In this paper, a straightforward plug-and-play voltage ripple mitigator (RM) is proposed. Unlike existing voltage ripple reduction methods, the proposed device can be attached to the dc link of a hybrid ac-dc power system without modifying the host system itself. In particular, a local bus-voltage control scheme is employed to achieve the plug-and-play operation. With the requirement of the dc-link voltage measurement only, this device can be operated as a standalone module. Theoretical analysis and experimental work on a boost-type power factor correction rectification system have been successfully performed to validate the effectiveness of the ripple-mitigating function, the hot-swap operation and the nonintrusive property of the RM. Practical results obtained from a 110-W miniature hybrid ac-dc power system comprising an ac/dc converter and two resistive loads are included to demonstrate some of the functions of the RM.