UCC28070 iTHD improvement solution for low Vbus setting at 230Vac input (universal input range)?

Team,

May I know if there is a solution to improve iTHD for the Vbus set at 375V for a 230Vac input?

I've tried to fine tune the voltage loop, current loop, Vsense cap, Vbus cap, and CT current signal looks good.

Looks like to set the Vbus higher can make the iTHD lower, we get 2~3% improvement by set the Vbus 4V higher.

But since the customer choose the output cap voltage rating at 400V, so there is a Vbus voltage limitation.

Thank you.