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Regeneration with Instaspin

Rahul Sharma
Expert 2725 points

Dear team,

I am using f28069 launchpad. I know the concept of Regeneration in Instaspin that is 4-quadrant based.

Also One thing i know that in Regeneration we will command negative Iq_ref value.I can control the regen current with Iq_ref command but my question is for Voltage.

I am using Lab5a (current control).

And if i give one scenario in which my battery voltage is at 100V, Motor's back-emf constant is 1V/100rpm. Now if my motor is at 3000 rpm and i applied brakes then it would produce voltage of around 30V( Back-emf depends upon rpm and thus not constant). In that case how Instaspin is managing internally for Regeneration. As according to me voltage should be constant to charge a battery. Is Instaspin is making constant voltage by  software part? (Please correct me if i am wrong).

Also i have been told that  "The regenerative brake will boost dc_bus voltage". Then i want to know how it is being boosted? as from battery it is 100V and from motor is coming 30V.

Thanks.

  • 0
    Expert 2725 points

    Hello,

    Any suggestion?

  • 0 in reply to Rahul Sharma
    Genius 5885 points
    You will need better understanding of power electronics. But quickly it can be said that an inverter is just a buck-boost converter. Buck form DC-link to machine, and boost from machine to DC-link. So in regenerative mode inverter boosts the voltage up to the DC-link level.

    As for boosting DC-link voltage, this is the case when DC-link is supplied with grid through diode rectifer. As the rectifier can not reverse the power flow, all the mechanical energy that was regenerated can only be stored in DC-link capacitors, thus you should observe rise of DC-link voltage. Such systems usually have "brakeing resistor" do dissipate the energy.

    If you supply DC-link with battery you should observe only minimal increase of DC-link voltage, as the battery can reverse power flow.