Felipe Alejandro Uribe

Microgrids have extended their use when connected to or isolated from the grid, where decentralized control architectures are increasingly being used due to their inherent advantages. Among controllers, the non-communicated type allows the problems introduced by the use of communication systems to be avoided; however, these type of controllers are generally limited to performing first-level control actions, precisely due to the lack of information caused by the absence of a communication network. This work proposes an algorithm for a non-communicated controller to (a) identify which of the power sources are connected to a microgrid and (b) calculate the load power; both of these actions only require local measurements and allow the microgrid performance to be improved. The proposal aims at identifying the power sources by analyzing the electromechanical oscillations that occur in microgrids that are fed by inertia-enabled inverters and synchronous generators using droop controllers. This is used to automatically adjust the power sharing ratio between sources based on the generation capacity and load of a microgrid. Numerical simulations that clearly show the advantages are used to support the effectiveness of the proposal.

This paper introduces new techniques for scaling reduction and subconductor shape error compensation, aimed at minimizing computational effort and shortening the processing time needed for square and circular conductor subdivision methods in estimating the frequency-dependent impedance parameters of concentric and arbitrarily segmented underground cables. By designing a new image of the cable cross-section at a reduced scale, the computational demand and thus the processing time are decreased by order of magnitude compared to other subconductor reduction methods, while still ensuring high precision in the numerical estimation of the cables' frequency-dependent series impedance parameters. The results are corroborated using the analytical solution for concentric or coaxial cables based on Schelkunoff's transmission line theory. Validation is performed using the finite element method with boundary layer properties for cables with arbitrary physical symmetry for the segmented three-phase underground power cable

This paper introduces an innovative method for studying dynamic noise electrical signals through orthogonal base vector decomposition. This approach effectively harnesses the properties of an orthogonal basis, even amid noise, utilizing a generalized Fourier series framework to enhance understanding and accuracy. Central to this methodology is the main component function, which enables the decomposition of noise and error functions based on both the correlation index and generalized Fourier approximated series. We present compelling test applications that analyze harmonic, interharmonic, and real measured signals using Chebyshev orthogonal polynomials, Legendre polynomial approximations, and Fourier series approximations. This method not only proves to be efficient with remarkable accuracy but also maintains a low computational burden, making it highly practical for real-world applications. By employing the correlation coefficient of the polynomials and function approximations, we provide a qualitative comparison that underscores the accuracy of signal synthesis against the traditional Fourier theory. In conclusion, the insights and characteristics derived from this research empower the extraction of crucial modal component information on the propagation, attenuation, and velocities of the electrical signals under investigation. This advancement holds significant promise for future applications in the field.

In this article, the design and implementation of a compact and portable six-port reflectometer for measuring the reflection coefficient at 2.4 GHz is presented. The proposed design utilizes reduced-size components, such as an RF generator and an acquisition board, achieving a portable solution that can be used outside the RF laboratory. In this design, the six-port circuit consists of only two microstrip directional couplers with an angularly equidistant distribution of their q points. This configuration facilitates the implementation of the reflectometer, reducing complexity without sacrificing accuracy, even when compared to a commercial VNA. This design is an attractive and efficient alternative for research projects requiring the use of six-port reflectometry technique.

Harmonic, dynamic transient, and electromagnetic induction signals can propagate at very high speeds through the electrical network, causing insulation breakdown damage to system equipment or severely damaging sensitive electronic control devices, requiring costly maintenance repairs or replacement due to permanent loss. To prevent possible economically significant damage, it is crucial to have timely measurements of voltages and currents using a high-speed digital phosphor oscilloscope and mass storage in the sampling to obtain an accurate and timely diagnosis. The problem here is that when a very high sampling rate is used with a digital phosphor oscilloscope for the precise recording of the phenomenon, due to uncertainty at the trigger time, or by setting a wide recording aperture on the time scale, the process of extracting information for further signal processing becomes a problem of a lot of information that requires a lot of computing time and computational resources. Although there are different decimation methods for sampling rate, these are usually very slow and inefficient because they partly depend on an engineer analyst’s technical criteria and experience. This paper presents a new application of the compressed sensing method with a new improved and validated basis pursuit reconstruction algorithm for dynamic electrical signals of the harmonic and transient type, drastically reducing the number of samples and the processing time without losing accuracy in the results. The harmonic signal under study of 6.25k samples was reduced to a subsampling range between 100-3.7k samples with a minimum processing time of 0.1053s. The transient signal with 10k samples, was reduced to a range of 500-2.7k samples with a minimum processing time of 0.0861s. In both cases, the accuracy of the reconstructed signals is very high according to their validation using Parseval’s Theorem.

This paper introduces a new method for analyzing electrical signals useful to track harmonics amplitude through the use of a simple linear Kalman Filter with high accuracy and computational efficiency. The key idea in this paper is based on the vector extraction properties of the orthogonal base decomposition of the electrical signal which usually correlates with noise and different signal modes depending on its physical origin. This vector extraction preserves a proportional time-frequency energy relation for each harmonic’s magnitude, from which we can propose a discriminating criterion related to this method’s accuracy, validated here through Parseval’s Theorem.

An efficient and simple design of a 2.4 GHz six-port circuit for a reflectometer is analyzed and presented. This circuit matches with the ideal q-points symmetrical distribution of the Engen's criteria, implemented with only two microstrip power dividers. The first is a 90 directional hybrid coupler and the second is a symmetrical five-port junction. This six-port configuration has a single sided microstrip structure formed with basic regular geometric figures, avoiding the use of additional elements into the circuit. The design and theoretical basis here presented, simplifies the process of implementing a six-port reflectometer, as a great alternative for measuring high frequency signals. The six-port design is an intricate technical task for those who want to implement this measuring instrument.

Breast cancer is one of the more aggressive diseases with a high worldwide death rate in women. The early detection and timely treatment are the best methods to save life patients. Thus, the development of a new technique for medical research can represent an invaluable tool. The aim of this paper is to present an accurate and efficient numerical technique based in The Fast Slant Stack Transform as an aid to detect spiculated masses and architectural tissue distortion hidden in digital mammograms. This technique is efficient because performs this task in a very short computer processing time. The technique is validated testing 50 study cases taken from a scientific medical mammogram database. Finally, a sensitivity analysis confirms the accuracy of the here proposed technique as a promising one option particularly in developing countries where digital mammograms are highly preferred for the reduced diagnostic costs.