  We present a nonlinear equivalent resistance tracking method to optimize the
power output for solar arrays. Tracking an equivalent resistance results in
nonlinear voltage step sizes in the gradient descent search loop. We introduce
a new model for the combined solar module along with a DC-DC converter which
results in a highly nonlinear dynamical system due to the inherent
non-linearity of the PV cell topology and the switched DC-DC converter system.
To guarantee stability over a range of possible operating regimes, we utilize a
feedback linearization control approach to exponentially converge to the
setpoint. Simulations are presented to illustrate the performance and
robustness of the proposed technique.
