Performance Simulation Of Photovoltaic System Battery

Solar energy, despite being inexhaustible, has a major shortcoming; it is intermittent. As a result, there’s a need for it to be stored for later use. The widely used energy storage in photovoltaic system applications is the leadacid battery and the knowledge of its state-of-charge (SOC) is important in effecting efficient control and energy management. However, SOC cannot be measured while the battery is connected to the system. This study adjusts and validates two estimation models: battery state-of-charge model using ampere-hour counting method and battery charge voltage model. For the battery state-of-charge model, the SOC is estimated by integrating the charge/discharge current over time while the battery charge voltage characteristic response is modelled by using the equation-fit method which expresses the battery charge voltage variations by a 5th order polynomial in terms of the state-of-charge and current. These models are realized using the MATLAB program. The battery charge voltage model is corrected for errors which may result from reduced charge voltage due to variation of solar radiation using the battery state-of-charge model. Moreover, the starting SOC needed in the state-of-charge model is estimated using the charge voltage model. The accuracies of the models are verified using various laboratory experiments. Keywords-Charging efficiency, Lead–acid battery, Photovoltaic system, State-of-charge