A Matching Scheduling Control Strategy Based on Modulation Wave Reconstruction for the Single-Phase Photovoltaic Cascaded Multilevel Inverter

Abstract

The single-phase cascaded multilevel inverter (CMI) becomes an attractive solution for grid-connected photovoltaic (PV) power generation owing to its several advantages, such as the scalable modularity, the ability to reach the component level maximum power point tracking (MPPT), and the multilevel output voltage. However, the PV power of each H-bridge (HB) is uneven due to unequal illumination and partial shading of the PV panels, which may lead to overmodulation and further deteriorate the power quality of the grid-connected current. Existing methods to address this issue have not considered the effects on various operating conditions, and their application scope is limited. Therefore, this paper proposes a matching scheduling control strategy based on modulation wave reconstruction (MSMR). The relatively optimal modulation waveform of each HB is reconstructed scheduledly to match its PV power by detecting the operating conditions. Meanwhile, the PV power of each HB is adjusted to improve the ability to cope with the power unevenness. Finally, the proposed strategy is validated on a down-scaled experimental test bench.