distributed generation and storage: exploring the...

© University of Wisconsin November 2010

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Distributed Generation and Storage:Exploring the Microgrid

3rd Energy Storage SummitNovember 15-17, 2010, Chicago, IL

Bob LasseterUniversity of Wisconsin - Madison

16 November 2010

© University of Wisconsin April 2010

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Electrical Power System

Customers

Power Plants(200-1000 MW)

Transmission networkLines (~100 mi)

DistributionSubstation

DistributionTransformer

DistributionLine (~10 mi)

High Voltage Transmission Network Issues

– Generation/transmission efficiency (~25%)

– Peaking generation capacity (~20%)

– Cascading blackout 2003

– Penetration of intermittent sources

– Building new generation and transmission

+ Smart controls & ~ 99.9% reliable

+ Evolutionary changes (most technology is proven)

Power Distribution System Issues

–~100 year old technology

– Poor reliability

– Basically uncontrolled radial feeders

– Most problems are reported by customers

+ Prime for Smart grid concepts


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Power System Reliability

Stand-aloneSteam Generation

1900 1950 2000

Year

Electricity Reliability(in “9”s)

10 9 8 7 6 5 4 3 2 1 0

(3 ms/yr)

(30 ms/yr)

(0.3 sec/yr)

(3 sec/yr)

(30 sec/yr)

(5 min/yr)

(1 hr/yr)

(9 hr/yr)

(3-4 day/yr)

(1 mo/yr)

Interconnected CentralStation Generation

DER-basedDistributionSystem

RobustG&T

Local Reliability

Higher efficiency

Renewables

Smarter components

*EPRI

Greater need forsophisticatedenergy services


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Electrical Power System

Customers

Conventional UtilityPower Plant(~1000 MW)

Transmission Line (~100 mi)

DistributionSubstation

DistributionTransformer

DistributionLine (~10 mi)

DER-based DistributionPower Plant(~1000 MW)

Transmission Line (~100 mi)

Robustgeneration &transmission

DER-baseddistribution


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DER TechnologiesDispatchable Sources (10kW ~ 3 MW)• Internal combustion-engine generator• Small gas turbines generators• Microturbines• Fuel cellsIntermittent Sources•Wind turbines•PhotovoltaicStorage•Batteries•Ultra-capacitors•Fly-wheels

Electrical vehicles?


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Smart Distribution“When it comes to a utility figuring out howto manage this wide, dynamic set of resourcesand control points, the only way they can dothat efficiently is to break their networksdown into small nodes i.e. microgrids– andthen add a level of control on top of it.”

Dave Pacyna, senior vice president of Siemens Energy’s North American


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Microgrids

A microgrid is an integrated energy systemconsisting of interconnected loads anddistributed energy resources which as anintegrated system can operate in parallel withthe grid or in an intentional island mode.


Microgrid: Fast Controls and Communications

Utility SystemPrimary Connection

(13.2 kV)

Utility SystemInterface Control(Synchronization, faultprotection, islanding

detection, etc.)

Isolating Device(opens during micro-

grid mode)

Heat Distribution

1.2 MVA

0.8 MVA

1.4 MVA

GeneratorStep Up

Transformer

GenGenGen

GeneratorProtection

andControl

Paralleling Bus (4.8 kV)

1.75MVA

1.75MVA

1.75MVA

Heat Recoveredfrom ICE Units

Loadcontrol

Communication & ControlSignal Path

Issues:• Loss of control &communication

• Extensive siteengineering

• Costly heatdistribution system.

• Complex voltage &power balancingsystem

• Speed of response

EPRI: Campus Microgrid System: CEC Workshop


CERTS Microgrid: Local Control

Utility SystemPrimary Connection

(13.2 kV)

Smart Switch Heat Distribution

1.2 MVA 0.8 MVA

1.4 MVAParalleling Bus (4.8 kV)

CERTSGen

CERTSGen

CERTSGen

• Local Control (nomaster control)

• Plug & Play Model(avoids extensive siteengineering, designerrors & allowsplacement nearheat/cooling loads)

• Units control power &voltage using localinformation only

CERTSStorage


Multi-CERTS Microgrids

Microgrid + CHP

• Mixed building based microgrid• Enhances use of waist heat• Peer-to-Peer and Plug & Play Model• Each DER unit has embedded

CERTS controls

Microgrid with localCombined Heat & Power Microgrid + CHP

13.2 kV

120 kV

Smart Switch Other loads

Lc L

c Lc

LLCHP

PV

Storage

PV

Controller

CHP


Current CERTS Microgrid Field Demonstration Projects• DOE Phase III: CERTS/AEP Test Site (PV and ac storage)

• CEC/SMUD: Microgrid Demonstration (3-100 kW, CHP, UPS, PV &

export)

• DOE/Chevron Energy Solutions: Distribution Microgrid (12 kV, static

switch, storage, diesel generation, fuel cell and PV).

• CERL/Odyssian Technology: Scalable & Deployable Microgrids

(research on microgrid controller)

• Air Force/Sandia: Maxwell Air force base (100kw NG and 2 existing

diesels)• CERL/Ft. Sill Army: (2-190kW NG generators, 400KW ZBB Battery, 30 kW PV)


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Microgrids and storageSystem approach (Currently one DER unit, IEEE 1547)

Support high penetration of DER (Ca. expects 100s of thousands of DER units)

Support use of waste heat (efficiency ~ 80%)

Reduces transmission losses

Support intermittent sources

Enhance robustness and reliability

Promote self healing

Eliminate need for fast central controls


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CERTS Microgrid Control Concept*

• Voltage Control (V vs. Q droop)• Each unit has an overload capacity• The islanded system operates over a

well defined frequency range (±0.5Hz).This frequency is key for:• Transfer load among units• Intelligent load and source

shedding.• Automatic re-synchronizing to the

network.

