SG3.pdf

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Modelling and Simulation inSmart Grid Demos

Roger C. DuganSr. Technical Executive

IEEE ISGT Europe 2011Manchester, UK7 December 2011

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2 2011 Electric Power Research Institute, Inc. All rights reserved.

What is the Smart Grid?

Smart Grid means different things to different people Communications and control

Not typically represented in distribution systemanalysis

Distributed resources

Generation, storage, demand response, microgrids

Some of these issues have been addressed

Monitoring (AMI, etc.)

Intelligent protection

Energy efficiency

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What Kind of Analysis Tools are Needed?

What can be done if more is known about the system?

What different approaches to DSA tools?

Expected:

Convergence of distribution monitoring anddistribution state estimation (DSE) into DMS

Selected relevant issues are discussed in thispresentation

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State of the Art

Most DSA tools can perform 3-phase analysis Some (e.g., EPRI OpenDSS) more than three phases

Most tools were originally designed for static power flow

A few can perform power flows over time

Tools and techniques designed for uniprocessors

Satisfactory for the time being future ??

Many (most?) exploit radial nature of feeders

For simulation efficiencies Harmonics analysis is optional

If available

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State of the Art, contd

Frequency-domain tools are preferred for DSA Time-domain tools do exist

Dynamics analysis (electromechanical transients) isuncommon

Planning and operational tools (DMS) are often separate

Secondary (LV) has been ignored

Changing!

Loads modeled by time-invariant ZIP models

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Needs Envisioned by EPRI

Sequential time simulation In various time steps

Meshed network solution capability

Better modeling of Smart Grid controllers

Advanced load and generation modeling

High phase order modeling ( >3 phases)

Stray voltage (NEV), crowded ROWs, etc.

Integrated harmonics NEV requires 1st and 3rd

User-defined (scriptable) behavior

Dynamics for DG evaluations

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7/327 2011 Electric Power Research Institute, Inc. All rights reserved.

EPRIs Vision

Distribution planning and distribution managementsystems (DMS) with access to real time loading andcontrol data will converge into a unified set of analysistools.

Real-time analysis and planninganalysis will merge into common tools.

Distribution system analysis tools will continue to play animportant role, although they might appear in a much

different form than today.

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Tackling Smart Grid Issues

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Modeling for Distributed Generation

Voltage rise and regulation, Voltage fluctuations,

Protective relaying and control functions,

Impact on short-circuit analysis,

Impact on fault location and clearing practices,

Interconnection transformer,

Transformer configuration,

Harmonics, Response to system imbalances

e.g. open-conductor faults due to failing splices.

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Example of an Expected DG Problem

Regulator taps upto compensate for

voltage drop

Voltage overshoots as

power output ramps up

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Root of Problem

Voltage Profile w/ DG

0.0 2.0 4.0 6.0

Distance from Substation (km)

0.90

0.95

1.00

1.05

1.10

p.u. Voltage

High Voltages Distribution

Systems designed

for voltage DROP,

not voltage RISE.

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Time Sequential Simulation

Electric vehicle charging (minutes, hours)

Solar and wind generation (seconds)

Dispatchable generation (minutes to hours)

Storage simulations (minutes to hours)

Energy efficiency (hours)

Distribution state estimation (seconds, minutes)

End use load models (minutes to hours) End use thermal models (minutes to hours)

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Modeling for Unbalances

Very important for North American systems Symmetrical component model and an unbalanced phase-

domain model can yield quite different results.

A symmetrical component model uses only the positive- and zero-sequence impedancesassumes balance

Asymmetries yield impedances that are not balanced betweenphases.

Many distribution system analysis tools can perform full 3-phaseanalysis;

A few programs can go beyond 3-phases.

Many circuits include multiple feeders sharing right-of-ways

We have analyzed circuits with 17 conductors on the samepole sharing a common neutral

(as well as several communications messengers).

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Example

FEEDER A FEEDER B

380.0 A

364.6 A

348.6 A

543.7 A

525.2 A

509.6 A

54.4 A

A

B

C

A

B

C

Shield

%I2/I1= 3.85% %I2/I1= 4.09%

I2 = Negative Sequence

I1 = Positive Sequence

A B C

515 A 519 A 518 A

Feeder A

IAVG=517 A

A B C

357 A 359 A 359 A

Feeder B

IAVG=358 A

Symmetrical Component ModelUnbalanced model

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Large Systems

A key capability 5000 10000 bus systems are routine today

Smart Grid requires solution of multiple feederssimultaneously

Goal:

100,000 to 1,000,000 nodes

Parallel computing could enable this

Requires new algorithms

HPC (High Performance Computing) ?

