Energy management by using point of common coupling frequency as an agent for islanded microgrids

This study presents an islanded AC microgrid system composed of distributed generations (DGs) and an energy storage system. The valve-regulated lead acid battery bank is used as the energy storage device. A non-linear energy management control strategy is proposed by utilising the point of common coupling (PCC) frequency as an agent for all the constituent units, which avoids any communication lines among the constituent units. Based on the system modelling, the stability criterion for the proposed control strategy has been established. The proposed energy management is effective even when the battery is fully charged and DGs can supply more power than the load consumption. For this extreme situation, all DGs can automatically reduce their output power until the battery works in float charge state. The effectiveness of the proposed strategy is verified by simulation and experimental results.