Reduced Order Modeling for Coolingregister.ansys.com.cn/ansyschina/minisite/201411_em... ·...

© 2011 ANSYS, Inc. September 25, 2014

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Reduced Order Modeling for Cooling -Battery/Electronics/Electric Machine Case Studies

Xiao Hu Scott Stanton ANSYS Inc.


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Motivation of using ROMs

Introduction of LTI ROM LTI stands for linear and time invariant Advanced version of Foster network approach

Introduction of SVD ROM SVD stands for singular value decomposition

Coupling of ROMs with electrical circuit models

Outline


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CFD as a general thermal analysis tool is accurate.

Can be computationally expensive for large models running transient CFD analysis

ROM can significantly reduce the model size and simulation time.

Motivation of Reduced Order Model (ROM)


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1. Create the CFD model 2. Generate step responses

4. Simulate inside Simplorer

3. Generate the LTI ROM Use Simplorer

LTI ROM for Cooling ICEPAK


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Example : An IGBT Model

The IGBT device consists of 4 IGBT’s and 4 diodes. The device is cooled by cold plate below


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The number of CFD runs is equal to the number of inputs (8 runs)

The runs were done automatically using Icepak

Create the Step Responses in Icepak


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Step responses due to DIODE are shown below.

Both small and large time scale exist.

Self-heating is much larger than cross-heat.

The DIODE has strong impact on IGBT_A , but not much on IGBT_A.3

Only one of the eight sets of impulse responses are shown.

There are 64 step responses in total.

IGBT Device Step Response


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In simplorer ROM model is created based on the step responses.

Create the LTI ROM in Simplorer

8 inputs (power dissipation) and 8 outputs (temperature)


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Sample heat profile

LTI ROM vs CFD Results

Similar profiles were givens as inputs to all IGBT’s and Diodes

To validate the LTI ROM results, same heat profiles are used in both LTI ROM and CFD and then results compared.


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LTI ROM runs in less than 2 seconds.

LTI ROM vs CFD Run-Time

CFD runs in 2 hours


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Example : A GM Battery Module

The module consists of 16 cells. Hybrid mesh with a mesh count

of 3 million.


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LTI ROM gives the same results as CFD. LTI ROM runs in less than 2 seconds while the CFD runs 2 hours on one single CPU.

X. Hu, S. Lin, S. Stanton, W. Lian, “A Foster Network Thermal Model for HEV/EV Battery Modeling,” IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 47, NO. 4, JULY/AUGUST 2011 X. Hu, S. Lin, S. Stanton, W. Lian, “A State Space Thermal Model for HEV/EV Battery Modeling", SAE 2011-01-1364

Heat Profile

LTI ROM for GM Battery Module


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Cold plate liquid cooling system : - Simplified cold plate without streams fluid design, - Glycol solution at 70°C, - Forced convection environment at 70°C.

Icepak Model of the Cooling System


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Import Icepak model into Simplorer

Computation and creation of the ROM from all the .out files generated by Icepak analysis

New wizard helping on the setup and configuration of the LTI ROM creation

Comparison of the transient response of the 3D model and the 1D LTI ROM

Icepak-Simplorer LTI ROM


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The LTI ROM can give temperature solution at user specified locations, but not temperature fields.

SVD ROM technology allows for quick temperature field calculation in addition to average temperature calculation.

Meet the SVD ROM

S. Asgari, X. Hu, M. Tsuk, S. Kaushik, “Application of POD plus LTI ROM to Battery Thermal Modeling: SISO Case,” SAE congress 2014. X. Hu, S. Asgari, I. Yavuz, S. Stanton, C-C Hsu, Z. Shi, B. Wang, H-K Chu, “A Transient Reduced Order Model for Battery Thermal Management Based on Singular Value Decomposition,“ ECCE 2014.

VS


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Animation is a Trajectory


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1. Create the CFD model 2. Generate step responses Cannot use Icepak Can only use FLUENT

4. Simulate inside Simplorer

3. Extract SVD ROM Use Simplorer

SVD ROM for Cooling

5. Post-process results in Fluent

ANSYS Fluent

ANSYS Fluent


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Convective cooling channels used.

Four IGBTs and four diodes generating heat. Icepak is used to create the mesh.

Fluent model is exported from Icepak. Mesh size : 900 K.

SVD ROM : An IGBT Model


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SVD ROM vs. Fluent CFD

Similar profiles were givens as inputs to all IGBT’s and Diodes

To validate the SVD ROM results, same heat profiles are used in both SVD ROM and CFD and then results compared.


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SVD ROM vs. Fluent CFD

CFD (15 sec)

SVD ROM (15 sec)

CFD (30 sec) CFD (45 sec) CFD (60 sec)

SVD ROM (30 sec)

SVD ROM (45 sec)

SVD ROM (60 sec)

While the two sets of results look very similar, the SVD ROM runs orders of magnitude faster!


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Animation from SVD ROM

Such an animation takes about 10 min to create!


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SVD ROM Validation: GM 16 Cell Test Case

CFD (200 sec)

SVD ROM (200 sec)


SVD ROM (400 sec)

SVD ROM (600 sec)

SVD ROM (800 sec)

X. Hu, S. Asgari, I. Yavuz, S. Stanton, C-C Hsu, Z. Shi, B. Wang, H-K Chu, “A Transient Reduced Order Model for Battery Thermal Management Based on Singular Value Decomposition,“ ECCE 2014.


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Temperature Distribution - Animation

Temperature calculated from CFD. 5 hr simulation time with 6 CPUs.

Temperature calculated from SVD ROM. 0.5 hr simulation time with 1 CPU.

X. Hu, S. Asgari, I. Yavuz, S. Stanton, C-C Hsu, Z. Shi, B. Wang, H-K Chu, “A Transient Reduced Order Model for Battery Thermal Management Based on Singular Value Decomposition,“ ECCE 2014.


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SVD ROM Validation

CFD (10 sec)

SVD ROM (10 sec)


SVD ROM (20 sec)

SVD ROM (30 sec)

SVD ROM (40 sec)


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SVD ROM Validation: Prius Motor

CFD (200 sec)

SVD ROM (200 sec)


SVD ROM (400 sec)

SVD ROM (600 sec)

SVD ROM (800 sec)

X. Hu, S. Lin, S. Stanton, “A Transient Reduced Order Model for Electric Machines Based on Singular Value Decomposition,“ ITEC 2014.


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ECM calculates heat source and sends it to the two ROMs.

LTI ROM calculates average temperature and sends it to ECM.

SVD ROM calculates temperature distribution.

GM Battery Module – ECM Coupled with ROMs


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ROMs/ECM Coupled Results LTI ROM calculates average temperature.

SVD ROM calculates temperature field. Needs to be post-processed back in FLUENT.

ECM calculates electrical performance.

Average Cell Temperature Battery Voltage as a Function of Time


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Complete Drive System Simulation

3-phase currents (left) and junction temperature of IGBTs and diodes (right).


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Conclusion

LTI ROM has shown to give similar results as CFD but runs orders of magnitude faster. SVD ROM helps calculate temperature field,

which gives more information than LTI ROM. Both ROMs can be used in conjunction with

electrical circuit models to have two-way coupled simulation.


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Q&A

Xiao Hu 734-213-1261 [email protected]

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