This document presents a model of a solar photovoltaic system under partial shading conditions. It describes using a particle swarm optimization algorithm to efficiently track the maximum power point from a PV array with a non-linear power-voltage characteristic caused by partial shading. The PV array is modeled and simulated in MATLAB/Simulink to demonstrate multiple local maxima under partial shading. A boost converter interfaced with the PV array uses the PSO algorithm and PI controller to extract the optimal voltage from the solar array. Simulation results show the developed model can produce a higher output voltage under partial shading conditions.