1. COMPERE Project Meeting Dr Dawei Xiang 03/11/2008

2. Contents IGBT terminal characteristics simulation
VSI characteristic harmonics simulation
Problems
IV. Further work plan
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3. IGBT terminal characteristics simulation
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4. Aims of study
To build a detailed simulation model for understanding the fundamentals of device operation and analysis of device Failure Modes and Mechanisms and their effects (FMMEA).
To form a basis for power converter terminal characteristics study and CM method research.
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5. IGBT degradation and its effects
Devices are subjected to interrelated thermal, electrical and mechanical stresses.
Failure locations
Failure causes
Failure mechanisms
Failure effects
Die-attach solder
temperature swings
Different CTEs
Thermal gradients
Active area (A),
Thermal resistance (Rjc)
Temperature (T)
Gate oxide
High temperature
High electric field
Over voltage
High current density
Time dependant dielectric breakdown
Hot electrons
Mosfet channel threshold voltage (Vt)
Mosfet channel transconductance (Kp)
FMMEA analysis of IGBT
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6. Saber physic-based IGBT model
Hefner IGBT model
Advantages:
Detailed physic model
Electrothermal simulation available
Experimentally verified
Disadvantages:
Difficult to parameterize
Encryption of MAST template
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7. Case study
Considering a IGBT under the stresses caused by high temperature and high current, the effects of die-attach solder fatigue and/or gate oxide degradation are simulated by artificially changing the corresponding parameters in the Saber physics-based IGBT model.
Case 1
Case 2
Case 3
Case 4
Case 5
degraded parameters
T↑:
27°=>50°
A↓33%
Vt↑10%
Kp↓10%
A↓, Vt↑, Kp↓, T↑
Combinations of IGBT parameters to simulate
the solder fatigue and/or gate oxide degradation
IGBTs: hgtg27n120bn (1200V/27A)
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8. Simulated circuits DC characteristics analysis circuit
dynamic characteristics analysis circuit
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9. Simulation results (case 1: T↑)
a) Ic-Vge
Vge(th): no effect
gfs: 130 S=>143 S (↑10%)
b) Ic-Vce
For Vge=11V
Vce0:1.25V=>0.9V (↓28%)
Ron: 0.05Ω=>0.015Ω (↓70%)
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10. Simulation results (case 1: T↑)
c) Turn on
td(on): no effect
tr: no effect
d) Turn off
td(off): 300ns=>200ns (↓33%)
trv: 150ns=>500ns (↑233%)
tf1: no effect
Itail0: 2A=>12A (↑500%)
tf2: 0.8us=>5us (↑525%)
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11. Simulation results (case 5)
a) Ic-Vge
Vge(th): 8 V=>8.6 V (↑7.5%)
gfs: 130 S=>106 S (↓18.4%)
b) Ic-Vce
For Vge=11V
Vce0: 1.25V=>0.9V (↓28%)
Ron: 0.05Ω=>0.027Ω (↓46%)
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12. Simulation results (case 5)
c) Turn on
td(on): 97 ns=>113ns (↑6%)
tr: no effect
d) Turn off
td(off): 300ns=>200ns (↓33%)
trv: 150ns=>400ns (↑166%)
tf1: no effect
Itail0: 2A=>8A (↑300%)
tf2: 0.8us=>1.8us (↑125%)
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13. Simulation results (case 2: A↓)
Fault detection based on
gate voltage Monitoring [1]
Simulated turn on transient
[1] M. Rodriguez, A. Claudio, D. Theilliol et al., “A new fault detection technique for IGBT based on gate voltage monitoring,” in IEEE Power Electronics Specialists Conference, June 2007, pp
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14. Results and discussions
IGBT terminal characteristics affected by aging (NE: No Effect)
Characteristics
Aging parameters
VGE(th)
gfs
VCE0
Ron
td(on) tr
td(off)
trv tf
Case 1: T↑ NE ↑ ↓
Case 2: A ↓
Case 3: Vt↑
Case 4: Kp↓
Case 5: A↓, Vt↑, Kp↓, T↑
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15. Results and discussions
Temperature influences the carrier mobility, high-level lifetime, which leads to the changes of device DC and dynamic characteristics.
Reduced die-attach area increases the base resistance so as to the total on-state resistance, while the turn-on transient is affected by the Agd so as to the Cgdj.
The tapped electrons in gate oxide reduces the Vt, which influences the DC characteristics and the dynamic delay times: td(on) and td(off).
The gate oxide degradation influences the transconductance which can mainly be reflected on the device DC characteristics.
Case 5 illustrates the combined aging effects caused by the solder fatigue and gate oxide degradation. Simulation results show there exists the change of device terminal characteristics due to aging, which can be used for CM.
