In power factor correction I have seen many paper they use PLL to generate reference signal. but it is also possible to sense input voltage and generate reference signal. is it mandatory to use PLL ?
Dear Ankit,
This is because of the quality of the reference signal produced by the PLL. It is so that the PLL takes the distorted and noisy input signal and filter it out to get a clean reference signal having the same frequency and nearly the same phase of the input signal. The PLL acts as adaptive narrow band pass filter that produces clean output signal tracing the input signal in frequency and to some extent the phase. The PLL is the circuit of synchronization. This thanks to its loop filter that can be made very narrow and its voltage controlled oscillator that it tracked to the input signal. The PLL is used also in communications for carrier and clock regeneration for sake of synchronization.
wish you success
Dear Ankit,
This is because of the quality of the reference signal produced by the PLL. It is so that the PLL takes the distorted and noisy input signal and filter it out to get a clean reference signal having the same frequency and nearly the same phase of the input signal. The PLL acts as adaptive narrow band pass filter that produces clean output signal tracing the input signal in frequency and to some extent the phase. The PLL is the circuit of synchronization. This thanks to its loop filter that can be made very narrow and its voltage controlled oscillator that it tracked to the input signal. The PLL is used also in communications for carrier and clock regeneration for sake of synchronization.
wish you success
No...Even I am not using PLL as I am a beginner in research.You can directly generate the reference by sensing input voltage.
Friend Ankit Singh:
What are you doing about power factor correction?, do you want better?, do you know wich is?, and what instruments have you employment for measurement it?
Dear Ankit.
The grid voltage normally has some harmonic content. In consequence, if you use directly this voltage to generate the current reference of your rectifier, the current will have the same harmonic content of the voltage. Here, we have a problem, some additional components of real power appears because there are components of voltage and current at more than one frequency. However, this effect is not evident when the voltage has a low harmonic content (THD below 5% for example).
If you use a PLL, the generated current reference can have a really low harmonic content (THD below 0.5%) and hence, the real power is only produced at the fundamental frequency as expected and desired.
We have some results published in the following three papers. These works are closer to the practical issues than the theoretical ones.
"A simple digital sinusoidal reference generator for grid-synchronized power electronics applications"
"Digital control of a single-phase boost rectifier with power factor correction using a dsPIC"
"Digitally implemented sliding-mode control of a single-phase dual-boost PFC rectifier"
I have designed several PFC stages, never using a PLL, and they work very well in different girds and countries. To use a PLL seems to me an extreme case for a very special poluted supply. We do not have to be perfectionists.
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