microgrids future of smart grids

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NTUA

Microgrids –

The future of Small Grids

Nikos [email protected]

National Technical University of Athens, Greece



NTUAWhat are MICROGRIDS ?

Interconnection of small,modular generation tolow voltage distributionsystems forms a new typeof power system, theMicrogrid .Microgrids can beconnected to the main

power network or be

operated islanded, in acoordinated, controlledway.



NTUA Technical, economical andenvironmental benefits

• Energy efficiency• Minimisation of the overall energy consumption• Improved environmental impact

• Improvement of energy system reliability andresilience• Network benefits

• Cost efficient electricity infrastructurereplacement strategies



NTUAEnergy Efficiency - Combined Heat and Power

Prof. Dr. J. Schmid

Up to now:

• Central power stations• Decentral heat production

In Future:• Decentral combined heatand power

1/3 less consumption offossil sources of energy100 % Oil / Gas

exchange of electrical energy

100 %power station

50 % electrical energy

50 %unusedwaste heat

50 % fossil fuel



NTUAClimate & Power Disasters:

Normal in the future?

London(28 August

2003)

Spain(Winter 2002 )

Storms(1999) € 10.8billion

Denmark,South Sweden

(23 September 2003)

Heatwave(2003)20,000

deaths?

Floods(2002) € 30billion

Italy(28 September

2003) Greec(12 July2004)

Croatia(23 Septem

2003)



NTUA

50 million customers in USA and Canada63 000 MW lost ≈ 11 %

Cost ≈ 4 – 10 billion $ US



NTUAPotential for DG to improve service quality

G G G

DG

G G G

DG

DG

-Mediumscale DG

Central generation

Small-scale DG

Voltagelevel

Securityof supply Securityof supplyDistribution of CMLs



NTUA

Installation and Replacement timeDistributions of Substation Equipment

1 9 4 0

1 9 5 0

1 9 6 0

1 9 7 0

1 9 8 0

1 9 9 0

2 0 0 0

2 0 1 0

2 0 2 0

2 0 3 0

2 0 4 0

2 0 5 0

C I G R E S C 3 7



NTUANetwork Benefits –

Value of Micro Generation

LV Distribution

MV Distribution

HV Distribution

Transmission

Central Generation

MicroGeneration

~ .02-.04 €/kWh

~ .05-.07 €/kWh

~.1-.15 €/kWh

~.03-.05 €/kWh



NTUA Technical Challenges for Microgrids

• Relatively large imbalances between load andgeneration to be managed (significant load

participation required, need for new technologies,review of the boundaries of microgrids)• Specific network characteristics (strong interaction

between active and reactive power, control andmarket implications)• Small size (challenging management)

• Use of different generation technologies (primemovers)

• Presence of power electronic interfaces• Protection and Safety



NTUAMarket and Regulatory Challenges

• coordinated but decentralised energy trading andmanagement

• market mechanisms to ensure efficient, fair and securesupply and demand balancing

• development of islanded and interconnected price-basedenergy and ancillary services arrangements forcongestion management

• secure and open access to the network and efficientallocation of network costs

• alternative ownership structures, energy serviceproviders

• new roles and responsibilities of supply company,distribution company, and consumer/customer



NTUAEC MICROGRIDS Project

GREAT BRITAIN• UMIST• URENCO

PORTUGAL• EDP• INESC

SPAIN• LABEIN

NETHERLANDS• EMforce

GREECE• NTUA• PPC /NAMD&RESD• GERMANOS

GERMANY• SMA• ISET

FRANCE• EDF• Ecole des Mines de Paris/ARMINES

• CENERG

“Large Scale Integration of Micro-Generation to Low Voltage GridsContract : ENK5-CT-2002-00610

ARMINES

CENERG

ISET

ICCS / NTUAGERMANOS

EDF

SMA

UMISTURENCO

PPC/NAMD&RESD

LABEIN

14 PARTNERS,7 EU COUNTRIES

INESCEDP

http://microgrids.power.ece.ntua.gr



NTUAR&D Objectives

– Contribute to increase the share of renewables and toreduce GHG emissions;

– Study the operation of Microgrids in normal and islandingconditions;

– Optimize the operation of local generation sources; – Develop and demonstrate control strategies to ensure

efficient, reliable and economic operation;

– Simulate and demonstrate a Microgid in lab conditions; – Define protection and grounding schemes; – Define communication infrastructure and protocols; – Identify legal, administrative and regulatory barriers and

propose measures to eliminate them;



NTUAMicrogrids Highlights

• Control philosophies (hierarchical vs. distributed)• Energy management within and outside of the

distributed power system• Device and interface response and intelligence

requirements

• Quantification of reliability benefits• Steady State and Dynamic Analysis Tools• Laboratory Microgrids



NTUAMicrogrids – Hierarchical Control

MicroGrid Central Controller (MGCC) promotes technicaland economical operation, interface with loads and microsources and DMS; provides set points or supervises LC and

MC; MC and LC Controllers : interfaces to controlinterruptible loads and micro sources

Centralized vs.Decentralized

Control

MV LV

DMSDMSMGCCMGCC

DCAC

PV

MC

LC

MC ACDC

LC

Storage

LC

~ CHPMC

Micro Turbine

MC

Fuel CellMCAC

DC

LCACDC

~

FlywheelMCAC

DC



NTUAMultiAgent System for Microgrids

• Autonomous Local Controllers• Distributed Intelligence

• Reduced communication needs• Open Architecture, Plug n’ Playoperation

• FIPA organization• Java Based Platforms

• Agent CommunicationLanguage

Microgrid Microgrid

......

