Showing papers on "Harmonics published in 1990"
TL;DR: In this article, a combined system of a shunt passive filter and a small rated series active filter was proposed to compensate for harmonics in power systems, and the results showed that the combined system was far superior in efficiency to conventional shunt active filters.
Abstract: A novel approach to compensating for harmonics in power systems is presented. It is a combined system of a shunt passive filter and a small rated series active filter. The compensation principle is described, and some filtering characteristics are discussed in detail. Excellent practicability and validity to compensate for harmonics in power systems are demonstrated experimentally. Although the source harmonic voltage was only 1%, the source harmonic current reached about 10% before the series active filter was started. After it was started, no harmonic current flowed into the shunt passive filter. In addition, no harmonic voltage appeared at the terminals of the shunt passive filter, because the source harmonic voltage was applied to the series active filter. The total loss of the series active filter was less than 40 W. It is concluded that the combined system is far superior in efficiency to conventional shunt active filters. >
656 citations
Journal Article•
573 citations
07 Oct 1990
TL;DR: In this paper, the authors explore the dependency of the conduction losses of a bridge leg of a PWM power converter system with a high pulse rate on the shape of the phase modulation functions.
Abstract: The authors explore the dependency of the conduction losses of a bridge leg of a pulsewidth modulation (PWM) power converter system with a high pulse rate on the shape of the phase modulation functions. This is done for modulation methods that are optimized with respect to minimum harmonic current RMS values. The results are compared to the results gained for simple sinusoidal modulation. Besides conduction losses, the switching losses of the electric valves are calculated. The main topic is the determination of those power loss components of a PWM converter system that can be (besides the harmonic losses) influenced by the modulation method selected. As the calculations show, these modulation methods allow a significant increase of the effective switching frequency. The optimal modulation as calculated leads to a reduction of the harmonic power loss in the upper modulation region. Furthermore, due to the frequency modulation the spectrum is spread out to a wider frequency band as compared to operation with constant pulse frequency. >
571 citations
TL;DR: In this article, four experiments were reported that deal with pitch perception of harmonic complex tones containing up to 11 successive harmonics, and the question was raised whether the pitch percept of the missing fundamental is mediated only by low-order resolvable harmonics or whether it can also be conveyed by high-order harmonics that the cochlea fails to resolve.
Abstract: Four experiments are reported that deal with pitch perception of harmonic complex tones containing up to 11 successive harmonics. In particular, the question is raised whether the pitch percept of the missing fundamental is mediated only by low‐order resolvable harmonics, or whether it can also be conveyed by high‐order harmonics that the cochlea fails to resolve. Melodic interval identification performance was found to remain significantly above chance level even if the range of harmonics extended from the 20th to the 30th. Just‐noticeable differences (jnd) in the pitch of the missing fundamental were found to increase with increasing harmonic order, but to level off when all harmonics are above the 12th. These results are consistent with the notion of the existence of two distinct neural pitch mechanisms in the auditory system, but are, in principle, also compatible with a single central‐spectrum mechanism that uses the interspike interval histograms of auditory‐nerve fibers as inputs.
340 citations
11 Jun 1990
TL;DR: In this article, a power control system for a doubly fed wound rotor induction generator was developed, which applies a control method using a rotating reference frame fixed on the gap flux of the generator, and can control active and reactive power independently and stably.
Abstract: A power control system for a doubly fed wound rotor induction generator has been developed. This power control system applies a control method using a rotating reference frame fixed on the gap flux of the generator, and can control active and reactive power independently and stably. The characteristics of the control system have been proved by experiment. Harmonic currents fed to the rotor windings are transmitted to the stator winding changing its frequency. The transmitting characteristics of the harmonic currents have been analyzed and verified by experiments. >
296 citations
TL;DR: In this paper, the authors expanded on the physical meaning of the reactive power in nonsinusoidal situations, and showed that the total reactive power Q/sub F/ is composed from four distinctive types of elementary reactive powers.
