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Objective: This work involves a convex-based mathematical reformulation of the optimal power flow problem in DC networks. The objective of the proposed optimization model corresponds to the minimization of the power losses throughout all the network branches considering a convex conic model that ensures finding the global optimum solution. Methodology: This work is split into three stages. The first stage presents the mathematical model of optimal power flow for DC networks and all the geometric features that make it non-convex. The second stage presents the convex reformulation from a second-order conic relaxation. The third stage shows the main characteristics of the DC system under study, as well as the optimal solution of the power flow problem and its comparisons with some methods reported in the specialized literature. Results: The numerical validations demonstrate that the proposed convex optimal power flow model obtains the same solution as the exact model of the problem with an efficiency of 100%, which is in contrast with the variability of the results that are presented by the metaheuristic techniques reported as comparison methodologies. Conclusions: The proposed second-order conic relaxation ensured the convexity of the solution space and, therefore, the finding of the optimal solution at each execution, in addition to demonstrating that, for optimal power flow problems in DC networks, the numerical performance is better than most of the comparative metaheuristic methods and that the solution provided by the proposed relaxation is equivalent to that provided by the exact model. Resumen Objetivo: Este trabajo plantea una reformulación matemática de naturaleza convexa del problema de flujo de potencia óptimo en redes de corriente continua (DC). El objetivo del modelo de optimización propuesto corresponde a la minimización de las pérdidas de potencia en todas las ramas de la red considerando un modelo cónico convexo que garantice el hallazgo de la solución óptima global. Metodología: Este trabajo está dividido en tres etapas: la primera presenta el modelo matemático de flujo de potencia óptimo para redes DC y todas las características geométricas que lo hacen no convexo; la segunda presenta la reformulación convexa a partir de una relajación cónica de segundo orden; la tercera etapa presenta las principales características del sistema DC bajo estudio, además de la solución óptima del problema de flujo de potencia y sus comparaciones con algunos métodos reportados en la literatura especializada. Resultados: Las validaciones numéricas demuestran que el modelo de flujo de potencia óptimo convexo propuesto encuentra la misma solución el modelo exacto del problema y tiene una eficiencia del 100%, lo cual contrasta con la variabilidad de resultados que presentan las técnicas metaheurísticas reportadas como métodos de comparación. Conclusiones: La relajación cónica de segundo orden propuesta garantizó la convexidad del espacio de soluciones, y, por tanto, el hallazgo de la solución óptima en cada ejecución. Además, demostró que, para problemas de flujo de potencia óptimo en redes DC, tiene el mejor desempeño numérico que la mayoría de los métodos metaheurísticos comparativos; y que la solución provista por la relajación propuesta es equivalente a la proveída por el modelo exacto.

A Possible Classification for Metaheuristic Optimization Algorithms in Engineering and Science

Objective: This paper presents a hybrid optimization methodology for the optimal location and sizing of distributed generators (DG) in electrical distribution networks. We propose a mixed-integer nonlinear problem (MINLP) model for the mathematical formulation, whose objective function is the minimizing of power losses due to the Joule effect in conductors. The constraints we considered include active and reactive power balance, voltage regulation, percentage of penetration of DG into the distribution network, and the total amount of DG allowed in such network. Methodology: To solve the MINLP model, we employed a master-slave strategy that uses the Chu-Beasley genetic algorithm (CBGA) and the optimal power flow (OPF) model as the master and slave algorithms, respectively. This hybrid technique helps reduce the complexity of the MINLP model by eliminating binary variables through the master algorithm and then solving the resulting nonlinear problem (NLP), which corresponds to the OPF model, and uses a classical interior-point method available in MATLAB's fmincon toolbox. Results: We tested the efficiency and robustness of the proposed methodology in 33- and 69-node radial distribution networks. The results show its high performance in terms of power loss reduction and final sizing of DG. Conclusions: The results obtained in the test systems under analysis reveal that there is a direct and proportional relationship between technical losses, the percentage of distributed generation penetration, and the number of generators available. Resumen Objetivo: En este documento se presenta una metodología de optimización híbrida para la ubicación y el tamaño óptimos de generadores distribuidos (DG) en redes de distribución eléctrica. Se propone un modelo de problema no lineal de enteros mixtos (MINLP) para la formulación matemática, cuya función objetivo es la minimización de las pérdidas de potencia debido al efecto Joule en los conductores. Las restricciones incluyen el equilibrio de potencia activa y reactiva, regulación del voltaje, porcentaje de penetración de las DG en la red de distribución y las DG totales permitidas en dicha red. Metodología: Para resolver el modelo MINLP, se emplea una estrategia maestro-esclavo que utiliza el algoritmo genético Chu-Beasley (CBGA) y el modelo de flujo de potencia óptimo (OPF) como algoritmos maestro y esclavo, respectivamente. Esta técnica híbrida ayuda a reducir la complejidad del modelo MINLP al eliminar las variables binarias a través del algoritmo maestro y luego resolver el problema no lineal resultante (PNL) que corresponde al modelo OPF, utilizando un método clásico de punto interior disponible en la caja de herramientas fmincon de MATLAB Resultados: Se prueba la eficiencia y la solidez de la metodología propuesta en redes de distribución radial de 33 y 69 nodos. Los resultados muestran un alto rendimiento en términos de reducción de pérdida de potencia y dimensionamiento final de DG. Conclusiones: Existe una relación directa y proporcional entre las pérdidas técnicas, el porcentaje de penetración de generación distribuida y el número de generadores disponible.

