Energy management strategy of multiple supercapacitors in an autonomous DC microgrid using adaptive virtual impedance

Supercapacitors (SCs) are increasingly used in energy storage system (ESS) to tackle the fast power transients. They can be used individually or together with other energy storage units like batteries. In a microgrid, multiple SCs could be installed at different locations without communication among each other. This paper addresses the energy management strategy (EMS) of multiple SCs in a DC microgrid, where the distributed generation (DGs) units and energy storage units are controlled with the plug-n-play feature. A novel EMS is proposed, which uses the state of charge (SOC) based adaptive virtual impedance to facilitate the transient power sharing among the parallel SCs without physical communications. The detailed analysis and design procedure are explained based on an example microgrid system with two SCs and one battery energy storage connected in parallel through the DC/DC converters. The effectiveness of the proposed method is verified by simulation and experimental results.