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

Matthew Rylander

Senior Project Engineer

PV Distribution System Modeling Workshop

May 6, 2014

Increasing Hosting Capacity with

Advanced Inverter Functions

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


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


Step 1: PV Deployment

Baseline – No PV

20% Customers with PV



Beyond…

PV Systems

Process is

repeated

100’s of times

to capture

many

possible

scenarios


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

Max

imu

m F

ee

de

r V

olt

age

(Vp

u)

Total PV Penetraion of Deployment (MW)

Minimum Hosting Capacity

Maximum Hosting Capacity

A B C

Wo

rst-

Ca

se R

esu

lt fo

r E

ach

Un

iqu

e P

V D

ep

loym

ent

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.

Ma

xim

um

Fe

ed

er

Vo

lta

ge

s (

pu)


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)

Ma

xim

um

Fe

ed

er

Vo

lta

ge

(pu

)

Ma

xim

um

Fe

ed

er

Vo

lta

ge

s (

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


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


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

Wat

ts G

en

era

ted

(%)

Local Voltage (pu)

0

100

0.9 0.95 1 1.05 1.1 1.15

Wat

ts G

en

era

ted

(%)

Local Voltage (pu)

-50

0

50

-0.2 -0.1 0 0.1 0.2

Re

acti

ve C

urr

ent

(%)

Local Voltage Change (pu)


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


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

Max

imu

m F

ee

de

r V

olt

age

(pu

)

Total PV (kW)



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



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

Feed

er

Po

we

r (k

W)

Total PV (kW)

Control Off 98% pfVolt-Var 1 Volt-Var 295% pf Volt-Watt 1Dyn-Var Volt-Watt 2

-500

0

500

1000

1500

2000

2500

3000

3500

4000

0 2000 4000 6000 8000 10000

Feed

er

Po

we

r (k

var)

Total PV (kW)

Control Off 98% pf

Volt-Var 1 Volt-Var 2

95% pf Volt-Watt 1

Dyn-Var Volt-Watt 2


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)

Co

ntr

ol





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)

Co

ntr

ol

Customer-Owned PV

Advanced Inverter Summary





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





Inverter Settings are Critical

% A

vaila

ble

Var

s

% voltage

100%

0.95

1.05

-100%

1.0V

% A

vaila

ble

Var

s

% 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

PV

Te

rmin

al V

olt

age

(p

u)

Time (seconds)

1

1.01

1.02

1.03

1.04

1.05

0 60 120 180 240 300 360 420 480 540

PV

Te

rmin

al V

olt

age

(p

u)

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

PV

Te

rmin

al V

olt

age

(p

u)

Time (seconds)

If wrong setpoints are used, adverse

impacts can occur

0

0.5

1

PV

Act

ive

P

ow

er

Volt-var B


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


Together…Shaping the Future of Electricity

Government & Nonprofit

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