This paper presents the development of a prototype 400W alkaline fuel cell power conditioner. The power conditioner serves to boost the 4V DC produced by the fuel cell into 400V DC suitable for conversion to 230Vrms AC to power domestic loads. To compensate for the slow transient behaviour of the fuel cell a power flow buffer, incorporating supercapacitor energy storage has been developed which interfaces directly to the 400V DC bus. The result is a modular system where communication between system blocks is minimal and control is achieved by monitoring the 400V DC bus. Simulation results and experimental measurements are given for the prototype system, as well as a discussion of the practical design issues of the power electronic converters designed to operate with high voltage transformation ratios.