Harmonic Compensation Strategy for Single-Phase Cascaded H-Bridge PV Inverter Under Unbalanced Power Conditions

Cascaded H-bridge (CHB) inverter has the advantages of easy modularization, the low harmonic content of output current, and that all power units are capable of achieving independent maximum power point tracking (MPPT). However, aging or partial shielding of photovoltaic (PV) panels will lead to the unbalanced output power of each PV module, which will result in the overmodulation of H-bridges and increased harmonic components of the grid current. In this article, a novel harmonic compensation strategy for single-phase CHB inverter is proposed, it can extend the linear modulation range of single-phase CHB inverters to about 1.27. Moreover, this strategy will not reduce energy harvesting, and also can maintain the system to operate in the unit power factor. Simulation and experimental results all verify the effectiveness of the proposed strategy.