Memory error when refreshing

I would suggest ensuring that you only include the columns that you require.

Also possibly some of the data has a high level of cardionality, which is causing the data not to compress as efficiently as it should?

Another tip is if you are doing any calculated columns in the Power BI Model, to move the ones that you can into the Query Editor. The reason for this is that due to the columns being computed before the xVelocity engine completes it's tasks, this will cause the columns to be more efficiently compressed. Which in turn could save you memory.