Improved P&O-MPPT strategy based on new design of small-signal model used for voltage regulation of solar

Abstract

This paper proposes a new design of small-signal model, used in the voltage loop of a solar system. The internal functioning of this system is considered fully unknown at standard test condition (STC) where a corresponding model is completely unavailable. The main idea consists on considering the nonlinear solar system behavior as a black box and only corresponding input-output samples are previously recorded by user. These samples are employed to estimate the parameters of a desired linear small-signal model, in which a first Graphical User Interface (GUI) of Matlab®/Identification/Toolbox™ is used. As the step-procedure needed to design this model type has never been addressed in any previous work, it will highlight therefore the key contribution of this paper. Subsequently, the resulting previous model is then used to synthesize a voltage PID controller where their parameters are tuned using guidelines, available in a second GUI of Matlab®/Control/Toolbox™. It allows overcoming perfectly the inherent ripple problems of standard the maximum power point tracking (MPPT) strategy utilizing the direct implementation of the perturb and observe (P&O) algorithm. As the combination of previous strategy with the synthetized voltage PID controller highlights the improved P&O-MPPT strategy. Indeed, the performances of both standard and improved P&O-MPPT strategies are compared where the simulation results prove the superiority of the improved P&O-MPPT control strategy over the standard one in terms of trade-off between the MPP tracking in steady state and the MPP speed convergence in transient state where any existing ripple problems are completely solved.