Overview of Circuit Simulation Programs

ECE 546 DIGITAL COMPUTATIONAL TECHNIQUES FOR ELECTRONIC CIRCUITS

January 8, 2008

Oleg Wasynczuk

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

More-Electric Aircraft Power System

Modeling Approaches

Synchronous Machine Subsystem Models

Distributed Parameter Coupled Circuit Steady State

)( uxfx

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IZEeV j ~~

jEe

jXRZ

I~

V~

Power Electronic Subsystem ModelsAverage ValueDetailed

)( uxfx

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)()(

)()( );(

iiiif

if

iiiiii

sgst

ttsdtd

,,

,

1

110

x

Txxxfx

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, …)

Circuit-Based Approaches

Circuit-Based Approaches

Example Subsystem

(Motor Controller)

Circuit-Based Approaches

Circuit-Based Approaches

Resistor-Companion Circuit

15

2

1

654

321321

9

8

7

k

SS

S

S

v

v

v

ggg

gggggggg

i

i

i

i

i

Update Formula

O(n3) computational complexity where n = number of non-datum nodes

Circuit-Based Approaches

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, …)

System-Based Approaches

Hierarchical system definition

System-Based Approaches

Common Simulink Component Models

System-Based Approaches

System-Based Approaches

1

1

1

0

1p

i

ikiki

p

i

iki

k th ,xfxx

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 01

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!

System-Based Approaches

Computational Complexity

System-Based Approaches

Dilemma

Simulink Algorithms

Shampine and Reichelt, The MATLAB ODE Suite, SIAM J. Sci. Comput.,Vol. 18, No. 1, pp. 1-22, January 1997.

System-Based Approaches

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, …)

Finite-Element Based Approaches

4000-10000 Nodes

uSaa

M dtd

FEA

Conventional Parallel Computing Paradigm

Conventional Parallel Computing Paradigm

Conventional Parallel Computing Paradigm

Conventional Parallel Computing Paradigm

At best m-fold reduction in computation time assuming zero communication latency

Computational gain further bounded by Amdahl’s Law

p

T)α1(αTT 1

1 p where serial portion 1,0α

therefore

α

1S

)α1(α

1

T

TS 1

pp

p

Distributed Heterogeneous Simulation (DHS)

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)

Sample DHS Computer Setup

DHS Concept

Much better than M-fold (potentially M3) improvement in speed

DHS Links Environment

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, ScramnetTM, MyrinetTM,...)

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

More-Electric Aircraft Power System

Optimum Allocation

Optimum Allocation

Optimum Allocation

18.5 speedup with 4 computers