71 research outputs found

    Interharmonics Analysis and Mitigation in Adjustable Speed Drives

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    Effects of modulation techniques on the input current interharmonics of Adjustable Speed Drives

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    Adjustable speed drives (ASDs) based on a three-phase front-end diode rectifier connected to a rearend inverter may generate interharmonic distortion in the grid. The interharmonic components can create power quality problems in the distribution networks such as interference with the ripple control signals, and consequently they can hamper the normal operation of the grid. This paper presents the effect of the symmetrical regularly sampled space vector modulation and discontinuous pulse width modulation-30° lag (DPWM2) techniques, as the most popular modulation methods in the ASD applications, on the drive's input current interharmonic magnitudes. Further investigations are also devoted to the cases where the random modulation technique is applied to the selected modulation strategies. The comparative results show how different modulation techniques can influence the ASD's input current interharmonics and consequently may not be a suitable choice of modulation from an interharmonics perspective. Finally, the theoretical analysis and simulation studies are validated with obtained experimental results on a 7.5-kW motor drive system

    Analysis of the use of the Hanning Window for the measurement of interharmonic distortion caused by close tones in IEC standard framework

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    Producción CientíficaThe widespread use of devices based on power electronics and other nonlinear loads has led to an increase in harmonic distortion that affects the quality of power systems. Therefore, the correct measurement of harmonic and interharmonic content is necessary. The International Electrotechnical Commission (IEC) standards define the concepts of spectral and time grouping required for such measurements. This paper demonstrates that the procedures defined in the IEC standards are not sufficiently accurate when several close interharmonic tones interact due to the lack of stability of the values that the Discrete Fourier Transform obtains in each sampling window, and to the inaccuracy in the measurement of interharmonic groups and rates when using the Hanning window. This paper proposes novel solutions based on time aggregation and the use of other groupings and alternative windows. The results obtained are compared with the results produced by applying the rectangular window indicated in the standards, using sensitivity analysis varying one of the tones and using experimental results measuring the output signals of frequency inverters driving induction motors. The proposed method achieves greater accuracy and stability in the measurement of spectral groupings and their related distortion rates in signals with abundant and dispersed interharmonic content

    A Phase-Shifting MPPT to Mitigate Interharmonics from Cascaded H-Bridge PV Inverters

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    Assessing the benefits and risks of application of inverter drives in industry

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    This paper presents the impact assessment of converters installed in an industrial plant on the power quality in internal power grid of the plant. The analysis of real measurements showed that the installation of inverter drives, despite many benefits, as energy savings, that have been reported in the paper, can also cause many problems. We observed multiple issues related to failures in the control and automation systems that could be due to the interference generated by simultaneous operation of inverter drives

    Enhanced Phase-Shifted Current Control for Harmonic Cancellation in Three-Phase Multiple Adjustable Speed Drive Systems

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    A phase-shifted current control can be employed to mitigate certain harmonics induced by the diode rectifiers and silicon-controlled rectifiers as the front ends of multiple parallel adjustable speed drive (ASD) systems. However, the effectiveness of the phase-shifted control relies on the loading condition of each drive unit as well as the number of drives in parallel. In order to enhance the harmonic cancellation by means of the phase-shifted current control, the currents drawn by the rectifiers should be maintained almost at the same level. Thus, this paper first analyzes the impact of unequal loading among the parallel drives, and a scheme to enhance the performance is introduced to improve the quality of the total grid current, where partial loading operation should be enabled. Simulation and experimental case studies on multidrive systems have demonstrated that the enhanced phase-shifted current control is a cost-effective solution to multiple ASD systems in terms of harmonic cancellation

    Grid-Friendly High-Reliability Photovoltaic Systems

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    Advances in power quality analysis techniques for electrical machines and drives: a review

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    The electric machines are the elements most used at an industry level, and they represent the major power consumption of the productive processes. Particularly speaking, among all electric machines, the motors and their drives play a key role since they literally allow the motion interchange in the industrial processes; it could be said that they are the medullar column for moving the rest of the mechanical parts. Hence, their proper operation must be guaranteed in order to raise, as much as possible, their efficiency, and, as consequence, bring out the economic benefits. This review presents a general overview of the reported works that address the efficiency topic in motors and drives and in the power quality of the electric grid. This study speaks about the relationship existing between the motors and drives that induces electric disturbances into the grid, affecting its power quality, and also how these power disturbances present in the electrical network adversely affect, in turn, the motors and drives. In addition, the reported techniques that tackle the detection, classification, and mitigations of power quality disturbances are discussed. Additionally, several works are reviewed in order to present the panorama that show the evolution and advances in the techniques and tendencies in both senses: motors and drives affecting the power source quality and the power quality disturbances affecting the efficiency of motors and drives. A discussion of trends in techniques and future work about power quality analysis from the motors and drives efficiency viewpoint is provided. Finally, some prompts are made about alternative methods that could help in overcome the gaps until now detected in the reported approaches referring to the detection, classification and mitigation of power disturbances with views toward the improvement of the efficiency of motors and drives.Peer ReviewedPostprint (published version
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