El brote actual de la enfermedad por coronavirus (COVID-19), que se informó por primera vez en Wuhan, China, el 31 de diciembre de 2019, ha dejado un saldo al 19 de abril de 2020 de más de 3500000 infectados y 160000 muertes en 185 países. En este trabajo utilizamos un modelo basado en el Método de Cadena Microscópica de Markov (MCMM, Markov Microscopic Chain Approach) para estimar la propagación del COVID-19 en la ciudad de Pereira (Risaralda-Colombia). Este modelo incorpora importantes aspectos de la población, relacionados con: ubicación espacial dentro de la ciudad discretizada por comunas, movilidad entre comunas, estratificación por grupos de edad y separación de individuos en siete compartimientos epidemiológicos. Este modelo se utiliza para predecir, en una línea de tiempo, la incidencia de epidemias en poblaciones geolocalizadas, lo que se traduce en una herramienta indicadora para tomar medidas de control. Así, el resultado de la metodología caracteriza la evolución en el tiempo y el espacio de la proporción de los individuos en cada uno de los compartimientos epidemiológicos y en cada grupo etario. Los datos que se refieren a COVID-19, desde la municipalidad de Pereira, hasta el 20 de abril de 2020, se utilizan para alimentar el modelo y obtener las proyecciones espacio-temporales. Los resultados presentados consideran múltiples escenarios de movilidad, de forma que el aplanamiento de las curvas de los diferentes compartimientos epidemiológicos pueda ser visualizados de acuerdo a diferentes estrategias de confinamiento. Por tratarse de un modelo espacio-temporal, los resultados del modelo pueden ser presentados fácilmente como mapas de calor sobre cada uno de los compartimientos epidemiológicos, a fin de facilitar los procesos de toma de decisiones.

En este artículo se presenta una metodología para la estimación de parámetros en transformadores de distribuciónconsiderando medidas de tensión y corriente mediante un modelo matemático de programación no lineal (PNL).Este modelo de programación es desarrollado a través de la aplicación de las leyes de Kirchhoff al modelo del circuitoequivalente del transformador. Para resolver el modelo de PNL resultante se emplea el sistema de modelado algebraicogeneral conocido como GAMS. La metodología de optimización propuesta se desarrolla a manera de tutorial conun ejemplo de implementación el cual corresponde a un transformador monofásico de 20 kVA y una relación detransformación de 8000/240 V. Los resultados numéricos muestran que la estimación paramétrica en transformadoresmediante el modelo de PNL propuesto representa adecuadamente el comportamiento eléctrico de estos dispositivosen relación consu funcionamiento para diferentes escenarios de carga a los que se encuentren sometidos. Todas lassimulaciones fueron realizadas con la versión 25.1.3 de GAMS licenciado por la Universidad Tecnológica de Bolívar

This paper addresses the problem of the optimal stabilization of DC microgrids using a hierarchical control design. A recursive optimal power flow formulation is proposed in the tertiary stage that ensures the global optimum finding due to the convexity of the proposed quadratic optimization model in determining the equilibrium operative point of the DC microgrid as a function of the demand and generation inputs. An exact feedback controller with integral action is applied in the primary and secondary controller layers, which ensures asymptotic stability in the sense of Lyapunov for the voltage variables. The dynamical model of the network is obtained in a set of reduced nodes that only includes constant power terminals interfaced through power electronic converters. This reduced model is obtained by applying Kron’s reduction to the linear loads and step nodes in the DC grid. Numerical simulations in a DC microgrid with radial structure demonstrate the effectiveness and robustness of the proposed hierarchical controller in maintaining the stability of all the voltage profiles in the DC microgrid, independent of the load and generation variations.

