This paper presents a straightforward approach to analyze the 2nd harmonic currents in modular multilevel converters. The submodule capacitor voltage ripple is derived based upon the capacitor’s charge variations instead of commonly used energy variations, resulting in simplified calculations and an explicit expression for the voltage ripple to calculate the ripple value and select a proper SM capacitor size. Using analysis of the dc-side loop, a closed-form expression for 2nd harmonics in the arm currents is obtained considering SM redundancy. To validate the theoretical analyses, a 101-level, 500-MW half-bridge MMC is simulated in PSCAD/EMTDC. Experimental results of a downscaled laboratory setup are also presented. Comprehensive comparisons of the theoretical results obtained by the proposed method against simulation and experimental results as well as against an existing method demonstrate its superior accuracy.