Аннотация:
Cascade H-bridge (CHB) inverter is an attractive choice for integration of DC sources of
different nature, e.g., for distributed generation with energy storage, photovoltaic generation, etc. In
general, non-equal DC voltage sources can affect the total harmonic distortion (THD) of the CHB by
introducing undesirable low-frequency subharmonics. This paper investigates different level-shifted
(LS) and phase-shifted (PS) pulse width modulation (PWM) strategies for single- and three-phase
cascade H-bridge inverters with non-equal DC sources from the load current THD minimization
perspective. The best current quality is provided by LS PWM, as reported in the literature. The paper
provides a simple time domain explanation of LS PWM superiority. However, PS PWM may be
a preferable choice for practical applications due to fair power and loss sharing across individual
H-bridges. The paper explains how to obtain the best current quality by PS PWM carriers’ order
arrangement (DC sources switching sequence selection).