La Universidad Tecnológica de Pereira (UTP), a través de la Vicerrectoría de Investigaciones Innovación y Extensión, busca promover la extensión universitaria como una estrategia que permite el intercambio, la aplicación y la integración del conocimiento científico, tecnológico, artístico y cultural; al igual que la vinculación con la realidad social, cultural, económica y productiva de la región y del país, al darle valor a las capacidades institucionales y al generar una articulación e integración entre la docencia y la investigación, la cual permita la identificación de problemáticas y la propuesta de alternativas de solución; además de las oportunidades en el sector externo para realizar intervenciones y alianzas que conduzcan a fortalecer y aportar al desarrollo económico, cultural y el bienestar de la comunidad en general. En este sentido, para el año 2019 se ofertó, a los miembros de la comunidad universitaria, la «Convocatoria interna para la financiación de proyectos de extensión social, cultural y artístico» cuya ejecución se realizaría en el año 2020 y cuyo objetivo era fomentar el desarrollo de proyectos de carácter social, cultural, artístico, los cuales permitieran la solución y transformación de problemáticas que involucrarán o beneficiarán sectores de diferentes comunidades Apropiación social del conocimiento CONTENIDO Población beneficiada ...............................................................................................54 Conclusiones..............................................................................................................54 Fotografías..................................................................................................................55 Bibliografía .................................................................................................................58 Capítulo cuatro Generación de Apropiación Social del Conocimiento en Temas de Procesamiento, Bioconservación y Nutrición, a los Productores del Mercado Agroecológico de la Universidad Tecnológica de Pereira Alimentos para la Vida...................................................................................................................................63 Resumen .....................................................................................................................64 Abstract.......................................................................................................................65 Introducción...............................................................................................................65 Objetivos.....................................................................................................................66 Objetivo general.........................................................................................................66 Objetivos específicos.................................................................................................66 Metodología ..............................................................................................................67 Resultados...................................................................................................................68 Población beneficiada ...............................................................................................70 Conclusiones..............................................................................................................71 Bibliografía .................................................................................................................71 Fotografías..................................................................................................................74 Capítulo cinco Cursos de refuerzo basados en aprendizaje activo, social y cultural, para afrontar el contexto de la enseñanza en ingeniería desde una visión interdisciplinaria............................................................................................................79 Resumen .....................................................................................................................79 Abstract ......................................................................................................................80 Introducción...............................................................................................................81 Objetivos.....................................................................................................................84 Objetivo general.........................................................................................................84 Objetivos específicos.................................................................................................84 Metodología ...............................................................................................................85 Resultados...................................................................................................................88 Población beneficiada ...............................................................................................89 Conclusiones..............................................................................................................89 Bibliografía .................................................................................................................90 Capítulo seis Laboratorios andantes: Fotografía estenopeica como interfaz cultural de la memoria colectiva..........................................................................................................95 Resumen .....................................................................................................................95 Abstract ......................................................................................................................96 Introducción...............................................................................................................97 Objetivos.................................................................................................................. 101 Objetivo general...................................................................................................... 101 Objetivos específicos.............................................................................................. 101 Metodología ........................................................................................................... 101 Resultados................................................................................................................ 105 Conclusiones........................................................................................................... 108 Bibliografía .............................................................................................................. 109 Capítulo siete Divulgación académica y cultural de los productos turísticos y rol del arenero artesanal en el turismo de la Virginia, Risaralda.................................................. 113 Resumen .................................................................................................................. 113 Abstract ................................................................................................................... 114 Introducción............................................................................................................ 114 Objetivos.................................................................................................................. 116 Objetivo general...................................................................................................... 116 Objetivos específicos.............................................................................................. 116 Metodología ............................................................................................................ 117 Resultados................................................................................................................ 117 Población beneficiada ............................................................................................ 119 Conclusiones........................................................................................................... 120 Bibliografía .............................................................................................................. 120 Capítulo ocho Proyecto de actualización en cirugía general........................................................ 125 Resumen .................................................................................................................. 125 Abstract.................................................................................................................... 126 Introducción............................................................................................................ 127 Objetivos.................................................................................................................. 127 Objetivo general...................................................................................................... 127 Objetivos específicos.............................................................................................. 128 Metodología ............................................................................................................ 128 Resultados................................................................................................................ 128 Población beneficiada ............................................................................................ 140 Conclusiones........................................................................................................... 141 Bibliografía .............................................................................................................. 141 Capítulo nueve Implementación de metodologías de enseñanza/aprendizaje en niños de tercera infancia y adolescentes a través de conceptos y proyectos de la aeronáutica (Aerokid)....................................................................................................................... 145 Resumen .................................................................................................................. 145 Abstract.................................................................................................................... 146 Introducción............................................................................................................ 147 Objetivos.................................................................................................................. 148 Objetivo general...................................................................................................... 148 Objetivos específicos.............................................................................................. 148 Metodología ............................................................................................................ 148 Resultados................................................................................................................ 158 Población beneficiada ............................................................................................ 158 Conclusiones........................................................................................................... 158 Bibliografía .............................................................................................................. 159 Capítulo diez “Contagio: Cursos de Extensión de Educadores Noveles para Población Migrante”...................................................................................................................... 163 Resumen .................................................................................................................. 163 Abstract.................................................................................................................... 164 Introducción............................................................................................................ 165 Objetivos.................................................................................................................. 166 Objetivo general...................................................................................................... 166 Objetivos específicos.............................................................................................. 166 Metodología ............................................................................................................ 167 Población beneficiada ............................................................................................ 169 Evento de cierre, 19 de noviembre: Narrativas migratorias: experiencias de viaje............................................................................................... 170 Medios de difusión................................................................................................ .171 Datos sobre la inscripción de los cursillistas....................................................... 171 Sobre la migración.................................................................................................. 173 Conclusiones........................................................................................................... 173 Bibliografía .............................................................................................................. 177 Capítulo once Los mercados agroecológicos en Pereira, Dosquebradas y Santa Rosa: una expresión de dinámicas sociales y economías posibles....................................... 181 Resumen .................................................................................................................. 181 Abstract.................................................................................................................... 182 Introducción............................................................................................................ 183 Objetivos.................................................................................................................. 185 Objetivo general...................................................................................................... 185 Objetivos específicos.............................................................................................. 185 Metodología ............................................................................................................ 185 Resultados................................................................................................................ 187 Población beneficiada ............................................................................................ 196 Conclusiones........................................................................................................... 198 Bibliografía .............................................................................................................. 200 Capítulo doce Identificación e implementación de medidas integrales basadas en minería de datos para la disminución de la deserción al interior de la facultad de ingenierías de la Universidad Tecnológica de Pereira ......................................... 205 Resumen .................................................................................................................. 205 Abstract.................................................................................................................... 206 Introducción............................................................................................................ 206 Objetivos ................................................................................................................. 208 Objetivo general...................................................................................................... 208 Objetivos específicos.............................................................................................. 208 Metodología ............................................................................................................ 208 Resultados................................................................................................................ 209 Resultados preliminares......................................................................................... 225 Población beneficiada ........................................................................................... 226 Conclusiones........................................................................................................... 226 Bibliografía .............................................................................................................. 227

