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Chair of
Sustainable Electric Networks
and Sources of Energy
Smart Grids and Integration of
Renewable Energies
Professor Kai Strunz, TU Berlin
Intelligent City Forum, Berlin, 30 May 2011
Overview
1. Historic Background
2. Power System Structure Today
3. Future Trends
4. Introduction to Smart Grid
5. Smart Grid Solutions
6. Wrap-Up
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1. Historic Background
a) AC vs. DC
b) First DC electricity supply
c) Origin of voltage drop
d) Reducing voltage drop
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1. Historic Background:
AC vs. DC
Thomas Edison (1847-1931)
 Born on 11th of February
1847 in Ohio, USA
 Died 1931 84 years old
 Brilliant in math and
nature sciences
 With 1093 Patents in his
name one of the greatest
inventor of all times
Nikola Tesla (1856-1943)
 Born on 9th of July 1856
in Croatien
 Died 1943 86 years old
 Brilliant with 800 patents
 Went 1884 in the USA
 Worked as an assistant
in Edison‘s lab
 His AC-motor was remarkable
 Opened his first research laboratory
in New Jersey in 1874
 One of the most important
inventions is light bulb
Supported DC
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Developed AC
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1. Historic Background:
First DC electricity supply
Historical development
The first power plant
 In 1880 Edison founded the Edison
Electric Illuminating Company New York
 In 1882 the Edison’s Pearl Street power
plant in Manhattan started operation
 It is the first power plant for electric
lightning
 Distributed direct current with 110 Volt
direct voltage
110 V
time
 A year after the start of the operation
10000 lamps were supplied
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1. Historic Background:
Origin of voltage drop
Voltage at a load with direct current
I
Rleiter
VQ
Vlast  I Rlast 
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Vlast
VQ
Rlast  Rleiter
Rlast
Rlast
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1. Historic Background:
Reducing the voltage drop
Direct Current (DC)
Alternating Current (AC)
 Voltage the load:
Vlast  I Rlast 
 With AC, the voltage is transformable
VQ
Rlast  Rleiter
Rlast
 VQ can be easily increased with a
transformer
N1
 Reducing the voltage drop through
reducing Rleiter
 Disadvantage:
• Thicker cables required
• Heavier cables required
• Expensive installation
• Difficulties in practice
N2
N2
VQ
N1
VQ
Victory of AC
thanks to technical benefits
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2. Power System Structure Today
a) Hierarchical buildup
b) Generation sector
c) Transmission sector
d) Distribution sector
• An example of Medium Voltage (MV) distribution network
• An example of Low Voltage (LV) distribution network
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2. Power System Structure Today
Hierarchical buildup
Generation
High Voltage Transmission Network
Medium Voltage Distribution Network
Low Voltage Distribution Network
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2. Power System Structure Today
Generation sector
 Responsible for generating power
demanded by consumers
 Traditionally based on large power
plants:
• Thermal power plants
 Fossil-fueled power plants
Source: http://www.treehugger.com
 Nuclear power plants
• Hydro power plants
Source: http://library.thinkquest.org
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2. Power System Structure Today
German generation system
Installed capacity
137.5 GW
(2007)
Energy production
share
mostly lignite (23.5 %), nuclear
(23.3 %) and hard coal (20.1 %)
(2008)
Main renewable
resources in generation
sector
wind power, hydro power, biomass
and solar power
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2. Power System Structure Today
Transmission system
 Responsible for transmitting
electric power from power plants to
distribution networks
 High Voltage transmission system
in Germany comprises lines with
following voltage levels:
 380 kV
 220 kV
Source: http://www.vnf.com
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2. Power System Structure Today
An example of medium voltage distribution network
Feeder 1
Feeder 2
Bus
Load
Transformer
Power switch
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2. Power System Structure Today
An example of low voltage distribution network
Load
Bus
20 kV
Residence
Grounding
Mast
Platform
Commerce
400 V
35 m
30 m
Industry
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3. Future Trends
a) Large-scale renewable generation
b) Distributed Generation (DG)
c) Energy storage systems (ESS)
d) E-mobility
•
•
•
•
Electric vehicles
Interaction with the grid
Possible challenges for the grid
Approaches to handle EV charging load
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3. Future Trends
Large-scale renewable generation
Source:
http://papundits.files.wordpress.com
Off-shore wind farm
Source: http://static.timesofmalta.com
On-shore wind farm
Source: http://blisstree.com
Solar power plant
