First order frequency-domain analytical model for resonant converters in CCM

Abstract

Fundamental harmonic approximation (FHA) is a general analysis method for diode-bridge rectifier in resonant converters. However, the accuracy of FHA is low in some wireless power transfer (WPT) applications, as the current has distortions due to different compensation networks. Also, there are researches on increasing the power density of resonant converters by injecting third harmonic. In such case, FHA no longer holds true. As the diode-bridge rectifier is a well-known harmonic source, numerous modeling methods for Grid connected AC/DC converters have been addressed. However, most of them have all kinds of limitations and cannot be applied to resonant converter directly. This paper proposes a frequency-domain analytical model for resonant converters in CCM, considering any load and source situation. The advantage of the proposed model is a truly first order solution and a general model for all resonant converters. Two test systems have been constructed in simulation and calculation to verify the proposed model. One is a resonant converter with both fundamental and third harmonic components, the other one is an LCC compensated wireless charger.