1

Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

DC-Microgrids Worldwide

Fraunhofer IISB InstallationJulian Kaiser julian.kaiser@iisb.fraunhofer.de

Group DC Grids

www.iisb.fraunhofer.de/dc-grids

2

Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

SAP

380 VDC

INTEL

380 VDC

Fraunhofer IISB

380 VDC

Univ. CA

380 VDC

380 VDC

380 VDC

ETSI

260/380/400VDC

China Mobile

380 VDC

NTT Group

380 VDC

North American

Telecom; 380 VDC

Green (CH)

380 VDC

Netpower

350/380 VDC

NEXTEK

NextEnergy

NextHome

380 VDC

Bachmann

380 VDC

China Telecom

240/380 VDC

ARDA Power

380 VDC

Data Centers

Telecom

Demo Infrastructure

Industry and R&D Consortia, Standardization

IEC SEG4

Worldwide Activities

DC-Installations Worldwide

3

Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

„DC components and grid“

European project

(2012 – 2015)

Reduce device size and cost

Increase efficiency and solar

power usage

Less conduction losses

Origin: DCC+G

4

Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

First test installation for

demonstration purposes

at Fraunhofer IISB in

Erlangen

Various renewable energy

sources like photovoltaic

and µCHP

Typical loads for office

buildings

Power ~20 kW

Still in use today with

some modifications –

integration into building-

wide DC microgrid

Origin: DCC+G

5

Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

Application Platform for Decentralized Energy Systems

DC-Microgrid

Today: SEEDs

=> The DC-Microgrid as Interface for Various Energy Systems

6

Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

PV200 kW

24/48 V

+/- 380 VDC LVDC Grid

400 VAC AC Grid (3φ)

Photovoltaic Li-Ion Batteries

(3x 20 kWh, 3x 100 kWp)

DC Charging AC GridChemical Storage

(elektrolyzer

LOHC fuel cell)

Office Building

The High-Power DC Grid at Fraunhofer IISBin field operation for peak load shaping

Lig

hti

ng

Wo

rk P

lac

es

25

0 A

25

0 A

25

0 A

25

0 A

25

0 A 25

0 A

(1.600 A backbone)

Grid Structure

7

Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

Building A Building B

Outdoor Installations

Grid Structure

8

Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

Bidirectional

100 kW AC/DC11x channels

80 – 250 A, main busbars up to 1600 AControl

Power supply

Main distribution cabinet

High-power DC switches

for bipolar operation

Pre- and discharge

resistors where needed

Voltage and current

measurement for every

channel

Data logging to

database via Modbus

Online monitoring

Overcurrent protection

Insulation monitoring

Power Distribution

9

Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

Input/Output Connectors

(Current Sensor −380 VDC)

Current Sensor +380 VDC

Precharge Contactor

Discharge Contactor

PLC

Main Contactor / Circuit Breaker

ABB Tmax T4 for +380 VDC

(Main Contactor / Circuit Breaker)

(ABB Tmax T4 for -380 VDC)

DC-Backbone

1600 A, 1000 V

Resistors for Pre- and Discharge

A

+380 VDC

−380 VDC

0 VDC

V

Power Distribution

Main distribution cabinet

High-power DC switches

for bipolar operation

Pre- and discharge

resistors where needed

Voltage and current

measurement for every

channel

Data logging to

database via Modbus

Online monitoring

Overcurrent protection

Insulation monitoring

10

Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

High-power DC

switches ABB Tmax

Remote actuation

Overcurrent protection

Connection of large

sources and loads

MCCB style (four pole)

Remote actuation

Overcurrent protection

Connection of branch

circuits and smaller

devices

Insulation monitoring

for IT-system

Several distributed

and coordinated

devices

DC cabling

Color coding

according to latest

version of IEC 60445

Power Distribution

11

Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

Features

Battery storage with up to 14 modules

Energy per rack: 20 kWh

Nominal power per rack: 100 kW

Voltage range: 315 V – 567 V

Lifetime 15.000 (full cycles)

Temperature range: -30°C…+55°C

Energy Storage Systems

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Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

AC

DC

Resonant Converter

PFC

Unit

DC-Link

Capacitor

NO

PFC

EMC

Filter

NO

FilterSmaller

DC Lighting

Conversion of electronic AC lamp

ballast for fluorescent lighting

Connection to the DC-link

Operation with 380 V is possible

Control and switching either with

bus system (EIB/KNX) or with

semiconductor switch

380 V DC LED lighting (from DCC+G)

48 V DC LED lighting for offices and laboratories

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Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

Bidirectional isolated

48 V supply for every

office

Compact low-cost non-

isolated converters for

office appliances

(laptop, monitor)

Safety for users

High efficiency

Optional energy

storage for distributed

USV functionality

Office DC Power Supply

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Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

Power

Electronics

EMC-Filter

Contactors

Cable

Cooling

EMC-

Filter

Power

Electronics

Co

nta

cto

rs

Non-isolated electric

vehicle DC charging

Modular power

electronic converters

for easy scalability

Flexible power sharing

between vehicles

High efficiency and

compact volume

For future vehicle

requirements up to

1000 V and 150 kW

Bipolar load (760 V)

High Power DC Charging

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Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

440

410400

380

360

330

260

0

DC

gri

d v

olt

ag

e

in V

olt

Voltage Specification used in the Fraunhofer DC-Grid

Self-protection

Transient over-voltage

Stationary over-voltage

Nominal voltage range

Stationary under-voltage

Transient under-voltage

Special function range

Operation with specified functionality

Switch-off for self-protection allowed

Transient operation with limited functionality and power derating

To be used for various protection and safety functions

Emergency mode (e.g.): only dedicated loads, like emergency

lighting or IT-server, are allowed to stay operational

Operation with full functionality, power derating allowed

Operation with full functionality, power derating allowed

Transient operation with limited functionality and power derating

Behavior of devices and components

Grid Voltage Regulation

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Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