This paper presents a comparative analysis of six different iterative power flow methods applied to AC distribution networks, which have been recently reported in the scientific literature. These power flow methods are (i) successive approximations, (ii) matricial backward/forward method, (iii) triangular-based approach, (iv) product linearization method, (v) hyperbolic linearization method, and (vi) diagonal approximation method. The first three methods and the last one are formulated without recurring derivatives, and they can be directly formulated in the complex domain, the fourth and fifth methods are based on the linear approximation of the power balance equations that are also formulated in the complex domain. The numerical comparison involves three main aspects: the convergence rate, processing time, and the number of iterations calculated using the classical Newton–Raphson method as the reference case. Numerical results from two test feeders composed of 34 and 85 nodes demonstrate that the derivative-free methods have linear convergence, and the methods that use derivatives in their formulation have quadratic convergence.

Microgrids are a part of the power system that consists of one or more units of distributed generation and are expected to remain in operation after being disconnected from the system. Since they rely on overlying networks, frequency control is very important for network-independent operation. Some of the most common problems in independently operating microgrids are frequency sustainability and its fluctuations. The main purpose of this study is to control the frequency of a microgrid in island mode in different scenarios. The objective function is defined based on time and changes in the system frequency. Thus, the variable parameters of the PID controller are transformed into an optimization problem and are solved through the hybrid PSO-GSA algorithm. The study considers four scenarios: (a) a microgrid dynamic model and optimal PID controller coefficients; (b) variable velocity disturbance applied to the studied system in order to observe power changes and the microgrid frequency; (c) stepped load changes applied to the studied system; and (d) the proposed methods on the standard test function. Simulations under different operating conditions are performed, indicating improvements in the stability of microgrid frequency fluctuations by means of the proposed control method. © 2022 by the authors.

This paper deals with new power flow formulations for AC distribution networks. The power flow problem is approximated using Laurent's series expansion method over the product between voltage variables in the power balance equations, which proportionates a mathematical structure similar to the conventional Newton-Raphson method. The proposed model is developed in complex variables, which decreases the number of calculations needed and prevents the transformation of the load flow model into polar coordinates. Numerical results confirm that the proposed method is faster regarding computational time and the total number of iterations required; besides, one of the main advantages of this approach is dealing with radial or mesh grids. All simulations are conducted in the programming environment in MATLAB software.

Time-delay is inherent to communications schemes in power systems, and in a closed loop strategy the presence of latencies increases inter-area oscillations and security problems in tie-lines. Recently, Wide Area Measurement Systems (WAMS) have been introduced to improve observability and overcome slow-rate communications from traditional Supervisory Control and Data Acquisition (SCADA). However, there is a need for tackling time-delays in control strategies based in WAMS. For this purpose, this paper proposes an Enhanced Time Delay Compensator (ETDC) approach which manages varying time delays introducing the perspective of network latency instead dead time, also, ETDC takes advantage of real signals and measurements transmission procedure in WAMS building a closed-loop memory control for power systems. The strength of the proposal was tested satisfactorily in a widely studied benchmark model in which inter-area oscillations were excited properly.

