Light and shadow - when is MPP-tracking at the module level worthwhile?

Recently, companies such as SolarEdge Technologies, National Semiconductors and Enphase Energy and others have brought products onto the market which allow maximum power point tracking (MPP-tracking) at the module level. These companies promise significant increases in yield through the use of their technologies. This paper attempts to highlight under which conditions the distributed MPP-tracking has an advantage over the conventional string approach.