Comparative analysis of carrier schemes for PWM in multilevel PUC inverter for PV applications

This paper presents an evaluation of two modulation methods for the seven-level packed U cell (PUC) inverter for photovoltaic applications. The PUC is a multilevel inverter which has less number of switching devices than the conventional multilevel inverters. The PUC inverter is in modular configuration consisting of one U-cell and four additional power switches, one dc link and an auxiliary capacitor. A U cell is called an arrangement of two power switches and one flying or clamping capacitor. In this paper, the level-shifted (LS-PWM) and phase-shifted PWM (PS-PWM) for triangular carrier are presented and compared. Harmonic analysis for both the cases has been performed and phase-shifted triangular carrier has been found to have the minimum harmonics. The difference in harmonics of the two modulation methods for the triangular carrier is confirmed by the theoretical approach and verified by simulation in MATLAB® Simulink environment, and simulation results are presented and discussed in the paper.