Predictive Control of Grid-Connected Modified-CHB With Reserve Batteries in Photovoltaic Application Under Asymmetric Operating Condition

The system stability and injection of maximum active power to the grid are among the most important technical issues in cascaded H-bridge (CHB) based photovoltaic (PV) systems, especially when the irradiation of PV arrays connected to CHB cells are not uniform. In other words, the unequal irradiation of PV arrays leads to the unbalanced output power of H-bridge cells, which causes overmodulation and increased grid current total harmonic distortion in the CHB inverter. Conventional control methods cannot maintain the stability of a grid-connected CHB inverter under asymmetric operating conditions. So, this article proposes a new CHB-based structure with reserve batteries and a novel modulation technique to stabilize the system in heavy mismatching conditions and avoid overmodulation. Furthermore, the number of switches and series batteries is reduced, and the number of output voltage levels is increased compared to the conventional PV-CHB system with energy storage. The validity of the proposed solution is verified by simulation in MATLAB/Simulink, and then the experimental results are presented to confirm the theoretical and simulation results.