," Energy, vol. 134, pp. 458-468, Sept. 2017.
N. B. Arias, S. Hashemi, P. B. Andersen, C. Træholt, and
R. Romero, "Distribution system services provided by electric
vehicles: Recent status, challenges, and future prospects,"
IEEE Trans. Intell. Transp. Syst., Jan. 2019. doi: 10.1109/
TITS.2018.2889439.
Smart Electric Power Alliance, "Utilities and electric
vehicles: Evolving to unlock grid value," Mar. 2018. [Online].
Available: https://sepapower.org/resource/utilities-electricvehicles-evolving-unlock-grid-value/
J. Wamburu, S. Lee, P. Shenoy, and D. Irwin, "Analyzing distribution transformers at city scale and the impact of EVs
and storage," in Proc. Ninth Int. Conf. Future Energy Systems,
2018, pp. 157-167.
Pacific Gas and Electric Company, "Smart grid annual
report," 2018. [Online]. Available: https://www.pge.com/pge_
global/common/pdfs/safety/how-the-system-works/electricsystems/smart-grid/AnnualReport2018.pdf

Biographies
Jonathan Coignard (jonathan.coignard@gmail.com) is with
Lawrence Berkeley National Laboratory, Berkeley, California.
Pamela MacDougall (pmacdougall@lbl.gov) is with
Lawrence Berkeley National Laboratory, Berkeley, California.
Franz Stadtmueller (F1SI@pge.com) is with Pacific Gas
and Electric Company, San Francisco, California.
Evangelos Vrettos (evrettos@lbl.gov) is with Lawrence
Berkeley National Laboratory, Berkeley, California.

https://www.synapse-energy.com/sites/default/files/EVs-Not-Crashing-Grid-17-025_0.pdf https://www.synapse-energy.com/sites/default/files/EVs-Not-Crashing-Grid-17-025_0.pdf https://sepapower.org/resource/utilities-electric-vehicles-evolving-unlock-grid-value/ https://sepapower.org/resource/utilities-electric-vehicles-evolving-unlock-grid-value/ https://www.pge.com/pge_global/common/pdfs/safety/how-the-system-works/electric-systems/smart-grid/AnnualReport2018.pdf https://www.pge.com/pge_global/common/pdfs/safety/how-the-system-works/electric-systems/smart-grid/AnnualReport2018.pdf

IEEE Electrification - June 2019

Table of Contents for the Digital Edition of IEEE Electrification - June 2019