Editorial

3 pages, 157 KiB

Open AccessEditorial

Symmetry in Renewable Energy and Power Systems II—Including Wind Energy and Fluid Energy

by Alfredo Alcayde and Francisco Manzano-Agugliaro

Symmetry 2022, 14(8), 1644; https://doi.org/10.3390/sym14081644 - 10 Aug 2022

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This Special Issue has focused on symmetry in renewable energy and energy systems II—including wind energy and fluid power [...] Full article

(This article belongs to the Special Issue Symmetry in Renewable Energy and Power Systems)

Research

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11 pages, 296 KiB

Open AccessArticle

Second-Order Cone Approximation for Voltage Stability Analysis in Direct-Current Networks

by Oscar Danilo Montoya, Walter Gil-González and Alexander Molina-Cabrera

Symmetry 2020, 12(10), 1587; https://doi.org/10.3390/sym12101587 - 24 Sep 2020

Cited by 1 | Viewed by 1757

Abstract

In this study, the voltage stability margin for direct current (DC) networks in the presence of constant power loads is analyzed using a proposed convex mathematical reformulation. This convex model is developed by employing a second-order cone programming (SOCP) optimization that transforms the [...] Read more.

In this study, the voltage stability margin for direct current (DC) networks in the presence of constant power loads is analyzed using a proposed convex mathematical reformulation. This convex model is developed by employing a second-order cone programming (SOCP) optimization that transforms the non-linear non-convex original formulation by reformulating the power balance constraint. The main advantage of the SOCP model is that the optimal global solution of a problem can be obtained by transforming hyperbolic constraints into norm constraints. Two test systems are considered to validate the proposed SOCP model. Both systems have been reported in specialized literature with 6 and 69 nodes. Three comparative methods are considered: (a) the Newton-Raphson approximation based on the determinants of the Jacobian matrices, (b) semidefinite programming models, and (c) the exact non-linear formulation. All the numerical simulations are conducted using the MATLAB and GAMS software. The effectiveness of the proposed SOCP model in addressing the voltage stability problem in DC grids is verified by comparing the objective function values and processing time. Full article

(This article belongs to the Special Issue Symmetry in Renewable Energy and Power Systems)

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23 pages, 8261 KiB

Open AccessArticle

Coordinated Control and Dynamic Optimal Dispatch of Islanded Microgrid System Based on GWO

by Yuting Wang, Chunhua Li and Kang Yang

Symmetry 2020, 12(8), 1366; https://doi.org/10.3390/sym12081366 - 17 Aug 2020

Cited by 6 | Viewed by 2018

Abstract

As an effective carrier of renewable distributed power sources, such as wind power and photovoltaics, microgrids have attracted increasing attention as the energy crisis becomes more serious. This paper focuses on the symmetry between the dynamic optimal dispatch and the coordinated control of [...] Read more.

As an effective carrier of renewable distributed power sources, such as wind power and photovoltaics, microgrids have attracted increasing attention as the energy crisis becomes more serious. This paper focuses on the symmetry between the dynamic optimal dispatch and the coordinated control of islanded microgrid to determine the optimal system configuration that can reliably meet energy needs. In order to solve energy management problems, operating costs and environmental benefits, a novel methodology that combines dynamic optimal dispatch and Grey Wolf Optimizer (GWO) is developed in this study to obtain the best output of different system components. This is to minimize the total cost of microgrid power generation and reduce pollutant emissions. In addition, a comparison is carried out between GWO and Particle Swarm Optimization (PSO). Moreover, the comparison between system configurations in six different scenarios and the effectiveness of GWO in solving optimization problems are presented. Finally, the simulation results show that GWO is more effective than PSO in determining the optimization parameters and the utilization rate of renewable energy in different scenarios is up to 92.96%. The simulations and experimental results verify the successful performance of the research method proposed in this study. Full article

(This article belongs to the Special Issue Symmetry in Renewable Energy and Power Systems)

