Re: %THD reduction
LvW,
I agree with venkataganeshj. I would add one more comment to his answer #: If you use a bandpass filter with the center frequency equal to the sine wave frequency, then the output of the filter will not be phase shifted with respect to the input. However, the complexity of the filter will be greater for the same amount of harmonic attenuation.
Regards,
Kral
Added after 4 minutes:
Sorry! I got LvW's and venkataganeshj's names interchanged in my reply. Also, I meant to say "...answer #2".