looking ahead – epri r&d – advanced technologies to …

Aminul Huque, Ph.D. Sr. Project Engineer, Integration of Distributed Renewables, EPRI

Workshop on Achieving High Penetrations of PV

Solar Power International, September 14, 2012

Looking Ahead – EPRI R&D – Advanced Technologies to Manage and Integrate Distributed PV

2 © 2012 Electric Power Research Institute, Inc. All rights reserved.

Inverter – Role in PV Plants?

PV inverter converts DC energy from solar modules in to AC energy and interface the PV system with electricity grid

Inverter Functionality Today What it Can Do Tomorrow ?

• Harvesting maximum power from PV array

• Matching plant output with grid voltage and frequency

• Providing safety by providing unintentional islanding protection

• Providing grid-support for stability

• Improving PV system reliability

• Reducing PV Balance of Plant Cost

DC Power AC Power


Smart Grid Vision for Advanced Inverters

Smart, Grid-Friendly Distributed Solar and Storage Systems as Beneficial Distribution System Assets

Inverters with smart-grid functionality can double DER capacity on the grid


How to Coordinate with Existing Controls?


Challenge to Integrate Smart Inverters

• Many manufacturers… Many proprietary protocols • Distribution Management Systems in infancy

3Ph lines

1Ph lines

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http://solarenergy.advanced-energy.com/images/RBU/PowerStation_1.jpg�


2011 2010 2012 2009

September 2010 SEP2 Mapping is Launched

December 2011 Phase 2 Common Functions Published

September 2011 SEP2 Mapping Resumes

March 2010 EPRI Publishes Phase 1 Results: Common Functions for DER

June 2010 IEC TC57 WG17 Adopts Common Functions, begins modeling

61850-90-7 Development

December 2010 DNP3.org Releases First Protocol Mapping

DNP3

February 2012 SunSpec.org Releases First ModBus Draft

Addressing Communication Standard Challenge

March 2009 Launch of the Smart DER Communication Initiative


Smart-Grid Ready PV Inverter with Utility Communication

• Three key components – Developing smart-grid ready inverters – Demonstrating utility connectedness with smart-inverter – Demonstrate utility controlled unintentional islanding prevention


Utility Participants

DOE Project Demo Sites EPRI Collaborating Utilities

DTE Energy

SDG&E

National Grid

Hydro One

Xcel Energy KCP&L

AEP

GRE


• Voltage regulation and reactive support – Volt-VAR control – Power factor setting – Dynamic reactive current support

• Active Power & ramp rate limiting • Volt-watt control • Frequency-watt control • Dynamic response/LV ride-through • Storage inverter specific functions

– Direct charge/discharge management

– Price-based charge/discharge function

– Real power smoothing function – Load and generation following

function • Other Functions…

Inverter Grid Support Functionality

Example Volt-VAR Behavior (EPRI, 1023059)

LVRT in German MV Grid Code


VAR Support

-200

-150

-100

-50

0

50

100

150

200

-400

-300

-200

-100

0

100

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9.2 9.205 9.21 9.215 9.22 9.225 9.23 9.235 9.24 9.245 9.25

Curr

ent

(A)

Volta

ge (V

)

Time (s)

Capacitive

Inductive

Grid Voltage

Inverter Current

Finer steps and faster response compared to cap banks


Active Power Output Settings 100% 25% 75%

050

100150200250300350400450

4.5 6.5 8.5 10.5 12.5 14.5 16.5 18.5 20.5

DC

Volta

ge &

Cur

rent

Time (s)

Vdc Idc Modbus

-400

-300

-200

-100

0

100

200

300

400

AC

Volta

ge &

Cur

rent

Va Ia

390Vdc

3 Phase Output current ramp(only phase A shown)

DC Current ramp for 100%-25%-75% Curtailment

Modbus Signal(not actual voltage)

Modbus Signal(not actual voltage)


Voltage Sag/Interruption Ride-Through Improving Grid Reliability

-600

-400

-200

0

200

400

600

Volta

ge (V

)

-40

-30

-20

-10

0

10

20

30

40

2.05 2.25 2.45 2.65 2.85 3.05 3.25 3.45 3.65

Curr

ent (

A)

Time (s)

6 Cycle Interuption

Inverter Current

Grid Voltage

Inverter able to ride through momentary interruptions


Voltage Sag/Interruption Ride-Through

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 20 40 60 80 100 120 140 160 180 200

Perc

ent S

ag D

epth

Perc

ent N

omin

al V

olta

ge R

emai

ning

Event Duration (# of cycles @ 60Hz)

L-L (VAB) Sag L-N (1 ph) Sag L-N (all 3 ph) Sag

Above LinesInverter Ride-thru

Below LinesInverter Trips


Voltage Swell Ride-Through

100%

105%

110%

115%

120%

125%

130%

0 20 40 60 80 100 120 140 160 180 200

Perc

ent V

olta

ge S

wel

l of N

omin

al

Event Duration (# of cycles @ 60Hz)

