Simulation of IGBT converter

E. Rudnyi

CADFEM GmbH

erudnyi@cadfem.de

Outline

The work has been done for the ECPE workshop Thermal

Engineering of Power Electronics Systems, 2009

Overview

Thermal Simulation in Icepak

Compact Thermal Model through Model Order Reduction

1

European Center for Power Electronics

2

IGBT Converter

Insulated Gate Bipolar Transistor:

Very efficient – thermal losses about just 5%

However 20 kW converter produces 1 kW power dissipation.

Electrothermal simulation is required:

Electrical properties of IGBT depends on temperature;

Too high temperatures reduces reliability and durability.

3

Tc

Tj

4

The Model of the Converter

Original Model Model in Icepro

Model in Icepak

Simplifying the Heat sink In Icepro

5

Power dissipation, materials, boundary conditions

6

Mesh

7

Solution - convergence

8

Typical Simulation Results

9

Comparison with Experimental Measurements

10

0

10

20

30

40

50

60

70

80

trial1 trial2 trial3 trial4

T1ex

T1sim

T2ex

T2sim

Tref_ex

Tref_sim

Transient Simulation in Icepak

Flow is developed: We need to

solve only energy equation.

11

From Finite Elements to System Simulation

12

Physics &

Geometry

System of

n ODEs

Reduced

System of

r << n ODEs

FEM MOR

Electrothermal Simulation with IGBTs:

From ANSYS Workbench to System Level

13

Model Order Reduction

Relatively new technology

Solid mathematical background:

Approximation of large scale

dynamic systems

Dynamic simulation:

Harmonic or transient simulation

Industry application level:

Linear dynamic systems

14

Model Reduction as Projection

Projection onto low-

dimensional subspace

How to find subspace?

Mode superposition is not the best way to do it.

zx V

x V

z

=

uxx BKE

uzz BVKVVEVV TTT

E

Er

Transferring Model from Icepak to Workbench

15

)( bulkTThAQ

MOR for ANSYS: http://ModelReduction.com

16

FULL files

Linear Dynamic

System, ODEsCxy

BuKxxExM

MOR Algorithm

Small dimensional

matrices

Current version 2.5

Workbench

ANSYS Model

Simulink,

Simplorer, VerilogA,

…

Model Reduction: Inputs and Outputs

12 inputs and outputs have been defined

17

Model reduction

Dimension of the model in ANSYS is about 900 K DoFs.

Dimension of the reduced model is 15 DoFs per input = 15*12 = 180.

The reduced model covers all heat sources and thermal cross talk at

once.

Transient simulation when 1 W has been applied only on device.

Step response.

On the next slides there is comparison between the simulation of the

full model in ANSYS and the reduced model for T_A1. This curve

corresponds to thermal impedance.

18

Comparison

Red line – ANSYS, green line – reduced model. Difference is close to

the line thickness. For such accuracy, one needs 15 DoFs per input.

19

Comparison

Relative error between results in ANSYS and reduced model.

20

Comparison with Measurements

Cooling curves from the stationary state with:

75 W on IGBTs

0 W on diodes

T ambient = 28.5

Using point T2 (P2) and the average on the upper face of IGBT T_B2

for comparison with the measurements

21

Temperatures on IGBTs

22

Temperatures under IGBTs

23

Simulation in Simplorer

24

Thermal Domain

Electrical Domain

0

R1 R2 R3

MASS_ROT1

A

A

A

IN_A

IN_B

IN_C

OUT_A

OUT_B

OUT_C

U2Simplorer4

A

B

C

N

ROT1

ROT2

Induction_Motor_20kW

Q

Ambient

P1

P2

P3

P4

P5

P6

P7

P8

P9

P1

0

P1

1

P1

2

P_

RE

F

z_um z_vm z_wm

z_wpz_vpz_up

+

V

VM311 R6 R5 R4

E1

MechanicalDomain

Conclusion

Icepak to quickly simulation IGBT converter

Compact dynamic thermal model are necessary

Transfer to ANSYS Workbench with convection boundary conditions

Compact thermal model are obtained through model reduction

25