distribution grid

7/28/2019 Distribution Grid

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TITRE PRESENTATION 11

07/07/2013


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DISTRIBUTION GRID

Ronnie Belmans


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Radial network

Energy supplied top-downfrom feeder

TRADITIONAL DISTRIBUTION GRID:FROM FEEDER TO METER


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DISTRIBUTION GRID FLANDERS:FACTS AND FIGURES

3,075 feeders

29,546 km of medium-voltage lines

29,331 distribution transformers 24,820 distribution cabins

6,203 switching posts

52,473 km of low-voltage lines

1,796,083 connections

2,580,279 meters


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3 technological drivers

Power electronics (PE) becomes ubiquitous in loads,generators and grids

More power produced (and stored) near consumers:Distributed Energy Resources (DER)

Increased importance ofPower Quality (PQ): moredisturbances and more sensitive devices

3 socio-economic tendencies

Liberalization of energy markets

More sustainable energy(renewable and high-quality)

Non-guaranteed security of supply

EVOLUTION IN ELECTRICAL ENERGY


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DER TECHNOLOGIES

Distributed Generation:

Reciprocating engines Gas turbines Micro-turbines Fuel cells Photovoltaic panels

Wind turbines CHP configuration

Energy Storage Batteries

Flywheels

Supercapacitors

Rev. fuel cells

Superconducting coils

. . -

.

Powder IronToroids

ArmatureWinding

Holders

Housing

Endcap

FieldWinding

& Bobbin

Rotor


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POWER ELECTRONIC DOMINATEDGRIDS

Source: KEMA


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GRID OF TOMORROW ?

Local generation

Local storage Controllable loads

Power quality and reliabilityis a big issue

Systems future size? Growth:

o Consumption rises annually by 2-3%o

Investments in production: very uncertain What is accepted? What is possible in regulatory framework?

Short-term: make balance by introducing DG? Long-term: more storage and/or activate loads?


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MICROGRID ?

Grids may even separate from central supply

No net power exchange: total autonomy

Important aspect, characterizing a Microgrid Ancillary Servicesare all delivered internally

Balancing the active and reactive power

Stabilizing the grid: frequency, voltage

Providing quality and reliability: unbalance, harmonics,

Is a Microgrid new ?

It all started that way, before interconnection

In fact, no: the grid behind certain UPS systems is

driven like a microgrid with one generator


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DG%

t

HOW MUCH LOCAL SOURCES CANA DISTRIBUTION GRID ACCEPT ?

Distribution grid was neverbuilt for local powerinjection, only top-down power delivery

Electrical power balance, anytime, in any grid:Electricity produced - system losses= electricity consumed storage

Barriers to overcome: Power quality & reliability

Control, or the lack of Safety Societal issues Economic aspects


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POWER QUALITY & RELIABILITY

Problem:

Bidirectional power flows

Distorted voltage profile

Vanishing stabilizing inertia

More harmonic distortion

More unbalance

Technological solution:

Power electronics may be configuredto enhance PQ

DG units can be used as backupsupply


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EXAMPLE: MV CABLE GRID

Substationconnectingto HV-grid

Location:Leuven-Haasrode,Brabanthal +SME-zone


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IMPACT OF WIND TURBINE

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CONTROL, OR THE LACK OF

Problem:

Generators are NOTdispatched in principle

Weather-driven (manyrenewables)

Heat-demand driven (CHP) Stabilising and balancing in

cable-dominated distributiongrids is not as easy as in HVgrids

reactive power voltage

active power frequency


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NETWORKED SYSTEM OPERATIONS

Solutions: Higher level of control required to coordinate balancing, grid

parameters ?

Advande control technologies

Future technologies, under investigation

Distributed stability control Contribution of power electronic front-ends

Market-based control Scheduling local load and production, by setting up a micro-

exchange (see example)

Management of power quality Customize quality and reliability level

Alternative networks E.g. stick to 50 Hz frequency ? Go DC (again) ?

