I have DC motor(75 KW, 400V , 1700/2400RPM, field 8/5 A, ), i want to run the motor above its base speed upto 2000RPM using Siemens make simrog DC Drive, plz someone tell me the procedure?

I do not know the Siemens drive, but you will need to use field weakening in order to increase the speed.

You can either increase the armature voltage or decrease the field voltage to increase the rpm on shunt, compound, or series wound hp dc machines larger than 7.5 hp. PMDC smaller hp machines require only armature voltage to be increased, because they have no field windings.

in this case u have to enable the field weakening mode the torque will be less and u have to tune the drive for this application please read the sinamics DCM manual under field weakening tuning or in the siomreg manual