This 3phase rectifier connected to 2 capacitors and we use r1 to make the center between 2 capacitor is very close to ground voltage =0 v so can someone help me to understand how this happen

 

The circuit makes little sense. What is it's purpose?

 

the circuit makes little sense. What is it's purpose?

is used as input for buck converter

 

If you want tomake sure that the voltage is equally divided you will need two resistors, one over each capacitor. How is the ground on R1 related to the rest of the circuit?

 

is used as input for buck converter

Well you can't get that from your posted circuit.

For a three phase bridge rectifier you only need 6 diodes (see the bottom of this page).

 

Well you can't get that from your posted circuit.

For a three phase bridge rectifier you only need 6 diodes (see the bottom of this page).

I too caught the bridge isn't right... but it actually should work. OP has 12 diodes instead of the traditional 6, but the extra's are in parallel with the ones required so it is good.

However, the ground on R1 is not referenced any where else, so the point is floating.

I would guess you are attempting to get a positive and negative output from the 3 phase bridge: I do not believe you can do that.