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How make a V/f control with a F28335?

Altair Forum User

Submitted by linklessa on Mon, 12/14/2009 - 17:27

Hi. I'm new in this area and need to do a V/f control for a inductoin machine.

I didn't understand which block I have to use. There are three that I guess can be used:

Space Vector Generator (Magnitude, Frequency); Space Vector Generator (PWM); V/Hz Profile Generator;

But I didnt'n understand very well how this blocks works... Somebody can help me? I need to do a simple V/f control (I guess is simple).

There are some example that I can use? I see some topics abaout it, but I think that is not the same for me...

Thanks

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Altair Forum User

Submitted by Anders89 on Mon, 12/14/2009 - 21:56.

This post,How to use SV PWM in vissim/ecd?, discusses V/f ACI control for the LF2407. You use the 32 bit TI blocks for equivalent control on the F28335. I have attached examples below.

Unable to find an attachment - read this blog

Altair Forum User

Submitted by linklessa on Mon, 12/14/2009 - 22:46.

I want to do this control in V/f mode, but I want to increase the frequency and voltage with a certain time, until reaches the especified value, like a acceleration ramp.

How can I do this?

Altair Forum User

Submitted by Anders89 on Tue, 12/15/2009 - 04:01.

VisSim automatically sets up the hardware timer to cause precise execution of your control function at the sample rate given in the Simulation Properties dialog. The Volts/Hertz and Mag/Freq Space Vector Generator blocks work together to give you the frequency-based voltage ramp you desire.
The Volts/Hertz profile block takes 5 parameters:
'Low Frequency Point' = start of voltage amplification
'High Frequency Point' = end of voltage amplification
Voltage at HFP = Voltage at High Frequency Point
Voltage at LFP = Voltage at Low Frequency Point
slope = slope of voltage ramp from LFT to HFP

Note that all parameters are prescaled to fraction of full scale. So if your actual max voltage is 220V, and you want voltage at HFP=180, then 180/220=.818 in the dialog setting, likewise, the frequencies are a fraction of the max frequency given by the scaling in the Mag/Freq Space Vector Generator block. In that block, a scaling of 1 gives a 60 degree advance per tick. For a sampling rate of 6 kHz, you get one complete cycle per millisec for 1 kHz waveform rates. To get 50Hz (20 millisec) cycles, use a scaling of 1/20, or .05.

Altair Forum User

Submitted by linklessa on Tue, 12/15/2009 - 22:48.

Where I can see the sampling rate?

If the values are in pu units, how can I do the correct scale for 60 Hz?

Altair Forum User

Submitted by linklessa on Mon, 12/14/2009 - 22:37.

I tried to download this in the DSP, but isn't work. I already changed the blocks to 32-bits and 28335.

This only works in real time? I can't download this to run independently of the PC?

Altair Forum User

Submitted by Anders89 on Tue, 12/15/2009 - 05:22.

And yes it can run independently of the PC. The F2833x DMC support lib was missing the entry point for the V/f control block. Unzip the attached lib to your \vissim70\dsp\lib directory, and you should be able to build, download and run the previously attached diagrams.

Unable to find an attachment - read this blog