PFC zero crossing distortion. The current has lots of distortion when AC voltage zero level.

Hi Andy,
Your question I believe is why is distortion present around the zero crossing.
This distortion is present in all pfc converters. Its main cause is that there is very little voltage to drive the inductor around these zero crossings.
The drain source capacitance of the FET tends to resonate with the boost inductor and you see this ringing. At light loads the capacitor on the DC side of the bridge rectifier will have a higher voltage than the input AC line and this leads to a flat spot around the zero crossing if the value of capacitance is too high. Some pfc controllers increase the on time around the zero crossing in order to reduce this effect but I believe the UCC2817 does not have this feature.
Hope this answers your question.
Regards
John

I need some additional circuit to solve this issue.

Get it

Thanks