Alfonso Bachiller-Soler

A Lab Setup Illustrating Thyristor-Assisted Under-Load Tap Changers

This paper proposes a simple enough yet challenging lab setup illustrating the application of power electronics to power system devices through a thyristor-assisted under-load tap changer. After a preliminary analysis of the special switching concepts involved in this application, a thorough description of the main steps comprising the proposed experiment is carried out. This lab setup has been included in the electrical engineering curriculum (major in power engineering) of most senior undergraduate students (fifth year in several European countries).

Computer-aided teaching of state-variable formulation for LTI circuits

The state‐variable formulation is the most widely used approach for the transient analysis of dynamic circuits. This paper illustrates the use of the Matlab environment to obtain the state‐variable equations of LTI circuits for educational purposes. The system of equations is obtained by systematically formulating and rearranging the cut‐set equations associated with the so‐called proper tree. The setup developed in this paper is intended for a basic course on Linear Circuit Theory, which is mandatory in any Electrical Engineering curriculum, but it could be adapted to any other Engineering course involving first‐order differential equations.

Correction to "A Comparison of Techniques for State-Space Transient Analysis of Transmission Lines"

This paper reviews and compares several methods to analytically obtain the transient response of transmission lines in the time domain, in those cases where frequency independent parameters can be assumed. The distributed-parameter line is modeled by the cascaded connection of a number of lumped-parameter /spl pi/ circuits, each one representing a fraction of the line length, leading to a linear time-invariant (LTI) circuit. The associated state-space equations are formulated, allowing explicit expressions for the state variables to be written in the time domain. The solution is then obtained by means of three different approaches, all of them requiring that the natural frequencies be previously computed, namely: eigenvector-based procedure, Vandermonde matrix method, and Lagrange interpolation formula. Numerical integration by the trapezoidal rule is also considered for comparison. Two kinds of test results are presented. First, accuracy of the results provided by the LTI lumped-parameter model are compared with those obtained using the Electromagnetic Transients Program. Second, a comparison is performed in terms of the computational cost involved in each method. Two cases of practical interest are assessed, namely solving from scratch the state equations and updating the solution for a new set of initial conditions.

An interactive educational tool for the teaching of manoeuvres in electrical substations

The philosophy of safety at work is one of the bases for the operation of electrical installations, with particular relevance in the manoeuvres in electrical substations. The curriculum for Electrical Engineering students should include such knowledge. This article presents an educational tool currently in use, which has demonstrated its full effectiveness in achieving the implementation of safe working methods in the planning and execution of manoeuvres in electrical substations.

Computational assessment of methods to analytically obtain the transient response of LTI circuits

This paper reviews and compares the computational cost of several methods to analytically obtain the natural response of linear time-invariant (LTI) circuits. In particular, the analysis is focused on three methods: eigensystem-based procedure, Vandermonde matrix method and Lagrange interpolation formula. The computational cost of repeated solutions, in which only the initial conditions change, is also studied. Finally, the computational cost of the eigensystem-based approach, the winner of the analytical class of methods, is compared with that of the numerical integration approach for different number of integration steps and scenarios. Copyright