Rely heavily on intensified communication: interdependency


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EXAMPLE: TERTIARY CONTROL ONLOCAL MARKET

DG units locally share loads dynamically based on marginalcost functions, cleared on market

P P

MC MC

MC

P

P1oldP1new P

2oldP

2new

equal marginal cost

translated

translated & mirrored


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EXAMPLE: TERTIARY CONTROL ONLOCAL MARKET

Prices are set by marginal cost functions of generators: Real-time pricing

Real-time measurements

Network limitations introduce price-differences betweennodes

Safety and PQ issues similar to congestion in transmissiongrid

Demand side management Optimizing consumption

Load reacts to external signals as prices

Overall need for advanced metering


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SAFETY

Problem:

Power system is designed for top-downpower flow

Local source contributes to the short-circuit current in case of fault

Fault effects more severe

Difficult to isolate fault location

Bidirectional flows Selectivity principle in danger: no

backup higher in the grid for failingprotection device

Conservative approach on unintentional

islanding Solution:

New activeprotection system necessary

G

G


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SOCIETAL ISSUES

Problems:

Environmental effects Global: more emissions due to

non-optimal operation oftraditional power plants

Local effects as power isproduced on-the-spot, e.g. visualpollution

Making power locally oftenrequires transportinfrastructure for (more)primary energy

Problem is shifted from electricaldistribution grid to, for instance,gas distribution grid!

Solution:

Multi-energyvector approach Open debate on

security of supply


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ECONOMIC ISSUES

Problems:

Pay-backuncertain in liberalizedmarket Chaotic green and efficient power

production Reliability or PQ enhancement difficult

to quantify

System costs More complicated system operation Local units offer ancillary services

System losses generally increase

Who pays for technologicaladaptations in the grid ? Who willfinance the backbone powersystem?

Too much socialization causes publicresistance

Solution: Interdisciplinary

regulation, notonly legal

Need some realderegulation


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SYSTEM LOSSES EXAMPLE

DG introduction

does not meanlowered losses

Optimum is 2/3power at 2/3distance

Other injectionsgenerally causehigher systemlosses

HV subst.

Load distributed along feeder cable

DG

Zero pointAfter DG

Before DG

Power flow along cable


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BALANCING QUESTION, AGAIN

Fundamental electrical power balance,at all times is the boundary condition:

Electricity produced - system losses= electricity consumed storage

All sorts of reserves will decrease in the future Role of storage? Storage also means cycle losses! Next step in enabling technologies

Usablestorage Activated intelligent loads (DSM technology), also playing

on a market as mentioned in example? Boundary condition: minimize losses


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HOW FAR CAN WE GO?

Large optimization exercise, considering thedifferent technical barriers:

Optimal proliferation, taking into account localenergetic opportunities, e.g. renewables options

Unit behavior towards grid: technology choice control paradigm

Is the same level ofreliability still desired ?

Level of introduction of new additionaltechnologies (storage, activated loads)

Optima are different, depending on stakeholder

E.g. grid operator vs. client


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OPTIMIZATION EXAMPLE

Total problem yields a huge mixed integer-

continuous optimization problem Optimization goals: voltage quality penalty, minimum

losses, minimum costs

Complexity: sample grid yields 240 siting options for

simple domestic CHP and PV scenario needadvanced maths

Results are different hourly and vary with time ofyear,

e.g. during day: PV opportunities in peak hours: CHP helpful


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Current grid:

Interconnection

Higher PQ level required

DER looking around the corner History repeats: after 100 years the idea of locally supplied,

independent grids is back

Microgrids, being responsible for own ancillary services

Maximum (optimal?) level of penetration of DER

= difficult optimization exercise Special (technological) measures are necessary

E.g. in system control, mainly balancing

Not only technology push, but also customer pull

CONCLUSION


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FILM: DISPOWER PROJECT

Example: DISPOWER project

Distributed Generation with High Penetration of

Renewable Energy Sources Film avaiable at http://english.mvv-

energie-ag.de/

(company innovation)
http://english.mvv-energie-ag.de/http://english.mvv-energie-ag.de/http://english.mvv-energie-ag.de/http://english.mvv-energie-ag.de/http://english.mvv-energie-ag.de/http://english.mvv-energie-ag.de/http://english.mvv-energie-ag.de/


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