Small-Signal Modeling of the Single-Phase Asymmetrical Cascaded Multilevel Inverter

This paper presents a small-signal model of the single-phase asymmetrical cascaded h-bridge multilevel inverter (ACHMI), mainly related to several applications like voltage/current controllers design, power factor control and active power filter, related or not to photovoltaic (PV) systems. The multilevel inverter considered in this work has the asymmetrical configuration, and its individual dc-link voltages are scaled by the factor (1:2:6:.), which guarantee a low Total Harmonic Distortion (THD) in the output voltage. The proposed small-signal model is presented step-by-step considering a case of study related to 3 h-bridge series connected in order to compose the asymmetrical cascaded multilevel inverter topology. An average model ('large-signal model') is also presented and both models are discussed in terms of linearization and disturbance rejection around an operational point. A computational model has been developed and tested in MATLAB/SIMULINK environment. Simulation results are presented and discussed in terms of model validation. Tracking performance from the small-signal model was pursued and some conclusions are also presented. Briefly, the model performance validated the approach method of modeling and its capability to emulate the dynamical behavior of the asymmetrical cascaded topology.