This paper deals with the problem of the optimal placement and sizing of distributed generators (DGs) in alternating current (AC) distribution networks by proposing a hybrid master&ndash, slave optimization procedure. In the master stage, the discrete version of the sine&ndash, cosine algorithm (SCA) determines the optimal location of the DGs, i.e., the nodes where these must be located, by using an integer codification. In the slave stage, the problem of the optimal sizing of the DGs is solved through the implementation of the second-order cone programming (SOCP) equivalent model to obtain solutions for the resulting optimal power flow problem. As the main advantage, the proposed approach allows converting the original mixed-integer nonlinear programming formulation into a mixed-integer SOCP equivalent. That is, each combination of nodes provided by the master level SCA algorithm to locate distributed generators brings an optimal solution in terms of its sizing, since SOCP is a convex optimization model that ensures the global optimum finding. Numerical validations of the proposed hybrid SCA-SOCP to optimal placement and sizing of DGs in AC distribution networks show its capacity to find global optimal solutions. Some classical distribution networks (33 and 69 nodes) were tested, and some comparisons were made using reported results from literature. In addition, simulation cases with unity and variable power factor are made, including the possibility of locating photovoltaic sources considering daily load and generation curves. All the simulations were carried out in the MATLAB software using the CVX optimization tool.

This paper presents an integrated methodology applied to photovoltaic (PV) plants for improving the dynamic performance of electric power systems. The proposed methodology is based on primary frequency control, which adds an ancillary signal to the voltage reference of the DC-link for the voltage source converter (VSC) in order to reduce power oscillations. This ancillary signal is computed by relating the energy stored in the VSC of the DC-link and the energy stored in the synchronous machine’s shaft. In addition, the methodology considers the operating limits of the VSC, which prioritizes active power over reactive power. Furthermore, the VSC control is assessed with interconnection and damping assignment passivity-based control (IDA-PBC), as well as compared to conventional PI control. IDA-PBC is employed to design a Lyapunov asymptotically stable controller using the Hamiltonian structural properties of the open-loop model of the VSC. A 12-bus test system that considers PV plants is employed to compare the proposed IDA-PBC control with a classical proportional-integral control approach. The impact of the proposed methodology is analyzed in four scenarios with different PV penetration levels (10%, 30%, 50%, and 80%) and four large disturbances in the test power system. In addition, a decrease in the inertia of the synchronous machines from 100 to 25% is analyzed. The time-domain simulation results show that the frequency oscillations are reduced by 16.8%, 38.43%, 37.53%, and 76.94% in comparison with the case where the proposed methodology was not implemented. The simulations were conducted using the SimPowerSystems toolbox of the MATLAB/Simulink software. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

This paper deals with a classical problem in power system analysis regarding the optimal location and sizing of distributed generators (DGs) in direct current (DC) distribution networks using the mathematical optimization. This optimization problem is divided into two sub-problems as follows: the optimal location of DGs is a problem, with those with a binary structure being the first sub-problem, and the optimal sizing of DGs with a nonlinear programming (NLP) structure is the second sub-problem. These problems originate from a general mixed-integer nonlinear programming model (MINLP), which corresponds to an NP-hard optimization problem. It is not possible to provide the global optimum with conventional programming methods. A mixed-integer semidefinite programming (MI-SDP) model is proposed to address this problem, where the binary part is solved via the branch and bound (B&amp, B) methods and the NLP part is solved via convex optimization (i.e., SDP). The main advantage of the proposed MI-SDP model is the possibility of guaranteeing a global optimum solution if each of the nodes in the B&amp, B search is convex, as is ensured by the SDP method. Numerical validations in two test feeders composed of 21 and 69 nodes demonstrate that in all of these problems, the optimal global solution is reached by the MI-SDP approach, compared to the classical metaheuristic and hybrid programming models reported in the literature. All the simulations have been carried out using the MATLAB software with the CVX tool and the Mosek solver.

The problem associated with economic dispatch of battery energy storage systems (BESSs) in alternating current (AC) distribution networks is addressed in this paper through convex optimization. The exact nonlinear programming model that represents the economic dispatch problem is transformed into a second-order cone programming (SOCP) model, thereby guaranteeing the global optimal solution-finding due to the conic (i.e., convex) structure of the solution space. The proposed economic dispatch model of the BESS considers the possibility of injecting/absorbing active and reactive power, in turn, enabling the dynamical apparent power compensation in the distribution network. A basic control design based on passivity-based control theory is introduced in order to show the possibility of independently controlling both powers (i.e., active and reactive). The computational validation of the proposed SOCP model in a medium-voltage test feeder composed of 33 nodes demonstrates the efficiency of convex optimization for solving nonlinear programming models via conic approximations. All numerical validations have been carried out in the general algebraic modeling system. Fil: Montoya Giraldo, Oscar Danilo. Universidad Distrital Francisco José de Caldas; Colombia. Universidad Tecnológica de Bolívar; Colombia Fil: Gil González, Walter. Institución Universitaria Pascual Bravo; Colombia Fil: Serra, Federico Martin. Universidad Nacional de San Luis. Facultad de Ingeniería y Ciencias Agropecuarias. Laboratorio de Control Automático; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Investigaciones en Tecnología Química. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Investigaciones en Tecnología Química; Argentina Fil: Hernández, Jesus C.. Universidad de Jaén; España Fil: Molina-Cabrera, Alexander. Universidad Tecnológica de Pereira; Colombia

