Wolfgang
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 Posted:
Thu Dec 16, 2004 12:52 pm Post subject:
Re: implementation of PLL |
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Hello jkm,
If you have at least two line voltages measured make dq-Transformation and
"fix" the resulting vector by changing omega slightly.
(If you don't have a weak net you can use a very slow PI-control for that.)
Some people having only one voltage measured determine sin/cos-correlation
factors to determine phase each period and make
a correction afterwards.
Be aware: Most People don't change frequency as net's frequency is very
stable. They only determine a correction factor once a
period and add/subtract a "peace of phase" to stay synchronuous in next
period.
For assembly language programming:
- have a sin-table in memory.
- apply MAC operation to voltage using sin-table
- give out correction value at period end
- ready
A hint:
I've never seen the real need to do assembly programming for 3ph power
electronics as they mostly aren't the ultra cheap mass market product.
As most people run a control loop related to the PWM frequency (e.g.
8kHz switching frequency using measured values in a 4kHz/8kHz or 16kHz
loop) normaly the phase determination is done within this loop as a very
small task.
Second hint:
Don't know but as TI has motor control specializsed DSP's (your's too ?)
I'm shure that you can find prototype code for this ...
(Don't do things others have done for you ...)
Good
luck, Wolfgang
"jkm" <jkrushna@rediffmail.com> schrieb im Newsbeitrag
news:6beddc36.0412152119.621f4c05@posting.google.com...
| Quote: | I am a research scholar working in Power System related to Power
Electronics devices. In my work I have to use PLL through assembly
langeage programming (by TMS320LF2407A EVM board in Code Composer 2000
environment) for detecting the instantanous frequency of a 3ph
transmission line. any one can help me to implement the same?
regards
jkm |
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