A Flexible DC–DC Converter with Multi-Directional Power Flow Capabilities for Power Management and Delivery Module in a Hybrid Electric Aircraft

Abstract

The development of fully electric and hybrid electric aircraft using fuel cells and batteries has lately received much attention since the technology can contribute to achieving an emission-free world. For hybridisation of fuel cells and batteries, the challenge of integrating different voltage sources to supply power to different loads at different voltage levels has to be met. Presently, this is achieved by using a combination of complex passive circuitry and DC–DC converters. In this paper, a new galvanically isolated DC–DC converter topology is proposed; it integrates a battery and fuel cells as input sources and supplies power to a high voltage (HV) and a low voltage (LV) load simultaneously. The converter enables power flow from the sources to the load, as well as between the sources and power flow back towards the battery during recuperation for recharging the battery during flight. The functionality of the converter design is verified using a real-time (RT) hardware-in-the-loop (HiL) test. The proposed concept is easily scalable and can be adopted in any fuel cell and battery drive train of all-electric flights of different sizes.

Switching Logic for a Direct Hybrid Electric Powertrain

“…In a direct hybrid, however, the battery and the fuel cell are connected in parallel without a DC/DC converter that adapts the voltage levels Different hybridization concepts exist, and the usual approach is the connection via a DC/DC converter. This approach is for instance used by Bhattacharya et al [19] and Ng et al [16], where the connection of the hybrid system is achieved via a DC/DC converter to adapt the voltage level. However, the use of a direct hybrid without DC/DC has advantages [20] even though this approach is not yet state of the art.…”

“…The most common hybridization method is to link the fuel cell and the battery with the help of one or even two DC/DC converters that adjust the voltage levels of both energy sources to the load voltage [16,19]. In a direct hybrid, however, the battery and the fuel cell are connected in parallel without a DC/DC converter that adapts the voltage levels [14,21].…”

Optimal Sizing of Fuel Cell and Battery in a Direct-Hybrid for Electric Aircraft

“…The development of suitable tanks as well as the integration into the aircraft is currently an important research topic [16,17]. The usual approach is to connect the fuel cell and the battery into a hybrid system with the help of one or even two DC/DC converters that adapt the voltage levels of both energy sources to that of the load [18]. There are several studies on the design and sizing of components using DC/DC converters.…”