advanced inverter impacts and methods to determine recommended settings

1. © 2016 Electric Power Research Institute, Inc. All rights reserved.
Matthew Rylander, EPRI
Jeff Smith, EPRI
Robert Broderick, SNL
Barry Mather, NREL
May 10, 2016
Advanced Inverter Impacts
and Methods to Determine
Recommended Settings
Analysis to Inform CA Grid
Integration Rules for PV

2. 2
© 2016 Electric Power Research Institute, Inc. All rights reserved.
Outline
California Solar Initiative project overview
Explain simple methods to derive settings
Illustrate distribution feeder response to settings
Today’s Key Takeaway:
Simple methods to derive settings

3. 3
© 2016 Electric Power Research Institute, Inc. All rights reserved.
Project Overview
Project Goal
 Determine advanced inverter
settings to accommodate more
PV without system upgrades
– Power factor, volt-var, volt-watt
– Settings and/or methods to
determine settings
.3 1.0
1.9
2.7 2.5
3.2
4.6
.7
.9
1.2 1.8
2.6
3.6
.3
.3
.5
.8
1.3
1.8
2.4
.9
1.9
3.3
4.7
5.6
7.6
10.6
2010 2011 2012 2013 2014 2015 2016
Utility Commercial Residential
Industry Challenge
 Landscape is changing
– Distributed resources
 New challenges for utilities
– Accommodate more PV
– Use Advanced Inverters
Impact
Below
Threshold
Impact
Depends
Impact
Above
Threshold
Setting 3
Setting 2
Setting 1
Unity Power
Factor

4. 4
© 2016 Electric Power Research Institute, Inc. All rights reserved.
Approach to Derive/Test Recommended Settings/Methods
Select
Feeders
Develop
Methods to
Derive
Settings
Apply
Methods and
Determine
Feeder Impact
Final
Deliverable
Summer 2016

5. 5
© 2016 Electric Power Research Institute, Inc. All rights reserved.
Select Feeders

6. 6
© 2016 Electric Power Research Institute, Inc. All rights reserved.
Feeders Selected from Previous Analysis*
Utility 1
Utility 2
Utility 3
Impact
Below
Threshold
Impact
Depends
Impact
Above
Threshold
CPUC-CSI3
*Alternatives to the 15%
Rule: Final Project
Summary. EPRI, Palo
Alto, CA: 2015.
3002006594.

7. 7
© 2016 Electric Power Research Institute, Inc. All rights reserved.
Selected Feeder Details
Criteria for feeder selection
Utility
Feeder characteristics
Hosting capacity
Feeder
Name
Peak Load
(MW)
Farthest
3-phase
Bus (km)
PV Hosting
Capacity
Nominal
Voltage
683 3.6 17.9 Low 12 kV
631 3.4 11.7 Moderate 12 kV
888 2.2 2.8 Low 4 kV
2885 9.2 11.9 Low 12 kV
281 16.7 10.3 High 21 kV
2921 6.4 15.5 Moderate 12 kV
420 5.0 4.7 High 12 kV

8. 8
© 2016 Electric Power Research Institute, Inc. All rights reserved.
Develop Methods to Derive Settings

9. 9
© 2016 Electric Power Research Institute, Inc. All rights reserved.
Level Complexity Power Factor Volt-var Volt-watt
0 None Unity Power Factor
Disabled,
Unity Power Factor
Disabled,
Unity Power Factor
1 Low
Based on Feeder
X/R Ratio
Generic Setting Generic Setting
2 Medium
Based on Feeder
Model and PV
Location
Based on Feeder
Model and PV
Location
Not Applied
3 High
Based on Feeder
Model and PV
Location
Based on Feeder
Model, PV Location,
and Service
Transformer
Impedance
Not Applied
Methods to Derive Settings

