• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 83 subscribers
  • Views 508 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TMS320F28069: Trigonometric calculation

Arash Tahghighi
Intellectual 630 points
Part Number: TMS320F28069
Other Parts Discussed in Thread: TIDM-1007, TIDM-1000

Hi

I am power electronic engineer and I'm going to develop a three phase grid tie solar inverter. I have some questions.

Questions1  what is the fastest method in park transform calculation which involved with trigonometric calculation tms320f28069  and tms320f28377 platforms?

Question2 in a multi rate control ISR (one for setep up converter and one for inverter) haw can we manage to prevent undeterministic control routine timing? Because one isr if every 10 us  and the other one is every 50 us, I can't figure out how to manage them

Question3 in 3phase converter the software  PLL add more trigonometic calculation which add mote latency.  Is there any way to do these calculation out of isr?

Thanks

  • 0
    TI__Genius 11955 points

    Questions1  what is the fastest method in park transform calculation which involved with trigonometric calculation tms320f28069  and tms320f28377 platforms?

    Please use TUV instructions to get the fastest park transform.

    Question2 in a multi rate control ISR (one for setup up converter and one for inverter) haw can we manage to prevent undeterministic control routine timing? Because one isr if every 10 us  and the other one is every 50 us, I can't figure out how to manage them

    Inside 10uS ISR (FAST ISR) you can schedule to do 20% of the calculation that you do in your 50 Usec ISR (SLOW ISR). Then continue this way for 5 consecutive cycles of FAST ISRs. That way you can have single 10uS ISR and inside it will be your SLOW ISR

    Question3 in 3phase converter the software  PLL add more trigonometic calculation which add mote latency.  Is there any way to do these calculation out of isr?

    Where you do those calculation (meaning how fast you do those calculation) will depend on the system response characteristics. So if the PLL is for 3 phase 60Hz AC input, You should at least run that PLL at about 10kHz rate to get a reasonable PLL response.

    Shamim

  • 0 in reply to Shamim Choudhury
    Intellectual 630 points

    Hi

    Thanks for reply

    I couldn't find any thing about TUV , do you have sample code or document for that? Is it applicable for both platforms I mentioned in my question?  Is it general for trigonometric calculation ?

    I like your solution for multirate ISR , but haw can I divide slow control algorithm into 5 subtasks?  Can u give me some advise?  Plz

    Thanks

  • 0 in reply to Shamim Choudhury
    Intellectual 630 points

    Hi

    I'm still waiting for reply

    Thanks

  • 0 in reply to Shamim Choudhury
    Intellectual 630 points

    Hi

    Did u read my question? This is urgent

    Plz

  • 0 in reply to Arash Tahghighi
    TI__Genius 11955 points

    My apologies for the typo in my response. For fastest calculation of trigonometric function please use TMU instructions available in many of our latest MCUs.

    TMS320F28069 does not use these TMU instructions. However you can use the CPU power to calculate these instructions.

    TMS320F28377x uses TMU instructions. For an overview on TMU please see the appnote (SPRY288B) at:

    http://www.ti.com/lit/an/spry288b/spry288b.pdf?ts=1590505525278

    You can also read SPRACN0A at:

    http://www.ti.com/lit/an/spracn0a/spracn0a.pdf?ts=1590504945450

    There are many reference designs where we used TMU instructions. For example please see TIDM-1000, TIDM-1007. In these we have used TMU instructions to implement PLL (phase locked loop) functions.

    Shamim