Three-Phase Series Resonant DC-DC Boost Converter With Double LLC Resonant Tanks and Variable Frequency Control

This paper proposes a three-phase inverter combined with two LLC resonant tanks series resonant DC-DC boost converter with variable frequency control. The three-phase inverter side of the proposed circuit is connected to identical two-level LLC tanks to ensure balanced resonant currents. The proposed converter requires less switching devices and transformers as compared to the conventional interleaved LLC resonant converter, which competitively offers higher efficiency and reduced size and cost. Furthermore, the proposed converter works above the resonant frequency to achieve zero voltage switching (ZVS) for the entire operating frequency range (42.5kHz <f(s)< 50kHz) for all switches. Variable frequency controller is considered in order to obtain better stability for diverse loads. Therefore, the proposed converter will have the ability to respond to the load changes by varying the switching frequency to the value that fulfils the requirement. In order to verify the improvement of the proposed converter, the converter performance is compared to conventional interleaved LLC resonant converter. The theoretical outcomes are confirmed through simulation studies using MATLAB/SIMULINK and validated experimentally using a laboratory prototype. Selected results are presented to verify the effectiveness of the proposed converter.