2014 PV Distribution System Modeling Workshop: Increasing Hosting Capacity with Advanced Inverter Functions: Matt Rylander, EPRI

1. Matthew Rylander
Senior Project Engineer
PV Distribution System Modeling Workshop
May 6, 2014
Increasing Hosting Capacity with
Advanced Inverter Functions

2. 2© 2014 Electric Power Research Institute, Inc. All rights reserved.
Overview
Objective
• Demonstrate, via simulation, higher feeder PV hosting capacity via use of
advanced inverter functions
Outline
• Method for analysis
– Possible PV deployments
– Advanced inverter functions
– Feeder end-use load
– Feeder response metrics
• Analysis results
• Summary of findings

3. 3© 2014 Electric Power Research Institute, Inc. All rights reserved.
Method for Analysis
Step 1: Create thousands of possible PV deployments
– Utility-scale PV
– Customer-owned PV
Step 2: Run all PV deployments from zero to full output
while holding all controls fixed
– Observe feeder-wide impact
• Voltage Magnitude
• Voltage Deviation
– Repeat for different load conditions
Step 3: Repeat step 2 with advanced inverter functions

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Step 1: PV Deployment
Baseline – No PV
20% Customers with PV
30% Customers with PV
50% Customers with PV
Beyond…
PV Systems
Process is
repeated
100’s of times
to capture
many
possible
scenarios

5. 5© 2014 Electric Power Research Institute, Inc. All rights reserved.
Step 2: PV Impact Analysis
• Voltage Magnitude
– Primary voltage nodes should be < 1.05 Vpu
– Secondary voltage nodes should be < 1.05 Vpu
• Voltage Deviation
– Primary voltage nodes should be < 0.03 Vpu
– Secondary voltage nodes should be < 0.05 Vpu
1.035
1.04
1.045
1.05
1.055
1.06
1.065
1.07
0 0.5 1 1.5 2
MaximumFeederVoltage(Vpu)
Total PV Penetraionof Deployment (MW)
Minimum Hosting Capacity
Maximum Hosting Capacity
A B C
Worst-CaseResultforEach
UniquePVDeployment
Increasing penetration (MW)
Threshold of violation
A – All penetrations in
this region are
acceptable, regardless
of location
B – Some penetrations
in this region are
acceptable, site specific
C – No penetrations in
this region are
acceptable, regardless
of location
Details on analysis method:
Stochastic Analysis to Determine
Feeder Hosting Capacity for
Distributed Solar PV. EPRI, Palo
Alto, CA: 2012. 1026640.
MaximumFeederVoltages(pu)

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Step 3: Impact of Advanced Inverters
PV at Unity Power Factor PV with Volt/var Control
2500 cases shown
Each point = highest primary voltage
ANSI voltage limit
ANSI voltage limit
Increasing penetration (kW)
MaximumFeederVoltage(pu)
MaximumFeederVoltages(pu)
Increasing penetration (kW)
No observable violations regardless of PV size/location
Possible violations based upon PV size/location
Observable violations occur regardless of size/location
Minimum Hosting Capacity
Maximum Hosting Capacity Minimum Hosting Capacity Max Hosting Capacity

7. 7© 2014 Electric Power Research Institute, Inc. All rights reserved.
Advanced Inverter Functions
• Absorbing reactive power at constant power factor
– Unity power factor (Base case, control off)
– 98% power factor
– 95% power factor
• Inverter voltage determines reactive power output
Volt-Var 1 Volt-Var 2

8. 8© 2014 Electric Power Research Institute, Inc. All rights reserved.
Advanced Inverter Control, cont.
• Inverter voltage determines active power output
• Dynamic control of reactive power output based on voltage
deviation
Volt-Watt 1 Volt-Watt 2
0
100
0.9 0.95 1 1.05 1.1 1.15
WattsGenerated(%)
Local Voltage (pu)
0
100
0.9 0.95 1 1.05 1.1 1.15
WattsGenerated(%)
Local Voltage (pu)
-50
0
50
-0.2 -0.1 0 0.1 0.2
ReactiveCurrent(%)
Local Voltage Change (pu)

9. 9© 2014 Electric Power Research Institute, Inc. All rights reserved.
Utility Feeder
Feeder
Characteristics
Feeder
Voltage (kV) 12.47
Peak Load ~ 6 MW
Minimum Load 0.7
Existing PV (MW) 1.7
Substation LTC Yes
Feeder Regulators 3
Capacitors
2 – fixed
3 – voltage controlled
Total Circuit Miles 58
Feeder “Footprint” 35 mi2
Sub
Reg
Cap

