Suppression of Intermediate Capacitor Current Ripple in Two-Stage FSBB-LLC Converter

A PV-oriented two-stage DC-DC converter is structured in this paper to boost voltage from solar panels to a high, stable level suitable for grid integration. The four-switch buck-boost converter (FSBB) is adopted as the front stage converter, applying the quadrilateral inductor current modulation (QCM) method. The full-bridge LLC resonant converter is selected as the rear stage converter, functioned as a DC transformer (DCX) with fixed operating frequency. A two-stage coordinated control method is proposed to suppress the current ripple of the intermediate bus capacitor. By adjusting the frequency and phase relationship between the front-end and rear-end converters, the amplitude and effective values of the intermediate bus capacitor current ripple are lowered. The overall performance of the converter is enhanced with the extended lifespan of its components and improved system stability. A simulation model is structured in the end to verify the effectiveness of the control method.