Droop control - a method to control a grid without a superordinate master

The grid voltage (Vgrid) serves as the

central control parameter

All feed-in converters behave like

voltage sources with internal resistance

Advantages

No superordinate grid controller

necessary

Maximum in reliability, availability and

flexibility

High level functions can be realized by

changing the droop characteristics

Challenges

Ensuring unconditional dynamic grid

stability

Grid Voltage Regulation

17

Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

Droop control - a method to control a grid without a superordinate master

The grid voltage (Vgrid) serves as the

central control parameter

All feed-in converters behave like

voltage sources with internal resistance

Advantages

No superordinate grid controller

necessary

Maximum in reliability, availability and

flexibility

High level functions can be realized by

changing the droop characteristics

Challenges

Ensuring unconditional dynamic grid

stability

0,950 0,975 1,000 1,025 1,050

-1,2

-1,0

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

AC/DC

PV

Battery

Infe

ed

Po

wer

[pu

]

Grid-Side Terminal Voltage [pu]

0,950 0,975 1,000 1,025 1,050

-1,2

-1,0

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1/RD,Bat

1/RD,PV

AC/DC

PV

Battery

Infe

ed

Curr

en

t [p

u]

1/RD,AC/DC

Grid Voltage Regulation

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Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

Rs

vTest

iRight

ZLeft ZRightIBias

iLeft

TPRBS

Functional principle:

10 100 1000 10000 100000

-180

-90

0

90

180

Phas

e [°

]

Frequenz [Hz]

-40

-30

-20

-10

0

10

20

Messung Zirp-Testsignal

Messung PRBS-Testsignal

Simulation Linearmodell

Bet

rag [

dB

]

Example (DC/DC Converter (Grid Manager)):

How to measure stability in a DC grid?

Grid Stability and Measurement

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Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

“Protection concept and devices for future direct current grids”

See presentation at ICDCM 2019 for current results

Funding volume ca. 1.700.00 Mio. €

Duration 12/2016 – 11/2019

DC-Schutzorgane (“DC safety elements”) ■ BMWi Research Project

Current DC Projects

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Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

Funding volume ca. 10.000.000 €

Duration: 07/16 – 06/19

Increasing industrial plant energy

efficiency by 10 %

Reducing cost for devices up to 20 %

DC-Industrie ■ BMWi Research Project

Current DC Projects

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Fraunhofer Institute of Integrated Systems and Device Technology

Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

Bernd Wunder

Schottkystrasse 10, 91058 Erlangen

Tel.: 09131/761-597

bernd.wunder@iisb.fraunhofer.de

www.iisb.fraunhofer.de

Your Partner for

leading-edge

Power Electronics

22

Julian Kaiser

Intelligent Energy Systems / DC Grids

© Fraunhofer IISB

PublicationsY. Han, J. Kaiser, L. Ott, M. Schulz, F. Fersterra, B. Wunder, M. März: Non-isolated three-port DC/DC converter for ±380 VDC

microgrids. PCIM, Nuremberg 2016

L. Ott, J. Kaiser, K. Gosses, Y. Han, B. Wunder, M. März: Model-Based Fault Current Estimation for Low Fault-Energy in

380 VDC Distribution Systems. INTELEC 2016, Austin, TX, 2016

Wunder, B., Ott, L., Han, Y., Kaiser, J., März, M.: Voltage Control and Stabilization of Distributed and Centralized DC Micro

Grids. PCIM, Nuremberg 2015

Wunder, B., Ott, L., Kaiser, J., Han, Y., Fersterra, F., März, M.: Overview of Different Topologies and Control Strategies for

DC Micro Grids. IEEE ICDCM, Atlanta, 2015

Wunder, B., Kaiser, J., Fersterra, F., Ott, L., Han, März, M.: Energy Distribution with DC Microgrids in Commercial Buildings

with Power Electronics. EDST, Vienna, 2015

Ott, L., Han, Y., Stephani, O., Kaiser, J., Wunder, B., Maerz, M.: Modelling and Measuring Complex Impedances of Power

Electronic Converters for Stability Assessment of Low-Voltage DC-Grids, ICDCM, Atlanta, 2015

Ott, L., Han, Y., Wunder, B., Kaiser, J., Fersterra, F., Schulz, M., Maerz, M.: An Advanced Voltage Droop Control Concept for

Grid-Tied and Autonomous DC Microgrids. INTELEC, Osaka, 2015

Weiss, R., Ott, L., Boeke, U.: Energy Efficient Low-Voltage DC-Grids for Commercial Buildings. ICDCM, Atlanta, 2015

Rykov, K.; Duarte, J. L.; Szpek, M; Olsson, J.; Zeltner, S.; Ott, L.: Converter Impedance Characterization for Stability Analysis of

Low-Voltage DC-Grids. ISGT 2014, Washington D. C., 2014

K. Rykov, L. Ott, J. L. Duarte, E. Lomonova: Modelling of Aggregated Operation of Power Modules in Low-Voltage DC Grids.

EPE, Laapeeranta, 2014

Rykov, K.; Duarte, J. L.; Szpek, M; Olsson, J.; Zeltner, S.; Ott, L.: Converter Impedance Characterization for Stability Analysis of

Low-Voltage DC-Grids. ISGT 2014, Washington D.C., 2014