 Good news: increasing penetration of large-scale renewable with significant
installed capacity
 Bad news: intermittent generation with a considerable forecast uncertainty
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3. Future Trends
Distributed Generation (DG)
Source:
http://www.finehomebuilding.com
Roof-mounted solar panels
Source:
http://www.powergenworldwide.com
Combine heat and power (CHP) unit
Increasing penetration of roof-mounted solar panels and micro combined heat and
power (CHP) units in low voltage (LV) distribution network
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3. Future Trends
Energy Storage Systems (ESS)
Source: http://softtoyssoftware.com
Source: http://www.shpegs.org/cawegs.html
Battery storage system
Compressed air storage system
Source: http://www.altenergymag.com
Pumped-storage system
Energy storage systems used to compensate intermittency of renewable
generation
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3. Future Trends
E-mobility: Definition and realization form
 Definition:
Using electricity as the energy vector for the road electric vehicles
 Realization form:
Large-scale market introduction of plug-in hybrid electric vehicles (PHEV) and
battery electric vehicles (BEV)
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3. Future Trends
E-mobility: Electric vehicles
 Battery electric vehicles (BEVs):
• The propulsion system consists of an electric motor
• The electric motor uses the electric energy stored in vehicle battery
packs
 Plug-in hybrid electric vehicles (PHEVs):
• The propulsion system consists of an electric motor and an internal
combustion engine (ICE)
• The electric motor and the ICE use the energy stored in vehicle battery
packs and fuel tank, respectively
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3. Future Trends
E-mobility: Interaction with the grid
 Massive integration of EVs introduces new challenges and opportunities to
the grid
 From the power system side, EVs can be regarded as:
• Simple loads: when the EV owner wants to charge the batteries at a
certain rate in a specified time (dumb charging)
• Responsive loads: when the EV owner defines a time interval for the
charging process, allowing some management structure to control the
charging rate (smart charging)
• Storage devices: when the EV owner allows batteries to inject power to
the grid upon request (vehicle-to-grid operation)
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3. Future Trends
E-mobility: Possible challenges for the grid
 Significant grid operational problems are expected in case of considering EVs
as simple loads, particularly if grid peak time coincides with EV charging
periods:
• Increase in grid overall peak demand
• Congestion problems in areas of the grid already heavily loaded
• Voltage profile problems mainly in radial networks
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3. Future Trends
E-mobility: Possible challenges for the grid
 Effect of dumb charging of EV batteries on Germany’s electricity demand
assuming a 10% share for electric vehicles:
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3. Future Trends
E-mobility: Approaches to handle EV charging load
 In the case of congestion due to EV charging, two possible solutions can be
suggested:
• Plan for grid expansion so that the reinforced network is able to handle the
new EV battery charging loads
• Develop a smart management system for charging EV batteries to
optimize charging times and fully benefit from EV battery storage potential
 The first way requires high grid investments
 The second approach tries to benefit from the already existing infrastructure to
minimize new possible investment costs, and is thus preferred where possible
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4. Introduction to Smart Grid
a) Motivation
• Need for effective integration of new trends
• Need for changing the role of demand side from passive to active
b) Power system structural change under smart grid paradigm
c) Key benefits of smart grid
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4. Introduction to Smart Grid
Motivation: Need for effective integration of new trends
 The new trends in power system offer many challenges and opportunities
 Current power system paradigm cannot accommodate the new trends in power
systems in an effective way
 For example:
• Intermittency of large-scale renewable resources makes the traditional
dispatching as known from thermal power plants impossible
• Distributed energy resources close to the consumer alter the power flows on
distribution networks
• Electric vehicles are new resources that are new loads but can also provide
support to network operation
 The smart grid is to support the integration of such new trends
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4. Introduction to Smart Grid
Motivation: Need for changing the role of demand side from
passive to active
 Presently, demand side is a passive part in the power system
 Changing demand side role from passive to active may offer the following benefits:
