Vertipaq is an engine which was found in Power Pivot for Analysis server in SQL Server 2008 R2. Basically, it is used for data compression. Data retrieval and calculations are happening at much faster rate as it holds the compressed data in memory. It is also called xVelocity and it has been added to SQL Server 2012. As a result, it is delivering very huge performance improvements for data warehouse and business intelligence solutions.
Columnstore index using this compression algorithm technology.
This algorithm using following compression techniques.
Check this link, for detailed information about VertiPaq Compression techniques.