Browsing by Author "De Angelo, Cristian Hernan"

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Global Optimal Stabilization of MT-HVDC Systems: Inverse Optimal Control Approach
(2021-11-17) Montoya, Oscar Danilo; Gil-González, Walter; Martin Serra, Federico; De Angelo, Cristian Hernan; Hernández, Jesus C.
The stabilization problem of multi-terminal high-voltage direct current (MT-HVDC) systems feeding constant power loads is addressed in this paper using an inverse optimal control (IOC). A hierarchical control structure using a convex optimization model in the secondary control stage and the IOC in the primary control stage is proposed to determine the set of references that allows the stabilization of the network under load variations. The main advantage of the IOC is that this control method ensures the closed-loop stability of the whole MT-HVDC system using a control Lyapunov function to determine the optimal control law. Numerical results in a reduced version of the CIGRE MT-HVDC system show the effectiveness of the IOC to stabilize the system under large disturbance scenarios, such as short-circuit events and topology changes. All the simulations are carried out in the MATLAB/Simulink environment.
Heuristic Methodology for Planning AC Rural Medium-Voltage Distribution Grids
(2021-08-20) Montoya, Oscar Danilo; Serra, Federico Martin; De Angelo, Cristian Hernan; Chamorro, Harold R.; Alvarado-Barrios, Lázaro
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.
Nonlinear control for a DC–DC converter with dual active bridges in a DC microgrid
(2022-10-29) Esteban, Francisco D.; Serra, Federico M.; De Angelo, Cristian Hernan; Montoya, Oscar D.
This work presents a new control strategy for a DC–DC converter with dual active bridges used to interconnect two feeders in a DC microgrid. The proposed control strategy allows regulating the output voltage of the converter while maintaining the mean primary and secondary current value of the high-frequency transformer at zero, in order to avoid magnetic saturation. The controller is designed using the nonlinear control strategy based on feedback linearization, which is based on the converter generalized space-state averaged model. The performance of the proposed controller is validated via simulation and experimental results.
On the efficiency in electrical networks with ac and dc operation technologies: A comparative study at the distribution stage
(2020-08-20) Montoya, Oscar Danilo; Martín-Serra, Federico; De Angelo, Cristian Hernan
This research deals with the efficiency comparison between AC and DC distribution networks that can provide electricity to rural and urban areas from the point of view of grid energy losses and greenhouse gas emissions impact. Configurations for medium- and low-voltage networks are analyzed via optimal power flow analysis by adding voltage regulation and devices capabilities sources in the mathematical formulation. Renewable energy resources such as wind and photovoltaic are considered using typical daily generation curves. Batteries are formulated with a linear representation taking into account operative bounds suggested by manufacturers. Numerical results in two electrical networks with 0.24 kV and 12.66 kV (with radial and meshed configurations) are performed with constant power loads at all the nodes. These simulations confirm that power distribution with DC technology is more efficient regarding energy losses, voltage profiles and greenhouse emissions than its AC counterpart. All the numerical results are tested in the General Algebraic Modeling System widely known as GAMS.
On the use of the p-q theory for harmonic currents cancellation with shunt active filter
(VSB-Technical University of Ostrava, 2019) Serra F.M.; Montoya O.D.; De Angelo, Cristian Hernan; Forchetti D.G.
Discussion and mathematical proof on necessary and sufficient conditions for the application of the p-q theory for compensating the harmonic currents consumed by non-linear load using a shunt active filter are presented. These conditions over instantaneous active and reactive powers were not addressed before and must be considered on the design of new control strategies based on p-q theory. Theoretical demonstration is proposed and an application example with simulations results is used to validate the theoretical results. © 2019 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING.
Voltage regulation of an isolated DC microgrid with a constant power load: a passivity-based control design
(2021-08-28) Magaldi, Guillermo Luciano; Serra, Federico Martin; De Angelo, Cristian Hernan; Montoya, Oscar Danilo; Giral-Ramírez, Diego Armando
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