It all depends the needs , for each case to look into.
In your case, you can use the grid as your “battery” using the grid if needed.
I have no idea what the equipment requirements are in your case, i know that the controller you posted the link of would be some / give some trouble to sync it with your grid. I is build to governor your engine speed with the grid frequency, your engine needs to run about 3,3 % faster then grid… so, i am not sure how to come around that, the simple way.
My case, needing a set that creates a “grid independency” in case of and or a total off grid solution.
1: Any hybrid grid converter can do
2: Can be enlarged or enhanced in a modular fashion
3: but above all, it reduces your need for a constant rpm per load on your engine… low loads can use low rpm and vice versa
Having the option using inductive motors to run as generator is very positive, in any configuration, but will they produce in off grid mode ? and what would be the cost to make that happen ?
In any case, your CHP project has my full attention, looking forward so see you making progress.
Grid tied inverters are the cheapest but not all are the same quality ( same as car audio amplifiers, some have big numbers but small bang’s )
Edit: ad link to some USA inverters