Quote:
Originally Posted by e*clipse
Ok, I'm still trying to wrap my head around this; here are some relivant papers on the subject.
The first one is a thesis, which actually describes it quite well on pages 37-40.
http://eprints.usm.my/9031/1/DESIGN_...POLAR_SPWM.pdf
This is an excerpt from a book from the guy who came up with the concept (I think)
The Industrial Electronics Handbook - J. David Irwin - Google Books
It seems like it should be possible to implement a 3-phase FOC control with this topology, even though most papers I can find only talk about single phase. It also seems to be implemented with comparators and triangular reference frequencies(at least in explanation) The PIC basically uses an interrupt and counter to produce the triangle. I guess this would really require a modification to the SVM that's done near the end of the control loop.
One thing that seems very interesting is the diodes are used as active switching devices critical for the operation, not just current dump paths for the inductor. The result is an effective switching frequency that is double of the base frequency. That's ok with me, I was planning to run mine at a higher base frequency anyway. 
-E*clipse |
The frequency doubling is not really related to the method itself.
It just occurs because since each PWM only takes care of half of the sine wave, rather than the full sine have as it happens with bipolar schemes (center aligned PWM). That also results in twice the resolution or half the ripple, with a resulting decrease in the THD.
Check this paper for a 3 phase implementation and explanation
AN4429 or here
Freescale