José Antonio Rosendo Macías

Self-tuning of Kalman filters for harmonic computation

This paper addresses the problem of tuning Kalman filters so that they can properly track harmonic fluctuations. A method for self-tuning of the model error covariance is presented and tested, showing fast adaptive capability under sudden changes of the input signal.

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.

Fast harmonic computation for digital relaying

It has been shown that the fast Fourier transform of a sequence which slides over a time-limited rectangular window can be carried out in a nonrecursive manner by means of O(N) computations. The same idea is applied in this paper to the digital relaying field, where only certain isolated harmonics, rather than the full spectrum, are needed, leading to O(log/sub 2/N) computations per harmonic. The particular case N=16 has been used for comparison purposes, showing that the new technique is less expensive than other nonrecursive algorithms in the literature.

Recursive formulation of short-time discrete trigonometric transforms

Recursive formulations of the moving-window discrete Fourier transform (DFT) are well known. However, recursive versions of other useful discrete transforms, like the moving-window discrete cosine transform (DCT), discrete sine transform (DST), or discrete Hartley transform (DHT), have not been developed so far. In this paper, second-order recursive expressions for the DCT, DST, and DHT, intended for real-valued windowed sequences, are presented.

Efficient computation of the running discrete Haar transform

This paper presents a new algorithm to compute the running discrete Haar wavelet transform of N samples which reduces the computational complexity to O(log/sub 2/(N)).

Application of generalized phasors to eigenvector and natural response computation of LTI circuits

This paper focuses on the natural response computation of linear time-invariant (LTI) circuits, in those cases in which a closed-form solution, rather than numerical integration of the state-variable equations, is preferable. A computationally efficient procedure is presented to individually obtain the eigenvectors of matrix A, both for distinct and repeated eigenvalues. Instead of performing orthogonal matrix transformations, the proposed method relies on the solution of the nodal equations corresponding to a zero-input circuit in the generalized phasor domain. This allows propagation of natural modes to be computed by means of a simple procedure that closely resembles conventional ac analysis.

Computation of Running Averages

This brief presents and compares several recursive and nonrecursive techniques for the efficient computation of the running average of discrete signals. First of all, the standard recursive algorithm is considered and its long-term accuracy is assessed when the floating-point arithmetic is employed. A cheap refreshing strategy is proposed as a means of keeping the computed value close enough to the exact one. Then, two alternative nonrecursive algorithms, requiring only log2N additions, are developed, which are as reliable and accurate as the direct implementation

Kalman filter tuning for digital protection applications

This paper addresses the problem of tuning Kalman filters so that they can properly track signal fluctuations in digital relaying applications. The role of each parameter involved in the filter is discussed and adequate values are presented. Particular attention is paid to the covariance matrix of the model error, which is determinant for the filter adaptive capability.

Self-tuning of Kalman filters for digital protection applications

This paper addresses the problem of tuning Kalman filters so that they can properly track signal fluctuations in digital relaying applications. A method for self-tuning of the model error covariance is presented and tested. The proposed iterative algorithm quickly adapts to sudden changes of the input signal, even in the presence of other harmonics and DC components.

Modeling the magnetic coupling of double-circuit lines in state estimation

This letter shows that discarding the direct-sequence magnetic coupling between double-circuit lines may lead in certain cases to unacceptable errors in state estimation. Then, a simple methodology is proposed that considers the mutual terms through equivalent corrections to existing power measurements.