Modular multilevel converter modulation using fundamental switching selective harmonic elimination method

Abstract

This paper address the issue of low order harmonics in a modular multilevel converter (MMC). Using fundamental switching selective harmonic elimination (SHE), the control angles are calculated from nonlinear equations by Newton-Raphson method. The selective harmonic elimination equations are solved in such a way that the first switching angle is used to control the magnitude of the fundamental voltage and the remaining angles are used to eliminate the lowest odd, non-triplen harmonics components as they dominate the total harmonic distortion of the converter. The concept is validated using a 9-level detailed model of MMC in PSCAD/EMTDC®. The simulation result shows a good agreement with theoretical analysis and in comparison with conventional sinusoidal pulse width modulation (SPWM), the proposed method, eliminates low order harmonics, leading to a low total harmonic distortion.