Battery-supercapacitor hybrid energy storage system with reduced low frequency input current ripple

Battery-supercapacitor hybrid energy storage systems (HESSs) are popular as a way of extending the battery lifetime by reducing the battery current fluctuations. In conventional single phase HESSs, both the second-order harmonic power component and the fast power fluctuations are allocated to the supercapacitor. However, the ripple current component leads to supercapacitor degradation due to its internal heating. In this paper, a current-feedback ripple current reduction method is applied to a single-phase battery-supercapacitor HESS in order to alleviate the second-order harmonic supercapacitor current component. Effectiveness of the ripple current reduction method is theoretically analyzed. Experimental results show that the current-feedback method is able to significantly decrease the second-order harmonic component in the supercapacitor current without introducing additional harmonics.