Negative Sequence Harmonics Research Articles

Three-Phase Distortion Analysis based on Space-Vector Locus Diagrams

This work deals with the use of the space vector concept to characterize the harmonic content of a three-phase voltage/current. It is shown that the shape of the trajectory of the space vector on the complex plane (i.e., the locus diagram) provides information about its harmonic content. In particular, it is shown that each harmonic contributes to the locus diagram with a number of lobes depending on the relative angular frequency between the harmonic and the fundamental component. To this aim, the different contributions of positive-sequence and negative-sequence harmonics is explained and put into evidence with specific examples. The expressions for the magnitude and phase of the space vector as functions of the harmonics are derived analytically. Numerical examples are provided to show how the locus diagram can represent a three-phase quantity with positive-sequence and negative-sequence harmonics.

HARMONIC CLASSIFIER FOR EFFICIENCY INDUCTION MOTORS USING ANN

Modern electrical systems have a significant presence of electronic loads, which in turn produce negative impacts on distribution systems and loads, this has motivated their study to be increasingly prioritized, aiming to reduce their impacts from corrective actions. Harmonics are classified as positive, negative, and zero sequence, and their impacts on loads can vary according to the harmonic present. In the case of electric motors, negative sequence harmonics result in the greatest impacts. This work presents a classifier of existing harmonics in the input waveform of electric motors classes IE2, IE3 and IE4 using artificial neural networks (ANN), for that purpose, negative (2nd), positive (7th) and zero sequence harmonics (3rd) were applied separately and combined in the electric motors, the data was exported for a classification algorithm to identify existing harmonics. The results show how the algorithm presents good approximations of the present harmonics, mainly with those of positive and negative sequence.

Generalized Active Disturbance Rejection With Reduced-Order Vector Resonant Control for PMSM Current Disturbances Suppression

A control strategy that combines a novel reduced-order vector resonant controller and a generalized active disturbance rejection control (ROVR-GADRC) is proposed in this paper to suppress the current disturbances containing periodic harmonics of permanent magnet synchronous motor (PMSM). Firstly, the ROVR controller is designed, which integrates the advantages of both the complex coefficient filter and the vector resonant controller. Compared with the existing resonant control methods, the proposed ROVR can separate and extract the positive and negative sequence harmonics, and avoid the phase delay and peak point simultaneously. Secondly, a generalized extended state observer (GESO) is introduced to enhance the suppression of low-frequency disturbance. Then, the composite control strategy is developed. Besides, the stability, disturbance rejection performance, parameters configuration, robustness and tracking performance of the proposed ROVR-GADRC are comprehensively analyzed. The proposed current controller simultaneously performs harmonics suppression of specific phase sequence and other unknown disturbances attenuation. Finally, the feasibility and effectiveness of the proposed method is verified on a PMSM platform through the experimental results.

Three-Phase Phase-Locked Loop Algorithms Based on Sliding Modes

This article proposes a family of phase-locked loop schemes based on sliding modes. The use of sliding mode algorithms ensures fast response and global stability. In particular, two new algorithms are presented, both based on a complex framework for representing three-phase signals. This article compares the obtained algorithms with the traditional schemes, and a faster response is obtained when sliding modes are used. Additionally, as an application example, the algorithm is combined with a complex-coefficient filter that allows an easy identification of both positive and negative sequence harmonics. The proposed algorithms are illustrated by numerical simulations and experimentally validated using a digital signal processor.

A Novel Filter Structure to Suppress Circulating Currents Based on the Sequence of Sideband Harmonics for High-Power Interleaved Motor-Drive Systems

In this paper, a novel filter structure to suppress circulating currents is proposed based on the sequence of pulsewidth modulation voltage harmonics for high-power interleaved motor-drive systems. The sideband harmonics can be divided into positive-, negative-, and zero-sequence components. Through 120° interleaving among three paralleled inverters, a majority of positive- and negative-sequence harmonics are phase shifted. By these phase shifts, the differential-mode circulating currents between the paralleled ac–dc converters can be suppressed with the proposed filters, which have an identical structure to the three-phase common-mode chokes. Such a structure highly benefits the design and manufacturability for high-power applications where a choice of magnetic-core shapes is limited. Compared to coupled inductors (CIs) with cyclic-cascade or monolithic configurations, the number of magnetic cores can be reduced by one-third. Peak flux-linkages of the proposed filters and the conventional CIs were compared to estimate the size reduction in case of flux-limited designs. Considering the whole modulation index range, which may be required in the motor-drive systems, the maximum flux-linkage can be reduced by 50%. Prototype filters are built and showed a 33% reduction in weight and size compared to the conventional CIs. The validity of the proposed filter is verified through the simulation and a small-scale experiment.

Sub-Harmonics in Wind Driven SM-DFIG in the Super-Synchronous Range of Operation

In this paper the sub-harmonics associated with a specially designed single machine brushless doubly fed induction generator (SM-BDFIG) are analyzed at supersynchronous speeds. The SM-BDFIG is coupled to a variable speed wind turbine, and its rotor circuit is connected to a 3phase rectifier feeding Li-ion batteries. A mathematical model, using Fourier expansion, is developed to define the subharmonics created by the time harmonics of the rotor currents irrespective of any other space or time harmonics due to winding distribution, unbalanced grid phases, or presence of harmonics in the grid voltages. The effect of the positive and negative sequence harmonics on the performance of the generator is then presented, showing the speed ranges within which these sub-harmonics are most effective, as well as the speed ranges within which these sub-harmonics are least effective. The obtained results help to design a SM-BDFIG with less harmonic distortion, hence improving its performance in wind energy conversion systems.