Flyer: Medium-Voltage Power Electronics

medium-voltage power electronics circuits can be much smaller, thereby reducing material, volume and costs for inductors and capacitors. Our engineers...

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F R A U N H O F E R I N S T I T U T e for so l ar ener g y s y ste m s ise



1 PV power plant. 2 Test bench for the characterization of medium-voltage power semiconductors.

MEDIUM-VOLTAGE POWER ELECTRONICS It is obvious that power electronics will

Special Lab Equipment

gain importance in future electrical power

„„40 kV / 64 kW DC source

grids. Indeed, the increasing share of

„„36 kV / 60 kW resistive load

renewables such as PV and wind requires

„„30 kVDC / 1 MHz high-precision voltage

Fraunhofer Institute for

a rising number of converters and power

Solar Energy Systems ISE

conditioners between generators and

Heidenhofstr. 2

consumers. Also, the demand for low-

79110 Freiburg, Germany

and medium-voltage power converters will increase both for grid feed-in and

Business Area

grid support.

Energy Efficient Power Electronics

dividers „„15 MHz high-bandwidth current transducers „„high-precision power analyzers up to 36 kVAC / 1 kA „„development environments for μC, DSP and FPGA

Power electronics for medium-voltage

„„numerous simulation software

Dr. Olivier Stalter

applications is one of the main research

„„precision RLC analyzers (up to

Phone +49 761 4588-5467

fields in the business area Energy Efficient

150 A bias / 3 MHz bandwidth)

Power Electronics at Fraunhofer ISE. We

„„semiconductor test bench up to 20 kV

Dirk Kranzer

investigate new concepts and develop

„„shielded test area for high voltages

Phone +49 761 4588-5546

innovative technical solutions for the next

„„400 V / 3 – 36 kV / 100 kVA adjustable

generation of medium-voltage power Jürgen Thoma

converters. In particular, the use of new

Phone +49 761 4588-5099

Silicon Carbide (SiC) semiconductors with high breakdown voltages opens up many

[email protected]

opportunities and allows new standards to be defined for efficiency, reliability and cost March 2014






High Voltage SiC Power Switches

Consequently, the passive components in

electronics in transformerless circuits. In

Power semiconductors are the key

medium-voltage power electronics circuits

railway technologies, 16.7 Hz transformers

components of any power electronics

can be much smaller, thereby reducing

could be replaced by medium-frequency

circuit. Because of their wide band-gap,

material, volume and costs for inductors

transformers with associated medium-

their high breakdown voltage and their

and capacitors.

voltage power electronics.

power semiconductors allowed building

Our engineers are also working on the new


highly efficient and compact DC / DC

challenges set to be met by the gate-supply

We provide our skills and expertise from

converters and inverters in the low-voltage

and control of HV SiC-transistors. In most

consulting to complete hardware and

range over the past few years.

applications, a galvanic isolation between

software developments for renewable,

driver circuit and driver supply has to be

railway and aviation power systems.

excellent thermal conductivity, SiC-based

Recently, SiC devices with breakdown

ensured. Also, the very high slew rates of

voltages of 10 kV and higher have been

voltage and current have to be controlled.

developed. This voltage rating noticeably

We develop highly sophisticated analog and digital control circuits for inverters

surpasses that of commercial Si devices,

Fields of Application

and converters with high switching

such as 6.5 kV IGBTs. The breakdown

Current PV power plants using central

frequencies. The programming of DSPs

voltage rating of this new device

inverters are usually restricted to DC

and FPGAs based on complex control

generation has not nearly reached its

voltages below 1,500 V and are coupled via

algorithms and simulations with tools like

limit. We continously receive a supply of

50 Hz transformers to the medium-voltage

MATLAB® / Simulink® and PLECS® is part

the latest SiC High Voltage (HV) power

grid. However, PV power plants already

of our daily work.

semiconductors – for example, MOSFETs,

exceed several 100 MVA. Therefore, higher

IGBTs, diodes and GTOs that provide

system voltages within the plant would

Our specific electrical and thermal

numerous innovative opportunities for

make both technical and economical sense.

simulations of power electronic circuits

medium-voltage applications.

Using HV SiC power devices makes it

serve as the basis of schematic designs,

possible to build highly efficient converters

PCB layouts and mechanical setups for the

Our advanced lab equipment allows us

connected directly to the medium-voltage

prototypes of inverters and converters at

to characterize the electrical properties

grid. A higher voltage level reduces current

low and medium-voltage levels.

of HV SiC devices. It has already been

and hence the cross sections. Finally, the

validated that their forward voltages

use of 50 Hz transformers can be avoided.

In addition to hardware design, we can support in the choice of semiconductors,

and switching energies are low even at very high temperatures. Such values

Another major application of HV

device ratings and the dimensioning of

cannot be reached with Si transistors.

SiC-based devices is in static reactive

custom power modules.

The low switching losses allow much

power compensators (STATCOMs). These

higher switching frequencies compared to

systems participate in the stabilization

state-of-the-art Si technologies. Indeed, the

of power grids and are usually based

switching frequency can be increased from

on low-voltage converters and 50 Hz

1 kHz for Si devices to 10 – 20 kHz for SiC

transformers. In the future, they could

1 10 kV SiC MOSFET with integrated SiC JBS

devices respectively.

also be replaced by medium-voltage


2 Medium-voltage DC / DC converter. 3 HV-IGBT with gate driver.