Abstract: The author expands on the physical meaning of the reactive power in nonsinusoidal situations. The sinusoidal waveform case is surveyed, viewing the active current as a component of identical waveform with the voltage. This approach, when extended to nonsinusoidal waveforms, supports Fryze's model for apparent power, S/sup 2/=p/sup 2/+Q/sup 2//sub F/. It is proved that the total reactive power Q/sub F/ is composed from four distinctive types of elementary reactive powers. Each of the basic reactive powers is identified as the amplitude of an oscillation of instantaneous power. The separation of Q/sub F/ in Q/sub 1/, the reactive power at the system frequency, and in Q/sub H/, the reactive power at harmonic frequencies, is recommended as an effective mean for monitoring filter efficacy and power-factor compensation. Two major recommendations are supported by the results of this study: abolish the power model using distortion power, and measure the active power of the system frequency separately from the active power of the harmonics. >
265 citations
TL;DR: An active power filter using quad-series voltage-source pulsewidth-modulated (PWM) converters to suppress AC harmonics by injecting compensating currents into the AC system is described in this article.
Abstract: An active power filter using quad-series voltage-source pulse-width-modulated (PWM) converters to suppress AC harmonics by injecting compensating currents into the AC system is described. The circuit used to calculate the compensating current references, the compensation characteristics, and the capability of the DC capacitor are discussed theoretically and experimentally. A control circuit for the DC capacitor voltage is proposed. The discussions focus on transient states, based on the instantaneous reactive power theory. A passive LC filter is designed to remove the switching voltage and current ripples caused by the PWM converters at the AC side. Some experimental results that illustrate the details of the study are shown. >
228 citations
07 Oct 1990
TL;DR: In this paper, a new saturation model for induction machines that can be easily extended to other types of AC machines is presented, where saturation is responsible for the generation of flux space harmonic components traveling in the air gap with the same synchronous speed as the fundamental flux component, with the third being the dominant harmonic component.
Abstract: A new saturation model for induction machines that can be easily extended to other types of AC machines is presented. It is shown that saturation is responsible for the generation of flux space harmonic components traveling in the air gap with the same synchronous speed as the fundamental flux component, with the third being the dominant harmonic component. Superposition of the effects of the fundamental and third harmonic components of the air gap flux is utilized in order to model the saturation of the ferromagnetic parts of the machine. The concept of winding functions is used to derive the inductance terms relating to both stator and rotor winding components. In this approach, the air gap length is assumed to be variable, being a function of the position and level of the air gap flux. Terminal and torque values for steady and transient states are obtainable from the proposed model, with experimental results showing that the model proposed predicts spatial saturation effects with good accuracy. >
217 citations
TL;DR: In this article, an algorithm for optimizing shunt capacitor sizes on radial distribution lines with nonsinusoidal substation voltages such that the RMS voltages and their corresponding total harmonic distortion lie within prescribed values is presented.
Abstract: An algorithm for optimizing shunt capacitor sizes on radial distribution lines with nonsinusoidal substation voltages such that the RMS voltages and their corresponding total harmonic distortion lie within prescribed values is presented. The problem is formulated as a combinatorial optimization problem with inequality constraints. A simple heuristic numerical algorithm that is based on the method of local variations is proposed to determine an optimal solution. An example shows that optimal capacitor sizes found by neglecting the harmonic components may result in unacceptable voltage distortion levels. >
215 citations
TL;DR: In this paper, a series of in-flight experiments on the active contrl of propeller-induced passenger cabin noise in a B.Ae. 748 aircraft were presented. But the results were limited to the first three harmonics of the blade passage frequency.
193 citations
11 Mar 1990
TL;DR: In this paper, an adaptive frequency domain control algorithm for a PWM switched active power line conditioner (PLC) is discussed, which minimizes harmonic current in the AC line and improves power factor to unity.
Abstract: An adaptive frequency domain control algorithm for a pulse width modulation (PWM) switched active power line conditioner (PLC) is discussed. An active power line conditioner that minimizes harmonic current in the AC line and improves power factor to unity is recommended. A six switch pulse width modulated current source inverter implements the active PLC. Simulation results of the PLC adaptive frequency domain control using the PWM switching algorithm are presented. >
TL;DR: In this paper, a model using those properties that have been developed shows the presence of a large number of odd harmonics, which can be described by using the dc tunneling limit.
Abstract: In cases in which the ponderomotive energy is much larger than the ionization energy, which correspond to the highintensity limit or to the low-frequency limit, harmonic generation in gases near the ionization threshold can be understood from a plasma-physics point of view. Multiphoton ionization, which can be described by using the dc tunneling limit, takes place in a time interval localized around the maximum of the electric field. The plasma current thus generated varies on the same fast time scale and is responsible for harmonic generation. A model using those properties that has been developed shows the presence of a large number of odd harmonics.
