CONVERTERS FOR RENEWABLE ENERGY APPLICATIONS by AHMAD SAEED Y. ALZAHRANI MISSOURI UNIVERSITY OF SCIENCE AND TECHNOLOGY
In Partial Fulfillment of the Requirements for the Degree
DOCTOR OF PHILOSOPHY
in
ELECTRICAL ENGINEERING- 2018
ABSTRACT
This dissertation proposes several advanced power electronic converters that are
suitable for integrating low-voltage dc input sources, such as photovoltaic (PV) solar panels,
to a high voltage dc bus in a 200 − 960 V dc distribution system. The proposed converters
operate in the continuous conduction mode (CCM) and offer desirable features such as lowvoltage stresses on components, continuous input currents, and the ability to integrate several
independent dc input sources. First, a family of scalable interleaved boost converters with
voltage multiplier cells (VMC) is introduced. Several possible combinations of Dickson
and Cockcroft-Walton VMCs are demonstrated and compared in terms of the voltage gain,
number of components, and input current sharing. This dissertation also presents a novel
VMC structure called Bi-fold Dickson. The novel VMC offers equal current sharing between
phases regardless of the number of stages, voltage ripple cancellation at each stage, and
does not require an output diode. A family of high-voltage-gain multilevel boost converters
is presented, with detailed example of the hybrid flyback and three-level boost converter.
In this family, the effective frequency seen by the magnetic element is multiple times
the switching frequency, and therefore smaller magnetic devices can be used. Theory of
operations, steady-state analysis, component selections, simulation, and efficiency analysis
are included for each proposed converter. The operation of the proposed converters was
further verified with 80 − 200 W hardware prototypes.
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