DC Load and Batteries Control Limitations for Photovoltaic Systems. Experimental Validation

Abstract—This study first presents an experimental control strategy of photovoltaic (PV) system composed of: PV array, dc–dc  power converters, electrolytic storage, and programmable dc electronic load. This control aims to extract maximum power from PV array and manages the power transfer through the dc load, respecting the available storage level. The designed system allows simultaneously the supply of a dc load and the charge or the discharge of the storage during the PV power production. The experimental results obtained with a dSPACE 1103 controller board show that the PV stand-alone system responds within certain limits that appear as soon as one of the storage thresholds is reached: either loss of energy produced, or insufficient energy toward the load. In urban area, it is proposed to overcome these limitations by connecting the utility grid with the PV system while maintaining the priority for self-feeding. The experimental results of this PV semi-isolated system are shown and discussed. For this first approach, the goal was to verify the technical feasibility of the suggested system controls. The final results are energetically relevant. Index Terms—AC–DC power converters, batteries, dc–dc power converters, maximum power point tracking (MPPT), photovoltaic (PV) power system, power grid, power system control.