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Low Voltage DC Grids Prof. Eberhard Waffenschmidt, Cologne University of Applied Science, Ulrich Böke, Philips Research Eindhoven 13. Mar. 2013
Low Voltage DC Grids
Prof. Eberhard Waffenschmidt,
Cologne University of Applied Science,
Ulrich Böke,
Philips Research Eindhoven
13. Mar. 2013
Content
� Application: Commercial Buildings
� AC conversion effort
� Efficiency
� Cable losses
� Experimental setup
Prof. Eberhard Waffenschmidt 2
DC Grids in Buildings
3Prof. Eberhard Waffenschmidt
Large lighting installations:
Office space
Supermarket
Photographs by
E. Waffenschmidt
Effort for AC to DC conversion
4Prof. Eberhard Waffenschmidt
Philips Xitanium 35 W LED driver
Lampentreiber mit AC-Teil
Typically, more than 50% of space can be saved
Input FilterBridge rectifier
Power factor
correction
Storage
electrolytic
capacitor
AC part =
Photograph by
U. Boeke
LED-driver comparison
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Yes, this is the same scale as on the left side.
Photographs by
L. Yseboodt
Lamp driver input stage
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Component AC supply DC wide
voltage range and
reverse polarity
protection
DC narrow
voltage range,
mechanical rev.
polarity protection
Filter Required
because of PFC
Required
because of DC-DC
Can be omitted
with linear driver
Rectifier Required Required for reverse
polarity
Omitted
Power factor
correction (PFC) /
DC-DC converter
Required
for P > 25W
Required to match
wide voltage range
Not necessary
Elcap storage Required
to avoid flickering
Required
because of dips
Can be omitted, if
dips are accepted
Linear LED driver
� High efficiency
possible
� If voltage range
is narrow
Prof. Eberhard Waffenschmidt 7
LED Output Power and Losses
0
0.2
0.4
0.6
0.8
1
1.2
0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2
Supply voltage Us / Umin
Po
we
r P
/ P
led
0%
20%
40%
60%
80%
100%
120%
Effic
ien
y
LED Power
Power Loss
Efficiency
η = 90%
∆U = ± 5%
Efficiency gain with DC
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Typical AC lamp driver:
~5 % losses
Filter Rectifier PFCElcap
storageLamp
driver
Efficiency gain with DC
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AC grid:
~5 %
rectifier
losses
DC grid:
~2 %
rectifier
losses
Eff. Gain: ~5 %
Simple supply from AC grid:
~3 %
cable
losses
~1 %
cable
losses
Photovoltaic
generator
DC micro grid in a Building
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With solar generator and battery storage
Lamps and air conditionAC mains connection
Photographs by
E. Waffenschmidt
Battery storage
Efficiency gain with DC
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AC grid:
~4%
losses
Gain:
~10..13% losses
Micro-grid with solar and storage:
DC grid:
~2..3%
losses
~2..3%
losses
~2..3%
losses
Operation voltage: Cable losses
12Prof. Eberhard Waffenschmidt
Same copper cable:
Relative cable losses
(equivalent to copper effort)
Remark:
380 Vdc requires
similar insulation as
230 Vac
Standardization on 380 V DC
� International Electrotechnical Commission (IEC)
� Many standards covering low voltage DC grid systems already
� SMB SG4 working group “LVDC distribution systems up to 1500V DC”
− Managing new standardization projects at IEC technical committees (TC)
� National standardization working groups
− Germany: TBINK-LVDC working group at DKE/VDE
� European Telecommunication Standardisation Institute (ETSI)
� European Standard: EN 300 132-3-1 V2.1.1 (2012-02)
− Value: Definition of DC appliance inrush current limits and measurement setup
� EMerge Alliance
� Standardization working group on 380 V DC power grids for datacenters
� Standardization working group on 380 V DC for campus and microgrids
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DCC+G - Direct Current Components & Grid
� Aims
� Demonstrate higher efficiency:
− 5 % of DC power grids
− 7 % of solar power systems
� Development of new power semiconductors
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European co-funded R&D Project
www.dcc-g.eu
Demo DC-Grid with Solar Support
� Grid Voltage
380 V DC
� Solar Modules
2 kWp
� 56 LED Lamps
37 W, adapted LED
drivers
� Reference system
with 230 V AC
� Operation since
2012
Prof. Eberhard Waffenschmidt 15
DC Micro grid
MPPConverter
SolarModules2 kWpk
54 LEDDC-Drivers + Lamps
37 Wdc
Rectifier
380V=
AC Reference
MainsGrid230V~
SolarModules12 kWpk
MPPConverter
and PV inverter
230V~
18 LEDDrivers+ Lamps 39 Wac
Demo DC-Grid with Solar Support
� Grid Voltage
380 V DC
� Solar Modules
2 kWp
� 56 LED Lamps
37 W, adapted LED
drivers
� Reference system
with 230 V AC
� Operation since
2012
Prof. Eberhard Waffenschmidt 16
Photographs by
E. Waffenschmidt
Conclusion
DC grids offers
� Miniaturisation of power electronic modules
� Lamp drivers with less components
� Less power losses in the system
…only with suitable specifications
� Narrow voltage tolerance
� Reasonable operating voltage like 380 V DC
Prof. Eberhard Waffenschmidt 17
Contact
18Prof. Eberhard Waffenschmidt
Corresponding author:
Prof. Dr. Eberhard Waffenschmidt
Electrical Grids,
Institute of Electrical Power Engineering,
Faculty of Information, Media and Electrical Egineering (F07)
Betzdorferstraße 2, Raum ZO 9-19
50679 Cologne, Germany
Tel. +49 221 8275 2020
http://www.f07.fh-koeln.de/fakultaet/personen/professoren/
eberhard.waffenschmidt/index.html
Co-author:
Ulrich Böke, Philips Research Eindhoven, The Netherlands