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15 pages, 5034 KiB

Open AccessArticle

Asymmetric Compensation of Reactive Power Using Thyristor-Controlled Reactors

by Martynas Šapurov, Vytautas Bleizgys, Algirdas Baskys, Aldas Dervinis, Edvardas Bielskis, Sarunas Paulikas, Nerijus Paulauskas and Vytautas Macaitis

Symmetry 2020, 12(6), 880; https://doi.org/10.3390/sym12060880 - 27 May 2020

Cited by 5 | Viewed by 2654

Abstract

The thyristor-controlled reactor (TCR) compensator for smooth asymmetric compensation of reactive power in a low-voltage utility grid is proposed in this work. Two different topologies of compensator were investigated: topology based on a single-cored three-phase reactor and topology with separate reactors for every [...] Read more.

The thyristor-controlled reactor (TCR) compensator for smooth asymmetric compensation of reactive power in a low-voltage utility grid is proposed in this work. Two different topologies of compensator were investigated: topology based on a single-cored three-phase reactor and topology with separate reactors for every phase. The investigation of the proposed TCR compensator was performed experimentally using a developed experimental test bench for 12 kVAr total reactive power. The obtained results show that employment of separate reactors for every phase allows us to control the reactive power in every phase independently, and that the TCR compensator with three single-phase reactors is suitable for smooth and asymmetric compensation of reactive power in a low-voltage utility grid. Full article

(This article belongs to the Special Issue Symmetry in Renewable Energy and Power Systems)

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15 pages, 936 KiB

Open AccessArticle

Direct Power Compensation in AC Distribution Networks with SCES Systems via PI-PBC Approach

by Walter Gil-González, Federico Martin Serra, Oscar Danilo Montoya, Carlos Alberto Ramírez and César Orozco-Henao

Symmetry 2020, 12(4), 666; https://doi.org/10.3390/sym12040666 - 23 Apr 2020

Cited by 10 | Viewed by 2359

Abstract

Here, we explore the possibility of employing proportional-integral passivity-based control (PI-PBC) to support active and reactive power in alternating current (AC) distribution networks by using a supercapacitor energy storage system. A direct power control approach is proposed by taking advantage of the Park’s [...] Read more.

Here, we explore the possibility of employing proportional-integral passivity-based control (PI-PBC) to support active and reactive power in alternating current (AC) distribution networks by using a supercapacitor energy storage system. A direct power control approach is proposed by taking advantage of the Park’s reference frame transform direct and quadrature currents (

i_{d}

and

i_{q}

) into active and reactive powers (p and q). Based on the open-loop Hamiltonian model of the system, we propose a closed-loop PI-PBC controller that takes advantage of Lyapunov’s stability to design a global tracking controller. Numerical simulations in MATLAB/Simulink demonstrate the efficiency and robustness of the proposed controller, especially for parametric uncertainties. Full article

(This article belongs to the Special Issue Symmetry in Renewable Energy and Power Systems)

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14 pages, 341 KiB

Open AccessArticle

Optimal Location and Sizing of PV Sources in DC Networks for Minimizing Greenhouse Emissions in Diesel Generators

by Oscar Danilo Montoya, Luis Fernando Grisales-Noreña, Walter Gil-González, Gerardo Alcalá and Quetzalcoatl Hernandez-Escobedo

Symmetry 2020, 12(2), 322; https://doi.org/10.3390/sym12020322 - 24 Feb 2020

Cited by 31 | Viewed by 3123

Abstract

This paper addresses the problem of the optimal location and sizing of photovoltaic (PV) sources in direct current (DC) electrical networks considering time-varying load and renewable generation curves. To represent this problem, a mixed-integer nonlinear programming (MINLP) model is developed. The main idea [...] Read more.

