Page 1 Dr.-Ing. Stefan Zeltner, 17th October, 2014, Erlangen © Fraunhofer IISB
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IISB JAHRESTAGUNG & CLUSTER-SEMINAR
NIEDERSPANNUNGS-GLEICHSTROMNETZE
Bidirektionaler AC/DC-Netzkoppler Bidirectional isolating AC/DC converter for coupling DC grids with the AC mains
based on a modular approach
Stefan Zeltner,
Stefan Endres, Jens Schmenger
Fraunhofer Institute for Integrated Systems and Device Technology IISB
Schottkystrasse 10 ● 91058 Erlangen ● Germany ● Tel. +49.9131.761.140, Fax -312
www.iisb.fraunhofer.de
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Bidirectional isolating AC/DC based on a modular approach
Content
• Introduction
• Future high voltage DC grid within buildings
• AC/DC in future DC micro grids
• Control of complex power electronic systems
• High power density systems
• State of art central control approach
• Proposed solution
• Decentralized control approach
• Using intelligent power units
• Advantages of proposed solution
• 3.7 kW bidirectional isolating AC/DC realized with IPUs
• Application
• DC Micro Grid Control System for optimized usage of
renewable energy in buildings
• Summary
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Bidirectional isolating AC/DC based on a modular approach
• Introduction – Future high voltage DC grid within
buildings
Bidirectional isolating
AC/DC converters are
used in smart micro or
nano grids for a safe
coupling of the DC grid
with the AC mains.
Page 4 Dr.-Ing. Stefan Zeltner, 17th October, 2014, Erlangen © Fraunhofer IISB
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Bidirectional isolating AC/DC based on a modular approach
• Introduction – AC/DC in future DC micro grids
Bidirectional isolating AC/DC converter is a complex power electronic system.
totem pole bridgeless PFC
with smoothing transformer
bidirectional isolating
resonant converter
Topology example:
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Gate Drive
Circuit
Bidirectional isolating AC/DC based on a modular approach
• Introduction – Control of complex power electronic
systems
ON: +15 V
OFF: -5 V
? Isolation barrier
12x !
Transfer of energy for gate drive
and data transfer necessary!
Microcontroller
(FPGA, DSP…)
G D
S
0 V
400 V
e.g.
10 … 50 kV/us
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passive
components
Power switches
PCB for control logic
PC
B fo
r po
we
r sw
itch
es
PC
B fo
r pa
ssiv
e
co
mp
on
en
ts
PCB for gate-driver
Bidirectional isolating AC/DC based on a modular approach
• Introduction – High power density systems
• Different devices need different
joining technologies.
• Goal for high power density
systems: “no air between devices”
• Examples for state of art high
power density systems.
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Bidirectional isolating AC/DC based on a modular approach
• Introduction – State of art central control approach
Page 8 Dr.-Ing. Stefan Zeltner, 17th October, 2014, Erlangen © Fraunhofer IISB
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Bidirectional isolating AC/DC based on a modular approach
• Proposed solution – Decentralized control approach
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• Integration of power module and passive devices
Intelligent power unit (IPU)
Bidirectional isolating AC/DC based on a modular approach
• Proposed solution – Using intelligent power units
• Change position of safe isolation barrier
• Introducing 2-wire connection
Plug&Play IPU for modular system designs
• Gate drive unit with uC
Intelligent gate drive unit
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Bidirectional isolating AC/DC based on a modular approach
• Advantages of proposed solution
Only 2-wires to control and supply
complete IPU (e.g. with 4/6/8 power
switches)
Precise timing of different IPUs possible
by synchronized 2-wire interfaces
Safe galvanic isolation by single
magnetic core
Insulation voltage only defined by
design of a single transformer
Reduced requirements to drive high
side switches (only functional safety
requirements)
Lowest possible coupling capacity (very
high common-mode transient immunity
– proofed by tests)
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Bidirectional isolating AC/DC based on a modular approach
• 3.7 kW bidirectional isolating AC/DC
realized with IPUs
The isolating AC/DC
is realized with 3
nearly identical IPUs.
IPUs
Battery
Rack
… and with 3 more plug&play
IPUs 3 additional DC/DC
converters integrated.
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Bidirectional isolating AC/DC based on a modular approach
• 3.7 kW bidirectional isolating AC/DC
realized with IPUs – Efficiency
Measurements
etasum ≈ 93% (with low cost Si IGBT solution)
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Bidirectional isolating AC/DC based on a modular approach
• 3.7 kW bidirectional isolating AC/DC
realized with IPUs – EMI Filter optimization
with smoothing transformer
without smoothing transformer
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Bidirectional isolating AC/DC based on a modular approach
• Application – DC Micro Grid Control System for
optimized usage of renewable energy in buildings
Page 15 Dr.-Ing. Stefan Zeltner, 17th October, 2014, Erlangen © Fraunhofer IISB
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Bidirectional isolating AC/DC based on a modular approach
• Summary
Problem to control complex power electronic systems, i.e. with a lot a active
switches (e.g. bidirectional, isolating AC/DC converter) was shown.
Problem can be solved by using a decentralized control approach based on novel
intelligent power units (IPUs) with a 2-wire interface for integrated power and
signal transfer.
Proof of concept: shown on the example of a 3.7 kW bidirectional isolating AC/DC
converter realized with three IPUs. AC/DC integrated in all-in-one DC micro grid
control system.
Page 16 Dr.-Ing. Stefan Zeltner, 17th October, 2014, Erlangen © Fraunhofer IISB
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Fraunhofer IISB – Your Partner
in Power Electronics
Thank you for your attention
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