Maximum power point tracking using ripple correlation and incremental conductance

A new method is presented in this paper for maximum power point (MPP) tracking in a system consisting of a photovoltaic (PV) generator, a boost converter, and their associated control. The boost converter may be supplying energy to charge a battery or to connect to a grid via a pulse width modulated (PWM) inverter. The method relies on the natural disturbance created by the switching operation of the converter, and on estimating the incremental and average conductance values of the PV generator output. It is based on a characteristic property which stipulates that the incremental and average inductances have the same absolute values at the MPP. Thus when operating at a voltage point higher than that of the MPP, the absolute incremental conductance is higher than the absolute average conductance and so the duty cycle of the converter needs to be increased. The required change in the duty cycle is obtained using a digital proportional-integral-derivative (PID) controller that aims to equalize the average and incremental inductances. A system simulation model from first concepts was developed in MATLAB taking into consideration implementation details of voltage and current measurements, their corresponding delays, and the presence of a junction capacitance. The paper presents the theory of MPP operation according to this method, the models of the different subsystems used in the simulation, and the implementation details of the PID controller as well as results on the tracking efficiency under various irradiance profiles.