This paper addresses the problem of the optimal location and sizing of photovoltaic (PV) sources in direct current (DC) electrical networks considering time-varying load and renewable generation curves. To represent this problem, a mixed-integer nonlinear programming (MINLP) model is developed. The main idea of including PV sources in the DC grid is minimizing the total greenhouse emissions produced by diesel generators in isolated areas. An artificial neural network is employed for short-term forecasting to deal with uncertainties in the PV power generation. The general algebraic modeling system (GAMS) package is employed to solve the MINLP model by using the CONOPT solver that works with mixed and integer variables. Numerical results demonstrate important reductions of harmful gas emissions to the atmosphere when PV sources are optimally integrated (size and location) to the DC grid. Full article

(This article belongs to the Special Issue Symmetry in Renewable Energy and Power Systems)

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15 pages, 4846 KiB

Open AccessFeature PaperArticle

A Simplified Method to Avoid Shadows at Parabolic-Trough Solar Collectors Facilities

by Nuria Novas, Aránzazu Fernández-García and Francisco Manzano-Agugliaro

Symmetry 2020, 12(2), 278; https://doi.org/10.3390/sym12020278 - 13 Feb 2020

Cited by 7 | Viewed by 2814

Abstract

Renewable energy today is no longer just an affordable alternative, but a requirement for mitigating global environmental problems such as climate change. Among renewable energies, the use of solar energy is one of the most widespread. Concentrating Solar Power (CSP) systems, however, is [...] Read more.

Renewable energy today is no longer just an affordable alternative, but a requirement for mitigating global environmental problems such as climate change. Among renewable energies, the use of solar energy is one of the most widespread. Concentrating Solar Power (CSP) systems, however, is not yet fully widespread despite having demonstrated great efficiency, mainly thanks to parabolic-trough collector (PTC) technology, both on a large scale and on a small scale for heating water in industry. One of the main drawbacks to this energy solution is the large size of the facilities. For this purpose, several models have been developed to avoid shadowing between the PTC lines as much as possible. In this study, the classic shadowing models between the PTC rows are reviewed. One of the major challenges is that they are studied geometrically as a fixed installation, while they are moving facilities, as they have a tracking movement of the sun. In this work, a new model is proposed to avoid shadowing by taking into account the movement of the facilities depending on their latitude. Secondly, the model is tested to an existing facility as a real case study located in southern Spain. The model is applied to the main existing installations in the northern hemisphere, thus showing the usefulness of the model for any PTC installation in the world. The shadow projected by a standard, the PTC (S) has been obtained by means of a polynomial approximation as a function of the latitude (Lat) given by S = 0.001 − Lat² + 0.0121 − Lat + 10.9 with R² of 99.8%. Finally, the model has been simplified to obtain in the standard case the shadows in the running time of a PTC facility. Full article

(This article belongs to the Special Issue Symmetry in Renewable Energy and Power Systems)

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15 pages, 7944 KiB

Open AccessArticle

Evolutionary Algorithms for Community Detection in Continental-Scale High-Voltage Transmission Grids

by Manuel Guerrero, Raul Baños, Consolación Gil, Francisco G. Montoya and Alfredo Alcayde

Symmetry 2019, 11(12), 1472; https://doi.org/10.3390/sym11121472 - 03 Dec 2019

Cited by 7 | Viewed by 2219

Abstract

Symmetry is a key concept in the study of power systems, not only because the admittance and Jacobian matrices used in power flow analysis are symmetrical, but because some previous studies have shown that in some real-world power grids there are complex symmetries. [...] Read more.