10. 10
© 2016 Electric Power Research Institute, Inc. All rights reserved.
Power Factor Control
Level 1 settings:
– Most simple method required to determine settings
– Setting is feeder specific
– Setting is based on the Median X/R ratio on the feeder
Level Method Data Requirements Power Factor Setting
1
Median X/R Ratio of all 3-
phase MV nodes to
determine power factor
Primary node X/R ratios
on feeder, number of
phases at each node
Single Setting on each
feeder
𝑃𝑃𝑃𝑃𝑃 𝑓𝑓𝑓𝑓𝑓𝑓 ≅
𝑋
𝑅�
𝑚𝑒𝑒𝑒𝑒𝑒
𝑋
𝑅�
𝑚𝑚𝑑𝑑𝑑𝑑
2
+ 1

11. 11
© 2016 Electric Power Research Institute, Inc. All rights reserved.
Volt-var Control
Level 1 settings:
– Wide bandwidth (does nothing when within 2% from nominal)
– Maximum reactive power output equivalent to 90% power factor when
real power is at full output (assumed that the inverter is 10% larger
than the PV system rating)

12. 12
© 2016 Electric Power Research Institute, Inc. All rights reserved.
Volt-watt Control
Level 1 settings:
– Delayed control (does not curtail power when voltage is within ANSI
limits)
– Reactive power control functions should be utilized before the inverter
voltage reaches the ANSI limit
– Active power curtailed to Zero at 1.1pu voltage

13. 13
© 2016 Electric Power Research Institute, Inc. All rights reserved.
Apply Methods and Determine Feeder
Response

14. 14
© 2016 Electric Power Research Institute, Inc. All rights reserved.
Feeder Response
 Feeder response based on same hosting capacity analysis used
in CPUC-CSI3 feeder analysis
– The thousands of stochastic PV scenarios were converted from unity
power factor for each of the settings/methods derived
 PV scenario correlated to Median hosting capacity used to
compare settings/methods
– Quantified by advanced inverter setting result minus result from unity
power factor
Median Hosting
Capacity:
Defined when 50% of the
analyzed scenarios have a
violation.
L1: Simple
L2: Moderate
L3: Complex

15. 16
© 2016 Electric Power Research Institute, Inc. All rights reserved.
Quantifying Overall Impact from the Method/Setting
Overall feeder impact is quantified by:
– Hosting Capacity
– Reactive Power
– Losses (assumed negligible)
Hosting
Capacity
Reactive
Power
Impact
Ratio

16. 17
© 2016 Electric Power Research Institute, Inc. All rights reserved.
Comparison of Overall Impact from Power Factor and Volt-var
 Power factor Level 1 and Level 2 have the least effective use of reactive power
 Level 3 power factor and Level 3 volt-var provided similar increase in hosting capacity
and also demand of reactive power, thus their overall ratio is comparable
 Volt-var Level 1 had low improvement in hosting capacity yet the control settings has
some of the most effective use of reactive power
Volt-varPowerFactor

17. 18
© 2016 Electric Power Research Institute, Inc. All rights reserved.
Conclusions
Power Factor Method Level 3 generally provides the most
benefit with regards to hosting capacity while effectively
using reactive power to do so
Volt-var Method Level 1 is the least complex and has one of
the most effective uses of reactive power
Volt-watt Method Level 1 should be used in conjunction with
power factor or volt-watt control while these reactive power
control functions should prevent the unnecessary curtailment
of active power when operated first

18. 19
© 2016 Electric Power Research Institute, Inc. All rights reserved.
Together…Shaping the Future of Electricity
Robert Broderick
rbroder@sandia.gov
505.844.8161
Jeff Smith
jsmith@epri.com
865.218.8069
Matthew Rylander
mrylander@epri.com
512.351.9938
Barry Mather
Barry.Mather@nrel.gov
303.275.4378

19. 20
© 2016 Electric Power Research Institute, Inc. All rights reserved.
References
Public Link to Reports Online
CSI:RD&D. (2015). Analysis to Inform California Grid Integration
Rules for PV. Available:
http://calsolarresearch.ca.gov/funded-projects/110-analysis-to-
inform-california-grid-integration-rules-for-pv
Alternatives to the 15% Rule: Modeling and Hosting Capacity Analysis of 16 Feeders. EPRI, Palo
Alto, CA: 2015. 3002005812.
Alternatives to the 15% Rule: Final Project Summary. EPRI, Palo Alto, CA: 2015. 3002006594.