Abstract—Many automotive companies are working in developing fuel cell powered Hybrid Electric Vehicles (HEV) because they offer a reduced emission and improves the fuel economy. The key technology for such development of fuel cell for propulsion is the power electronics. This paper reports different DC/DC converter topologies used to interface the fuel cell to the motor controllers in HEVs. The aim is to present a simple and practical boost converter topology with a coordinated control that can regulate both the output voltage and the input current simultaneously. The performance of the proposed power conditioning system is evaluated is simulation results under different dynamics. I. INTRODUCTION A considerable amount of research is in progress to develop fuel cells as energy conversion devices. Fuel cells are especially attractive because it is the only current technology capable of reducing vehicle emissions and fuel consumption by a large amount in a short period of time [1]. Fuel cells are presently being considered for use in automotive systems to replace the internal combustion engines in buses, vans, and ultimately passenger cars [2]. Fig. 1 portrays the electrical components required for fuel cell powered Hybrid Electric Vehicle (HEV). The DC voltage required for the three-phase inverter to control the AC motor is in the range of 200 to 500 volts, while the voltage of the fuel cell is in the order of 60V (for the commercially available 10 KW module). The fuel cell is the main power source, however its power density is low. A storage unit such as battery or ultra-capacitor banks must be integrated with this system, which is not shown for simplicity, to supply the peak power demand during transient conditions, since the dynamic response characteristics of fuel cells is much slower than that required for traction [3]. The DC/DC converter boosts the fuel cell voltage to the required voltage of the motor controller. The major challenge in designing automotive fuel cell power systems is converting the electrical output from the fuel cell into a usable power [4]. In addition, the DC/DC converter must be implemented cost effectively with suitable weight and volume. Many DC/DC converter topologies with their control strategies are proposed in the literature [5]. A push pull derived half bridge or full bridge type DC/DC converter with transformer isolation is suitable for the application, because of the higher power rating and the significant boost required in the DC voltage [6], [7]. Despite the simplicity of the control techniques for the isolated types of DC/DC converter, their main drawbacks are the additional weight of the transformer and their packaging volume. Resonant DC/DC converter is proposed to interface the fuel cell to the power train in [8], [9]. This type of converters has the privilege of reduced switching losses due to the soft witching. However, the large number of electrical components utilized to build the resonant converters beside that there is no direct method to control the input current are the disadvantageous of this converter topology. Fig. 1. block diagram of the fuel cell interface system. The objective of this paper is to present a simple DC/DC converter, shown in Fig. 2, with a robust controller for the fuel cell powered HEV. As a result, reducing the volume and weight of the converter will enable significant improvements in power density. The proposed controller can provide a programmable and regulated high voltage to the motor controller as well as controlling the input current of the fuel cell. It can handle the load dynamics and the variation of the input voltage of the fuel cell. Fig. 2. block diagram of the fuel cell interface system. M. I. Marei, S. Lambert, R. Pick, and M. M.A. Salama University of Waterloo, Waterloo, Ontario, Canada Tel. (519) 888 4567 x.7052, Email: mimmarei@engmail.uwaterloo.ca DC/DC Converters for Fuel Cell Powered Hybrid Electric Vehicle 0-7803-9280-9/05/$20.00 ©2005 IEEE. 556