[duckymcduckface]

Inverters are only used for DC to AC conversion, cogeneration sets are conventional prime mover setups that output 3-phase AC directly. The problem likely has to do with islanded grid stability, without the grid you have to take care of power factor correction and grid voltage regulation yourself, this can get pretty dicey if you don't have direct control or knowledge of the type of loads you'll have.

[eigenvector]

In an islanded mode of operation you also need to match load and generation to maintain system frequency, which is tough to do with cogen and non-controlled loads.

Basically, it can work, but the whole system is going to need to be engineered for it from the outset.