Performance optimization of the INC-COND fuzzy MPPT based on a variable step for photovoltaic systems

Abstract

In this paper, an optimization of the Incremental Conductance (Inc-Cond) maximum power point tracking (MPPT) algorithm is presented. The objective is to find a compromise between the detection time, which represents the maximum point tracking speed, and the accuracy, which determines the distance between the operating point and the desired point, and is therefore directly related to the efficiency. On the one hand, to achieve this objective, the proposed method uses a variable step that is determined based on the equality between the power produced and consumed by the load. The proposed optimisation method has the advantages of simplicity and low cost of implementation. In fact, the proposed optimization is based on the duty cycle and the PV voltage, which can be easily measured by the resistance bridge. On the other hand, the choice of a Quadratic Boost Converter (QBC) is justified by its high gain compared to the classical boost converter and its adaptability to low voltage PV sources. A section concerning the modelling of the PV source and QBC is presented. For reasons related to the non-linear behaviour of the QBC, a fuzzy logic controller is adopted for the adjustment of the PV voltage. Simulation results under Matlab/Simulink show the validity of the proposed method for several levels of irradiation and temperature. A comparison has shown the superior performance of the proposed method in terms of speed, accuracy, efficiency, and amplitude of ripples around the MPP.