% FILE: EETSepic.m
% Based on extra-credit work by Riley Pack - ECEN 5807 Homework #3
% DESCRIPTION: This script shows how the getZDZN function can be used to
%    get Bode plots of ZD, ZN, and Gvd in a SEPIC converter
%    where capacitor C1 is considered extra element
%    In the Simulink model 'syncSEPIC_EET' C1 is replaced by a voltage test source.  
%
%    The results show impedance interactions, as well as Gvd_old, and Gvd
%    without and with damping

clear all
close all
clc

% Values used to plot Gvd for the Sepic once ZN, ZD, and Gold are known.
C1 = 3.3e-6;
Rd = 4.4;
Cd = 10*C1;
s = tf('s');
% 
% undamped extra-element impedance
Z = 1/s/C1;
% damping: series connection of Rd and Cd
Zdamping = Rd + 1/s/Cd;
% damped extra-element impendace
Zdamped = Z*Zdamping/(Z+Zdamping);

% Find the EET transfer functions for the SEPIC in CCM with voltage
% injection at the port where C1 is connected.
[ZD ZN Gopen Gshort] = getZDZN('syncSEPIC_EET', 'vc', 'SyncSEPIC/vout', 'v1', 'SyncSEPIC/i1');

% Plot the results.
% Impedances
figure
% Bode plots
bode(ZN,ZD,Z,Zdamped,{2*pi*10,2*pi*1e5});
% Set line widths to 2, and show legend
linew = findobj(gcf,'Type','Line');
set(linew,'LineWidth',2);
legend('Show','Location','West');

% Gvd transfer functions
% Plot the damped Gvd when a series RC network is placed in parallel with
% C1 to cause ZD and ZN to interact with a resistive element instead of a
% capacitive element.
figure
% Gvd_old is Gvd with the extra element C1 open
Gvd_old = Gopen;
% Gvd is the transfer function with C1, but without damping
Gvd = minreal(Gopen*(1+ZN/Z)/(1+ZD/Z));
% Gvd_damp is the transfer function with damping
Gvd_damp = minreal(Gopen*(1+ZN/Zdamped)/(1+ZD/Zdamped));
% Bode plots
bode(Gopen,Gvd,Gvd_damp,{2*pi*10,2*pi*1e5});
% Set line widths to 2, and show legend
linew = findobj(gcf,'Type','Line');
set(linew,'LineWidth',2);
legend('Show','Location','SouthWest');