Boost Converter Inductor Design for High-Power Fuel Cells Using Pareto Optimisation for Single and Coupled Cores

Abstract: Hydrogen has been identified by the European Commission to be a competitive alternative to fossil fuels within the transport sector in the medium to long perspective. Because of this, an increased understanding is required of the electrical power train present within such vehicles. An integral aspect of these systems is the interface converter, which is located between the fuel cell and the rest of the power train. During the design process of high-powered fuel cell interface converters used in transport applications, it is important to achieve designs of low losses, size and cost. One of the most important parts to achieve these goals is the inductor present within the converter; this is generally the bulkiest part of the converter. To analyse how the inductor’s properties are affected by the converter topology, three different topologies have been analysed: the conventional single-phase boost converter and two versions a two-phase interleaved boost converter, where one uses two single inductors and the other an inversely coupled inductor. These three cases’ steady-state properties have then been characterised and used to select designs minimising either the self-inductance or the flux levels induced in the inductor, while maintaining a permissible input current ripple and continuous conduction mode throughout the converter’s operational region. Finally, a preliminary design framework has been developed for both the single and coupled inductors, where initially the so-called geometrical constant method and then a multiobjective optimisation method using evolutionary algorithms was used to design each inductor. Provided the optimisation framework was fed appropriate bounds and constraints, it was able to outperform the geometrical method. For the case of an inductor operating under a high DC bias, it was found that it is better to premiere a core material with a high saturation flux density over a reduction in the losses. Moreover, the inductor’s dimensions are reduced by using an inversely coupled core irrespective if the switching frequency was the same or halved compared to the test case of the conventional boost converter inductor. Irrespective of the switching frequency, a coupling factor of 0.55 is deemed to provide the best overall performance and most robust design at the price of a slightly worse transient response compared to using a stronger coupling.