Distribution Grid
Transcript of 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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