Abstract
A grid energy storage system for photo voltaic (PV) applications contains three different
power sources i.e., PV array, battery storage system and the grid. It is advisable to isolate these three
different sources to ensure the equipment safety. The configuration proposed in this paper provides
complete isolation between the three sources. A Power Balancing Control (PBC) method for this
configuration is proposed to operate the system in three different modes of operation. Control of a
dual active bridge (DAB)-based battery charger which provides a galvanic isolation between
batteries and other sources is explained briefly. Various modes of operation of a grid energy storage
system are also presented in this paper. Hardware-In-the-Loop (HIL) simulation is carried out to
check the performance of the system and the PBC algorithm. A power circuit (comprised of the
inverter, dual active bridge based battery charger, grid, PV cell, batteries, contactors, and switches)
is simulated and the controller hardware and user interface panel are connected as HIL with the
simulated power circuit through Real Time Digital Simulator (RTDS). HIL simulation results are
presented to explain the control operation, steady-state performance in different modes of operation
and the dynamic response of the system.