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Showing papers on "Harmonics published in 1976"


Journal ArticleDOI
TL;DR: In this paper, the problems and solutions of applying reactive compensation, either static or dynamic, to industrial power systems supplying large blocks of dc power from diode or thyristor converters are discussed.
Abstract: This paper discusses the problems and solutions of applying reactive compensation, either static or dynamic, to industrial power systems supplying large blocks of dc power from diode or thyristor converters. The resonance between power capacitors and system reactance can produce high harmonic voltages caused by the harmonic currents generated by converters. The interaction between these harmonic voltages and regulating systems can be minimized by the use of suitable filters. The design of these filters should eliminate the interaction between power system and load and reduce harmonic current flow. Different methods of reactive power control are also discussed.

173 citations


Journal ArticleDOI
TL;DR: In this paper, a new algorithm is described to solve the static, time-invariant weighted least-square state estimation problem for large-scale electric power systems, which is obtained through P-θ and Q-V decoupling and alternately iterating the active and reactive equations using fixed, simplified submatrices of the information matrix.
Abstract: A new algorithm is described to solve the static, time-invariant weighted least-square state-estimation problem for large-scale electric power systems. The solution is obtained through P-θ and Q-V decoupling and alternately iterating the active and reactive equations using fixed, simplified submatrices of the information matrix. Thus, a much faster algorithm is obtained yielding the exact solution and requiring little computer storage. The new method is compared with the basic "Weighted-least-square" and the "Line-Only" algorithms on a practical HV network.

104 citations


Journal ArticleDOI
TL;DR: In this paper, the authors describe analytical and experimental results for a new method of current harmonic reduction in thyristor converters, which is based on modifying the current waveforms on the d.c. windings of the converter transformer by injecting harmonic currents at a particular frequency.
Abstract: The paper describes analytical and experimental results for a new method of current harmonic reduction in thyristor converters. The principle of the method is to modify the current waveforms on the d.c. windings of the converter transformer by injecting harmonic currents at a particular frequency. In practice, third harmonic currents of the power frequency is most efficient. Experimental results carried out prove that the method is effective in reducing the alternating-current harmonics, and that it is applicable to any type of thyristor converters.

100 citations


Patent
08 Mar 1976
TL;DR: In this paper, a dual d-c level set scheme is proposed to minimize selected harmonics of the alternating voltage and the higher level is varied as a function of the amplitude command signal thereby to vary the amplitude of the fundamental voltage component, and means are provided for smoothly transitioning to a square wave mode of operation as the amplitude signal approaches 1.0 per unit.
Abstract: Alternating voltage for energizing an adjustable speed a-c motor is derived from unipolarity input voltage by means of electric power inverting apparatus comprising at least one pair of alternately conducting controllable electric valves. The conducting states of these valves are periodically switched by control means responsive to frequency and amplitude command signals, whereby the frequency and the amplitude of the fundamental component of the alternating voltage are varied as functions of the respective command signals. The control means includes means for implementing a triangle interception mode of pulse width modulation (PWM) of the alternating voltage so long as the amplitude command signal does not exceed a predetermined reference value (which is less than 1.0 per unit) and the speed of the motor does not exceed a predetermined reference speed, and the control means additionally includes means for implementing a "transition" PWM mode of operation whenever the amplitude command signal exceeds its reference value or the motor speed exceeds said reference speed. As disclosed herein the transition PWM mode implementing means is a dual d-c level set scheme in which the lower level is varied as a function of the higher level so as to minimize selected harmonics of the alternating voltage and the higher level is varied as a function of the amplitude command signal thereby to vary the amplitude of the fundamental voltage component, and means is provided for smoothly transitioning to a square wave mode of operation as the amplitude command signal approaches 1.0 per unit.

98 citations


Journal ArticleDOI
TL;DR: In this paper, a set of functions called Fermi-surface harmonics (FSH's) are defined to be polynomials of the Cartesian components of the electronic velocity orthonormalized on the Fermian surface.
Abstract: A set of functions called Fermi-surface harmonics (FSH's) are defined to be polynomials of the Cartesian components of the electronic velocity orthonormalized on the Fermi surface. These functions have many desirable properties, such as cell periodicity and a simple correspondence to spherical harmonics. However, there are many more linearly independent polynomials on a general surface than occur on a sphere. It is shown that this set is complete for simple Fermi surfaces; on general surfaces the mathematical question is not resolved but seems unlikely to cause physical difficulties. In the FSH representation, many problems take a particularly simple form. In particular the Boltzmann and Eliashberg equations are studied. By truncating at first-order polynomials, a slightly improved version of the usual variational solution for dc electrical conductivity is found. A convenient definition of Landau Fermi-liquid coefficients for antisotropic metals is suggested.

97 citations


Journal ArticleDOI
TL;DR: In this article, a closed-loop control system to reduce the reactive power required by electronic converters is proposed, where the instantaneous reactive power which consists of both displacement of fundamental current and harmonic distortion current is measured and compensated by a reactive power source connected parallel between the power lines and the converter.
Abstract: A closed-loop control system to reduce the reactive power required by electronic converters is proposed. The instantaneous reactive power which consists of both displacement of fundamental current and harmonic distortion current is measured and compensated by a reactive power source connected parallel between the power lines and the converter. A combination of a dc choke and a forced-commutated inverter is used for the reactive power source.

