Publication: Modified five-level llc resonant boost dc/dc converter
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Date
2024-07-01
Authors
Ali Idress, Rahel Bughneda
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Abstract
Multi-level resonant converters are effective for power conversion across various
applications, offering enhanced efficiency, reduced voltage stress, higher power
density, a wide input voltage range, and better EMC performance. These features make
them ideal for the renewable energy systems, electric vehicles, data centres, and
industrial use. Converters with more levels can improve total harmonic distortion
(THD) reduction, but they also increase the system's complexity and total switching
losses. This thesis proposes a modified multilevel LLC resonant DC-DC boost
converter with variable frequency and integrated control for modulation index, aiming
for optimal efficiency, steady output voltage gain, zero voltage switching (ZVS), and
wide load variation. All the selected parameters for the analysis were emphasized in
detail. Furthermore, the converter's performance was investigated under varying load
conditions at nominal input voltage and varying solar insolation at full load. It was
found that the proposed control system successfully responded to both changes and
maintained the output voltage at the desired value by varying the switching frequency
within a selected range, achieving a 1000V, 5kW output with 97.1% efficiency.
Additionally, the developed five-level LLC resonant converter exhibited different
behavior compared to conventional LLC resonant full/half-bridge converters, where
the switching frequency of these converters is consistently lower than the resonance
frequency under all load and input conditions. The theoretical parts and simulation
results obtained from MATLAB-SIMULINK simulations were validated
experimentally using a laboratory prototype. Selected findings were discussed to
illustrate the efficacy of the designed converter.