Analysis, design, and implementation of a static conductance-based MPPT method

Abstract

This paper introduces a maximum power point tracking (MPPT) method based on a power (P) versus static conductance (G) curve of a photovoltaic (PV) array. The maximum power point (MPP) is tracked by comparing the PV array instantaneous power to a varying power reference generated by the MPPT algorithm. The comparison error is used to reduce or increase the conductance at which the PV array is forced to operate until the MPP is reached. Simultaneously, the error is used to change the power reference until the trajectory of this reference in the P-G curve enters a limit cycle around the MPP. The P-G curve is derived from a piecewise linear approximation of the current versus voltage (I-V) curve, which facilitates the analytical description of the tracking operation. The technique reported can also be implemented by means of simple analog or digital circuitry and requires two sensors to measure the instantaneous PV array current and voltage. It uses only four tuning parameters, which are selected depending on the maximum value of the derivative of the power with respect to the conductance. The theoretical predictions are verified with simulations and experimental results. The latter shows that the procedure performs well enough to be favorably compared with the most efficient MPPT methods.