Power Distribution Method for Single-Phase Cascaded Multilevel Converters Based on Space Vector Modulation

Abstract

Cascaded H-bridge converters are interesting candidates for photovoltaic (PV) and energy storage systems, since PV panels and/or batteries can be directly connected to the input dc-side of each converter module. However, differences in the parameters of the batteries or variable ambient conditions may result in energy imbalances among the power modules. In these cases, conventional modulation strategies will lead to an increased distortion on the converter output voltage. Therefore, this paper proposes a generalized space vector modulation for single-phase cascaded H-bridge converters considering the power processed by each power module and maintaining a low-THD multilevel output voltage waveform. The proposed method improves the converter output voltage harmonic spectrum compared to the conventional phase-shifted modulation strategy in cases of power imbalance among modules. Experimental results are included to demonstrate the performance of the proposed method.