Optimal tuning of the novel voltage regulation controller considering the real model of the automatic voltage regulation system.

This paper deals with the optimal tuning of the controller for the real automatic voltage regulation (AVR) system of the synchronous generator (SG). For this purpose, firstly, a novel proportional-integral controller with two degrees of freedom and anti-windup protection for application in the AVR system is proposed. Secondly, in order to determine the optimal parameters of such a controller, the objective function which takes into account transient response characteristics, disturbance, and measurement noise rejection capabilities of the AVR system is presented. Furthermore, the adaptive modification of the existing metaheuristic African vultures optimization algorithm (AVOA) is introduced for controller parameters design. Finally, unlike the many existing papers in the available literature which use a simplified model of the AVR system, in this work the simulation model of the AVR system is realized by observing the technical documentation of the excitation system of the 40 MVA SG from a hydropower plant Perucica in Montenegro. The results obtained in this work have proven that the proposed AVR controller has superior performances compared with other frequently used controllers in real power plants, in terms of providing transient response quality of the SG terminal voltage, disturbance rejection, and measurement noise mitigation abilities. Additionally, increased convergence speed and improved criterion function value demonstrated that the proposed adaptive modification of the AVOA algorithm outperforms some of the most popular metaheuristic algorithms. © 2017 Elsevier Inc. All rights reserved.

Current-voltage curves of planar heterojunction perovskite solar cells - Novel expressions based on Lambert W function and Special Trans Function Theory.

INTRODUCTION: At the present time, much attention has been focused on new types of solar cells, called perovskite solar cells. They are highly efficient devices with more than 25% power conversion efficiency. However, perovskite solar cell performance has not yet been fully explored. OBJECTIVES: We aimed to mathematically investigate the analytical modeling of current-voltage curves of planar heterojunction perovskite solar cells using Perovich Special Trans Function Theory (STFT). Furthermore, we proposed novel analytical closed-form solutions for short-circuit current and open-circuit voltage of these cells in terms of STFT. We evaluated the safety for laying the theoretical foundation by comparing the accuracy of the proposed expressions by the known methods. METHODS: A novel hybrid metaheuristic algorithm, called particle swarm optimization (PSO) - evaporation rate water cycle algorithm (ERWCA), is proposed to determine equivalent circuit parameters of the perovskite solar cell. A novel objective function is introduced for estimating the parameters for that purpose too. RESULTS: It was shown that STFT is very applicable and efficient for representing current-voltage expressions of perovskite solar cells. STFT provides a more accurate solution and requires fewer order members than the solutions provided by the conventional Taylor series. Based on these expressions and numerical calculations, it is verified that the characteristic values ​​of variables (short-circuit current, no-load voltage, efficiency, and fill factor) were not accurately calculated in the literature. Also, parameters of equivalent circuits of these cells were not accurately estimated. The equivalent circuit parameters were determined using the algorithm proposed in this work, which fit the verified values ​​of characteristic quantities much better than the literature. CONCLUSION: This work lays the foundation for developing the planar-structured perovskite solar cell models, in which the proposed estimation method and expressions are highly effective and provide excellent results.

Single Diode Solar Cells-Improved Model and Exact Current-Voltage Analytical Solution Based on Lambert's W Function.

There are three standard equivalent circuit models of solar cells in the literature-single-diode, double-diode, and triple-diode models. In this paper, first, a modified version of the single diode model, called the Improved Single Diode Model (ISDM), is presented. This modification is realized by adding resistance in series with the diode to enable better power loss dissipation representation. Second, the mathematical expression for the current-voltage relation of this circuit is derived in terms of Lambert's W function and solved by using the special trans function theory. Third, a novel hybrid algorithm for solar cell parameters estimation is proposed. The proposed algorithm, called SA-MRFO, is used for the parameter estimation of the standard single diode and improved single diode models. The proposed model's accuracy and the proposed algorithm's efficiency are tested on a standard RTC France solar cell and SOLAREX module MSX 60. Furthermore, the experimental verification of the proposed circuit and the proposed solar cell parameter estimation algorithm on a solar laboratory module is also realized. Based on all the results obtained, it is shown that the proposed circuit significantly improves current-voltage solar cell representation in comparison with the standard single diode model and many results in the literature on the double diode and triple diode models. Additionally, it is shown that the proposed algorithm is effective and outperforms many literature algorithms in terms of accuracy and convergence speed.