LCL filter utilized in battery charging applications to achieve compact size and low ripple charging

In this paper, an LCL filter is proposed to replace L-type filter in a dc/dc converter for battery charging applications. The merits of using an LCL filter are compact size, and extremely low ripple of charging current. The ripple free charging can reduce the heat generated by the ripple of the charging current and improve the battery lifetime. Filter based controller is proposed to solve the control loop instability issue caused by LCL filter. Low-pass filter and notch filter based controllers are designed and compared. The controller robustness to the variation of the filter parameters is investigated. The proposed system and control methods are verified by simulation and experiment.