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The optimal expansion of AC medium-voltage distribution grids for rural applications is addressed in this study from a heuristic perspective. The optimal routes of a distribution feeder are selected by applying the concept of a minimum spanning tree by limiting the number of branches that are connected to a substation (mixed-integer linear programming formulation). In order to choose the caliber of the conductors for the selected feeder routes, the maximum expected current that is absorbed by the loads is calculated, thereby defining the minimum thermal bound of the conductor caliber. With the topology and the initial selection of the conductors, a tabu search algorithm (TSA) is implemented to refine the solution with the help of a three-phase power flow simulation in MATLAB for three different load conditions, i.e., maximum, medium, and minimum consumption with values of 100%, 60%, and 30%, respectively. This helps in calculating the annual costs of the energy losses that will be summed with the investment cost in conductors for determining the final costs of the planning project. Numerical simulations in two test feeders comprising 9 and 25 nodes with one substation show the effectiveness of the proposed methodology regarding the final grid planning cost; in addition, the heuristic selection of the calibers using the minimum expected current absorbed by the loads provides at least 70% of the calibers that are contained in the final solution of the problem. This demonstrates the importance of using adequate starting points to potentiate metaheuristic optimizers such as the TSA.

Passivity-based nonlinear control for an isolated microgrid system is proposed in this paper. The microgrid consists of a photovoltaic array and a battery energy storage connected to a point of common converters, supplying a constant power load. The purpose of this control strategy is to maintain the output direct current voltage in its reference value under load variations, improving battery interaction. The system is represented by its state space averaged model and the proposed controller is designed using the interconnection and damping assignment strategy, which allows obtaining controller parameters while ensuring the closed-loop system stability. The unknown constant power load is estimated using an observer based on the energy function of the system. The behavior of the proposed control strategy is validated with simulation and experimental results

This paper deals with the problem of the optimal selection and location of batteries in DC distribution grids by proposing a new mixed-integer convex model. The exact mixed-integer nonlinear model is transformed into a mixed-integer quadratic convex model (MIQC) by approximating the product among voltages in the power balance equations as a hyperplane. The most important characteristic of our proposal is that the MIQC formulations ensure the global optimum reaching via branch & bound methods and quadratic programming since each combination of the binary variables generates a node with a convex optimization subproblem. The formulation of the objective function is associated with the minimization of the energy losses for a daily operation scenario considering high renewable energy penetration. Numerical simulations show the effectiveness of the proposed MIQC model to reach the global optimum of the optimization model when compared with the exact optimization model in a 21-node test feeder. All the validations are carried out in the GAMS optimization software., QC 20211026

A nonlinear controller for an electric vehicle battery charger is proposed in this work. The controller allows charging the battery bank with constant current and constant voltage charging profile, while ensuring unity power factor and low distortion in the grid current. A single model is made for the complete system and the controller is designed using interconnection and damping assignment. The proposed controller ensures the closed-loop stability and allows decoupling the system avoiding disturbances in the electric grid and battery bank. The proposal is validated with simulation results., En este trabajo se presenta una estrategia de control no lineal para un cargador de baterías de vehículos eléctricos. El controlador propuesto permite realizar la recarga del banco de baterías mediante un perfil de carga a corriente y tensión constante mientras que asegura factor de potencia unitario y baja distorsión en la corriente de red. Se realiza un modelo único para todo el sistema a partir del cual se diseña el controlador utilizando asignación de interconexión y amortiguamiento. Esta estrategia asegura un controlador estable a lazo cerrado y permite desacoplar el sistema evitando que las perturbaciones del lado de la red afecten la carga de la batería y viceversa. La propuesta es validada mediante resultados de simulación.

This paper addresses the problem of sinusoidal voltage generation in linear loads using a voltage source inverter (VSI). The port-Hamiltonian structure in open-loop is used to design a passivity-based controller with proportional-integral gains (PI-PBC) in order to develop the control strategy. The main advantage of using passivity-based controllers corresponds to the possibility of guaranteeing asymptotic stability by transforming the trajectory tracking problem into a regulation control one. In addition to the PI-PBC, a linear load estimator is employed based on an integral formulation to determine the value of the equivalent conductance in the load, which reduces the number of current sensors. Numerical validations demonstrate that the sinusoidal voltage provided by the VSI to the load has a tracking error lower than $1~\%$, with harmonic distortions lower than $2.6~\%$, both for voltage and currents in the load. All the simulations were conducted in MATLAB/Simulink using the SimPowerSystems library version 2017a.