MPPT-Based Optimal Frequency Control of LLC Resonant Converter in PV-Powered EV Charging Stations

This paper presents a circuit-based modeling of MPPT controller for lead-acid battery charging in PV standalone systems using MATLAB/Simulink. The LLC resonant converter is employed as the DC-DC converter for the charge controller due to its efficiency advantages. However, most well-known MPPT algorithms are designed for PWM converters, whereas the LLC resonant converter uses PFM. Applying a PWM-based MPPT method to an LLC converter could might cause the loss of its soft switching characteristics. Therefore, an MPPT algorithm based on PFM is necessary. This paper proposes an optimal frequency control MPPT algorithm that adjusts the frequency offset around the resonant frequency using an improved P&O method. Simulation results are provided to demonstrate the algorithm’s validity and its capability to track the maximum power point under varying solar irradiance and temperature conditions.