L-L (VAB) Swell L-N (1 ph) Swell L-N (all 3 ph) Swell

Above LinesInverter Trips

(up to 125% which is limited by test equipment)

Below LinesInverter Ride Thru


High-Resolution System Monitoring

Collect high-resolution (1-sec) DER generation and environmental data Also capture power quality (PQ) events

(Sep 29, 2011)... 13:10 13:11 13:12 13:13 13:140

200

400

600

800

1000

1200

X: 29-Sep-2011 13:11:15Y: 157.9

AC

Pow

er (k

W)

1MW PV System Pow er Production Profile

Local Date & Time (Eastern)

X: 29-Sep-2011 13:11:40Y: 927.6

X: 29-Sep-2011 13:09:55Y: 908.6

X: 29-Sep-2011 13:10:20Y: 165.6

–743kW in 25 sec

(2.9% per sec)

+770kW in 25 sec

(3.0% per sec)


PV output monitored to understand variability High definition monitoring captures 1-sec data on any size PV system

2kW tracker in TX

1MW ground in TN

0.2kW pole in AL

200kW roof in CA


1MW PV System in Tennessee Solar resource and AC output recorded at 1-sec resolution

Imagery ©2011 DigitalGlobe, GeoEye, U.S. Geological Survey, USDA Farm Service Agency, Map data ©2011 Google

8 Pyranometers • 7 on PV system • 1 on single-module • Plane-of-array • 25° fixed tilt, south

1.0 MWdc • 3.5 acre • Four 260kW inverters • Data from Oct 2011

Pyranometer Single Module


Solar Resource Calendar – Single Pyranometer December 2011 at 1MW PV site in Tennessee

1 2 3

4 5 6 7 8 9 10

11 12 13 14 15 16 17

18 19 20 21 22 23 24

25 26 27 28 29 30 31

Thu Fri SatSun Mon Tue WedDecember 2011: Tennessee Plane-of-Array Irradiance

Calendar profiles are 1-minute averages derived from 1-sec data


Feeder Modeling and Impact Analysis

0.9

0.925

0.95

0.975

1

1.025

1.05

0 4 8 12 16 20

Hour

Vo

ltag

e (p

u)

0.9

0.925

0.95

0.975

1

1.025

1.05

0 4 8 12 16 20

Hour

Vo

ltag

e (p

u)PV Feeder Impact Analysis

(OpenDSS)

Feeder Impact Results

with adv functions

without adv functions

Apply Adv Inverter Functions

Detailed Feeder Models

Increase PV Penetration


DMS – DERMS Conceptual Architecture

Field Devices Distribution SCADA

Substation Devices

•Basic alarms •Displays •Archiving

Advanced Distribution Applications

•Data Management •Operating model •On-line power flow •Volt VAR •Auto restoration

DMS

Advanced Metering

System (AMI)

Outage Management

System (OMS)

Geographic Information

System (GIS)

Enterprise Service

Bus

ESB

DER Interfaces

•DER Monitoring •Smart Inverter Functions

Advanced DER

Applications

•Request VAR support •Request Watt support •Limit generation •DER forecast •Others

DERs

DERMS


Enhanced DMS Functionality with DERMS

Conventional Functionality

• SCADA • Volt-VAR Optimization • FLISR • Switching Orders • Load Forecast • Peak shaving • Others

Enhanced Functionality • Active distribution

Control • Enhanced VVO • Enhanced FLISR • Microgrid capability • Firm renewables • Market functions • Others


Preventing Unintentional Islanding

Method Description Effectiveness Cost Compatibility with grid support functions

Passive Monitor terminal voltage for trip conditions, but does not change inverter output to cause changes

Fair to poor, if high speed is needed

$ Good to excellent

Active Actively change inverter output to cause change

Excellent in single inverter cases

$$ Poor to very poor

Communication based

Relies on communication for system awareness

Excellent (?) $$$$ Excellent

Source: Michael Ropp, Northern Plains Power Technologies


Do We Need New Unintentional Islanding Prevention Method?

Most inverters use active anti-islanding

which rely on the creation of an abnormal voltage to detect island

formation

Key communication based methods?

• Direct transfer trip (DTT)

• Power Line Carrier Permissive (PLCP)

• Synchrophasor-based methods

Cost

Effectiveness

Equipment reliability

Coverage area

Grid support functions are all about correcting

abnormalities in the voltage/frequency to maintain grid stability

Conflicting


EPRI Smart-Inverter Demonstration Project

Grid Support

Building Advanced Functionality into Inverters

Deploying in Diverse Field Environments

Collaborating – Sharing Plans and Results, Building Industry Knowledgebase

• Detailed insight into who is doing what • Understanding different functions and architectures • Understanding impacts through modeling and monitoring • Take away new tools and resources to use in other cases

• Provide input to shape industry standards and future products


Together…Shaping the Future of Electricity Aminul Huque

[email protected] 865-218-8051

mailto:[email protected]�

looking ahead – epri r&d – advanced technologies to …

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