The large number of voltage levels in a modular multilevel converter (MMC) make staircase modulation a feasible alternative, particularly in high-power applications. However, staircase waveforms do not necessarily mean operation of the MMC submodules (SMs) at fundamental frequency. This paper presents an analysis of SM switching frequencies in staircase modulated MMCs and their correlation to the modulation index and load phase angle. A carrier based pulse-width modulation (CB-PWM) equivalent technique is also developed. The presented analysis demonstrates that CB-PWM techniques provide similar switching frequency with superior harmonic performance and improved voltage balancing characteristics at all modulation indices compared to staircase modulation. The theoretical analysis is verified with extensive simulation results for MMCs with different number of SMs and experimental results from a laboratory prototype.