Design and Control of a DC-DC Converter for Energy Recovery in an Electric Vehicle with a Fuel Cell and Supercapacitor packs

Abstract

The BEAMS Energy department in collaboration with the ATM department, at the ULB, has already participated for some years in the Shell Eco-Marathon. For this race the participating teams have to build a vehicle which must cover as many kilometers as possible with a certain quantity of energy. During the race only the driver is present in the vehicle. Given the goal of the race, a high efficiency of the complete powertrain is a priority in the design-phase.
They want to equip one of the two chassis, which are present at the service of BEAMS, with a hybrid powertrain consisting of a fuel cell (as primary energy source) and a supercapacitor (as a power peak rechargeable energy unit). Fuel cells and supercapacitors have complementary characteristics concerning energy and power density. Consequently engineers try to exploit these complementary properties in power sources for both stationary and mobile applications. The ATM department provides a PEM fuel cell for the realization of the vehicle. The supercapacitors still had to be purchased at the start of this dissertation.
On the end of last academic year two thesis-topics were proposed for the design of the desired hybrid propulsion. One of these two is realized by my fellow-student Lydie Straus, the second by me.
The objectives of the project can be summarized as follows:
* Modeling the operation of the various elements of the system using Simulink (MATLAB).
* Selecting the supercapacitor pack for the vehicle.
* The study of the control of the DC-DC converter interfacing the SC and the realization of this converter.
* The study of an algorithm that optimizes the transfer of energy between the various elements of the system.
* The testing of the unit on the vehicle or a testing bench envisaged for this purpose.

The workload was shared according to the specialization of Lydie and me. Lydie entirely ensured the design and the realization of the microcontroller card and the implementation of the control algorithm. I had been charged with the selection of the supercapacitor pack, the modeling of the components in Simulink, the study of the design and control of the DC-DC converter with a matching model in Simulink. The work was always done in close cooperation.

In the first chapter of this thesis, a general introduction of the problem is given which fits into the development of electric vehicles.

In the second chapter the problem is placed in a more general context and vision from which my affinity with the subject appears. Afterwards there is a little discussion concerning fuel cell electric vehicles. There is explained why we have chosen for the configuration as it is.

In chapter three, two basic topologies of DC-DC converters are briefly exposed: the step-up and stepdown converter. An is given from relevant equations. Then we present the theory of the interleaved bidirectional DC-DC converter.

In the fourth chapter the power sources of the hybrid powertrain are discussed: the fuel cell and the supercapacitor. Their characteristics and the modeling of both components have been summarized. The models were validated by means of tests. After the study of the characteristics of these two components we precede with the design the DC-DC converter. A single, double and three channels converter are compared in the last paragraph of this chapter.

The fifth chapter includes the discussion of the dynamic model and the design of the controller. Two control-methods for the regulation of the current are explained here. A validation of the controllers has been done with a SimPowerSystems model in Simulink.

Date of Award	16 Sept 2011
Original language	English
Supervisor	Joeri Van Mierlo (Co-promotor), Philippe Lataire (Jury), Christian Lacor (Jury), Johan Gyselinck (Promotor), Pierre Mathys (Jury) & Omar Hegazy (Advisor)