Connect two variable frequency drives to a single motor

First, paralleling inverters is common in both high hp and medium voltage applications. but the inverters must have a common controller. In other words both inverters are controlled by a single system. That isn't specifically 2 separate variable frequency drives on one motor. but similar. However, to operate a single motor from 2 drives is also possible if the variable frequency drives are filtered using a sinewave filter to remove the majority of the carrier frequency. Also, the fundamental frequencies must be synchronized, but that really shouldn't be difficult. Otherwise, the VFD drives will fight each other and may have circulating currents to the extent of the frequency misalignment. And finally it is a good idea to use a interphase transformer or balancing reactor. It is possible to develop a sinewave filter to incorporate a balancing reactor as the inductor portion of the sinewave filter.
In low voltage we are using that kind of approach when the application is critical and redundancy is required. The load can be controlled with reduced capacity if not all AC drives are in operation. For example with 4 VFD drives if one fails the other three can still be used to run at 75% of nominal power. We use drive sync application where the separate standard variable frequency drives are syncronized via fast bus. It is enough to have the drive sync application, fast bus between drives and AC chokes in the outputs. Another situation is when the motor has separate windings driven by separate drives with drive sync. in this case chokes not necessary. Another benefit is the possibility to have an optimized form factor of drive: several small ones instead of one large variable frequency in places where one large does not fit.