MMCs for HVDC applications normally adopt a distributed control system to manage considerable submodules in the system. The manufacturing tolerance of crystal oscillators for local controllers introduces controller clock discrepancy and eventually leads to the asynchrony of triangular carriers implemented in individual submodule for phase-shifted PWM scheme. The submodule asynchrony introduces harmonics around the carrier frequency. The asynchronous switching actions deteriorate the performance and stability of MMCs. Models describing the arm currents, capacitor voltages, and arm voltages with the presence of submodule asynchrony are proposed. Good agreements have been achieved between the theoretical calculations and experimental results.