Comparison of PWM Techniques for Modular Multilevel Converter: A Comparison Based on Different Voltage Level Waveforms

Various pulse width modulation (PWM) techniques for modular multilevel converter (MMC) are studied and compared in this work. The analysis of both level-shift (LS) methods and phase-shift (PS) methods are conducted. This analysis is based on the fundamental pulse and pattern generations which only result from the comparison of triangular carrier and sinusoidal reference signals. The two fundamental PWM methods (LS and PS methods), are used for N+1 or 2N+1 phase-to-neutral voltage levels at the output of the converter. A comparative study is carried out on the basis of the spectral quality of the output voltage waveforms. Numerical Simulation are performed under MATLAB/Simulink environment for various PWM techniques in order to verify the effectiveness of the presented techniques for the different levels.