Regardless of the driver, centrifugal pump load will theoretically increase as the cube of the speed increases. The VFD motor typically is rated constant horsepower (or kW) above its line frequency speed.  The VFD and motor combination must have the power capability to drive the pump at the highest speed. 
 
If the example 100kW pump load was at say, 2000 rpm, and the motor base speed at line frequency was 1750 rpm, the motor power rating would need to be at least 100kW at 1750 rpm.