Changing Your Circuit Parameters
Introduction
Each time that you change a parameter of the powerlib library
blocks, you have to restart the simulation to evaluate the state-space
model and update the parameters of the nonlinear models. However,
you can change any source parameter (Magnitude, Frequency, or Phase)
during the simulation. The modification takes place as soon as you
apply the modification or close the source block menu.
As for the Simulink blocks, all the powerlib library
block parameters that you specify in the dialog box can contain MATLAB expressions
using symbolic variable names. Before running the simulation, you
must assign a value to each of these variables in your MATLAB workspace.
This allows you to perform parametric studies by changing the parameter
values in a MATLAB script.
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Example of MATLAB Script Performing a Parametric Study
Suppose that you want to perform a parametric study in a circuit
named my_circuit to find the impact of varying
an inductance on switching transients. You want to find the highest
overvoltage and the inductance value for which it occurred.
The inductance value of one of the blocks contains variable L1,
which should be defined in your workspace. L1 is
varied in 10 steps from 10 mH to 100 mH and the values to be tested
are saved in a vector, L1_vec. The voltage waveform
to be analyzed is stored in a ToWorkspace block in array format with V1 variable
name.
You can write a MATLAB M-file that loops on the 10 inductance
values and displays the worst case.
L1_vec= (10:10:100)*1e-3; % 10 inductances values 10/100 mH
V1_max=0;
for i=1:10
L1=L1_vec(i);
fprintf('Test No %d L1= %g H\n', i, L1);
sim('my_circuit'); % performs simulation
% memorize worst case
if max(abs(V1))>V1_max,
imax=i;
V1_max=max(abs(V1));
end
end
fprintf('Maximum overvoltage= %g V occured for L1=%g H\n', V1_max, L1_vec(imax));
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