Power control strategy of an off-grid PV/battery hybrid system implemented through the V2H concept for improving autonomy and lifespan

Solar PV/battery systems are one of the well-known and widely used renewable energy systems for the electrification of isolated areas worldwide. Since Photovoltaics output is not stable and varies throughout the day, a battery system is required to store the energy and provide it when needed, at high loads or limited sun. Given the challenges of autonomous operation, battery storage systems are exploited to smooth the supply from PV systems while presenting an operational strategy based on forecasting of power required. In addition, the V2H (Vehicle to Home) technology can be applied, so that an electric vehicle can utilize the excess electricity from the PV for charging, or to provide the necessary power, in order to satisfy the house needs when production is low or the utility electricity price is high. Hence battery depletion or operation at high voltage is avoided so lifespan to be increased. The aim of this study, is the design, control and monitoring of an autonomous solar energy system of 520W of power, operating at 24V through a DC Bus. The supplied power is autonomously determined according the available power from the panels, the total load demand and the batteries’ state of charge (SOC). A rule-based strategy is tested as the hybrid system will be monitored by the Multi Power Point Tracking (MPPT) in order to ensure voltage and frequency regulation. In the results it can be seen, that the battery acts as an auxiliary source for the PV, in order to avoid increased stress caused by high temperatures and constant 100% SoC operation. The MPPT was not active most of the time of the test, as the total 1.2kWh were generated, could easily handle the output required by the AC Bus. In total, battery SoH dropped only 0.3%, which is too low for AGM battery technology. Lastly utilization through the Vehicle to Home (V2H) system where the collaboration of an electric vehicle and this unit ensures maximum energy autonomy for the smart home, EV and PV factors leading to a sustainable off - grid system.