In this paper, a single-inductor multi-input single-output (SI-MISO) DC-DC boost converter is used for solar photovoltaic (PV) systems in DC or AC grids. The converter with N number of inputs combines energy from PV panels along with fuel cells (FCs) to maintain stability. By implementing a new switching algorithm in the converter, the output voltage of the converter and the power absorbed from each source can be controlled independently, resulting in a simple and unique controller. In addition, the multivariable control system can be controlled as N number of single-input single-output (SISO) systems without any delay between switches due to the small-signal model of the converter and the proposed proportional-integral-derivative (PID) cascade control scheme. For each PV source, an independent maximum power point tracking (MPPT) algorithm can be employed, and the current sharing among different sources can be achieved independently. The converter's operating modes and the designed controller are present in the paper. Experimental results using a 100-W prototype converter validate the accuracy and efficiency of the proposed control scheme.INDEX TERMS Multi-input single-output DC-DC converter, photovoltaic systems, proportional-integralderivative (PID) cascade control, renewable energy.