ansoft application notes

© 2008 Ansoft, LLC All rights reserved. Ansoft, LLC Proprietary

Simulating EMC/EMI Effects for High Power Inverter Systems

Emmanuel Batista Alstom

PearlVincent Delafosse, Ryan Magargle Ansoft [email protected]@[email protected]


Acknowledgments

This work has been based on the work of Emmanuel Batista, J.M. Dienot, M. Mermet-Guyennet

Special Thanks: –

P. Solomalala (Pearl/Alstom)

–

O.Roll, X. Legoar, D. Prestaux, –

X. Wu, M. Rosu, S. Kher (Ansoft)


Pearl: Power Electronics Associated Research Laboratory

Models-Simulation-FabricationEMCSolve multi-domain/temps/structure

Passive ComponentsActive Components

Packaging

Research

and Validation of technologies Development

and validation of prototypes

Viability

and maintenance

Design of methods

for conception


Motivation

•

High power IGBT based inverter systems have specific EMC/EMI requirements

•

The prediction of EMC/EMI fields is very difficult . Physical prototyping can result in long design cycles

•

Simulation tools can help with the use of several techniques

•

The physical quantities in the inverter that need accurate simulation are:–

Quantity of current going through the conductors–

Frequency dependent parasitics (RLC) between conductors –

IGBT characterization curves–

Power dissipation–

Emitted fields


Overview

•

Introduction to the power study•

Static electromagnetic field study

•

Parasitics extraction•

IGBT characterization

•

System simulation•

Emitted fields


AM3~

Traction SupplyPantograph Traction Motor

Introduction

Inverter Inverter LegIGBT Module Top Row

•

These

power converters

are used

in high

speed trains (TGV)


Introduction

6.5kV IGBT Module Characteristics

Baseplate

CollectorEmitter

IGBT Chips

Diode Chip

6.5kV6.5kV--600A 600A Module Module

24 IGBT and24 IGBT and

12 Diode Chips12 Diode Chips

Dielectric Gel

Packaging

Ceramic

Substrate


Introduction

6.5kV IGBT Module Analysis

•

Include package in IGBT performance

•

Find DC current distribution

•

Find switching currents for power dissipation

•

Use power dissipation to determine environmental electromagnetic fields


Model design developed

at

Alstom/Pearl

IGBT Module Pack 3D accurate model

Parameters Extraction

Electromagnetic (EM) study

Design and Couplings Model

IGBT Model

•

Tridimensional IGBT pack model and EM study

• Parasitic model extraction

• IGBT circuit model

Far Field Study

• Far Field Study for Electric Field EM

Introduction


Different

Modeling

techniques will

be

seen

•

Tridimensional IGBT pack model and EM study

• Parasitic model extraction

• IGBT circuit model

• Far Field Study for Electric Field EM

Finite Element MethodFinite Element Method

Boundary Element Method

Boundary Element Method

Finite Element

Method

Finite Element

MethodSystem SimulationSystem Simulation

Introduction


Overview

•


Static electromagnetic field study

•



•


Emitted fields


ElectroMagnetic Study

•

Module layout

verification

•

The module contains

8 IGBTs

in parallel: does

each

IGBT receive

the same

amount

of current?–

If the current

flows

un-evenly, this

will

cause mechanical

stress and reliability

issues.–

Electromagnetic

simulation is

required. We

use Maxwell3D.



•

The layout

in imported

from

the CAD tool•

The DC solver

is

used•

The input current

(600 A) is

defined•

The sink

(return current

path) is

defined

•

Outputs: conduction path

and current

distribution

600 A Sink



The structure is

meshed

using

automatic

and adaptive meshing

Current

DistributionIGBTs

on, Diodes off



•

The end IGBTs

see

less

current

than

the center ones.•

This can

cause reliability

issues as the center IGBTs

will

be

overloaded•

An optimization

of the copper

tracks

can

be

made in order

to equalize

the currents.

Igbt1a and Igbt4a have the highest

quantity

of current


Overview

•


Near field electromagnetic study

•



•


Emitted fields


Parasitics Extraction

•

Once the layout

is

optimized, the next

step

is

to extract

the resistance, inductance and capacitance (RLC) parameters

of the package.•

For this

we

use the boundary

element

method

in Q3D•

Example

for two

conductors



•

Frequency Dependent Effects•

Integrated power-electronic modules exhibit frequency-dependent behavior due to eddy current and skin effects.

•

In these cases, it may not be sufficient to rely on resistance and inductance extracted at a single operating frequency

•

For example, coax

conductors:

Low Frequency High Frequency

Samegeometry

Different frequency

=

Different Parasitics


•

Extracting parameters is straightforward as the nets are automatically assigned.


