Active Power Sharing Scheme in a PV Integrated DC Microgrid With Composite Energy Storage Devices

This paper presents a combined application of battery and supercapacitor as composite energy storage devices (CESDs) in the DC microgrid. The purpose of CESD is to compensate the power imbalance caused by the intermittency of renewable sources and varying load demands. The power allocation in the composite energy storage system is a major concern and also it remains a challenging issue in conventional techniques. Hence, in this article, the problem is resolved by implementing an improved mixed droop technique (IMDT) with optimized steady-state as well as transient performances. With the proposed technique, the supercapacitor compensates all the fast power fluctuations in the system, while the battery supplies only the average power at steady-state. This control strategy advances the consistency of the system, dynamic restoration of the DC bus voltage, and reduces current stress from the battery units. MATLAB simulation is conducted to validate the effectiveness of the proposed strategy. Also, the scheme is verified for a large-scale 71 kW PV generating system through simulation.

Keywords: — DC microgrid, composite energy storage devices, active power sharing schemes, improved mixed droop technique, and automatic DC bus voltage restoration.