Analysis of an LCL-T Type Resonant Dc–Dc Converter by the Fundamental Harmonic Method

—The approximate expressions for calculating currents at an inverter’s output and at the input of the output rectifier, as well as the efficiency and load characteristics of a dc–dc converter, are obtained on the basis of a linear equivalent circuit of a dc–dc converter under the assumption that the current is sinusoidal at the inverter’s output. A fundamental harmonic method is used for this purpose. We compare characteristics of a dc–dc converter obtained theoretically by taking into account and not taking into account the active resistance of the LC circuit and also with characteristics obtained using the Simulink model. It is shown that calculations performed with the help of the fundamental harmonic method are in good agreement with real parameters of a dc–dc converter of LCL-T type. The obtained relationships make it possible to identify features of the dc–dc converter, and, if we compare the results with the results of imitation simulation, we will be able to determine possible errors of the method caused mainly by nonsinusoidal current consumed from the inverter bridge.