Microgrid

MO

MGCC

LC LCLC

LC ...

DN OAgent

Agent Agent Agent

AgentAgent

AgentAgent

Grid Level

ManagementLevel

FieldLevel



NTUA

• Microgrid Serving its own needs using its localproduction, when beneficial (Good Citizen)(Good Citizen)

MGCC minimises operation costs based on: – Prices in the open power market – Forecasted demand and renewable power production – Bids of the Microgrid producers and consumers. – Technical constraints

• Microgrid buys and sells power to the grid via anEnergy Service provider (Ideal Citizen)(Ideal Citizen)

MGCC maximizes value of the Microgrid, i.e. maximizesrevenues by exchanging power with the grid based on similarinputs

Participation of Microgrids in

Energy Markets



NTUA

Study CaseLV Feeder with DGsources

0.4 kV

uk=4%, r k=1%, Dyn1120/0.4 kV, 50 Hz, 400 kVA

3+N3 Ω

20 kV

Off-load TC19-21 kV in 5 steps

80 Ω

10 Ω

80 Ω

3x70mm2 Al XLPE +54.6mm 2 AAACTwisted Cable

30 m

80 Ω 80 Ω 80 Ω

80 Ω

Single residencialconsumer 3Φ , I

s=40 A

Smax=15 kVAS0=5.7 kVA

4x6 mm 2 Cu

20 m4x25 mm 2 Cu

3+N3+N+PE

3+N+PE

20 m

30 Ω

30 m

4x16 mm 2 Cu

2 Ω

Possible neutral bridgeto adjacent LV network

80 Ω

80 Ω

20 m

Single residencial

consumer 3Φ , Is=40 ASmax=15 kVAS0=5.7 kVA

Group of 4 residences4 x 3 Φ , Is=40 ASmax=50 kVAS0=23 kVA

3+N+PE

1+N+PE

3+N+PE

3+N+PE

3+N+PE

Appartment building5 x 3 Φ , Is=40 A8 x 1 Φ , Is=40 ASmax=72 kVAS0=57 kVA

Appartment building1 x 3 Φ , Is=40 A6 x 1 Φ , Is=40 ASmax=47 kVAS0=25 kVA

3x50 mm 2 Al +35mm 2 Cu XLPE

Pole-to-pole distance = 35 m

Overhead line4x120 mm 2 Al XLPE

twisted cable

80 Ω

Other lines

4x6 mm 2 Cu

Flywheel storageRating to bedetermined

~~~

Microturbine3Φ , 30 kW

Photovoltaics1Φ , 3 kW

30 Ω

Photovoltaics

1Φ

, 4x2.5 kW

~Wind Turbine3Φ , 15 kW

Circuit Breaker instead of fuses

80 Ω

30 m

4x16 mm 2 Cu

Fuel Cell3Φ , 30 kW

10 Ω

~

Circuit Breaker Possible sectionalizing CB



NTUA Highlight: MGCC Simulation Tool



NTUA

Good Citizen Cost Reduction : 12.29 %27% reduction in CO 2 emissions

Model Citizen Cost reduction : 18.66%Load & Power exchange with the grid (residential feeder)

-30

-20-10

01020304050

60708090

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hour

k W

Power exchanged w ith the grid Load Pattern

Residential Feeder with DGs



NTUAHighlight: Reliability Assessment

FLOL (ev/yr) LOLE (hrs/yr) LOEE (kWh/yr)Infeed Capacity 100%

(no DGs) 2,130 23,93 2279,03

Infeed Capacity 80%(no DGs) 58,14 124,91 3101,52

Infeed Capacity 80%

(with Wind + PV) 14,02 41,67 2039,41

Infeed Capacity 80%(all DGs) 2,28 15,70 716,36

System Maximum Load Demand: 188 kWCapacity of System Infeed: 210 kW (100%)Installed DGs: 15 kW Wind, 13 kW PVs, 30 kW Fuel Cells, 30 kW Microturbines



NTUADeMoTec at ISET



NTUALaboratory installation at NTUA

0 100 200 300 400 500-200

-100

0

100

200

300

400

500

600

Time (s)

P ( W )

Pgrid

Pbat

Ppv

P load

0 100 200 300 400 50049.9

49.95

50

50.05

50.1

50.15

Time (s)

f ( H z ) f grid

f mg

0 100 200 300 400 500220

222

224

226

228

230

Time (s)

U ( V )

Umg

Ugrid



NTUAImplementation of the flywheel energy

storage system by UM

Flywheel

Inverter interface



NTUA

Development of Electronic Switch

-300

0

300

400 420 440 460 480 500 520 540 560 580 600

-100

-80

-60

-40

-20

0

20

40

60

80

100

400 420 440 460 480 500 520 540 560 580 600-1000

-800

-600

-400

-200

0

200

400

600

800

1000

v M i c r o G r i d

[ v ]

islandgrid connected

I M i c r o G r i d

[ A ]

time [ms]

I G r i d

[ A ]



NTUA

Highlight: Modelling and Simulation

Two battery invs + two PVs + one WT - Isolation + wind fluctuations

P,Q per phase Battery Inverter A I per phase Battery Inverter A



NTUAConclusions

• Microgrids: A possible paradigm for future LV powersystems

• Distinct advantages regarding efficiency, reliability,network support, environment, economics

• Challenging technical and regulatory issues• Promising solutions, needs for field demonstrations

http://microgrids.power.ece.ntua.gr

microgrids future of smart grids

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