A Software Package For Electric EngineeringAnalysis And Design

Abstract

A new software package developed in the Electronic Department of the University of Genova is presented. SAM-1 program is able to perform digital simulation of electric networks, control systems, electrical drives and physical systems described by means of linear and non linear differential equation sets. Particularly, the author is developing a library of macromodels for all the most significant power electronic circuital topologies and for electric machines. The implementation methodologies and two macromodels are presented and the simulation results are discussed to verify that SAM-1 program can be successfully used as a CAD tool for the design and analysis of electric circuits and particularly the power electronics ones. INTRODUCTION In these last years the software packages have become a necessary tool for engineering analysis and design. Particularly, electric engineering general purpose software packages such as EMTP, Saber, ELDO [1] are heavily employed in order to verify the operating conditions of electrical plants, transmission systems and electrical drives with relevant control circuits. They can be also successfully used to design innovative electrical configurations or to analyze misoperating conditions in order to realize protective relais coordination. However, special purpose software packages sometimes can be developed if particular topologies have to be studied, if calculation times become unreasonably long, or if convergence problems arise. Transactions on Engineering Sciences vol 3, © 1993 WIT Press, www.witpress.com, ISSN 1743-3533 106 Software Applications in Electrical Engineering In this paper a new software tool developed in the Electronic Department of the University of Genova, called SAM-1 Program, will be presented [2]. This CAD tool consists of an evolution of the CSS1 Program, a software package oriented to the analysis of control and regulation systems. SAM-1 PROGRAM CHARACTERISTICS SAM-1 Program is a general purpose package able to perform digital simulation of electric networks, control systems, electrical drives and all physical systems containing both linear and non-linear elements. Substantially, SAM-1 numerically solves high order linear and non linear differential equations sets using Runge-Kutta method both of second and fourth order. If the 2 order Runge-Kutta method is utilized, analyzing a status equations set: x = ax + bn with x(0) = XQ (1) fixing a certain At integration step and starting from x^, it is possible to obtain x as Xn + l = Xn + x'n At (2) where x^ is the weighed derivative equal to: x'n = Xx + i/2 = x (nAt + 1/2 At) = Xn + in • 1/2 At (3) A graphic interpretation in the case of only one equation may be useful as shown in Fig. 1. If particular systems have to be studied, the 2° order RungeKutta method can result inadequate. Infact, approximation becomes too bad if integration steps are too large. Thus a 4^ order Runge-Kutta method has been included. To briefly explain this method, starting from a point (0, yo) and fixed an integration step, if the equation to solve is: y = f(x,y) (4) it is necessary to obtain: Transactions on Engineering Sciences vol 3, © 1993 WIT Press, www.witpress.com, ISSN 1743-3533 Software Applications in Electrical Engineering 107