ALTIVAR 312 and mppt power tracking for a solar pumping system

Wedge · Dec 3, 2014

Hi all,

I need to perform the following pid control using an altivar312, want to read the DC bus voltage (that is the solar panels voltage), and use a pid control to keep this voltage constant in order to make a mppt follower. The idea is to change the frequency driven to the motor. If dc bus voltage increases increase the frequency, if dc bus voltage decreases reduce the frequency. The voltage reference will be given using a trimmer conected to the Ai1 input in the vfd.

But do not know how to read the dc bus voltage and how to connect it to an analog input to be used as the signal to be controlled by the pid.

If someone have some experience on this matter and can give some hint, it will be wellcomed. I want to do the homework, not asking for a complete solution. Just some idea, or some comment. I am reading the technical docs for the altivar 312. Want to understand how the vfd work. I am not an electrician, just have some little technical skill.

All the best.

Bobster · Dec 3, 2014

Do the solar panels have an analogue output available, 0-20ma, 4-20ma, 0-10V?

What type of panels are they?

Wedge · Dec 3, 2014

RoB2 said:
Do the solar panels have an analogue output available, 0-20ma, 4-20ma, 0-10V?

What type of panels are they?

Dear sir,

No, the panels do not have an output, 0-20 mA, 4-20 mA, or 0-10 V.

The solar panels have a maximum power point voltage of 48 Vdc, a maximum power point amperage of 4.58 A, an open circuit voltage of 56 Vdc, and a short circuit current of 5.35 Amps. Their maximum power point power is 220 Watts.

What I am trying to do, is to keep the dc voltage constant. Will wire seven solar panels and thus will have 7*48=336 Vdc, and will connect this dc voltage directly to the dc bus of the VFD. As the 230 V 50 Hz waveform has a peak of 230*sqrt(2)=325 Volts, the VFD will have in the dc bus the same voltage level that it has when it is connected to the power grid.

The solar panels have the maximum power point with a nearly voltage constant, and this is what I need: to keep the voltage coming from the solar panels constant. But can not find a way to do this with an altivar. Maybe will do it with another brand.

Thanks for your answer.

Will continue reading all the answers provided, and if I find a way to do it will explain it, still reading the manuals.

Lot of work to do.

SheffSimon · Dec 4, 2014

On a lot of VFD's the DC bus voltage is available as a parameter in the drive, which you can then map to an analog o/p. Not on the Altivar unfortunately, but certainly on Siemens Micromaster.

So you could use https://www.phoenixcontact.com/onli...id=2811116&library=usen&pcck=P-14-08-04&tab=1

Not cheap though....

Bobster · Dec 4, 2014

^^^ This suggestion would be the easiest way of making the Altivar do what you want.

The Altivar will produce it's own 24VDC source to power the transducer.

Wedge · Dec 4, 2014

SheffSimon said:
On a lot of VFD's the DC bus voltage is available as a parameter in the drive, which you can then map to an analog o/p. Not on the Altivar unfortunately, but certainly on Siemens Micromaster.

So you could use https://www.phoenixcontact.com/onli...id=2811116&library=usen&pcck=P-14-08-04&tab=1

Not cheap though....

Dear SheffSimon,

Many thanks for your answer, have downloaded the voltage transducer datasheet.

This solves the problem. I can use the 24 Vdc source from the altivar to power the transducer.

Then with a potentiometer will set the reference voltage and the vfd will change freq to keep voltage constant.

Or just read other brand manuals and look for a vfd that can perform this without a transducer.

Thanks a lot for your advise.

PROBLEM SOLVED!.