Taking a schematic and using some part hints make no inverter. Designing such devive takes you several weeks to months of engineering work and requires a lot of experience.

By the way - what is a "20kva-inverter" ? Your question is so fuzzy that you might get thousends of schematics and millions of component hints. You can only filter them by telling us which input, which output voltage, AC or DC, number of phases, required efficiency, safety regulations, protections etc.

Sorry, but do you really know what you are going to do ?

Regards