TL;DR: In this paper, an approach that accounts for the time-varying nature of the fundamental and harmonic components is developed to detect high-impedance faults accompanied by variations in the 60 Hz and harmonic component.
Abstract: High-impedance faults are accompanied by variations in the 60 Hz and harmonic components. An approach that accounts for the time-varying nature of the fundamental and harmonic components is developed. This approach is based on Kalman-filtering theory to obtain the best estimation of the time variations of the fundamental and harmonic components. Four actual recorded data sets for staged arcing fault on different types of soil are investigated by the proposed Kalman-filtering technique. The time variations of fundamental and low-order harmonic components significantly contribute to high-impedance fault detection using the features presented. >
01 Jul 1990
TL;DR: In this article, the authors presented an analysis of the space vector PWM waveform to obtain its spectrum based on a novel decomposition technique, illustrated by considering the harmonics of a regularly sampled asymmetrical sinusoidal PWM Waveform, which is in fact a partial solution to the Space vector harmonics.
Abstract: While most traditional PWM inverters use the asymmetrical regularly sampled triangulation technique to generate waveforms, a recently reported space vector PWM method is rapidly gaining favour in the industrial drives arena as an alternative technique. The paper presents an analysis of the space vector PWM waveform to obtain its spectrum. The analysis is based on a novel decomposition technique, illustrated by considering the harmonics of a regularly sampled asymmetrical sinusoidal PWM waveform, which is in fact a partial solution to the space vector harmonics. The calculated harmonics show close agreement with measured harmonics from an experimental microprocessor-controlled inverter operating with the same waveform parameters.
TL;DR: In this paper, a theoretical study and a model for the numerical simulation of the nonlinear electrical response, including the harmonic generation rate calculation, of a p-i-n InGaAs photodiode under high-illumination conditions are discussed.
Abstract: A theoretical study and a model for the numerical simulation of the nonlinear electrical response, including the harmonic-generation rate calculation, of a p-i-n InGaAs photodiode under high-illumination conditions are discussed. The device structure is described. An algorithm, which is based on a finite-difference calculation, is used to calculate the temporal electrical response of the device to a microwave optical input signal. The different harmonics in the power spectrum are obtained using the fast Fourier transform (FFT) calculation. This model is a tool for designing the p-i-n photodiode and determining the conditions for its utilization in order to avoid the electrical response nonlinearity. >
TL;DR: In this article, a general package for harmonic-domain computation is described, consisting of a set of routines which can be used by developers of programs for power system harmonic applications, and the most basic routines have been listed.
Abstract: A general package for harmonic-domain computation is described. It consists of a set of routines which can be used by developers of programs for power system harmonic applications. The most basic routines have been listed. The package represents nonlinear characteristics by fitting the characteristic with a polynomial, for which special harmonic domain processing via convolutions has been developed, or by directly applying a fast Fourier transform. A model in the form of a differential equation is derived for the electric arc. It is based on simple energy balance considerations and therefore is expected to be generally valid. The computational results compare well with existing measurements. The arc model can be used for discharge lamps or for arc furnaces. >
TL;DR: In this article, neural networks are applied to make initial estimates of harmonic sources in a power system with nonlinear loads, which are then used as pseudomeasurements for harmonic state estimation, which further improves the measurements.
Abstract: Neural networks are applied to make initial estimates of harmonic sources in a power system with nonlinear loads The initial estimates are then used as pseudomeasurements for harmonic state estimation, which further improves the measurements This approach permits measurement of harmonics with relatively few permanent harmonic measuring instruments Simulation tests show that the trained neural networks are able to produce acceptable estimates for varying harmonic sources and that the state estimator will generally pull these estimates closer to the correct values The process successfully identified and monitored a suspected harmonic source that had not previously been measured >
TL;DR: In this article, a passive wave-shaping method for single-phase diode rectifiers is presented, which maintains high-input power factor, lowers rectifier current stresses, and lowers the volt-ampere (VA) rating of the associated reactive components.
