A control method for grid-friendly photovoltaic systems with hybrid energy storage units

This paper proposed a systematic control strategy to make the interconnected photovoltaic (PV) systems more grid-friendly. The investigated PV system comprises PV arrays, lead-acid battery, super-capacitor, DC/DC and DC/AC power converters. In order to make this system work as a classical generator to participate in grid regulation, the constant active/reactive power control is implemented in the controller of the DC/AC converter which connects the DC bus of the PV system and the main grid. The DC bus voltage is coordinately controlled by super-capacitor and battery. The maximum power point tracking (MPPT) control is applied to extract maximum power from PV panels. The power management scenarios for the interconnected PV system were discussed and the experiment results were given to validate the feasibility of the proposed control strategy as well.