An enhanced three-phase battery energy storage system for frequency control in microgrids

This paper presents a three-phase battery energy storage system (BESS) operating in both microgrid (MG) connected and islanded modes. When connected to the MG, an enhanced frequency controller, covering the main two frequency control levels, i.e. primary and secondary, governs the BESS active power. If the MG power quality worsens below a certain level, the system is able to switch in island mode and to supply the local loads. The reconnection is accomplished only after the BESS voltage is smoothly resynchronized with the MG voltage. The proposed control solution for a three-phase BESS is assessed by means of computer simulations.