• Decrease in peak demand
• Delay in grid expansion
• Better utilization of assets in generation, transmission and distribution sectors
• Higher energy efficiency of power system
• More economic operation of the power system
 To actively involve the consumers in power system operation, they need to be
incentivized
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4. Introduction to Smart Grid
Motivation: Need for changing the role of demand side from
passive to active
 Correct incentives to consumers for acting in the optimum way requires providing
them real-time or near-real-time data of their consumption costs
 Providing the consumers with real-time or near-real-time information cannot be
achieved using present power system metering and communication infrastructure
 Smart grid promotes shift to a new paradigm: From “Supply follows Demand” to
“Demand follows Supply”
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4. Introduction to Smart Grid
Today’s hierarchical grid
Smart grid
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4. Introduction to Smart Grid
Key benefits of smart grid
 Effective integration of all types and sizes of electrical generation and storage
systems
 Increase in number of smaller, distributed resources – shift to a more
decentralized model
 Improved reliability of supply
 Improved monitoring, diagnosis, and response to power quality issues
 Supply of various grades of power quality at different pricing levels
 Operational improvements
 Asset management improvements
 Active involvement of demand side in power system operation through
Demand Side Management (DSM) concept
 Enable aggregation of resources through Virtual Power Plants (VPPs)
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5. Smart Grid Solutions
a) Demand Side Management (DSM)
•
•
•
•
DSM in a Smart Home
DSM via control centre
DSM and use of energy storage systems
Applying DSM in terms of smart charging of EV batteries
b) Virtual Power Plant (VPP)
• VPP concept
• Structure of VPP
• Definition of entities involved in VPP operation
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5. Smart Grid Solutions
Demand Side Mangement (DSM) in a „Smart Home“
 Smart Home is any private area equipped with smart
meter
 Modern ICT allows energy management
of a private household
 Flexible demand as a function of price
Household Connection
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5. Smart Grid Solutions
Demand side mangement (DSM) via control centre
Control Centre:
Control
Generation
Demand
Smart Meter
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5. Smart Grid Solutions
DSM and use of energy storage systems to compensate
intermittency of renewable resources
On
Off
Speicher
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5. Smart Grid Solutions
Applying DSM in terms of smart charging of EV batteries
Effect of smart charging of EV batteries in Germany’s electricity demand
assuming a 10% share for electric vehicles:
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5. Smart Grid Solutions
Virtual Power Plant (VPP) concept
 Individual capacities of DER units are often too small to enter the market
 Various DER units including controllable dispersed generation, storage, and
loads grouped and coordinated as a single unit can form a VPP
 The VPP would be able to participate in the market and offer:
• Generation capacity
• Ancillary services including voltage support and frequency regulation
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5. Smart Grid Solutions
Virtual Power Plant (VPP) concept
 Individual capacities of DER units are often too small to enter the market
 Various DER units including controllable dispersed generation, storage, and
loads grouped and coordinated as a single unit can form a VPP
 The VPP would be able to participate in the market and offer:
• Generation capacity
• Ancillary services including voltage support and frequency regulation
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5. Smart Grid Solutions
Structure of VPP
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5. Smart Grid Solutions
Definition of entities involved in VPP operation
 Aggregator: The entity which aggregates and sells the permission to
regulate the power consumption or generation rate of EVs and other DERs
within a VPP to the market
 Charging Point (CP): The place where electric vehicles (EVs) plug in to
exchange power with the grid
 Charging Point Manager (CPM): The owner and the operator of public
charging points
 Disribution System Operator (DSO): The entity responsible for safe and
secure operation of distribution network
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6. Wrap-Up
 Through the usage of many and new renewable and distributed resources, a
complex heterogeneous system emerges
 A shift in paradigm is essential to the success: From “Supply follows
Demand” to “Demand follows Supply”
 Smart Grid technology is critical to this shift
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