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16. II. VSI characteristic harmonics simulation
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17. Aims of study
To investigate the effect of the devices aging on the power converter characteristic harmonics.
To form a basis for the study of harmonic resonance based power converter CM method.
To built a simulation model to investigate other power converter terminal characteristics affected by device aging, eg. EMI characteristics.
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18. Origin of characteristic harmonics
Origin of characteristics harmonics in one phase
PWM voltage waveforms for positive current
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19. Simulated 3-phase VSI in Saber
Case study
Simulated 3-phase VSI in Saber
DC link voltage: Vdc=600V Gate circuit parameters: Rg=12 Ω, lg=100nH
Switching frequency: fsw=10 kHz Dead time: td=2μs
Carrier frequency: fc=50 Hz Modulation ratio: M=0.8
IGBT: hgtg27n120bn (1200V/27A) Diode: hf50d120ace (1200V/50A)
Load inductance: Ll= mH Load resistance: Rl=10 Ω
The same 5 cases as previous were simulated where the IGBT parameters are changed to simulate the solder fatigue and/or gate oxide degradation
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20. Simulation results (case 1: T↑)
Spectrum of phase A current for 3-phase VSI before and after aging (T increasing)
ΔU5th= ΔI5th*Z5=( )* = V
ΔU7th= ΔI7th*Z7=( )* = V
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21. Results and discussions
Characteristics harmonics affected by aging
Harmonics
Aging parameters
ΔV5th (V)
ΔV7th (V)
Case 1: T↑
Case 2: A ↓
0.0158
0.0110
Case 3: Vt↑
0.0351
0.0288
Case 4: Kp↓
0.0024
0.0047
Case 5: A↓, Vt↑, Kp↓, T↑
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22. Results and discussions
The IGBT Vce0 and switching behavior determines the amplitude of characteristic harmonics through changing the V-A characteristics of output PWM voltage during aging.
Simulation results show that characteristics harmonics are more sensitive to the changes of temperature while the other factors may have slight effects on them.
Under the predefined simulation conditions, a deviation of about 0.3V can be reached for 5th harmonic. Such a variation falls in the range where our previous harmonic resonance method is capable of detecting.
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23. III. Problems
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24. Problems Power electronics modelling and simulation
As Saber model is difficult to be parameterized, which can be solved by using Angus’s devices model. And there comes the problems of obtaining the permission of this model for the research of the project.
Conflicting results of IGBT characteristics degradation
Our simulation results show that Ron decreases with the rise in temperature because of the negative temperature coefficient of resistance for p-n junction [2]. While some literatures reported an increase of Vce(sat) after aging which was explained by the consequence of increased channel resistance [3].
[2] Nishad Patil, Diganta Das, Kai Goebe and Michael Pecht, “Failure Precursors for Insulated Gate Bipolar Transistors (IGBTs),” 2008.
[3] Maiga, C.O. Tala-Ighil, B. Toutah, H. Boudart, B., “Behaviour of punch-through and non-punch-through insulated gate bipolar transistors under high temperature gate bias stress”, IEEE International Symposium on Industrial Electronics, 2004, pp
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25. IV. Further work plan
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26. Terminal characteristics simulation
More simulations will be carried out to further study the terminal characteristics of device and converter under different conditions, eg. working point, ambient temperature and unbalanced operation.
Electrothermal simulations will be carried out in order to take the device self-heating effect in to account.
Detailed analysis will be made systematically to correlate the characteristics changes to the device conditions.
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27. Accelerated aging test
Over loading the IGBT by DC power supply for 1 hour to simulate a long period conduction stress operation.[4]
Regulating the gate voltage to allow case temperature to be increased up to 155°C
[4] A. Maouad, A. Hoffmann, A. Khoury, J.-P. Charles, “Characterization of high-density current stressed IGBTs and simulation with an adapted SPICE sub-circuit,” Microelectronics Reliability, 40, 2000, pp
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28. Accelerated aging test
Accelerated power cycling test system [5]
It normally takes 2-3 months to complete an aging test of approx. 600,000 cycles
[5] Xiong Y., Cheng X., Shen Z.J., Mi C., Wu H., Garg V., “A Prognostic and Warning System for Power Electronic Modules in Electric, Hybrid, and Fuel Cell Vehicles”, IEEE Industry Applications Conference, Oct. 2006, pp.1578 – 1584.
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29. Experimental verification on drive system
Rating: 400V /10kW
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30. New CM studies On-state resistance identification based CM
DC offset identification based CM
EMI characteristics based CM
low frequency
characteristics
high frequency
characteristics
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31. Initial idea for Ron identification
Synchronous machine:
460V/ 60Hz/ 200HP
Rs=2.01 mΩ
Ψs_transient decays during Us sudden drop from 1pu to 0.95pu
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32. Thanks for you attention!