Gate

net

Emitter

net

Collector

net


•

How do we set up the frequency sweep?–

Through Nyquist

sampling, we know that to capture a time step of Ts, we need to obtain frequency domain information up to:

–

For a time domain waveform with a risetime

of 80 ns, in order to capture the ringing in the time domain, we would want to capture at least 4 samples during this risetime. This implies a sampling time of 20 ns

•

We

need

to solve

up to 50 MHz (= 1/20ns)

stF

×=

21

max




•

The simulation outputs consist of the RLC matrices for different

frequencies



•

How do we

use the parasitics in the circuit simulator?•

Basic methodology:•

Compute N-port S parameters (frequency sweep)•

Convert this into information that circuit simulator understands•

Circuit simulator performs inverse FFT to find impulse response

•

Convolution is used to produce time-domain results

∫ ∞−−=⊗=→=

tdxtstxtstyjXjSjY τττωωω )()()()()()()()(

)())(()()1(

tkxtknstnyn

Nnk

ΔΔ−≅Δ ∑−−=

Vol

tage

876.5m

1.1

900.0m

950.0m

1.0

1.1

1.1

17.55u 20.00u18.00u 18.50u 19.00u 19.50uTime (Seconds)

Voltage versus Time Using Different 2D Extractor Mode

VM11.V [V] VM_Linear_1Hz_Model.V [V] VM_Linear_1MHz_Model.V [V] VM_Frequency_Model.V [V]

Damping

Phase

Copper shield

Silicon

Polyethylene

Silicon

Copper

Copper shield

Silicon

Polyethylene

Silicon

Copper


Overview

•


Near field electromagnetic study

•



•


Emitted fields


SIMPLORER 8

•

Simplorer 8 is

a circuit simulation tool

for solving

multi-domain

lumped

circuit problems.

•

Link projects

together

to achieve

dynamic

linking

of multiple simulations on a single sheet.


SIMPLORER 8

•

Modeling

•

New Parametrization

tool for IGBT

•

Enhanced SMPS Library -

Over 450 New VHDL-AMS DC/DC Converter Models in SMPS

Digital Co-simulation

•

Spice – Pspice integration

•

Enhancements

to individual

models

…


System Integration

•

How do we

import the results

from

Q3D?: Q3D dynamic link

•

2 Types of links: Single Frequency

or Frequency

dependent•

No need

to manually

import output file•

Simplorer incorporates

directly

the Q3D project

•

If some

results

are not available, Simplorer dynamically

launches

Q3D•

Parameters

and variables can

be

passed

between

S8 and Q3D


System Simulation

IGBT

Wattmeter

VcVg

Power Module from

Q3Dfor board

parasitics


IGBT Characterization

•

Accurate

models

of the semiconductors

are needed

to achieve

a good circuit simulation

•

Simplorer 8 offers

a parameterization

tool

for IGBTs•

The user needs

to import the data from

the datasheet

2 types of models

are available

in Simplorer 8: Basic Dynamic

and Average

Dynamic



Objective Average Basic Dynamic

Advanced Dynamic

DC characteristics

-

Transfer characteristic

Ic(Vge) accurate-

Output characteristic

Ic(Vce) accurate in the regions of voltage and current saturation-

Intrinsic temperature dependencyElectrical Dynamics

- Considered

Thermal Dynamics

Partial Fractional orContinued Fractional

Capacitance Models

- Default C(V)

Full access to the C(V) characteristics



Sub circuit of the basic dynamic IGBT model


SheetScan



•

Once all the curves

and data are entered, start

extraction•

The tool

fits

the data to the internal

Simplorer model using

Genetic

Algorithm


Characterization toolComponent dialog



Test Circuit

499.90 499.95 500.00 500.05 500.10 500.15 500.20 500.25 500.30Time [us]

0.00

500.00

1000.00

1500.00

2000.00

2500.00

3000.00

U1.

VC

E

-15.00

-10.00

-5.00

0.00

5.00

10.00

15.00

VM

2.V

[V]

-10.00

0.00

10.00

20.00

30.00

40.00

50.00

R2.

I [A

]

Ansoft Corporation Simplorer1switch_on

Curve InfoU1.VCE

TRVM2.V

TRR2.I

TR

999.00 999.50 1000.00 1000.50 1001.00 1001.50 1002.00 1002.50 1003.00Time [us]

0.00

500.00

1000.00

1500.00

2000.00

2500.00

U1.

VC

E

-15.00

-10.00

-5.00

0.00

5.00

10.00

15.00

VM

2.V

[V]

-10.00

0.00

10.00

20.00

30.00

40.00

50.00

R2.

I [A

]

Ansoft Corporation Simplorer1switch_offCurve Info

U1.VCETR

VM2.VTR

R2.ITR

Switch on

Switch off

Vce

Vce

Ic

Ic

rise time= 40 μsfall

time = 50

μs


System Simulation

2500 Voltage Source

Line Resistance and Line Inductance

Vg: Gate

Voltage (+/-15V)


System Simulation

•

Issue: •

Accurate

simulation of the switching

of the IGBTS requires

very

small

time steps

(hmin

= 10ps)•

System simulation requires

long time step

(t = 5ms)•

Simplorer allows

the user to dynamically

change hmin

and hmax

using

State Graphs. •

When

the switching

has occured, the time step

can

be

increased.

