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# what is the Vref in power converters and MPPT

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#### Antonaros

##### Newbie level 4
Hello there to everyone.

I am a student and i have to design and alalyse a power converter for pv applications in matlab/simulink.
Until now i find already a lot of informations and i think i am in a good way, but i have a query, what is the Vref in power converters and in MPPT.
MPPT (maximum power point tracking)

Exactly what value i have to choose for the Vref?

If anybody knows can you please help with this.

Thanks in advance for your time.

Regards
A.K

I think the value of vref will depend on what Vout you want. If you are using voltage feedback, then you will sample the output with a resistor divider and your vref will be equal to this Vfb. Hope this answers your question.

wow.. you have much more to learn. i agree with previous poster.. if i were to guess, i think your Vref referes to your desired REFERENCE voltage.

typically this may be between 0 - 5V (unipolar). you set a desired Vref value, say 2.5V, and your controller works to drive the output to 50% of its rated operating condition.

Mr.Cool

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

Hi i will help u if u send simulatiom model

SHIVA
M.Tech NIT

It is the PV module operating voltage (Vmp) that gives maximum power (Pmp). It is usually estimated as a fraction of the PV module open circuit voltage (Voc).

hello,
"Increase Vref" or "Decrease Vref" means that you should increase or decrease Vref voltage of the current regulator with small steps (with help of the PWM or DAC), changing the output current of the inverter (supplying to the utility grid). After changing of the Vref with one step (up or down) we should wait for time >= of the time delay constant of the entire system (PV+DC/DC+Inverter). When working with PV modules we can change their output current and should keep thier output voltage near the Vmpp (~0.75 Voc).

Best regards,
Taner

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