Instantaneous Ripple Energy Balancing Control to reduce Input Ripple Current in Grid connected BESS

The cascaded-H bridge converter (CHBC) has become one of the most popular converter topologies for grid-scale battery energy storage. The single phase inverter employed in CHBC modules draws low harmonic ripple power from the DC bus which results in ripple currents being drawn from the battery. The low frequency ripple current can severely degrade battery life. Moreover, a large DC bus capacitor is needed to limit the resulting DC bus voltage oscillations. This paper proposes an energy-balancing based control of a buck type active power filter (APF) to buffer the ripple power of multiple orders being drawn from the battery. Also, the proposed control allows utilizing a lower value of DC bus capacitor, which will result in reduced size and improved reliability. Real-time hardware-in-the-loop simulation results verify the validity of the proposed method.