LLC resonant DC-DC converter for grid-connected PV system

Abstract

Resonant DC-DC converters have been used widely as efficient alternatives for traditional DC-DC converters that suffer from the problems of high switching losses and low power density. Resonant converters implement soft switching mechanisms like zero current switching (ZCS) and zero voltage switching (ZVS) which allows for high frequency operation together with minimum switching losses. A resonant DC-DC converter is proposed for grid connected double stage photovoltaic (PV) system. A LLC resonant converter is applied to boost the PV array terminal voltage and carry out maximum power point tracking (MPPT). The incremental conductance concept is applied using a PI controller for maximum power extraction from the PV array. A neutral point clamped three level voltage source inverter (VSI) is used to interface the PV system with the grid. The VSI controller performs two tasks; regulating the voltage of the DC bus and synchronizing injected currents with grid voltages to realize a unity power factor. A simulation study executed in MATLAB/SIMULINK environment is presented to verify the dynamic response of the proposed system to different kinds of disturbance in solar irradiance.