In the Purchase Order Processing module, there is no standard functionality to automatically receive and invoice an order. This would need to be added by a developer.

However, in the Purchase Ledger module, there can be an authorisation process for purchase invoices - see here.  This is simpler than POP authorisation but may do what you need - and it does apply to imported transactions (as you mentioned "feed purchase invoices", which implies some degree of automation)

Of course there is a lot more to POP, but if you don't need to record what goods/services are being invoiced, you may find that posting the invoices directly to the Purchase Ledger meets your needs.