Summary
An event appearing when executing the DQ transformation to get the compensation references in power quality compensators is presented in this work, where new harmonics that had not existed initially are generated and inserted to the electric system. Although the new harmonics have low magnitude, they exist, and correct processing of control techniques should be guaranteed to avoid amplifying their magnitudes. The new harmonics are produced by the filtering act in the dq frame, since filter is not ideal. The appearance of the new harmonics occurs only if the d component is filtered to isolate the dc term in the dq reference frame. But, if both d and q signals are filtered, no new harmonics are generated. This phenomenon is studied for general unbalanced systems; detailed analyses, proofs, simulation, and experimental tests are presented to validate the existence of the generation of new harmonics.
This study introduces a novel methodology for early detection of stator short circuit faults in induction motors by using autoregressive (AR) model. The proposed algorithm is based on instantaneous space phasor (ISP) module of stator currents, which are mapped toα-βstator-fixed reference frame; then, the module is obtained, and the coefficients of the AR model for such module are estimated and evaluated by order selection criterion, which is used as fault signature. For comparative purposes, a spectral analysis of the ISP module by Discrete Fourier Transform (DFT) is performed; a comparison of both methodologies is obtained. To demonstrate the suitability of the proposed methodology for detecting and quantifying incipient short circuit stator faults, an induction motor was altered to induce different-degree fault scenarios during experimentation.
From voltage and current signals it is possible to obtain relevant information regarding 3-phase power supply features like signal amplitude, frequency, harmonic contents, phase, among others. This information is useful to solve problems like power quality monitoring, diagnosis of electrical machines, electric systems protection, and control. This work presents preliminary results on the design of a reconfigurable tool for electric parameter monitoring in 3-phase power systems based on low-cost field programmable gate array technology, which implements different algorithms depending on the application. Obtained results from two study cases show the feasibility of utilizing the proposed instrument for monitoring power quality indexes in 3-phase power systems.Index Terms--3-phase power systems; Power quality monitoring; Power supply unbalance; Reconfigurable architecture; Field programmable gate arrays.Φ
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