Improved Performance of Grid-Tied Photovoltaic Cascaded H-Bridge Inverter with Embedded Storage Units

Abstract

In this paper a grid-tied photovoltaic (PV) cascaded H-bridge (CHB) inverter with embedded storage units is proposed. The multi-input single-output inverter architecture allows a distributed maximum power point tracking (DMPPT) approach, thus mitigating the mismatch effects. The energy storage units (ESUs) embedded at each dc-link provides more flexibility to the power circuit compensating for the inherent variability of the PV sources. The proposed power system ensures a continuous power supply to the grid also in case of PV power fluctuations due to irradiance conditions as well as to the MPPT. In particular, the presence of a storage element allows a voltage sweep on the PV source to be implemented, thus guaranteeing the maximization of PV energy harvesting, with no detrimental effect on the power delivery to the utility network. The numerical results, carried out on a single-phase nineteen-level PV CHB inverter, reveal the improved performance of the proposed design and control technique.