energies Article An Improved Cuckoo Search Algorithm for Maximum Power Point Tracking of Photovoltaic Systems under Partial Shading Conditions Ali M. Eltamaly 1,2,3   Citation: Eltamaly, A.M. An Improved Cuckoo Search Algorithm for Maximum Power Point Tracking of Photovoltaic Systems under Partial Shading Conditions. Energies 2021, 14, 953. https://doi.org/10.3390/ en14040953 Received: 20 December 2020 Accepted: 8 February 2021 Published: 11 February 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Sustainable Energy Technologies Center, King Saud University, Riyadh 11421, Saudi Arabia; eltamaly@ksu.edu.sa; Tel.: +966-55-3334130 2 Electrical Engineering Department, Mansoura University, Mansoura 35516, Egypt 3 K.A. CARE Energy Research and Innovation Center, Riyadh 11451, Saudi Arabia Abstract: The problem of partial shading has serious effects on the performance of photovoltaic (PV) systems. Adding a bypass diode in shunt to each PV module avoids hot-spot phenomena, but causes multi-peaks in the power–voltage (P–V) characteristics of the PV array, which cause traditional maximum power point tracking (MPPT) techniques to become trapped in local peaks. This problem has forced researchers to search for smart techniques to track global peaks and prevent the possibility of convergence at local peaks. Swarm optimization techniques have been used to fill this shortcoming; unfortunately, however, these techniques suffer from unacceptably long convergence time. Cuckoo search (CS) is one of the fastest and most reliable optimization techniques, making it an ideal option to be used as an MPPT of PV systems under dynamic partial shading conditions. The standard CS algorithm has a long conversion time, high failure rate, and high oscillations at steady state; this paper aims to overcome these problems and to fill this research gap by improving the performance of the CS. The results obtained from this technique are compared to five swarm optimization techniques. The comparison study shows the superiority of the improved CS strategy introduced in this paper over the other swarm optimization techniques. Keywords: photovoltaic; MPPT; partial shading; cuckoo search; optimization techniques 1. Introduction Renewable energy systems, especially PV, are attracting more interest in recent decades due to their abundant and environmentally-friendly nature. Reducing the cost of energy generated from PV systems is an especially hot topic of research. Cost reduction efforts are generally done in one of two ways. The first one is improving the physical structure and materials of the PV cells, which is outside the scope of this paper. The second is improving the efficiency of the PV system through the power electronics circuits used with the PV array–this is the main focus of the paper. Due to the nonlinear relation between the P–V characteristics, a circuit is required to force the PV array to work at the terminal voltage associated with the maximum power. This can be accomplished using a DC-DC converter operated according to a control technique called maximum power point tracking (MPPT). Traditional MPPT techniques such as incremental conductance, perturb and observe (P&O), etc. [1] were efficiently used for this purpose in the case of uniform irradiance on all modules of the PV array–that is, where the P–V characteristic of the PV array contains only one peak. Partial shading conditions (PSC) may occur due to any physical object preventing solar irradiance from falling on some parts of the PV array. A bypass diode should be connected in shunt with each module in the PV array to prevent the hot-spot effect, which can damage the shaded modules. Meanwhile, PSC creates more than one peak in the P–V characteristics of the PV array. The traditional MPPT techniques may become trapped in one of the local peaks (LPs) and miss the tracking of the global peak Energies 2021, 14, 953. https://doi.org/10.3390/en14040953 https://www.mdpi.com/journal/energies