Design and evaluation of an active ripple filter with Rogowski-coil current sensing

An active ripple filter is an electronic circuit which cancels or suppresses the ripple current and EMI generated by the power stage of a power converter, thus reducing the passive filtration requirements. This paper presents the design and evaluation of a feedforward active ripple filter which employs a Rogowski coil for ripple current sensing. The design of the active filter is discussed in detail, including the advantages, tradeoffs, and limitations of the approach. Experimental results from a prototype converter system using this approach are presented, and quantitative comparisons are made between a hybrid passive/active filter and a purely passive filter. It is demonstrated that substantial improvements in filter mass and converter transient performance can be achieved using the proposed active ripple filtering method.