Performance Evaluation of Pulse Width Modulation Techniques for Losses Reduction in Modular Multilevel Flying Capacitor Converter

This paper presents the analysis and evaluation of power losses in a modular multilevel flying capacitor converter (MMFCC) controlled by three different pulse width modulation techniques. A new unipolar hybrid PWM scheme, which combines phase disposed PWM (PD-PWM) and phase shifted PWM (PS-PWM), is proposed. Detailed electrical and thermal models of the single star configured FC cells are implemented and simulated using MATLAB/SIMULINK and PLECS. The conduction and switching losses of semiconductor devices and power losses of floating capacitors in the simulated MMCC are evaluated. The results show that the proposed PWM scheme gives the lowest overall power losses and hence the highest efficiency of the three methods under different modulation index variations. Furthermore, the quality of the voltage waveform of the proposed method is as good as that obtained by using PS-PWM.