bidirektionaler ac/dc-netzkoppler - iisb.fraunhofer.de · bidirektionaler ac/dc-netzkoppler...

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

[email protected]

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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• 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.


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• 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


• 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


• 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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• Introduction – State of art central control approach


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• Proposed solution – Decentralized control approach


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• Integration of power module and passive devices

Intelligent power unit (IPU)


• 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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• 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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• 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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realized with IPUs – Efficiency

Measurements

etasum ≈ 93% (with low cost Si IGBT solution)


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realized with IPUs – EMI Filter optimization

with smoothing transformer

without smoothing transformer


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• Application – DC Micro Grid Control System for

optimized usage of renewable energy in buildings


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• 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.


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Fraunhofer IISB – Your Partner

in Power Electronics

Thank you for your attention

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