Applications of LVDC
EMPOWERED BY: KU LEUVEN, VITO, IMEC & UHASSELT 1
Current AC grid architecture
Similarities with datacenters:
Grid • Reliability
G G • Modular
15 kV
690V
400V
690V
400V
690V
400V
690V
400V
690V
400V
690V
400V
690V
400V
690V
400V
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Datacenters were the prime movers in DC technology
Economic drivers for DC in datacenters
Grid Uninterruptible power supply Cabling Rack-level
AC architecture
400 V (AC)
AC/DC DC/AC AC/DC PFC DC/DC 12 or 48 V (DC)
Storage
DC architecture
AC/DC DC/AC AC/DC PFC DC/DC 12 or 48 V (DC)
380 V (DC)
• 10% less energy losses (ABB Green.ch datacenter, 1 MW)
Storage
• 15% less upfront capital cost
• 33% less floor space occupied
Standards: ETSI EN 300 132-2 (260 to 400 V DC)
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Power electronics, inside adapters, convert AC into DC
DC/DC
AC/DC
Source: http://www.righto.com/2015/11/macbook-charger-teardown-surprising.html
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Power electronics, in converters, convert DC into AC.
Power electronics is the technology behind the energy transition
DC/AC
AC AC AC AC AC AC AC
DC/DC DC DC
DC
DC
DC
DC
DC
DC
DC
DC
DC
DC
DC DC
DC DC DC AC DC DC DC
Source: http://www.righto.com/2015/11/macbook-charger-teardown-surprising.html
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New drivers for DC in the datacenter world
Grid Uninterruptible power supply Cabling Rack-level
Introduce renewables
Decentralize storage
DC/DC Storage
DC architecture
AC/DC DC/AC DC/DC 12 or 48 V (DC)
380 V (DC)
Further increase in power density
Storage • DC decreases the number of parts and conversion losses
• DC reduces the cooling requirements
• Wide-bandgap power semiconductor devices
Bipolar +-380 V DC for reducing cabling and losses
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Advantages of LVDC technology in a nutshell
• Increased level of compatibility
• Efficiency gains (5-15%pt savings)
• Reliability improvement
• Upfront cost savings (-30%)
• Material resource savings
• Increased power transfer capability (voltage level dependent)
• Upfront cost savings
• Material resource savings
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Current AC grid architecture
Pro: proven technology
Grid Contra: transfer time, reliability, Diesel gensets
G G
15 kV
AC DC AC DC
DC AC DC DC
AC DC AC DC
690V
400V
DC AC DC DC
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Split DC bus architecture
Pro: less conversion stages, reduced level of harmonics
Grid Contra: mechanical current interruption
G G Challenges: local voltage control
15 kV
AC AC
DC DC
AC DC
DC DC
AC DC
1000V
380V
DC DC
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The advantages of LVDC for smart cities
Increased compatibility - LED DC-DC driver topologies
Source: J. L. Davis, K. Mills, R. Yaga, and C. Johnson, Solid State Lighting Reliability Part 2.
Springer, 2018.
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The advantages of LVDC for smart cities LED driver component failure distribution
More reliable LED driver designs? 70.0%
60.0%
50.0%
60.9%
40.0%
30.0% 17.4%13.0%
20.0% 8.7% 4.3% 4.3% 0.0%
10.0%
0.0%
• Dominant modes of failure in LED drivers in the O
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• LVDC: 17.3 to 26% less component failures [1] J. L. Davis, K. Mills, R. Yaga, and C. Johnson,
• Note: conclusion holds for this particular study and this Solid State Lighting Reliability Part 2. Springer, 2018.
particular LED driver. Be careful with extrapolation.
• Reliability of LED drivers and LED lighting fixtures should
be performed at the system level
• Power quality of DC systems should be carefully guarded to increase
the reliability of LED drivers
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Split DC bus architecture + battery storage
Pro: less conversion stages, reduced level of harmonics,
Grid standalone subgrids
G G Contra: mechanical current interruption
Challenges: local voltage control
15 kV
Battery storage enables
AC AC
stand-alone subgrids
DC DC
DC DC
DC DC
AC DC
DC DC
AC DC
1000V
380V
DC DC
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Bipolar DC bus architecture Less substations?
Pro: less conversion stages, reduced level of harmonics,
Grid cover longer distances
G G Contra: mechanical current interruption
Challenges: more complex voltage control/protection
15 kV
Three-wire bipolar LVDC
AC AC
architecture
DC DC
DC DC
DC DC
AC DC
DC DC
AC DC
+380V
-380V
DC DC
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Bipolar DC bus architecture with a single AC/DC
Pro: less conversion stages, reduced level of harmonics,
Grid cover longer distances
G G Contra: mechanical current interruption
Challenges: more complex voltage control/protection
15 kV
Neutral point clamped
AC/DC
AC
DC
DC DC
DC DC
AC DC
DC DC
AC DC
+380V
-380V
DC DC
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Asymmetric bipolar DC bus architecture
Pro: less conversion stages, reduced level of harmonics,
Grid cover longer distances ++, efficiency
G G Contra: mechanical current interruption, neutral currents
Challenges: more complex voltage control/protection
15 kV
Asymmetric voltage levels
AC AC
DC DC
DC DC
DC DC
AC DC
DC DC
+1000V
AC DC
-380V
DC DC
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Low-voltage DC test facility
A ±500V bipolar DC test grid developed in the SolSThore project
• Reconfigurable lab infrastructure
• 100 kW up to ±500V DC test grid
• Unipolar and bipolar configuration
• TN-S grounding or IT grounding
• Power flow monitoring
• Voltage measurements
• Power electronic converter testing
• Communication interfaces
• Connected to other labs
• Rooftop PV test site
• Battery laboratory
• EV Parking
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