Does using NaN instead of 0 give the desired result? See below.
clear all
close all
clc
Vo_max = 400;
Pout = 1000;
fs = 50e3;
Ts =1/ fs; % half of switching perior
T = 0.5 * Ts;
L = 50e-6;
Io =Pout / Vo_max;
n = 0.5;
R = Vo_max / Io;
k = ( T .* R )./ ( n.^2 .* L );
D = linspace( 0,0.5 , 100 );
D_buck= linspace( 0.0, 0.5, 1000);
D_boost= linspace( 0.0, 0.5, 1000);
M_buck = D_buck .* ( 1 - D_buck ) .* k;
M_boost = D_boost .* ( 1 - D_boost ) .* k;
% condition
M_buck (M_buck > 1) = NaN ;
M_boost(M_boost < 1) = NaN ;
[ D_lamda_buck , M_lamda_buck ] = meshgrid ( D_buck , M_buck );
[ D_lamda_boost , M_lamda_boost ] = meshgrid (D_boost , M_boost );
lamda_buck = ( ( 2 .* D_lamda_buck -1 ) + M_lamda_buck) .^2 ./ (( 8 .* D_lamda_buck .* ( 1 - D_lamda_buck ) .* ( M_lamda_buck +1) ) );
lamda_boost =( ( 2 .* D_lamda_boost -1 ) +1./M_lamda_boost ).^2 ./ (( 8 .* D_lamda_boost .* ( 1 - D_lamda_boost ) .* ( 1./M_lamda_boost +1) ) );
%% Plot figures
figure (1)
hold on
[C_buck ,h_lamda_buck]=contour(D_lamda_buck,M_lamda_buck,lamda_buck,[ 0.01 0.05 0.1 0.2 0.25 ], 'color','b');
clabel(C_buck,h_lamda_buck)
[C_boost ,h_lamda_boost]=contour(D_lamda_boost,M_lamda_boost,lamda_boost,[ 0.01 0.05 0.2 0.25 ],'color','r');
clabel(C_boost,h_lamda_boost)
axis([0 0.5 0.5 1.5])
xlabel(' D');
ylabel('M')
grid on
hold off
