(TI Designs: TIDM-HV-1PH-DCAC ). Selection of the L value and caps on the grid connected side.)
Hai,
i am developing a new inverter design using TIDM-HV-1PH-DCAC reference design.Presently i am designing the LCL Filter section.I happen to read the following statement , written in section 2.2.5
quoted "choose the grid side inductance such that the LCL resonance is greater than FSW/6".
But my major doubt is ,why was the inductor value chosen to be 0.94mH?
The switching frequency was found to be 20000Hz.
The Fsw/6 value was calculated to be 20000/6=3333.33Hz and the choosing the inductor value to be 0.94mH Would lead the LCL Filter Resonance to be 5933.226Hz.Even though the statement quoted ,denoted the Fsw/6 to be greater,the difference between both the frequencies seem to be almost 2500Hz.Is such a huge difference needed?Could you please tell me why a value (for inductor) ,was not chosen which would have lead to a resonating frequency somewhere near 3333.33Hz?
And besides that ,i happen to see the value of Cf being calculated,Is that the image of schematics which i have attached is common for both grid connect and voltage connected mode?The value was calculated as per the excel sheet "<sdk_install_path>\solutions\tidm_hv_1ph_dcac\hardware\baseboard\calculation.xlsx sheet sheet→Grid Conn. Li, Cf, Lg, Sel" to be around 1.02uF but unfortunately i couldn't find any such value in schematics..Where is it being implemented?.Is the 1mH inductor at the grid connected side ,the one which you calculated with the Excel sheet given with the design? The calculated value of Lg was found to be 940uH.have you implemented such that each path (L AND N) has 470uH to grid?
