A Theoretical and Experimental Analysis of N+1 and 2N+1 Phase-Shifted Carrier-Based PWM Strategies in Modular Multilevel Converters

This paper presents a detailed theoretical and experimental analysis of N + 1 and 2N + 1 phase-shifted carrier-based PWM strategies (PSPWM) in modular multilevel converters (MMC). The reason why N + 1 and 2N + 1 voltage levels can be generated with different shifted phase angles and sub-module numbers is explained via theoretical analysis, and the harmonic contents of different PWM strategies are analyzed and compared by analytical double Fourier analysis method. To verify the validity of the above analysis, inverter models were built in MATLAB/Simulink. Moreover, a small-scale prototype has been developed so as to provide detail experimental results.