Boost converter for PV
The circuit that you provide seems not as straight forward as many you will find and has the disadvantages of both having a transformer AND being non-isolated.

What is your application?
Whay do youi need 400 VDC?
What will you do with the 400V?
You say "at least least 400" - is higher acceptable?

This may relate exactly to what you want
 High Efficient Topologies for Next Generation Solar Inverter

As may this
 Design Concept for a Transformerless Solar Inverter. 

In the above page this circuit uses L3 and T5 to do the part that you are asking about.

 



Related:

More conceptual - but covers aspects you may need to know about
http://rtcmagazine.com/articles/view/103817