3832 IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 26, NO. 12, DECEMBER 2011 New Method to Filter HF Current Ripples Generated by Current-Fed DC/DC Converters Ahmed Shahin, Member, IEEE, Roghayeh Gavagsaz-Ghoachani, Jean-Philippe Martin, Serge Pierfederici, Bernard Davat, Member, IEEE, and Farid Meibody-Tabar Abstract—This paper presents a new method for filtering the HF current ripple generated by current-fed dc/dc converters. This method is based on the use of an active filter connected in parallel with the source, without any passive filter between the source and the power converter. The design of this new active filter and its as- sociated controllers are fully explained in the paper. Experimental results validate the proposed filtering method. The structure of the proposed active filter is patented at the World Intellectual Property Organization under the number WO/2008/132318. Index Terms—Active filter, chaos, current ripple, dc/dc converters. I. INTRODUCTION A LTERNATIVE energy sources like fuel cells are consid- ered one of the most promising sources of distributed energy due to their high efficiency, low environmental impact, and scalability. Unfortunately, multiple complications exist in such energy sources. For example, fuel cells cannot accept cur- rent in the reverse direction, do not perform well with current ripple, and have a low output voltage that varies with age. Fur- thermore, the output current responds slowly to load variations, and fuel cells are limited in overload capabilities [1], [2]. For these reasons, power dc/dc converters are often necessary to step up and regulate the user voltage. In order to reduce the current ripple in the input stage of current-fed dc/dc converters, many solutions have been proposed. Some authors use conventional current-fed push–pull isolated converters, which are limited for HF applications. This configuration has many components and this increases the losses. Although a distinguishing feature is that the input switching current ripple of these converters is ex- tremely low at duty cycles around 0.5 [3], [4]. Other authors Manuscript received June 23, 2010; revised November 10, 2010 and February 1, 2011; accepted March 11, 2011. Date of current version December 6, 2011. Recommended for publication by Associate Editor J.-L. Schanen. A. Shahin is with the Department of Electrical Engineering, the Faculty of Engineering, El-Mansoura University, El-Mansoura, Egypt, and also with the ´ Ecole Nationale Sup´ erieure d’´ electricit´ e et de M´ ecanique, Institut National Polytechnique de Lorraine, Nancy-Universit´ e, 54516 Nancy, France (e-mail: Ahmed.Shahin@ensem.inpl-nancy.fr). R. Gavagsaz-Ghoachani, J.-P. Martin, S. Pierfederici, B. Davat, and F. Meibody-Tabar are with the ´ Ecole Nationale Sup´ erieure d’´ electricit´ e et de M´ ecanique, Institut National Polytechnique de Lorraine, Nancy-Universit´ e, 54516 Nancy, France (e-mail: Roghayeh.Gavagsaz-Ghoachani@ensem. inpl-nancy.fr; Jean-Philippe.Martin@ensem.inpl-nancy.fr; Serge.Pierfederici@ ensem.inpl-nancy.fr; Bernard.Davat@ensem.inpl-nancy.fr; Farid.Meibody- Tabar@ensem.inpl-nancy.fr). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TPEL.2011.2134870 Fig. 1. Scheme of power architecture. propose to use isolated converter structures using zero-current switch or zero-voltage switch techniques with input filter in or- der to increase the switching frequency. This allows reduction of the current ripple rate but the converter contains an isolat- ing transformer [5]. Half-bridge inductive dc/dc converters can also be considered. They are deduced from an interleaved boost converter by introducing a transformer and a diode bridge at its output. However, the duty cycle must be greater than 0.5, and the leakage inductance of the transformer constitutes the main drawback of this structure, which can generate voltage spikes [6], [7]. Other authors use coupled inductance in the power converter with a hybrid filter. In this case, a special de- sign of the coupling inductance is needed [8]. Interleaved boost converters are also considered in [9]–[12] to minimize the HF switching ripple. This scheme at higher power can suffer from transformer flux imbalance and core-saturation problems. In [13], adding a low power converter, a mirror of the power converter, is proposed. To avoid circulating current, a capacitor bank is necessary and this structure presents the other drawback to be only efficient in steady state and under continuous-conduction mode (CCM). Another solution, which allows reducing the current ripple at the output stage of a static converter, is proposed in [14]. However, this solution needs continuous voltage source at the output stage of the converter and is used only for small power converters. In this paper, a new active filtering method to actively damp the current ripples generated by dc/dc converters is proposed. This filtering method can be applied for a wide range of power and is based on the connection of an active filter in paral- lel with the main converter (see Fig. 1). The control of this 0885-8993/$26.00 © 2011 IEEE