Maximum power point tracking in photovoltaic systems using adaptive control

Thesis submitted in the fulfillment of the requirement for the degree of Doctor of Philosophy by Pankaj Sahu Under the supervision of Dr. Rajiv Dey Doctor of Philosophy 2022

This work proposes various adjustable gain-based model reference adaptive control schemes for maximum power point tracking (MPPT) in photovoltaic (PV) systems. The proposed adjustable gain based MRAC schemes in MPPT ensure fast convergence speed with guaranteed transient performance and overall system stability under rapidly changing environmental conditions. The abovementioned performance is achieved without the need of high adaptation gain as required in conventional MRAC schemes in MPPT. The first level of control is the conventional ripple correlation control (RCC), used to obtain ripple-free optimal duty cycle in steady-state, which serves as input for the second level of control, which is the adjustable gain based MRAC controller. Conventional high-static adaptation gain MRAC scheme provides guaranteed transient performance in MPPT, but the high adaptation gain circumvents adverse effects on the system s stability and robustness. Moreover, in PV systems when environmental conditions are changing rapidly, gain requirement depends upon the magnitude of the error; therefore, a fixed high gain controller does not completely provide a solution to the dynamic behavior of non-linear PV systems under rapidly changing environmental conditions. This work attempts to overcome these issues using the proposed adjustable-gain based MRAC architectures, in which the adaptation gain is adjusted as a function of the tracking error, caused by the variations in environmental conditions. Mathematical model of the proposed schemes has been developed and stability has been proved using Lyapunov theory. To check the effectiveness of proposed control schemes, simulation studies have been done. Each of the proposed scheme have been validated with the experimental analysis and performance comparisons have also been done.