Mathematical model and control of a three-level boost converter used as electronic interface for fuel cell vehicles

Several topologies of dc-dc converters have been developed seeking a high voltage gain, high capability to power processing and high efficiency. The complete modeling of these devices allows the proper choice of components, as well as the design of controllers. This paper presents an average and small-signal modeling of the three-level boost converter (TLBC) characterized by reduced stress on switches, low electromagnetic interference and low voltage and current ripple. The static voltage gain of the converter is calculated based on the developed model and the influence of all parasitic resistances is evaluated, resulting in a graphical analysis and equations that allow the design of the components. Theoretical analysis and the mathematical results obtained are validated through simulations. A cascade control for terminal voltage is developed using PI controllers designed by the frequency response and root locus diagram obtained by the modeling. The results verify that the output voltage is maintained at the reference value in a vehicular application.

I. Introduction

For a fuel cell (FC) vehicle application, some characteristics of dc-dc converters that are interfaced with the dc bus are necessary, such as high efficiency, compactness, smaller volume and weight of components, low cost and high voltage gain [1], [2]. Furthermore, low frequency current ripple has a big impact on fuel cell efficiency, hydrogen consumption and life-spam [2], [3]. High current ripples can cause more degradation in the FC [2].