Comparison of LCL resonant converter with fixed frequency, and variable frequency controllers

This paper presents a three element DC-DC resonant converter type LCL. The proposed converter provides high output voltage gain with wide zero voltage switching (ZVS) operating range. The converter achieves wide load variation by utilizing fixed frequency (duty-cycle), and variable frequency control, where the gain of the converter is analyzed in relation with the tank impedance that depends on the switching frequency to resonant frequency ratio. Moreover, the utilizing of the magnetizing inductance ensures the achievement of the ZVS for all switches. The proposed converter with both control methods were simulated using MATLAB-SIMULINK. It was found that by controlling the duty cycle, the resonant tank sinusoidal waveforms were missing at load changes. However, with variable frequency control the resonant converters behave well compared to fixed frequency control in term of keeping the tank resonant variables. Besides, it was noticed that both control methods have the ability to deal with output voltage regulation.