This paper deals with the global stabilization of the reaction wheel pendulum (RWP) in the discrete-time domain. The discrete-inverse optimal control approach via a control Lyapunov function (CLF) is employed to make the stabilization task. The main advantages of using this control methodology can be summarized as follows: (i) it guarantees exponential stability in closed-loop operation, and (ii) the inverse control law is optimal since it minimizes the cost functional of the system. Numerical simulations demonstrate that the RWP is stabilized with the discrete-inverse optimal control approach via a CLF with different settling times as a function of the control gains. Furthermore, parametric uncertainties and comparisons with nonlinear controllers such as passivity-based and Lyapunov-based approaches developed in the continuous-time domain have demonstrated the superiority of the proposed discrete control approach. All of these simulations have been implemented in the MATLAB software.

This paper addresses the convergence analysis of the triangular-based power flow (PF) method in alternating current radial distribution networks. The PF formulation is made via upper-triangular matrices, which enables finding a general iterative PF formula that does not require admittance matrix calculations. The convergence analysis of this iterative formula is carried out by applying the Banach fixed-point theorem (BFPT), which allows demonstrating that under an adequate voltage profile the triangular-based PF always converges. Numerical validations are made, on the well-known 33 and 69 distribution networks test systems. Gauss-seidel, newton-raphson, and backward/forward PF methods are considered for the sake of comparison. All the simulations are carried out in MATLAB software.

Automatic voltage regulators and power system stabilizers have been employed successfully to deal with fast dynamics associated to local oscillations phenomena. Whereas, inter-area oscillations damping in large power systems requires remote feedback controllers fed by Wide Area Monitoring Systems (WAMS). Although these improvements in the inter-area oscillations behavior have been effective, a new challenge emerges: reaching stability with a closed loop control despite latencies due to measurements taken far away from the control centre. The research was motivated by the need for modernization of power systems capable of dealing with control difficulties in centralised WAMS for damping inter-area oscillations in power systems caused by delays in the communication system. Herein, time delay and control problems are addressed separately. The time delay problem is solved by a database based time compensation solution relying on the most updated available state of the system. The control problem is solved by a Model Predictive Control (MPC) with terminal cost and constraint set to handle complexities due to nonlinearities of the power system, the large scale of the problem and the parametric variations. Both solutions work in a coordinated way with local controllers to implement a decentralised coordinated strategy that manages slow global dynamics and fast local dynamics as well. The integrated proposed approach is called Time-Delay-Tolerant Model Predictive Control (TDT-MPC). Coordinated and coherent performance of the two TDT-MPC components (Kalman compensator and MPC) is achieved thanks to unifying power system reference models for both strategies. The approach has been tested on the IEEE 39 system and validated with time domain nonlinear simulations, obtaining post-fault damped oscillations and a good tracking of new power references when tripping tie lines.

This paper deals with the problem of the optimal reconfiguration of medium voltage distribution networks by proposing a mixed-integer nonlinear programming (MINLP) model. This optimization model has as objective function the minimization of the total power losses in all the branches of the network constrained by active and reactive power balance equations, voltage regulation bounds and device capabilities, among others. The proposed MINLP formulation works with branch-to-node incidence that allows representing the active and reactive power flow in branches as a function of the real and imaginary parts of the voltages and currents. The solution of the MINLP model is reached through the general algebraic modeling system widely know as GAMS package by presenting it in a tutorial form. This software allows implementing in compact form the proposed model and solve it via branch and bound methods. Two test feeders composed by 5 and 14 nodes permits demonstrating the fidelity of the proposed MINLP model regarding power losses minimization when compared with literature reports.