Abstract: A novel passive waveshaping method for single-phase diode rectifiers is presented. It is shown that application of the proposed method maintains high-input power factor, lowers rectifier current stresses, and lowers the volt-ampere (VA) rating of the associated reactive components as compared to the standard diode rectifier. Relevant input and output current waveforms, component ratings, and power factor values are derived. Different modes of operation are discussed as a means of obtaining high performance. Key predictions, such as input/output waveforms and associated harmonic spectra, have been verified experimentally on a 1 kVA laboratory prototype unit. >
TL;DR: In this paper, a digital analyzer for measuring the power decomposition in a nonlinear or periodically time-variant load has been proposed, where the load is considered not as the receiver but as the source of energy.
Abstract: A nonlinear or periodically time-variant load sometimes has to be considered not as the receiver, but as the source of energy, at least for some harmonic frequencies. This can be explained in terms of its equivalent circuit, usually composed of passive elements and harmonic sources which make the power phenomena in such a circuit much more complex than in a linear circuit. The necessity of comprehension of these phenomena stems from the fact that they determine the efficiency of the power transmission and the possibility of power factor improvement. They also affect the energy accounts. A method is suggested for the apparent power decomposition into components related to current components of distinctively different physical interpretation. A digital analyzer for measuring these powers is described. >
15 Aug 1990-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, it was shown that the exponential gain of the fundamental radiation wavelength drives the third-harmonic bunching at a rate which is three times higher than the fundamental wavelength, leading to almost equal saturation bunching parameters on the fundamental and the harmonic wavelength.
Abstract: Properly taking into account the coupling between different harmonics in a high-gain free-electron laser (FEL), we demonstrate that the exponential gain of the fundamental radiation wavelength drives the third-harmonic bunching at a rate which is three times that of the fundamental. This leads to almost equal saturation bunching parameters on the fundamental and the harmonic wavelength. This is the underlying mechanism of the resonant-frequency tripling method in a two-wiggler FEL.
TL;DR: In this paper, a method that minimizes the influence of harmonics in the system voltage when performing a harmonic analysis of the arrester leakage current is presented, where a field probe is introduced to compensate for the harmonics.
Abstract: Various methods of determining the condition of zinc oxide (ZnO) surge arresters by means of measuring their leakage current are discussed. A method that minimizes the influence of harmonics in the system voltage when performing a harmonic analysis of the arrester leakage current presented. The presence of harmonics in the voltage has presented a great problem to earlier methods based on harmonic analysis, since these harmonics may interfere with the harmonics generated by the nonlinear resistance of the arrester. The favorable effect of the method presented is achieved by introducing a field probe which allows a compensation for the harmonics in the voltage. The main advantage of the new method is the low sensitivity to harmonics in the system voltage. >
TL;DR: In this paper, the effects of the many sources of harmonics which occur on distribution systems are discussed and contrasted with the single source from a high-impedance ground fault.
Abstract: The effects of the many sources of harmonics which occur on distribution systems are discussed and contrasted with the single source of harmonics from a high-impedance ground fault. Field data are presented which show the complexity of modeling the ambient harmonics and the simplicity of the change in the phasor value of the third harmonic which occurs due to a high-impedance ground fault. This phasor change is shown to be unique and predictable and hence suitable for use in detecting these faults. It is shown that variations in ambient harmonics may be greater than the change due to a high-impedance ground fault and must be considered in the fault detection system. Calculations of fault current harmonics are simpler than those for the ambient harmonics. >
TL;DR: Production of higher harmonics in a model atom described by a three-dimensional \ensuremath{\delta}-function potential in the presence of a monochromatic linearly polarized field is investigated.
Abstract: Production of higher harmonics in a model atom described by a three-dimensional \ensuremath{\delta}-function potential in the presence of a monochromatic linearly polarized field is investigated. The rates for production of the individual harmonics can be expressed as one-dimensional integrals. The only property of the atom that enters the model is its ionization energy. The results are in qualitative agreement with many of the data. In particular, the model exhibits a ``rising plateau.''
TL;DR: In this article, the role of propagation effects in high-order harmonic generation experiments was studied and the phase-matching integrals were calculated in the weak-field limit by taking into account the dispersion of the rare-gas medium at each harmonic frequency and the absorption of the harmonics.
Abstract: We study the role of propagation effects in high-order harmonic-generation experiments. The phase-matching integrals are calculated in the weak-field limit by taking into account the dispersion of the rare-gas medium at each harmonic frequency and the absorption of the harmonics. The refractive indices of the rare gases are deduced from a calculation of the dynamic polarizabilities within the framework of many-body perturbation theory and the random phase approximation. We also study the influence of the ionization of the gaseous medium and the presence of free electrons on the harmonic conversion efficiency by numerically integrating the propagation equation. These results are compared with experimental data.
