PWM signal goes to zero when using PID controller after MPPT (P&O) in PV system

I built a PV solar system in Simulink with an MPPT controller using the Perturb and Observe (P&O) algorithm. The system works fine with only the MPPT .

Then, I added a PID controller to improve performance. I set the error input to the PID as:

error = V_ref (from MPPT duty output) - V_PV (from PV array)

The PID output is then sent to the PWM Generator (DC-DC), which controls the IGBT in a buck converter. However, after adding the PID, the PWM signal becomes zero, and the system stops working properly — no switching occurs, and the output voltage drops.

[Adarsh]

Hi @mohamed ayad,

Can you verify if the output of PID controller is in valid range for the PWM generator's "Duty Cycle" i.e [0, 1]?

Answer 1

[Sabin]

Most likely the output of the PID controller is <=0 which will result in PWM signal to be 0. Double check the corectnes of the control structure and if there is any sign mismatch.