IEEE Power & Energy Magazine - July/August 2021 - 34

algorithm. As a result, the expected day-ahead net load
profile is created. The expected power factor for the dayahead
net load is predicted, and the reactive power schedule
of the BESS is determined to shift the power factor above
the desired power factor limit. Also, the expected day-ahead
voltage on the feeder is calculated to verify that it remains
within the allowable operation limits.
For the test, the day-ahead voltage was estimated based on
a regression analysis using historical measurements that determined
the node voltage as a function of the reactive power
flow. For the system to operate reliably during testing, the voltage
level needs to be monitored in real time for any voltage
breaches (predefined) and mitigated by overriding the reactive
power schedule to maintain the voltage within a nominal
range. The schedules will then be communicated with the
BESS controller. They are expected to provide load peak shaving,
valley filling, and power factor correction for the duration
of the test. Figure 7 presents the power factor correction concept
with reactive power support from the energy storage for a
sample leading power factor curve.
Four-Day Testing
As portrayed in Figure 8, the goal of the power factor correction
on a given day is to dispatch the BESS reactive power
so that the value of the power factor (blue line) at the selected
feeder location is higher than the desired power factor limit
(green line). Figure 8 illustrates a case where the reactive
power dispatch is effective in shifting the absolute value of the
power factor higher than 0.9 for the duration of the test.
In this test, the energy storage provided both active and
reactive power support to flatten the load and correct the power
factor at the point of interest while considering the circuit's
voltage limits. It should be noted that the ability of the system
to achieve desirable performance is highly dependent on the
accuracy of the load forecasts.
500
-500
Testing Period
-1,000
-1,500
-2,000
Desired Load
Actual Net Load
Actual Customer Load
Actual BESS Dispatch
figure 6. The BESS dispatch and load profile for a day (+ for
discharge and - for charge).
-0.7
-0.8
-0.9
1
Four-Day Testing
Making DER Optimization a Reality
DERs can deliver energy at the right time and locations to
potentially avoid the substantial utility costs associated with
building additional generation units, substations, and necessary
grid infrastructures. SCE is actively working to create
new market and revenue opportunities for DERs to provide
services to the local grid. Accordingly, DER tariff pilots have
been introduced to incentivize the deployment and operation
of DERs to defer a traditional infrastructure investment.
Ultimately, SCE's grid management system will enable the
economic optimization of DERs by allowing SCE to dispatch
them at specific occasions with the most value to the power
system to increase customers' revenue along with supporting
SCE's goals for clean, reliable, and affordable energy.
The vision of economically optimized utility expenditures
and the operation of the grid is not feasible with today's
technologies. The ability to perform complex analysis, possess
real-time awareness of the grid conditions, and seamlessly
coordinate the performance of millions of DERs and
grid equipment requires a modernized grid. Hence, the optimization
of DER operations is one of the forefront efforts
of grid modernization in utilities and is challenging due to
Power Factor
Power Factor With
Kilovolt Amps
Reactive Support
Desired
Test Duration
10
20
30 40 50
Power Factor
Time (15 min)
60 70 80 90
figure 7. The power factor correction of a sample leading
power factor with reactive power support.
34
ieee power & energy magazine
-0.2
-0.4
-0.6
-0.8
1
Testing
Period
Desired Power Factor Limit
Load Power Factor
Actual Power Factor
figure 8. The power factor correction for a day.
july/august 2021
Power (kW)
Power Factor
IEEE Power & Energy Magazine - July/August 2021

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