TL;DR: In this paper, a pseudomodulation algorithm for computer simulation of the effect on an experimental EPR spectrum that would occur if an additional field modulation were applied followed by eventual phase sensitive detection at the modulation frequency or at one its harmonics.
Abstract: This paper develops methodology for computer simulation of the effect on an experimental EPR spectrum that would occur if an additional field modulation were applied followed by eventual phase sensitive detection at the modulation frequency or at one its harmonics. The algorithm, which is called pseudomodulation, transforms the digitized spectrum and also filters the noise. If a second harmonic spectrum is desired in order to make subtle changes in curvature more apparent, it is shown that it is always preferable to obtain an experimental second harmonic spectrum. The signals are identical, but because of the filtering properties of the pseudomodulation algorithm, the noise is lower. Pseudomodulation should be applied to simulated spectra prior to fitting a model to data in order more precisely to simulate the experimental signal. It is argued that such fits ought to involve not only first harmonics but also higher harmonics, since the various harmonics are sensitive in different ways to input parameters in the spin Hamiltonian. Application of pseudomodulation to the EPR spectrum of the blue copper-protein azurin is described.
01 Nov 1990
TL;DR: In this paper, the detrimental effects of nonsinusoidal voltage on induction motor performance are described and the derating of induction motors due to harmonic distortion is discussed in detail, and a restriction for the second harmonic should be included on the harmonic distortion limits established by the ANSI/IEEE Standard 519, Apr. 1981.
Abstract: The detrimental effects of nonsinusoidal voltage on induction motor performance are described. The derating of induction motors due to harmonic distortion is discussed in detail. Derating of NEMA Design B induction motors of different output ratings and for two types of enclosures (drip-proof and totally enclosed) due to different cases of harmonic distortions are discussed. IEEE Standard 519 suggests that no derating of the motor would be necessary for a harmonic content of up to 5%. However, no limit is specified in regard to the individual harmonic content. The conclusion is that a restriction for the second harmonic should be included on the harmonic distortion limits established by the IEEE Guide for Harmonic Control and React Compensation of Static Pow Converters (ANSI/IEEE Standard 519, Apr. 1981), and derating in some cases should be considered for less than 5% harmonic distortion. Drip-proof machines are found to be less affected by harmonic distortion than totally enclosed machines. Efficiency plays an important role in the degree of derating. Less efficient machines would require a higher derating. It is also clear that smaller machines (less than 5 HP) are affected more by the harmonics than are larger machines. >
07 Oct 1990
TL;DR: In this article, a unified pulse width modulation (PWM) algorithm is presented that is derived from AC-AC matrix power converter theory, which can be used to implement either a voltage source or a current source inverter, using only conventional bridge topologies.
Abstract: A unified pulse width modulation (PWM) algorithm is presented that is derived from AC-AC matrix power converter theory. The algorithm can be used to implement either a voltage source or a current source inverter, using only conventional bridge topologies. The resultant modulation strategy produces minimal low-order AC harmonics, yet it is readily capable of being computed online in a single switching cycle by a low-cost microprocessor at switching frequencies of up to several kilohertz. The unified algorithm also has the desirable feature of independent control of the output waveform magnitude and frequency and provides for a wide range of operation without changing the switching frequency. Furthermore, the strategy guarantees DC source current continuity for the current source inverter topology while still allowing the AC output current to step change to a new value within one switching cycle. Theory, simulation results, and experimental results showing the unified algorithm in operation are presented. >
07 Oct 1990
TL;DR: In this article, the use of zigzag transformers for reducing harmonics in the neutral conductors of a three-phase, 208 V/120 V distribution system is presented.
Abstract: The use of zigzag transformers for reducing harmonics in the neutral conductors of a three-phase, 208 V/120 V distribution system is presented. Third-harmonic currents add up in the neutral conductor of the distribution system, thereby feeding nonlinear loads. Other solutions to this problem include derating the size of the distribution transformer by 50%. Application of the zigzag transformer eliminates the need for this derating. Measurements of current draw before and after the installation of a zigzag transformer are presented. >
TL;DR: In this paper, a dual-cell, non-linear dielectric spectrometer was used to study the ability of living cells to transduce exogenous electric field energy.