Symmetry is a key concept in the study of power systems, not only because the admittance and Jacobian matrices used in power flow analysis are symmetrical, but because some previous studies have shown that in some real-world power grids there are complex symmetries. In order to investigate the topological characteristics of power grids, this paper proposes the use of evolutionary algorithms for community detection using modularity density measures on networks representing supergrids in order to discover densely connected structures. Two evolutionary approaches (generational genetic algorithm, GGA+, and modularity and improved genetic algorithm, MIGA) were applied. The results obtained in two large networks representing supergrids (European grid and North American grid) provide insights on both the structure of the supergrid and the topological differences between different regions. Numerical and graphical results show how these evolutionary approaches clearly outperform to the well-known Louvain modularity method. In particular, the average value of modularity obtained by GGA+ in the European grid was 0.815, while an average of 0.827 was reached in the North American grid. These results outperform those obtained by MIGA and Louvain methods (0.801 and 0.766 in the European grid and 0.813 and 0.798 in the North American grid, respectively). Full article

(This article belongs to the Special Issue Symmetry in Renewable Energy and Power Systems)

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15 pages, 385 KiB

Open AccessArticle

Geometric Algebra in Nonsinusoidal Power Systems: A Case of Study for Passive Compensation

by Francisco G. Montoya

Symmetry 2019, 11(10), 1287; https://doi.org/10.3390/sym11101287 - 14 Oct 2019

Cited by 4 | Viewed by 2179

Abstract

New-generation power networks, such as microgrids, are being affected by the proliferation of nonlinear electronic systems, resulting in harmonic disturbances both in voltage and current that affect the symmetry of the system. This paper presents a method based on the application of geometric [...] Read more.

New-generation power networks, such as microgrids, are being affected by the proliferation of nonlinear electronic systems, resulting in harmonic disturbances both in voltage and current that affect the symmetry of the system. This paper presents a method based on the application of geometric algebra (GA) to the resolution of power flow in nonsinusoidal single-phase electrical systems for the correct determination of its components to achieve passive compensation of true quadrature current. It is demonstrated that traditional techniques based on the concepts of Budeanu, Fryze or IEEE1459 fail to determine the interaction between voltage and current and therefore, are not suitable for being used as a basis for the compensation of nonactive power components. An example is included that demonstrates the superiority of GA method and is compared to previous work where GA approaches and traditional methods have also been used. Full article

(This article belongs to the Special Issue Symmetry in Renewable Energy and Power Systems)

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15 pages, 5268 KiB

Open AccessArticle

A Hybrid Active Filter Using the Backstepping Controller for Harmonic Current Compensation

by Nora Daou, Francisco G. Montoya, Najib Ababssi and Yacine Djeghader

Symmetry 2019, 11(9), 1161; https://doi.org/10.3390/sym11091161 - 12 Sep 2019

Cited by 5 | Viewed by 3362

Abstract

This document presents a new hybrid combination of filters using passive and active elements because of the generalization in the use of non-linear loads that generate harmonics directly affecting the symmetry of energy transmission systems that influence the functioning of the electricity grid [...] Read more.

This document presents a new hybrid combination of filters using passive and active elements because of the generalization in the use of non-linear loads that generate harmonics directly affecting the symmetry of energy transmission systems that influence the functioning of the electricity grid and, consequently, the deterioration of power quality. In this context, active power filters represent one of the best solutions for improving power quality and compensating harmonic currents to get a symmetrical waveform. In addition, given the importance and occupation of the transmission network, it is necessary to control the stability of the system. Traditionally, passive filters were used to improve energy quality, but they have endured problems such as resonance, fixed remuneration, etc. In order to mitigate these problems, a hybrid HAPF active power filter is proposed combining a parallel active filter and a passive filter controlled by a backstepping algorithm strategy. This control strategy is compared with two other methods, namely the classical PI control, and the fuzzy logic control in order to verify the effectiveness and the level of symmetry of the backstepping controller proposed for the HAPF. The proposed backstepping controller inspires the notion of stability in Lyapunov’s sense. This work is carried out to improve the performance of the HAPF by the backstepping command. It perfectly compensates the harmonics according to standards. The results of simulations performed under the Matlab/Simulink environment show the efficiency and robustness of the proposed backstepping controller applied on HAPF, compared to other control methods. The HAPF with the backstepping controller shows a significant decrease in the THD harmonic distortion rate. Full article

(This article belongs to the Special Issue Symmetry in Renewable Energy and Power Systems)

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