What is the use of chloroform in the procedure of determining peroxide value?
Acetic acid is required for this method for exactly the reason you gave.  It also has the fortunate property of being miscible with many polar and non-polar solvents.  Because this is a method for the analysis of oil samples, it is necessary to chose a non-polar solvent capable of dissolving the sample that is also miscible with the acetic acid.  Chloroform is one solvent that fits that description nicely.

As a quick side-note, the use of chloroform in this test procedure is actually now discouraged by the Standard Methods for the Analysis of Oils, Fats and Derivatives.  Isooctane seems to be the preferred solvent, apparently for health and safety reasons.