*Research History CERTS MicrogridDOE– 1999-‐2002(Development of original concepts bench-‐scaletesFng )

CEC PIER – 2001-‐2006(ConstrucFon & compleFon of proof-‐of-‐concept onAEP CERTS Microgrid test bed)

DOE RDSI– 2006-‐2009(Value and technology assessment to enhance thebusiness case)

DOE Smart Grid – 2009-‐present(IntegraFon of variable renewablegeneraFon/storage)


Load Transfer

.

Assume two DER sources

P01 & P02 are dispatchedpowers while grid connected

For a step load (islanding orwhile islanded) The increasedload is ~ equally sharedbetween both sources

Transient Overload• Storage most robust• Syn machine and InVerde

could stall• PV has minimum overload

capabilities without dc storage.

∆P ∆P


Load Transfer & Stalling Issues

2-100kW CERTS sourcesA1: 90 kWA2 : 10 kWImport 90 kW

Opening Smart Switch loose 90 kWsA1: 90 + 47.5 =137.5 kWOverload 37.5 kWWill Stall if overload too long

Voltage sourcesCB31

CB41

P1=10 kW P2=90 kW

Load 190 kW

A1 A2

90 kW


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Lc

Lc

LcL

LCHP

PV

Storage

PV

CHP

Controller

Basic Building Block: Microgrid

Microgrid as a Grid Resource:• Provides a standard building block for “Smart

Distribution”.• Dispatchable bi-directional real & reactive power.• Multiple points of electrical coupling.• Islands & re-synchronizes autonomously• Controller interfaces with system controllers and

locally optimizes the microgrid operation.

Can have different features: CHP/UPS Microgrid, MixedMicrogrid & PV Microgrid.


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Basic Types of Microgrid

High Power Quality Microgrid with CCHP• UPS functions & effective use of waste heat• DER units must follow a peer-to-peer and plug-and-play concept

Mixed Microgrid• Higher voltages and power levels change the DER mix.• Synchronous generators and ac storage (different response times)• Plug-and-play

PV Microgrid• High export of PV• Reduce intermittent power fluctuations (storage and/or CHP units).• Need to back off PV output during islanding


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High Power Quality Microgrid with CCHPUPS functions & effective use of waste heatEach DER units must follow a peer-to-peer and plug-and-play concept

•Need fast response with overload capacity (i.e. InVerde, storage) or•DC storage as part of the source (i.e microturbines, fuel cells…)•No standalone ac storage

Examples• DOE: CERTS/AEP Test Site

• CEC/SMUD: Sacramento Municipal Utility District, Microgrid

Demonstration (3-100 kW, CCHP, UPS & export)


High Power Quality Microgrid with CCHP

Loads

60 kWSources

StaticSwitch

3-New 100 kW InVerde for SMUD Microgrid(InVerde is a CERTS compatible source)

CERTS/AEP Microgrid Test Bed


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Microgrids with slower DER units

Higher voltages and power levels change the DER mix.Synchronous generators and ac storage.Storage provides:

• Enhance reliability with Intentional islanding (smallest energy sizing)

• Arbitrage of energy price differentials (largest energy levels)

• Firm intermittent resources( DG and storage)(Loss of ac storage reduces microgrid flexibility).

ExampleDOE/Chevron Energy Solutions: (12 kV, 12 MW hour storage, diesel

generation, fuel cell and PV).CERL/Ft. Sill Army: (2-190kW NG generators, 400KW ZBB Battery, 30 kW

PV)


DOE/Chevron: Microgrid


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PV Microgrid: High export of PV

High levels of energy from PV in a CERTS microgrid•PV overload (i.e. islanding) requires dc storage

•Reduce intermittent power fluctuations (storage and/or CHP units).

•Need to back off PV output during islanding also requires ac or dcstorage

Active Research:UW test facility & CERTS/AEP test bed (100kW PV)


Storage in Microgrids

Peer-to-Peer Microgrids•DC storage needed for most sources including PV

•No AC storage

Mixed Microgrids (AC storage)•Needed for Islanding

•Arbitrage of energy price differentials

•Firm intermittent resources (also can use other sources & dc storage)


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Lc

Lc

LcL

LCHP

PV

Storage

PV

CHP

Controller

Microgrid is a basic building block

Microgrid :• Provides a standard building block for “Smart

Distribution”.• Dispatchable bi-directional real & reactive power.• Components include dispatchable generation,

renewable sources, storage, loads and a smart switch• Provides a system approach


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Smart Distribution: Coupled Microgrids

LcLc

LcL

LCHP

PV

Storage

PV

CHP

Controller

LcLc

LcL

LCHP

PV

Storage

PV

CHP

Controller

LcLc

LcL

LCHP

PV

Storage

PV

CHP

Controller

LcLc

LcL

LCHP

PV

Storage

PV

CHP

Controller

LcLc

LcL

LCHP

PV

Storage

PV

CHP

Controller

Distribution coordinator

SmartSwitch

High Voltage Network


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Questions ?

[email protected]


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Load

MWs fromgrid

Power from ICE generator

Power from storage

Loss of grid

Islanding on Loss of grid

Energy level

Combined Storage/Genset

Charging Discharging

• Constant Power from grid 24/7.• Storage is charged during low load periods.• Generation is run at optimum level during

high loads.• Storage follows load and provides fast power

balance during islanding.• Storage sizing

Islanding onlyArbitrage

sources

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