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2013 L. Ochoa - The University of Manchester OpenDSS Training Material 1/5 February 2013 1

OpenDSS Training Material

Part 1/5 - Distribution Modelling

Dr Luis(Nando) Ochoa

Lecturer in Smart Distribution Networks

[email protected]

February 2013


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Acknowledgement

Many slides in this presentation have used and/or adapted

content produced by Roger Dugan (EPRI, USA) who haskindly granted the corresponding permission.

Main repository of slides >> ftp://ftp.epri.com/
ftp://ftp.epri.com/ftp://ftp.epri.com/


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What is traditionally modelled?

Impacts of new loads or load growth? Voltage drops?

Capacity assessment (lines, transformers)?

Fault levels? Protection coordination?

Power losses? Balanced, radial distribution networks

Network expansion? Reinforcement? Reconfiguration? Reactivepower compensation?

... largely from the planning perspective rather than operational.


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The Context

Transmission

EHV Distribution

HV Distribution

LV Distribution

Unr

esponsive

Deman

d,noStorage

ConventionalGeneration

TODAY

Security

AgingAssets

Technology

Markets

ClimateChange

People

Transmission++ HVDC

EHV Distribution

HV Distribution

LV Distribution

Active,

ResponsiveDemandan

dStorage

Conv. Generation++ RES

FUTURE (Smart Grid)

DG100 MW

DGMW

DGMW

EV EHP


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Distributed Generation Today

Main Types of Distributed Generation (MW) according to the2011 Seven Year Statement from National Grid


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Photovoltaic Systems in the UK

(Feed-In Tariff) PV installedcapacity has exceeded 1GW

~70% is domestic

~25% is commercial

Typical domestic installations 1.5-3.5kWp per house

Housing associations

Eng Recommendation G83

16A per phase 13.68 kW

311.04 kW

Power factor 0.95 ind/cap

Source: Ofgem FIT Update, Sep 2012


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The Challenges

LV Distribution Networks (400V) Voltage rise/drops due to PV panels/EVs

Thermal limits: Are the wires fit for purpose?

More unbalances? etc.

HV Distribution Networks (6.6, 11kV) Voltage rise due to wind power (rural networks)

Increase in short circuit level (urban underground)

Power quality, Islanding and Protection

Increased energy losses? Variability? EHV Distribution Networks (33, 132kV)

Thermal limits

Stability and reserve requirements

Variability?

VoltageManagement

Observability

Controllability

Thermal,

Fault Mgmt

Integration ofSolutions

...


8/18 2013 L. Ochoa - The University of Manchester OpenDSS Training Material 1/5 February 2013 8

(Smart Grid) Modelling Challenges

Smart Grid means different things to different people

Low Carbon Technologies (Distributed Energy Resources)

Generation, Storage, Demand Response

Communications and control

Typically not represented in distribution network analysis

Monitoring

Protection

Energy Efficiency

... assuming all non-Smart Grid aspects can be modelled (whichare already significant challenges in some cases).



Modelling Challenges

Low carbon technologies Renewable generation (variable)

Demand response

Energy storage

0.0

0.5

1.0

1.5

2.0

2.5

161

121

181

241

301

361

421

481

541

601

661

721

781

841

901

961

1021

1081

1141

1201

1261

1321

1381

PowerOutput(kW)

Minute

0.2

0.4

0.6

0.8

1

0 4 8 12 16 20 24

(p.

u.

)

Wind Profi le Demand Profi le

Time (Hour)

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




Communications and control Smart meters deployed throughout the system

High-speed communications for metering and controls

Effective Distribution State Estimation

Distribution Network

Measurement (SCADA)

NMS Optimisation Engine:Optimal Set Points for active elements

(OLTCs, DG)

DistributionNM

S

NewS

etPoints

(SC

ADA)

Yes

No

Nom

constraintsViolations

DG SetPoints

Off Nom0.4

0.6

0.8

1.0

1 6 11 16 21 26 31 36 41 46 51 56 61

Setpoint(p.u)

Time (minutes)

DG-201 DG-206 DG-209




Improved energy efficiency End-use efficiency

Delivery efficiency

At the planning stage

Operationally, e.g., active volt-var regulation

0

50

100

150

200

250

300

350

5200 5250 5300 5350

Hour (1 Week)

Losses,

kW

Total Losses

Load Losses

No-Load Losses



Modelling Needs Today

Impacts of low carbon technologies Voltage rise/drop

(Dynamic) capacity assessment (lines, transformers)

Energy losses

Demand response Unbalanced, meshed distribution networks

Automatic restoration, Coordinated control of networkelements and participants

... integrating operational aspects into planning.



State of the Art in Modelling Capabilities

Full three-phase analysis Some can do more than 3 phases (OpenDSS)

Primarily peak demand capacity problem

Static power flow

A few perform sequential time (i.e., time-series) simulations

Tools designed for single processors

Mostly satisfactory for now




Several tools perform some form of meshed network analysis Weakly-meshed or highly-meshed

Many tools exploit radial nature of typical MV feeders for

computational efficiencies Increased demand for full network capabilities

Harmonic analysis is an optional feature

Frequency-domain tools are dominant in distribution planning




Dynamics analysis is not common in distribution planning

Planning and operations tools are generally separate modules

LV system is often ignored

But this is changing

Modelling of end-use loads is generally with time-invariant ZIP

models



Needs Envisioned by EPRI

Time-series simulation Meshed network solution capability

Better modelling of Smart Grid controllers

Advanced load and generation modelling

High phase order modelling (>3 phases)

Integrated harmonics

User-defined (scriptable) behaviour

Dynamics for distributed generation studies

...

Large systems, communication modelling, etc.



EPRIs Vision

Distribution planning and distribution management systems(DMS) with access to real-time loading and control data willconverge into a unified set of analysis tools.

Real-time analysis and planning analysis will merge intocommon 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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OpenDSS Training Material

Part 1/5 - Distribution Modelling

Dr Luis(Nando) Ochoa

Lecturer in Smart Distribution Networks

[email protected]

February 2013

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