Switching Steady state Switching


System Simulation

Vce, Vge, Ic

over time (Igbt3b)

Reduce Time Step HMin

IcVce

-Vge

VgeVce

Ic

Ic

VgeVce

Ic

VgeVce

Vge

Vce

Icg

c

e


Vce

Vg

Vge

Ic

Power

The power pulse duration is much smaller than the rise/fall time

of Ic

and Vce

System Simulation


System Simulation

Instantaneous power level through Igbt3a


System Simulation

Power levels of the full set of IGBT’s

on switch on


System Simulation

•

Igbt1a and Igbt4a receive the highest power levels.

•

This is consistent with the DC Conduction Maxwell3D solution

Igbt1a

Igbt4a


System Simulation

The fundamental frequencies of the power range between 16 and 54 MHz

t @ Pmax(μs)

t @ P <300W

(μs)

Freq(MHz)

Igbt1a 500.2262 500.2867 16.5Igbt1b 500.2193 500.2429 23.8Igbt2a 500.2241 500.2743 49.5Igbt2b 500.2182 500.2369 53.5Igbt3a 500.2294 500.2675 21Igbt3b 500.2178 500.2363 54Igbt4a 500.2256 500.2869 16.5Igbt4b 500.2191 500.2402 47.5


System Simulation

FTT of the power through Igbt1a

Most of the power level is below 110 MHz


Emitted Fields

•

There is

very

high

power going

through

the IGBTs

(almost

60 000 W in this

study) during

a very

short period

of time (60 ns). This switching

can

cause EMI issues in the inverter, but also

in the surrounding

equipment

•

To be

answered

using

the finite

element

method

in HFSS:

•

Will the module radiate? •

Are the field

levels

surrounding

the module within

mandated

levels?


Emitted Fields

•

The power pulse in the IGBTs

have most

of the energy

in the 16-

110 MHz range.•

The largest

metallic

piece

is

150 mm in the module•

There is

a chance of having

radiation if λ

< 4 * L = 600 mm. This is

for a frequency

of 500 MHz.

•

By itself, the module will

not radiate.

•

However, the power module in the train is

surrounded

by other

metallic

objects

than

can

be

fairly

large. These

objects

can

cause the radiation of electric

fields

during

switching.

Maxwell’s Equations

div D = ρ

curl E = -∂B/∂t

div B = 0

curl H = J + ∂D/∂t


Emitted Fields

•

Regulators

impose maximum levels

of electric

fields

close to electric

equipment.•

In the 10-110 MHz range:

Emax=61V/m

Exposure

limits

defined

by European

Community


Emitted Fields

•

Each

IGBT pad is

excited

using

lumped

ports•

The port lies between

the collector

and emitter

pads


Emitted Fields

•

The structure is

discretized

with

adaptive meshing. The meshing

frequency

is

100 MHz•

The frequency

sweep

ranges from

15MHz to 120 MHz


Emitted Fields

For each

frequency, the power amplitude is

entered

Spectrum (MHz)

Power (W)

E field at 1m for 1000w (V/m)

E field at 1m (V/m)

16.52892562 21439.97604 2.6312 56.4128649733.05785124 8635.09049 2.7994 24.1730723249.58677686 5579.619715 2.8731 16.030805466.11570248 4131.16773 3.063 12.65376676

82.6446281 3276.823585 3.4045 11.1559458999.17355372 2712.888158 3.8924 10.55964586115.7024793 2308.359536 4.4861 10.35553171

132.231405 2022.75744 4.905 9.921625241

Spectrum from

Simplorer

Outputs from

SimplorerInputs for HFSS

Outputs From

HFSS(normalized

results)Fields Levels


Emitted Fields

•

The E field

is

very

localized

close to the module even

at

100 MHz•

However, the very

high

power can

lead

to large values of E field

even

far from

the module•

This design is

fine at

110MHz.

mag

E @ 100 MHz, Power = 10 000W

Spectrum (MHz)Power

(W)Spectrum (MHz)Power

(W)E field at 1m

(V/ m)E field at 1m

(V/ m)115.7024793 2308.359536115.7024793 2308.359536 10.3555317110.35553171


Conclusion

•

We have seen that the combination of several simulation techniques can give a good approach to EMC/EMI issues, both in conduction and emission modes

•

Accurate prediction requires the use of Finite Element Methods, Boundary Element Methods, System Simulation along with Accurate Component

Characteristics

•

Package traces need optimization to balance current distribution

•

The simulated module does not radiate for the given harmonics, and is within regulated near field field limits.

ansoft application notes

Documents