This paper addresses the phase-balancing problem in three-phase power grids with the radial configuration from the perspective of master–slave optimization. The master stage corresponds to an improved version of the Chu and Beasley genetic algorithm, which is based on the multi-point mutation operator and the generation of solutions using a Gaussian normal distribution based on the exploration and exploitation schemes of the vortex search algorithm. The master stage is entrusted with determining the configuration of the phases by using an integer codification. In the slave stage, a power flow for imbalanced distribution grids based on the three-phase version of the successive approximation method was used to determine the costs of daily energy losses. The objective of the optimization model is to minimize the annual operative costs of the network by considering the daily active and reactive power curves. Numerical results from a modified version of the IEEE 37-node test feeder demonstrate that it is possible to reduce the annual operative costs of the network by approximately 20% by using optimal load balancing. In addition, numerical results demonstrated that the improved version of the CBGA is at least three times faster than the classical CBGA, this was obtained in the peak load case for a test feeder composed of 15 nodes, also, the improved version of the CBGA was nineteen times faster than the vortex search algorithm. Other comparisons with the sine–cosine algorithm and the black hole optimizer confirmed the efficiency of the proposed optimization method regarding running time and objective function values.

Phase balancing is a highly complex problem that consists of minimizing power losses by swapping generation and loads along a distribution feeder. Being a discrete and nonlinear problem, its solution is usually subject to the use of heuristic methods such as Genetic Algorithms or Particle Swarm Optimization. However, the representation of the feasible space is challenging for conventional approaches. This paper proposes a heuristic algorithm which is based on group-theory, an algebraic modeling that allows a compact and efficient representation of the feasible space. The proposed representation not only allows to develop an algorithm that guarantees feasibility along the generations, but also permits its implementation in the crossover and the mutation steps. Formal definitions of groups are presented and complemented with a matrix homomorphisms that allows the implementation of the algorithm. Numerical calculations on the IEEE 13, IEEE 37 and IEEE 123 nodes test feeders complement the proposed analysis and confirm the efficiency of what is proposed.

Debido al aumento de la carga y al creciente uso de energías alternativas en el sistema de potencia, este se ha vuelto más sensible a problemas de estabilidad de tensión. Si se considera que los métodos de análisis estático como el flujo de carga no evalúan de manera correcta la estabilidad de tensión, debido a que usan modelos simples para describir las componentes del sistema, y que los modelos dinámicos para el análisis de estabilidad de tensión son complejos y tienen un alto costo computacional,se evidencia la necesidad de desarrollar una metodología más precisa y eficiente.Se presenta un modelo basado en Redes Neuronales Artificiales (ANN, del inglés Artificial Neural Networks);estas tienen la capacidad de aprender y extraer las principales características de un conjunto de datos. Pueden ofrecer respuestas correctas para aquellas entradas que presentan variaciones causadas por los efectos del ruido o por las distorsiones del medio. Debido a que las ANN tienen habilidad para cambiar su estructura internadurante el entrenamientohan sido utilizadas para el desarrollo de este trabajo comomáquinas de estimacióndel margen de estabilidad de tensión del sistema de potencia a partir su estado. Los datos de entrenamiento se obtienen por medio de un flujo de carga que entrega las condiciones iníciales o las también conocidas variables de entrada a la red y luego, mediante funciones de energía, se obtienen los márgenes de estabilidad que para este caso son las salidas deseadas. Se muestran resultados para un sistema de prueba de cuatro nodos, donde la RN estima de forma cercana las estimaciones efectuadas mediante el uso de márgenes de estabilidad determinísticos.

Este documento presenta una metodología basada en algoritmos genéticos que permite adelantar el reordenamiento del parque de transformadores existente en el nivel de tensión I de los sistemas de distribución de Bogotá D.C., Colombia, con el fin de maximizar el reconocimiento de activos que el ente regulador CREG (Comisión Reguladora de Energía y Gas) realiza a los distintos operadores de red, según lo establecido en la resolución 097 de 2008. Para la aplicación del algoritmo se obtuvieron mediciones de potencia activa máxima para cada hora del año 2009 en un conjunto de 94 transformadores de diferentes capacidades, escogidos de forma aleatoria, instalados en el sistema de distribución de CODENSA S.A. ESP, empresa encargada de prestar el servicio de energía eléctrica en la ciudad de Bogotá D.C. Con esta información se construyeron curvas de carga diarias representativas y se elaboró una base de datos que contiene los costos operativos del movimiento de los equipos y de las tarifas, a partir de los cuales fue posible modelar la función objetivo y las restricciones del problema, obteniéndose un elevado número de combinaciones posibles (alrededor de 1*10(134)) debido al gran número de nodos y de transformadores presentes en el sistema de distribución. La búsqueda convencional de una solución en la anterior situación implicaría el empleo de tiempos prohibitivos, por lo cual se implementó un algoritmo genético clásico, obteniéndose de esta manera una solución óptima que ofrece una ganancia económica en el primer año, asociada al incremento en el cargo por uso, de $ 253.446.362,47 (COP), ganancias que podrían verse incrementadas considerablemente al ejecutar el algoritmo en parques de transformadores más grandes.This paper presents a methodology based on genetic algorithms that allows the reordering of the existing park transformers voltage level I of the distribution systems of Bogotá city, Colombia, in order to maximize the recognition of assets that the regulator CREG (Comisión Reguladora de Energía y Gas) made to the various network operators, as set out in resolution 097 of 2008. For the application of the algorithm, we obtained maximum active power measurements for each hour of the year 2009 in a number of transformers of different capacities, chosen at random, installed in the distribution system CODENSA SA ESP, the company that provides electric service in the Bogotá city. With this information we built representative daily load curves and developed a database that contains the operating costs of moving equipment and tariffs, from which it was possible to model the objective function and constraints of the problem, obtaining a high number of possible combinations (about 1*10(134)) due to the large number of nodes and processors present in the distribution system. Conventional search of a solution in the above situation implies the use of prohibitive times. For this reason we implemented a classical genetic algorithm, thus obtaining an optimal solution that offers a financial gain in the first year, associated with the increase in the usage charge, of $ 253.446.362,47 (COP), profits that could be increased considerably when running the algorithm on larger transformers parks.

