VTB Interface to FEMLAB

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VTB Interface toFEMLAB
VTB Conference 2004 Sep. 15, 2004

• Sharmin Basher, Antonello Monti
• Dept. of Electrical Engineering
• University of South Carolina
• Columbia, SC 29208

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Purpose of Study

• To provide a methodology to embed finite element
  analysis (FEA) in a circuit simulation
• The proposed method is implemented with reference
  to the design of a CEET transformer

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Purpose of Study

• FEMLAB-MATLAB-VTB interface provides user freedom
  to modify system component parameters and
  immediately investigate system response in VTB.

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Design Overview
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Significance on CEET Transformer Model

• Technique used to transfer electrical energy
  without electrical connection or physical contact
  via inductive coupling
• Underwater applications
• Electric vehicle battery recharging
• Transcutaneous energy transmission systems

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CEET System

• Executed using magnetic induction in transformers
  where energy from primary to secondary winding is
  transferred through the air

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CEET System

• Consists of relatively large separation between
  primary and secondary windings
• Yields large leakage inductance
• Low coupling coefficient

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FEA of CEET Transformer

• The Galerkin method for nodal finite elements is
  implemented in FEMLAB for transformation of
  differential equations to equivalent systems of
  algebraic equations
• Equation-based modeling or geometry-based
  modeling
• User provides parameters for underlying equations
  and FEMLAB creates mesh, solves system, and
  offers postprocessing

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FEMLAB Modeling

• Model Navigator

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FEMLAB Modeling

• Draw mode
• Dimensions in centimeters

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FEMLAB Modeling

• Boundary mode
• Define boundary conditions
• Boundary conditions are automatically set by
  FEMLAB to define a null value of the vector
  potential along the boundary

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FEMLAB Modeling

• Subdomain mode
• Specify application dependent and material
  properties

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FEMLAB Modeling

• Can specify values for each subdomain
  independently

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FEMLAB Modeling

• Mesh Generation

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FEMLAB Modeling

• Solving, postprocessing
• Magnetic flux density within transformer

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FEMLAB-MATLAB Interface

• Utilizing MATLAB for advanced postprocesing
• Allows for dynamic analysis of system response
• Overview

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FEMLAB-MATLAB Interface

• Save FEMLAB model as m-file
• Commands can be run directly from MATLAB command
  line and modified
• If vary current, see corresponding change in
  magnetic flux density of transformer

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FEMLAB-MATLAB Interface
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FEMLAB-MATLAB Interface

• From flux density values, can calculate nonlinear
  inductances

• When i1 and i2 are relatively large, relationship
  between fluxes and are nonlinear.

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FEMLAB-MATLAB Interface

• According to Faradays law

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FEMLAB-MATLAB Interface

• The following equation can be determined
• L11, L22, and M are nonlinear inductance values
  used to determine leakage inductance

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FEMLAB-MATLAB Interface

• Leakage inductances L1 and L2 can be determined
  from L11, L22, and M
• L1 and L2 are input to VTB model

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VTB CEET Model

• Leakage inductance values calculated in MATLAB
  are used in development of VTB Model
• Overview

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VTB CEET Transformer Representation

• CCCS and VCVS represent ideal transformer
• L1 and L2 are leakage inductances
• R1 and R2 are winding resistances

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Simulation Results

• New transformer model can be tested in VTB
  environment

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Simulation Results
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Conclusions

• Through interfacing of FEMLAB, MATLAB, and VTB we
  can obtain a dynamic model of a single phase
  transformer
• As current is varied in MATLAB environment, flux
  density is calculated in FEMLAB. These changes in
  flux density are used to calculate values of
  nonlinear inductances. VTB model uses nonlinear
  inductances as input and we can see the circuit
  simulation dynamically.