UCC28019A: Calculate the power factor using TINA TI for UCC28019

Hello Lin, 

I like this article on power factor that I found years ago.  I think it helps to explain a lot:
PF_THD_Power.pdf

For your simulation, I think that you need to add another power meter just after the voltmeter at the AC source. 
PF = Pin /  (Vrms x Irms)

Assuming Vrms is a perfect sine wave, then any distortions or phase shift of Irms should be separated out by the input power meter.
You can't use output power unless you know exactly the efficiency at any line and load condition. 

Please not that the PF of your real circuit will differ from your simulation unless you model the EMI filter as well.
Also, some real-world distortion of the input current may not be modeled perfectly or completely by this simulation because the model is simplified. 
Therefore real-world THDi can be higher and real-world PF will be a little lower, according to the equation in the article.  

Regards,
Ulrich