Power systems can experience poorly damped oscillations tendency which may cause loss of synchronism and security constraints infringement. This may be caused by disturbances in power consumption, failures, and recently by the presence of delays in monitoring process. In consequence, control systems, which must deal with delayed signals in monitoring and control, need to be designed to avoid instability in the system. This paper presents the application of a proposed Sliding Prediction Block which feeds a Model Predictive Control (MPC) aiming to increase the damping of oscillations in a nonlinear model of the delayed single-machine infinite-bus system (SMIB), and in the two area test case of Kundur. The proposed scheme controls the mechanical power to track the power reference at the infinite bus, and in Kundur system the method acts over the excitation system in one of its machines. Also, the analyzed cases consider delayed signals feeding the control strategy. Results show that combining the Sliding Prediction Block with Model Predictive Control (MPC) face effectively the time-delay problem.

When a power system is exposed to a major disturbance, the system exhibits a tendency towards poorly damped oscillations which may cause loss of synchronism; in consequence, control actions, which must deal with the presence of delays in monitoring and control signals, have to be performed to avoid an instability in the system. This paper presents the application of a nonlinear control strategy for the damping of oscillations in a delayed single-machine infinite-bus system. The damping of oscillations is achieved by acting over the mechanical power and tracking the electrical power reference at the infinite bus. Also, it is addressed the issue of time-delayed signals considering the electrical power at the infinite bus as a delayed remote signal. Results show that the proposed Smith predictor based backstepping control effectively resolves the time-delay problem, and its possible application to multi machine systems is promising.

Power systems control strategies that use global signals have shown better results than those based on local signals, but the remote signals are usually taken far away from the control center. Because of that, wide area power systems controlled using global signals are inherently delayed, and time delays jeopardize the stability of power systems. This paper presents a Kalman based time delay compensation strategy, which feed a Model Predictive Control (MPC) scheme to damp inter-area oscillations in power systems with latencies in their communications. A Kalman state estimator is employed to get the states. The proposal uses a dynamic reduced order model obtained using Hankel singular values. The methodology is promissory because it considers time delays in control schemes design processes, useful for either centralized or distributed wide area power system controllers based on widespread metering. This approach was validated for controlling inter-area oscillations in a test power system with two areas, 4 generators and a tie power line. Results suggest an enhancement of the power system dynamic performance upon the application of the method proposed.

Este documento presenta una metodología basada en algoritmos genéticos que permite adelantar el reordenamiento del parque de transformadores existente en el nivel de tensión I de los sistemas de distribución de Bogotá D.C., Colombia, con el fin de maximizar el reconocimiento de activos que el ente regulador CREG (Comisión Reguladora de Energía y Gas) realiza a los distintos operadores de red, según lo establecido en la resolución 097 de 2008. Para la aplicación del algoritmo se obtuvieron mediciones de potencia activa máxima para cada hora del año 2009 en un conjunto de 94 transformadores de diferentes capacidades, escogidos de forma aleatoria, instalados en el sistema de distribución de CODENSA S.A. ESP, empresa encargada de prestar el servicio de energía eléctrica en la ciudad de Bogotá D.C. Con esta información se construyeron curvas de carga diarias representativas y se elaboró una base de datos que contiene los costos operativos del movimiento de los equipos y de las tarifas, a partir de los cuales fue posible modelar la función objetivo y las restricciones del problema, obteniéndose un elevado número de combinaciones posibles (alrededor de 1*10(134)) debido al gran número de nodos y de transformadores presentes en el sistema de distribución. La búsqueda convencional de una solución en la anterior situación implicaría el empleo de tiempos prohibitivos, por lo cual se implementó un algoritmo genético clásico, obteniéndose de esta manera una solución óptima que ofrece una ganancia económica en el primer año, asociada al incremento en el cargo por uso, de $ 253.446.362,47 (COP), ganancias que podrían verse incrementadas considerablemente al ejecutar el algoritmo en parques de transformadores más grandes.