thanks a lot guys for your time to answer my question.
to give to understand better what i am trying to do is to design in Simulink a power converter for PV applications. ex. from 100Volts DC to 230Volts AC 50Hz grid connections.
Now this power converter most of cases comprise a DC/DC boost converter and a DC/AC bridge inverter.
In addition for the control method of both, DC/DC and DC/AC, a maximum power point tracker (MPPT) is used with combination of voltage mode control (VMC) or current mode control (CMC).
The Vref, where i am talking about, is the Vref in the MPPT algorithms and in the control methods.
For example in the P&O algorithm where is the classic and most in use algorithm at the final stages of the algorithm it says "Increase Vref" or "Decrease Vref" .
This is just one example of the Vref where i am talking about.
Thanks for your time.
Regards
A.K