Thanks, in other words, the battery would therefore be needed?
I am wondering if some system involving a controlled PFC to 400v, into a buck down to 350V , then to an inverter, then to the UUT, then back round to the pfc.....and round and round, etc etc.....could be do-able?...and make them all talk to each other so no battery needed......just some mains to put in there to replenish the system losses.......gives a good, high current test system, which works and wastes little power even though the UUT is supplied by mains level electricity, and is passing high current?