Power Injection Method to Diminish Power Imbalance in a Modular Multilevel Cascaded H-bridge Inverter Fed Single Phase Grid-connected PV System

Cascaded H-bridge multilevel inverters suit well for grid-connected PV applications because of their modularity. Each H-bridge module of a Cascaded H-bridge inverter is connected to a PV source. Power imbalance arises when the PV sources generate unequal power. The inequality in power generated by the PV sources can be due to non-uniform weather conditions, damage and dusting of panels, and faults in the system. Power imbalance forces the H-bridge modules into overmodulation, distorting the grid current and thus affecting the system's reliability. Hence, to improve the system's reliability, a power injection method that curtails the power imbalance in the PV system is proposed in this paper. An algorithm is also developed to detect the power imbalance in the system and to calculate the suitable power to be injected for diminishing the power imbalance. The proposed methodology is verified with the simulation results obtained on MATLAB-Simulink.