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Simulating with AMI Load Data

AMI verses Modeld (7/12/2010 to 7/17/2010)

0.96

0.97

0.98

0.99

1

1.01

1.02

1.03

1.04

20:00 8:00 20:00 8:00 20:00 8:00 20:00 8:00 20:00 8:00 20:00

Time

Voltage(PU)

Modeled

Measured

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Storage Element Model in OpenDSS

% Eff. Charge/DischargeIdle | Discharge | Charge

Idling Losses

kW, kvar

kWh

STORED

Other Key

Properties

% ReservekWhRated

kWhStored

%Stored

kWRated

etc.

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Basic Charge/Discharge Model for StorageModel

Example STORAGE Dispatch LoadShape

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1250 1300 1350 1400

Time, hr

Mult

Mult

Discharge Zone > 0.92

Charge Zone < 0.40Charge on Time

These Days

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Follow Mode

Example Daily Dispatch Curve

-1.5

-1

-0.5

0

0.5

1

1.5

0 5 10 15 20 25

time, Hr

Multiplier

Mult

Charge Cycle

Discharge Cycle

Example Follow Mode Solution (2 Days)

-250

-200

-150

-100

-50

0

50

100

150

200

250

0 8 16 24 32 40 48

time, h

kW

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

Power Discharged LoadShape kWh Stored

Charge/Discharge driven proportionately to apredefined curve

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StorageController Element in OpenDSS (CES Hub)

Discharge Mode

Charge Mode

kW Target

Discharge Time

Total Fleet kW CapacityTotal Fleet kWh

et. al.

Storage FleetSubstation

V, I

Comm Link

Time + Discharge rate

Peak Shaving

Load Following

Loadshape

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Hub Dispatch Modes Defined for AEP Demo

Time Turn ON at specific time

Peak Shave

Limit to a value

Follow

Time trigger and then shave

Loadshape

ScheduleCharge

Discharge

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Load Shapes With and Without Storage

Discharge Trigger @ Noon, 75 kWh Storage, 30% charge @ 2AM

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0 100 200 300 400 500 600

Hours

kW

0

10

20

30

40

50

60

70

80

"kWh Normal"

"kWh"kWh Stored

75 kWh Does a pretty good

job of clipping the peaks

unless triggered too early

Early

Too early drains storage

About right

Late

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Load Shapes With and Without Storage

Discharge Trigger @ Noon, 25 kWh Storage, 30% charge @ 2AM

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

150 170 190 210 230 250 270 290

Hours

kW

0

5

10

15

20

25

30

"kWh Normal"

"kWh"

kWh Stored

Early

Not enough Oomph

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Co-Simulation of Power andCommunications Systems

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The Question

Can you dispatch the 84 CES units fast enough tocompensate for the sudden loss of PV generation on aCloud Transient ?

Why it might not work: Communications latency

CES not in right location or insufficient capacity

Calls for a Hybrid simulation

Communications network (NS2)

Distribution network (OpenDSS)

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Modeling Communications

Clusters of

Storage Units

Voltage regulator (Reg1)

PV Location (PV1)

Solar Ramp Function

0 100 200 300

Seconds

0.00

0.20

0.40

0.60

0.80

1.00

p.u.

10%/s 5%/s

(dropout @ 20%)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.000 0.500 1.000 1.500 2.000

% Arrival vs time (S)

400mW

80mW

30mW

10mW

0 5 10 15 20 25 300.995

1.000

1.005

1.010

1.015

1.020

1.025

Time (seconds)

VoltageMagnitude(per

unit)

Base Phase a

Base Phase b

Base Phase c

Phase a

Phase b

Phase c

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How We Did It

OpenDSS

Extract

Time andCoordinates

NS2

DS Device

LoadProfile

Merge

Time andProfile

Wireless

Model

PowerCircuitModel

NS2 script toconfigure node

topology

Messagearrival times

Load profilesfor each DS

device

Loadprofiles

timed to DS

event arrival

OpenDSStopology for

DS devices

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OpenDSS Script (Snippet)

Set sec=20

Solve ! Init steady state at t=20

Sample

! Start the ramp down at 1 sec

Set sec=21

Generator.PV1.kW=(2500 250 -) ! Decrement 10%

Solve

Sample

Set sec=22

Generator.PV1.kW=(2500 500 -) ! Decrement another 10%

Solve

Sample

Set sec = 22.020834372 ! Unit 1 message arrives

storage.jo0235001304.state=discharging %discharge=11.9

Solve Sample

Set sec = 22.022028115 ! Unit 2 message arrives

storage.jo0235000257.state=discharging %discharge=11.9

Solve

Sample

Etc.

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Questions?

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