Ripple Suppression Method for Battery Energy Storage System Based on Separated Capacitor

In cascaded high voltage battery energy storage systems, second harmonic pulsating currents are introduced into the battery when the H-bridge unit interacts with the grid to absorb energy. This phenomenon increases system losses, reduces battery life, and jeopardizes battery safety. Traditional methods are usually used such as LC passive filtering; these solutions are simple but have the disadvantages of large device size and high cost. In order to solve these problems, this paper proposes a symmetric separation capacitor decoupling circuit. The DC active filter circuit is utilized to absorb the DC chain ripple current and reduce the ripple current flowing into the DC port of the cascaded H-bridge energy storage converter. This design provides a compact structure, reduces the cost of passive components, simplifies the control and effectively suppresses the pulsating power. Finally, the effectiveness of the active filtering method to reduce the DC chain ripple current is verified by simulation.