what are the implications of using a 45kW ACS580 ABB VSD on a 22kw induction motor?
It means the ACS580 will run nice and cool. The motor will only take the power it wants.

If it has programmable current limits, you may want to halve the default settings, to help protect the motor if it became overloaded, though the primary protection for this would be a thermal trip on the motor itself.