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

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. Saber ACSL Generator Power Converter SPICE Matlab Electrical network Controller

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

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 method for circuit coupling Across variables Through 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. SOLVERKERNELSOLVERKERNEL Y = J = U = ? Conductance matrix Past-history vector Node voltage vector Balancing element Hardware or procedural model Modified coupling (suggested) Pure hardware or procedural model (contributes no entries into Y) Flatwise (internal) model Modified Coupling is a way to make modular simulation stable

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 V(t) AB + _ I(t) y*y* I(t -  ) J(t) J(t -  )   AB I(t) V(t) Original 2-part system One possible solution Balancing element

15. Example system: DC motor drive Flat system, not modularModular 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 Simple CouplingModified Coupling Modular system, using motor as its own “model”

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