Enhancing Five-level Resonant Boost Converter for High Voltage Applications

Abstract

This work proposes a five-level LLC boost DC-DC resonant converter with a reduced switch count, designed to achieve wide input voltage ranges, high efficiency, and constant output voltage across various input and load conditions. The converter utilizes two diode-bypassed inverter topologies, reducing the switch count, size, and cost of the multilevel inverter while maintaining performance. The voltage gain is selected to provide an output of 1000V from an input range of 200V to 300V, with a switching frequency range of 57.10kHz to 158.64kHz. Simulations in MATLAB/Simulink confirm that the converter operates with a switching frequency consistently below the resonance frequency under all conditions, similar to five-level cascaded H-bridge inverters. The frequency controller ensures a stable 1000V output, achieving a full load efficiency of 93.66%. The diode-bypassed DC-link inverter is preferred over the diode-bypassed neutral-point inverter due to its higher efficiency at load currents below 3A, and comparable efficiency above 3A, all with a reduced switch count of five. The results show a 37.5% reduction in switch count, a 45% decrease in power loss, and a 5% improvement in efficiency with the diode-bypassed DC-link inverter.