Perturb and Observe MPPT algorithm only outputs maximum possible duty cycle

I am trying to simulate a Perturb and Observe MPPT algorithm in simulink for an PV array.

However I am maxing up the PWM duty cycle to maximum possible value of duty cycle (i.e. 85%). If I manually set the duty cycle using pulse generator I get maximum power between 30% to 35% but in my simulation it does directly to 85%.

In C/C++ we can debug (Step Over/Into) the program using GDB. Kindly advice how I can debug this issue.

Code

function [duty_cycle, dp_pv, dv_pv] = fcn(v_pv, i_pv, delta)

duty_cycle_max = 0.85;

duty_cycle_min = 0.0;

persistent p_pv_n

if isempty(p_pv_n)

p_pv_n = 0.0;

end

persistent v_pv_n

if isempty(v_pv_n)

v_pv_n = 0.0;

end

persistent duty_cycle_old

if isempty(duty_cycle_old)

duty_cycle_old = 0.0;

end

duty_cycle = 0.0;

p_pv = v_pv * i_pv;

dp_pv = p_pv - p_pv_n;

dv_pv = v_pv - v_pv_n;

if(dp_pv == 0)

return;

end

if(dp_pv > 0)

if(dv_pv > 0)

duty_cycle = duty_cycle_old + delta;

else

duty_cycle = duty_cycle_old - delta;

end

else

if(dv_pv > 0)

duty_cycle = duty_cycle_old - delta;

else

duty_cycle = duty_cycle_old + delta;

end

end

if(duty_cycle > duty_cycle_max)

duty_cycle = duty_cycle_max;

elseif (duty_cycle < duty_cycle_min)

duty_cycle = duty_cycle_min;

end

v_pv_n = v_pv;

p_pv_n = p_pv;

duty_cycle_old = duty_cycle;

end

Answer 1

[Benjamin Thompson]

If I create your MATLAB function block in a Simulink model and add your code, a MATLAB code editor window will open up. You can add debug breakpoints in here, using F12 key or using the menu or other ways. Then if you run the Simulink model the editor will stop at that breakpoint if it is reached. The editor will have buttons for step over, step in, step out, etc.