Model Prediction Control of LCC Resonant Converter Using Extended Describing Function

LCC resonant converter is often used as capacitor charging power supply (CCPS) due to its excellent characteristics. Constant power charging is now wide-adapted to increase the charging speed and utilize input grid capacity. However, during the charging process, it is difficult to accurately measure the output current, which makes it difficult to implement the constant power control. Therefore, the online model prediction control based on the Luenberger observer for LCC resonant converter under continuous current mode (CCM) is firstly proposed in this article, which can realize constant power or constant current charging as well as ZVS in the entire load range by adjusting the switching frequency. The observer is established by using the extended describing function (EDF) to obtain the state variables accurately. The relationship between the switching frequency and the average output current is obtained based on the quasi-steady state model. Finally, the proposed control strategy is verified by the simulation of a 2kW CCPS under CCM.