Nonlinear Equivalent Resistance-based Maximum Power Point Tracking (MPPT)

TL;DR

The paper addresses robust MPPT for PV systems involving a nonlinear PV diode model and a buck-boost converter, where fixed-step perturbations can fail near the maximum power point. It introduces a nonlinear equivalent-resistance tracking framework with an outer loop that uses the Lambert-W function to compute exact next operating points and an inner-loop feedback linearization to stabilize the nonlinear plant, achieving exponential convergence to the MPP. The approach demonstrates robustness to parasitic losses and rapid tracking, validated through simulations with realistic module and converter parameters. The method is scalable to PV arrays and offers a practical path toward faster, more reliable MPPT in real-world installations.

Abstract

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.

Figures (5)

• Figure 1: Regions I and II of I-V curve
• Figure 2: Solar Module and DC-DC Buck Boost Converter with Parasitic losses.
• Figure 3: I-V and P-V characteristics of the PV module considered.
• Figure 4: $R_{eq}$ and $G_{eq}$ profiles of the PV module in relation to $P_{pv}$ and $V_{pv}$
• Figure 5: Performance of Feedback Linearization Controller given in (\ref{['EQ:dGlobal']}) for two initial conditions.