Soheil Bakhshi starts off a series on incremental refresh in Power BI:
Incremental refresh, or in short, IR, refers to loading the data incrementally, which has been around in the world of ETL for data warehousing for a long time. Let us discuss incremental refresh (or incremental data loading) in a simple language to better understand how it works.
Read on for the explanation as well as how you can implement it in Power BI Desktop. There are a lot of instructions here but they include publication and testing as well as development.