Input voltage sliding mode control of the versatile buck-boost converter for photovoltaic applications

The versatile buck-boost converter presents interesting features, such as continuous input and output currents and ease of control in both step-up and step-down models. This paper addresses its use in low voltage photovoltaic applications where the nonlinear current source-like I-V static characteristic of the PV module requires the inclusion of an input capacitor in the original power stage structure. The sliding mode regulation of this additional input capacitor voltage is analyzed, considering a linear combination of the capacitor current, the voltage error, and the integral of the voltage error as the switching function. The performance of the designed controller that has been tested by simulation indicates that it can be easily combined with a conventional maximum power point tracking (MPPT) algorithm of perturb and observe type (P&O).