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Application model integration in the Virtual Test Bed

Application model integration in the Virtual Test Bed. http://vtb.engr.sc.edu. Roger A. Dougal Dept of Electrical Engineering University of South Carolina Columbia, SC 29208. The Prototyping Problem. Power electronics systems involve multiple disciplines and can be quite large

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Application model integration in the Virtual Test Bed

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  1. Application model integration in the Virtual Test Bed http://vtb.engr.sc.edu Roger A. Dougal Dept of Electrical Engineering University of South Carolina Columbia, SC 29208

  2. The Prototyping Problem • Power electronics systems involve multiple disciplines and can be quite large • Different contributors to the system design use different modeling and simulation tools for their parts of the system, often with different levels of abstraction • Eventually, there comes a need to integrate the various parts of the system into a comprehensive prototype (virtual prototype) • without re-writing all component models, • without each participant having to know the details of other models, and • without each participant having to own all of the simulation tools

  3. Ideal Solution • Select group of components in e.g. Matlab/Simulink, cut and paste into the “system” document. • Do the same with electric circuit file (e.g. SPICE) • Connect wires or signal flow paths between the parts. • Push the “simulate” button

  4. VTB supports the development of systems of complex systems by allowing independent creation of component models within each modeler’s area of expertise and using preferred languages. Power Converter Saber Controller Matlab Electricalnetwork Generator ACSL SPICE

  5. Dynamic Models System Schematic Editor Time Domain Solver Small Signal Stability Solver 3D Field Solver other solvers AC Translators SPICE ACSL Simulation Engine Wrappers Saber Matlab Visualization Engine Geometry Models Solid Model Editor DXF Texturing tools Inventor Animation tools 3D Studio Translators IGES EM Properties ProEng Wavefront other tools Lightwave

  6. Model Importation Methods • Equivalence objects (one-for-one replacement) • e.g. SPICE • Read and translate model description files • e.g. ACSL • Compile executable using tools in source program • e.g. Matlab • Give up • e.g. Saber (can’t translate encrypted objects)

  7. Model Translation • Translation requires expression of the imported model in a form acceptable to the solver • Translation methods are different depending on type of coupling • Data • Signal • Circuit

  8. Translation Difficulty • Data • “simple” • Signal • “simple” • Circuit • difficult - • circuit objects interaction with others via energy conservation principles • explicit model form may not match solver needs Literal translation of instructions

  9. VTB Uses RC/AC methodfor circuit coupling Through variables Across variables

  10. Algebraic Companion Form Discretized Equations Past History Vector System Jacobian matrix High order terms

  11. Jacobian Matrix Computation Techniques Manual differentiation (by hand) Numerical differentiation Symbolic differentiation

  12. Some instances do not admit Jacobian computation • Real Hardware • Insufficient computing time • where V(I) or I(V) is given explicitly • Some compiled objects Look for new methods to perform modular simulation Work at Taganrog University ….

  13. Modified Coupling is a way to make modular simulation stable Conductance matrix Flatwise (internal) model S O L V E R K E R N E L Y = ? Pure hardware or procedural model (contributes no entries into Y) Past-history vector J = Modified coupling (suggested) Node voltage vector Balancing element U = Hardware or procedural model

  14. Modified Coupling A method to reduce the remainder matrices Incorporate an approximate (or balancing) model of a part into the model of an adjacent part, then subtract its delayed reaction from its “current” reaction Original 2-part system I(t) A B V(t) Balancing element One possible solution V(t) I(t) t A B y* + _ I(t-t) J(t) J(t-t) t

  15. Example system: DC motor drive Simple Coupling Modified Coupling Flat system, not modular Modular system, using motor as its own “model” Modular system using motor as its own “model” Solution for flat system with numerical DC motor model Unstable solution for the modular system with simple coupling Stable solution for the modular system with modified coupling

  16. Conclusion • VTB seeks to integrate components of a system description across mod/sim tools • Methods include translation and wrapping • Some environments do not readily admit export/translation of models

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