Abstract

Flywheel systems are attractive in hybrid and electric vehicles due to their ability to handle power during acceleration and braking. The combination of a flywheel device with a battery source has several advantages such as high peak power capacity, high energy density and reduction in the number of charge/discharge cycles of the battery. A flywheel based all-electric driveline is investigated in this thesis. The novelty of the system consists in the use of a double wound flywheel machine, which divides the system in two different power levels. Due to this configuration, the system becomes efficient and can handle the power developed during fast dynamical processes. The complete driveline consists of three main components: the battery, the flywheel machine and the wheel motor. The High-Power (HP) side of the driveline connects the flywheel machine to the wheel motor, whereas the Low-Power (LP) side connects the flywheel machine to the battery. The connections of different components of the system are made electrically through power converter devices. The present thesis focuses on the electrical converters and control strategies used in the flywheel based all-electric driveline. The control of power converters is responsible for the logic and functionality of the driveline, being a challenging step within this project. Different power converter topologies have been investigated: a DC/DC plus a DC/AC converter on the LP side, and an AC/DC/AC converter on the HP side. The design and assembly of the power electronics and their control scheme have been successfully implemented. Different control strategies have been suggested and a complete scaled driveline has been assembled and tested based on previous simulation results. Results have confirmed the functionality of the driveline, where smoothed output power has been obtained from the battery, whereas the flywheel handles power transients on the traction side. An average efficiency of about 87% (battery to wheels) has been obtained. The power converter systems have been shown to be efficient and robust, with control strategies able to handle the peak energy flow in the system. A regenerative braking strategy has been simulated and a wheel-to-wheel efficiency of about 80% has been estimated.

Abstract

To reduce emissions of air traffic, future aircraft will install hybrid-electric propulsion systems. We require the load conditions over the time in service, to design these aircraft. In this paper, we propose a mission profile for a regional aircraft with a hybrid-electric propulsion system. We focused on regional aircraft, which are in service in Ireland and the United Kingdom (UK). The reference aircraft ATR\\,72-600 is a turboprop aircraft with a capacity of 70 passengers. To propose a mission profile, we have analyzed more than 6000 flights of four different aircraft of the same type. Input data is provided by online databases, which collect flight data. We are able to show that the maximum available power is needed for about 52 seconds during take-off and climb phase of the flight. The median flight time is 59 minutes and 30 seconds. The average required power is 53\\,\\% of the maximum power. The average traveled distance is 407\\,km, which is less than one third of the aircraft's maximum reach. These findings are needed for calculating the lifetime of drivetrain components of a hybrid or all electric aircraft. In our further work, we will design an electric machine for regional aircraft. This mission profile will be used to design different power train components.