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Objective: This work involves a convex-based mathematical reformulation for the optimal power flow problem in DC networks. The objective of the proposed optimization model corresponds to the minimization of the power losses through all the network branches considering a convex conic model that warranties finding the global optimal. Methodology: This is split into three stages: The first stage presents the mathematical model of optimal power flow for DC networks and all its 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; and the fourth stage presents 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 model of proposed convex optimal power flow 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 warrantied the convexity of the solution space and therefore, the finding of the optimal solution at each execution; besides of this, demonstrated that for optimal power flow problems in DC networks, the numerical performance is better than most of the comparative metaheuristic methods; and the provided solution by the proposed relaxation is equivalent to that provided by the exact model. Keywords: Direct current networks, second-order conic relaxation, non-linear programming model, convex optimization., Resumen Objetivo: Este trabajo plantea una reformulación matemática de naturaleza convexa para el 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: Está dividida en tres etapas: la primera presenta el modelo matemático de flujo de potencia óptimo para redes DC y todas sus 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; mientras que la cuarta etapa presenta 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 la solución provista por la relajación propuesta es equivalente a la proveída por el modelo exacto. Palabras clave: Redes de corriente continua, relajación cónica de segundo orden, modelo de programación no lineal, optimización convexa.

In this research paper, a combinatorial optimization approach is proposed for parameter estimation in single-phase transformers considering voltage and current measurements at the transformer terminals. This problem is represented through a nonlinear programming model (NLP), whose objective is to minimize the root mean square error between the measured voltage and current values and the calculated values from the equivalent model of the single-phase transformer. These values of voltage and current can be determined by applying Kirchhoff’s Laws to the model T of the transformer, where its parameters, series resistance and reactance as well as the magnetization resistance and reactance, i.e., R1, R′2,X1, X′2,Rc y Xm, are provided by the Hurricane Optimization Algorithm (HOA). The numerical results in the 4 kVA, 10 kVA and 15 kVA single-phase test transformers demonstrate the applicability of the proposed method since it allows the reduction of the average error between the measured and calculated electrical variables by 1000% compared to the methods reported in the specialized literature. This ensures that the parameters estimated by the proposed methodology, in each test transformer, are close to the real value with an accuracy error of less than 6%. Additionally, the computation times required by the algorithm to find the optimal solution are less than 1 second, which makes the proposed HOA robust, reliable, and efficient. All simulations were performed in the MATLAB programming environment. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

This research addresses the problem of the optimal placement and sizing of (PV) sources in medium voltage distribution grids through the application of the recently developed Newton metaheuristic optimization algorithm (NMA). The studied problem is formulated through a mixedinteger nonlinear programming model where the binary variables regard the installation of a PV source in a particular node, and the continuous variables are associated with power generations as well as the voltage magnitudes and angles, among others. To improve the performance of the NMA, we propose the implementation of a discrete–continuous codification where the discrete component deals with the location problem and the continuous component works with the sizing problem of the PV sources. The main advantage of the NMA is that it works based on the first and second derivatives of the fitness function considering an evolution formula that contains its current solution (xt i ) and the best current solution (xbest), where the former one allows location exploitation and the latter allows the global exploration of the solution space. To evaluate the fitness function and its derivatives, the successive approximation power flow method was implemented, which became the proposed solution strategy in a master–slave optimizer, where the master stage is governed by the NMA and the slave stage corresponds to the power flow method. Numerical results in the IEEE 34- and IEEE 85-bus systems show the effectiveness of the proposed optimization approach to minimize the total annual operative costs of the network when compared to the classical Chu and Beasley genetic algorithm and the MINLP solvers available in the general algebraic modeling system with reductions of 26.89% and 27.60% for each test feeder with respect to the benchmark cases.

Transportation electrification has demonstrated a significant position on power utilities and logistic companies, in terms of assets operation and management. Under this context, this paper presents the problem of seeking feasible and good quality routes for electric light commercial vehicles considering battery capacity and charging station siting on the power distribution system. Different transportation patterns for goods delivery are included, such as the capacitated vehicle routing problem and the shortest path problem for the last mile delivery. To solve the problem framed within a mixed integer linear mathematical model, the GAMS software is used and validated on a test instance conformed by a 19-customer transportation network, spatially combined with the IEEE 34 nodes power distribution system. The sensitivity analysis, performed during the computational experiments, show the behavior of the variables involved in the logistics operation, i.e., routing cost for each transport pattern. The trade-off between the battery capacity, the cost of the charging station installation, and energy losses on the power distribution system is also shown, including the energy consumption cost created by the charging operation.

Este proyecto nace de la iniciativa de actualizar y modificar un dron existente en el programa de Tecnología Eléctrica de la Facultad de Tecnología, e incursionar en el ámbito de la fotogrametría, aprovechando las capacidades del equipo para realizar rutas programadas. Al Dron existente se le realizó el acople de una cámara fotográfica convencional, que permite realizar tomas aéreas de gran calidad. En el campo de la electricidad se puede utilizar para realizar el levantamiento de terrenos e inspecciones donde existan o se tenga planeado instalar líneas de transmisión, entre otros.

