TIDA-01606: LCL filter design

Hi,

I used this app note as a general reference for boost converter calculations. 

plug Vo/vin = 1/(1-D) into equation 2 in the app note and you will get:

L = D(1-D)*Vo/(fs*ΔI) 

D(1-D) term is the highest when D = 0.5. 0.5(1-0.5) = 0.25 or 1/4.  this would give us the worst case or the min L we need:

L = Vo/(4*fs*ΔI) 

But Vo = VDC/2 for the 3L t type converter in our case.  Recall that the reference point for the boost is VDC/2.

L = VDC/(8*fsw*ΔI)

ΔI = Igrid_rated*%ripple

%ripple is a target ripple percentage that you would design for rule of thumb for the ripple current is 20 to 40% of the maximum inductor current.