Passivity-based Control of Single Phase Cascaded H-Bridge Grid-Connected Photovoltaic Inverter

This paper presents a nonlinear passivity-based control for a grid-connected cascaded H-Bridge (CHB) photovoltaic (PV) system. The proposed control system is based on a port-controlled Hamiltonian (PCH) model extracted from the synchronous reference frame (SRF) system. Grid current dynamics is included in this model. Compared to existing solutions, the proposed control method has a robust performance and enhances the stability of the CHB based PV system in the case of disturbances such as substantial unequal irradiance over distinct PV arrays or a sudden sag or swell in the grid voltage. This controller also provides the independent control of each dc-link voltage. Therefore, the individual maximum power point tracking (MPPT) algorithms can be realized in each PV array, and the harvested energy can be maximized. Finally, simulation results and experimental investigations are conducted to verify the effectiveness of the proposed strategy.