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Overview of Circuit Simulation Programs ECE 546 DIGITAL COMPUTATIONAL TECHNIQUES FOR ELECTRONIC CIRCUITS January 8, 2008 Oleg Wasynczuk

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Need for System-of-Subsystems Approach Complex engineered systems such as aircraft, modern automobiles, or the terrestrial electric power grid involve a broad spectrum of technologies and interactive subsystems that must work synergistically in order to operate properly Inter-dependencies between subsystems are becoming more and more prominent

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More-Electric Aircraft Power System

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Modeling Approaches

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Synchronous Machine Subsystem Models Distributed ParameterCoupled CircuitSteady State

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Power Electronic Subsystem Models Average ValueDetailed

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Simulation Approaches Circuit-Based Approaches (Spice, EMTP, Saber, PSIM, Simplorer) System-Based Approaches (Simulink, ACSL, Dymola) Block-diagram and/or differential equation oriented Extensive set of tool boxes including ASMG (Simulink, ACSL) Power System Blockset (Simulink) … Finite-Element-Based Approaches (Ansys, Maxwell, …)

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Circuit-Based Approaches

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Example Subsystem (Motor Controller)

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Circuit-Based Approaches

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Resistor-Companion Circuit

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Update Formula O(n 3 ) computational complexity where n = number of non- datum nodes Circuit-Based Approaches

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Simulation Approaches Circuit-Based Approaches (Spice, Saber, PSIM, Simplorer) System-Based Approaches (Simulink, ACSL, Dymola) Block-diagram and/or differential equation oriented Extensive set of tool boxes including ASMG (Simlink, ACSL) Power System Blockset (Simulink) … Finite-Element-Based Approaches (Ansys, Maxwell, …)

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System-Based Approaches Hierarchical system definition

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System-Based Approaches Common Simulink Component Models

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System-Based Approaches

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When user starts model, Simulink applies selected integration algorithm to approximate solution at discrete but not necessarily uniform instants of time General Multi-step Formula Implicit algorithms require solution of nonlinear equation (dimension = number of states) at each time step. Newton- Raphson iteration generally used. Explicit if

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System-Based Approaches Stiff System: A system with both fast and slow dynamics Stiffly Stable Integration Algorithm: the ability to increase the time step after fast transients subside Stiffly Stable Algorithms are implicit!

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System-Based Approaches Computational Complexity

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System-Based Approaches Dilemma

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Simulink Algorithms Shampine and Reichelt, The MATLAB ODE Suite, SIAM J. Sci. Comput., Vol. 18, No. 1, pp. 1-22, January System-Based Approaches

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Simulation Approaches Circuit-Based Approaches (Spice, Saber, PSIM, Simplorer) System-Based Approaches (Simulink, ACSL, Dymola) Block-diagram and/or differential equation oriented Extensive set of tool boxes including ASMG (Simulink, ACSL) Power System Blockset (Simulink) … Finite-Element-Based Approaches (Ansys, Maxwell, …)

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Finite-Element Based Approaches Nodes FEA

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Conventional Parallel Computing Paradigm

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At best m -fold reduction in computation time assuming zero communication latency Computational gain further bounded by Amdahl’s Law where serial portion therefore

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Distributed Heterogeneous Simulation (DHS)

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DHS Definition Synchronized interconnection of any number of dynamic subsystem simulations Developed using any combination of programs/languages Implemented on: Single computer/workstation/supercomputer Local area network (Intranet) Wide area network (Internet)

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Sample DHS Computer Setup

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DHS Concept Much better than M-fold (potentially M 3 ) improvement in speed

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DHS Links Environment

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Flexibility of DHS Heterogeneous platforms (Windows, Unix, Linux,...) Heterogeneous languages (ACSL, MATLAB/Simulink, Saber, EASY5, C, C++, FORTRAN, Java,…) Heterogeneous simulation approaches (single-rate, multi- rate, state model based, resistor-companion, finite difference/element,...) Heterogeneous networks (Ethernet, SCI, Scramnet TM, Myrinet TM,...)

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Use “best” language for each component/subsystem Proprietary information protected Super-linear increase in computational speed across a network of desktop computers No need to translate models into common language Legacy code can be used directly Conducive to team design/analysis Remote interconnection Eliminate need to develop average-value models for system stability assessment Real-time (hardware-in-the-loop) capability for some systems System Integrator(s) do not have to be familiar with the language(s) used to create subsystem simulation(s) Key Advantages of DHS

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More-Electric Aircraft Power System Optimum Allocation

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18.5 speedup with 4 computers

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