Incremental refresh feature is released  in May 2018, it is traditionally reserved for large models (Like more than 1 GB) in analysis servers for high-end scalability of data by publishing only to workspace in Power BI Service where Premium capacity is enabled for them. Eg: It will increase the speed and efficiency of data refresh by just refreshing the data changes in last 1 day -10 days instead of loading last 3 years of data. To enable it just right click on tables in fields pane and enable Incremental refresh.