This paper proposes a quadratic convex model for optimal operation of battery energy storage systems in a direct current (DC) network that approximates the original nonlinear non-convex one. The proposed quadratic convex model uses Taylor’s series expansion to transform the product between voltage variables in the power balance equations into a linear combination of them. Numerical simulations in the general algebraic modeling system (GAMS) for both models show small diferences in the daily energy losses, which are lower than 3.00%. The main advantage of the proposed quadratic model is that its optimal solution is achievable with interior point methods guaranteeing its uniqueness (convexity properties of the solution space and objective function), which is not possible to guarantee with the exact nonlinear non-convex model. The 30-bus DC test feeder with four distributed generators (with power generation forecast via artifcial neural networks with errors lower than 1% between real and predicted generation curves) and three batteries is used to validate the proposed convex and exact models. Numerical results obtained by GAMS show the efectiveness of the proposed quadratic convex model for diferent simulation scenarios tested, which was confrmed by the CVX tool for convex optimization in MATLAB

In the last decade, the deployment of electric vehicles (EVs) has been largely promoted. This development has increased challenges in the power systems in the context of planning and operation due to the massive amount of recharge needed for EVs. Furthermore, EVs may also offer new opportunities and can be used to support the grid to provide auxiliary services. In this regard, and considering the research around EVs and power grids, this paper presents a chronological background review of EVs and their interactions with power systems, particularly electric distribution networks, considering publications from the IEEE Xplore database. The review is extended from 1973 to 2019 and is developed via systematic classification using key categories that describe the types of interactions between EVs and power grids. These interactions are in the framework of the power quality, study of scenarios, electricity markets, demand response, demand management, power system stability, Vehicle-to-Grid (V2G) concept, and optimal location of battery swap and charging stations.

Los operadores de red están constantemente trabajando en mantener un nivel de confiabilidad apropiado en el suministro de energía y preservar la integridad de la vegetación que crece bajo las redes aéreas de distribución de energía. Por tal razón, en este artículo se proponen e implementan diferentes alternativas para gestionar de manera óptima el mantenimiento de la vegetación. El problema se representa a través de modelamiento matemático, en función de varios aspectos enmarcados en el manejo de la flora, basados en la capacidad técnica de la empresa y las metas de confiabilidad estipuladas por los organismos gubernamentales. En la solución del problema, se obtiene un programa de mantenimiento de la vegetación en términos de cuándo y dónde se debe realizar este, además de la asignación de los grupos de trabajo destinados para las labores de poda a lo largo del sistema de distribución. De esta manera, se minimiza el nivel de energía no servida y se optimizan los recursos financieros necesarios para este tipo de tareas.

Network operators work constantly to maintain an appropriate level of reliability in their power supply and to preserve the integrity of the vegetation growing underneath overhead power distribution systems. Accordingly, this article proposes and adopts different approaches to optimally manage vegetation maintenance in such field. Mathematical modeling is used to represent the problem in terms of several aspects involved in vegetation management, based on the technical capacity of the utility company and the reliability goals established by governmental regulatory entities. The solution is a vegetation maintenance schedule in terms of when, where, and which crews must perform the pruning activities along the distribution network. As a result, the Non-Served Energy Level NSEL is minimized and the financial resources earmarked for this type of maintenance tasks are optimized., Los operadores de red están constantemente trabajando en mantener un nivel de confiabilidad apropiado en el suministro de energía y preservar la integridad de la vegetación que crece bajo las redes aéreas de distribución de energía. Por tal razón, en este artículo se proponen e implementan diferentes alternativas para gestionar de manera óptima el mantenimiento de la vegetación. El problema se representa a través de modelamiento matemático, en función de varios aspectos enmarcados en el manejo de la flora, basados en la capacidad técnica de la empresa y las metas de confiabilidad estipuladas por los organismos gubernamentales. En la solución del problema, se obtiene un programa de mantenimiento de la vegetación en términos de cuándo y dónde se debe realizar este, además de la asignación de los grupos de trabajo destinados para las labores de poda a lo largo del sistema de distribución. De esta manera, se minimiza el nivel de energía no servida y se optimizan los recursos financieros necesarios para este tipo de tareas.

La introducción de vehículos eléctricos VEs representa una alternativa positiva y proactiva en la electrificación del sector de transporte. Desde el punto de vista de la reducción en la emisión de gases de efecto invernadero y el ruido, son notables los beneficios para el medio ambiente y la población en general. No obstante, la recarga masiva de VEs tendrá un impacto significativo en el sistema de distribución de energía eléctrica, creando inconvenientes en la calidad de la potencia, picos no deseados de demanda, perdidas de potencia en las líneas y problemas de caídas de tensión. Por otro lado, la batería es otro problema que afecta la adopción de VEs, específicamente para las compañías de transporte de mercancía, debido principalmente a la baja autonomía en distancia recorrida comparado con los vehículos de combustión interna.

Se presenta una descripción de la construcción de un prototipo de seguidor solar, incluyendo las características físicas de la estructura de soporte, el modelo lumínico artificial que reemplaza la luz natural y el movimiento del sol en la esfera celeste, los circuitos de acondicionamiento y de adquisición de señales mediante el seguimiento de variables como la potencia de salida del panel y la diferencia de tensión en las celdas fotovoltaicas encargadas de discriminar la posición del panel con respecto al sol.