Abstract:
This thesis presents new wide-ratio bidirectional hybrid DC-DC converters
used in supercapacitor storage, frequently employed for enhancing the
storage performances in microgrids or electric vehicles. The presented
topologies are developed from unidirectional hybrid structures which are
characterized by the use of switched cells consisting of identical capacitors
or inductors switched between series and parallel connection with the help
of diodes. By operating in this manner, the switching cells help achieve a
wider (higher in step-up converters or lower in step-down converters)
voltage conversion ratio, lower active switch stress, and smaller passive
components. The bidirectional structures achieve the same benefits as the
unidirectional topologies, with the added benefit of two quadrant
operation.
This work if focused on four converter topologies, from which three are
proposed by the author. The studied topologies are described analytically,
in order to obtain design equations and comparison metrics. Dynamic
analysis is performed to achieve a better hardware design of converters,
to assess their stability and to design current controllers. Digital
simulations are used to aid the design and analysis of the studied
converters. Experimental results are acquired for two hybrid topologies in
applications with a power scale up to 5kW. In order to measure efficiency
and test the influence of different switches, one topology was built using
MOSFETs and GaN-FETs. To eliminate some disadvantages, an improved
version is proposed for each of the studied topologies.
Power sharing strategies for supercapacitor storage in microgrid
applications are proposed and implemented with the help of a hybrid
converter. Their operation is tested trough experimental and digital
simulations.
