Abstract

Purpose – A standalone microgrid (MG) is able to use local renewable resources and reduce the loss in long
distance transmission. But the single-phase device in a standalone MG can cause the voltage unbalance
condition and additional power loss that reduces the cycle life of battery. This paper proposes an energy
management strategy for the battery/supercapacitor (SC) hybrid energy storage system (HESS) to improve the
transient performance of bus voltage under unbalanced load condition in a standalone AC microgrid (MG).
Design/methodology/approach – The SC has high power density and much more cycling times than
battery and thus to be controlled to absorb the transient and unbalanced active power as well as the reactive
power under unbalanced condition. Under the proposed energy management design, the battery only needs to
generate balanced power to balance the steady state power demand. The energy management strategy for
battery/SC HESS in a standalone AC MG is validated in simulation study using PSCAD/EMTDC.
Findings – The results show that the energy management strategy of HESS maintains the bus voltage and
eliminates the unbalance condition under single-phase load. In addition, with the SC to absorb the reactive
power and unbalanced active power, the unnecessary power loss in battery is reduced with shown less
accumulate depth of discharge and higher average efficiency.
Originality/value – With this technology, the service life of the HESS can be extended and the total cost can
be reduced.