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Utility-Scale PV at Maximum Load
Primary Voltage Magnitude
• Dyn-Var and Volt-Watt 2 controls help is minimal
• Volt-Watt 1, Volt-Var 1, and 95% pf controls help limit
voltage magnitude
Line indicates
average impact
from all PV
deployments
1.02
1.04
1.06
1.08
1.1
1.12
1.14
1.16
1.18
1.2
1.22
0 2000 4000 6000 8000 10000
MaximumFeederVoltage(pu)
Total PV (kW)

11. 11© 2014 Electric Power Research Institute, Inc. All rights reserved.
Utility-Scale PV at Maximum Load
Primary Voltage Deviation
• Dyn-Var and Volt-Watt 2 controls help in minimal
• Volt-Watt 1, Volt-Var 1, and 95% pf controls help limit
voltage deviation

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Utility-Scale PV at Maximum Load
Feeder Head Demand
• Volt-Watt controls limits PV active power output
• All other controls only impact the reactive power demand
– Bulk power system to provide or local resources
– 95% pf and Volt-Var 1 require the most reactive power
-6000
-4000
-2000
0
2000
4000
6000
8000
0 2000 4000 6000 8000 10000
FeederPower(kW)
Total PV (kW)
Control Off 98%pf
Volt-Var 1 Volt-Var 2
95%pf Volt-Watt 1
Dyn-Var Volt-Watt 2
-500
0
500
1000
1500
2000
2500
3000
3500
4000
0 2000 4000 6000 8000 10000
FeederPower(kvar)
Total PV (kW)
Control Off 98%pf
Volt-Var 1 Volt-Var 2
95%pf Volt-Watt 1
Dyn-Var Volt-Watt 2

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Utility-Scale PV
Advanced Inverter Summary
0 2000 4000 6000 8000 10000
Control Off
Volt-Var 1
Volt-Var 2
98%pf
95%pf
Volt-Watt 1
Volt-Watt 2
Dyn-Var
Feeder Hosting Capacity (kW)
Control
No observable violations regardless of PV size/location
Possible violations based upon PV size/location
Observable violations occur regardless of size/location

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0 1000 2000 3000 4000 5000
Control Off
Volt-Var 1
Volt-Var 2
98%pf
95%pf
Volt-Watt 1
Volt-Watt 2
Dyn-Var
Feeder Hosting Capacity (kW)
Control
Customer-Owned PV
Advanced Inverter Summary
No observable violations regardless of PV size/location
Possible violations based upon PV size/location
Observable violations occur regardless of size/location

15. 15© 2014 Electric Power Research Institute, Inc. All rights reserved.
Potential Adverse Impacts Due to Increased
Var Flow
PV @ Unity
Power Factor
PV @ 0.98
Power Factor
PV @ 0.95
Power Factor
Hosting Capacity Based on
Feeder Overvoltage (kW)
Hosting Capacity Based on
LTC/Line Regulator
Operations (kW)
Increased
hosting capacity
Decreased
hosting capacity
0 2000 4000 6000 8000 10000
P3
0 2000 4000 6000 8000 10000
P3
0 2000 4000 6000 8000 10000
P3
0 2000 4000 6000 8000 10000
P3
0 2000 4000 6000 8000 10000
P3
0 2000 4000 6000 8000 10000
P3
No observable violations regardless of PV size/location
Possible violations based upon PV size/location
Observable violations occur regardless of size/location

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Inverter Settings are Critical
%AvailableVars
% voltage
100%
0.95
1.05
-100%
1.0V
%AvailableVars
% voltage
100%
0.99
1.01
-100%
1.0
Volt-var A
1
1.01
1.02
1.03
1.04
1.05
0 60 120 180 240 300 360 420 480 540
PVTerminalVoltage(pu)
Time (seconds)
1
1.01
1.02
1.03
1.04
1.05
0 60 120 180 240 300 360 420 480 540
PVTerminalVoltage(pu)
Time (seconds)
Unity Power Factor
Volt-var A
Volt-var B
1
1.01
1.02
1.03
1.04
1.05
0 60 120 180 240 300 360 420 480 540
PVTerminalVoltage(pu)
Time (seconds)
If wrong setpoints are used, adverse
impacts can occur
0
0.5
1
PVActive
Power
Volt-var B

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Summary
• Feeder hosting capacity can increase with advanced
inverter functions
– Volt-Var and off-nominal power factor provides the
greatest benefit
• Volt-Var and power factor control requires reactive power
resources
– Requiring significant reactive power can have adverse
impact
• Inverter settings must be chosen carefully

18. 18© 2014 Electric Power Research Institute, Inc. All rights reserved.
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