65 citations


Journal ArticleDOI
TL;DR: In this paper, the capacitance of a nonlinear element is calculated for a non-linear element (C = C0 + αu2), when an ac voltage together with a dc voltage is applied.

51 citations


Journal ArticleDOI
TL;DR: In this article, a theoretical study of fifth-harmonic generation (FHG) in an isotropic media is presented, where two schemes are discussed: cascade generation and direct generation.
Abstract: This paper presents a theoretical study of fifth-harmonic generation (FHG) in an isotropic media. Two schemes are discussed-cascade generation in which the fifth harmonic results from successive nonlinear interactions in two separate elements, and direct generation where the fifth harmonic is produced in an isotropic media with third-and fifth-order nonlinear susceptibilities. In the plane-wave approximation almost full conversion of the pumping energy into the fifth harmonic is found to be possible. FHG with a focused Gaussian beam is also investigated. To determine the optimum conditions for FHG in the cascade scheme, the theory of four-wave mixing of light beams with arbitrary confocal parameters and waist locations is developed. In media with third- and fifth-order nonlinearity, the fifth harmonic results from step and direct processes. The interference between these two processes is discussed. Numerical calculations are presented for metal vapor-gas mixtures and Nd:glass laser pumping radiation.

40 citations


Journal ArticleDOI
TL;DR: In this paper, a density matrix transition rate matrix formalism is employed to compute the eight unique electron paramagnetic resonance signals at the first two harmonics of the applied Zeeman modulation.

38 citations


Journal ArticleDOI
TL;DR: In this article, a solution to Maxwell's equations subject to boundary conditions on counterwound helical wires is achieved, where the helices are contained in a cylindrical surface that is concentric to a perfectly conducting center conductor of circular cross section.
Abstract: A solution to Maxwell's equations subject to boundary conditions on counterwound helical wires is achieved. The helices are contained in a cylindrical surface that is concentric to a perfectly conducting center conductor of circular cross section. The permittivity of the annular region may be different from that of the external region. The excitation is taken to be symmetrical about the cable which leads to a considerable simplification of the formulation. The key step is to recognize that the assumed form of the current on the thin helical wires is a spatial harmonic expansion that leads to a doubly infinite expansion, in such harmonics, for the resultant fields. The inherent complication of the problem results from the intercoupling between the spatial harmonics of the helix currents. Various generalizations of the theory are also indicated.

32 citations


Journal ArticleDOI
TL;DR: In this paper, a theory for the input impedance of a short, cylindrical dipole antenna immersed in a warm anisotropic plasma which is described by the Boltzmann equation is presented.
Abstract: A theory is presented for the input impedance of a short, cylindrical dipole antenna immersed in a warm anisotropic plasma which is described by the kinetic theory (Boltzmann equation). The plasma is assumed to be homogeneous with collisions included. The input impedance is based on the induced EMF technique and a quasistatic approximation. The dipole is assumed to have a triangular current distribution along its axis. For a dipole oriented parallel to the static magnetic field, the input impedance is derived as a one-dimensional integral suitable for numerical integration. Under certain conditions, this integral can be evaluated giving analytical formulas valid near the second and third electron cyclotron harmonics. The results show new contributions to the input impedance due to the excitation of cyclotron harmonic waves which propagate near the harmonics of the electron cyclotron frequency. These harmonic effects are not predicted by either the cold or hydrodynamic theories.

Journal ArticleDOI
TL;DR: In this paper, the structure of the identification problem based on steady-state frequency response is considered for the class of nonlinear systems S_{M}, and two approaches using amplitude and phase measurements are presented, one of which requires measurements of only the first two harmonics of the steady state response.
Abstract: For the class of nonlinear systems S_{M} , the structure of the identification problem based on steady-state frequency response is considered. Two approaches using amplitude and phase measurements are presented, one of which requires measurements of only the first two harmonics of the steady-state response. Furthermore it is shown that with a minimum phase restriction the system can be identified from amplitude measurements of the first two harmonics. In each case we obtain a considerable reduction in the number of measurements and inputs required by previous approaches.

PatentDOI
T. Paoli1
TL;DR: In this article, a dual-frequency technique for measuring high-order derivatives by frequency mixing is described, which utilizes an ac modulation at two distinct but synchronous frequencies to produce a derivative signal at a useful difference frequency, which is unique to the order of the derivative being measured.
Abstract: A dual-frequency technique for electronically measuring high-order derivatives by frequency mixing is described. The technique utilizes an ac modulation at two distinct but synchronous frequencies to produce a derivative signal at a useful difference frequency, which is unique to the order of the derivative being measured. By appropriate selection of the frequencies, significant advantages are obtained compared to the conventional method in which derivatives are measured at harmonics of a single frequency. The technique is illustrated with a practical measurement of the second derivative of the electrical characteristic of a silicon rectifier diode.

Patent
18 Aug 1976
TL;DR: In this paper, an electromagnetic article detection system of the type where a saturable magnetic target generates harmonics of an alternating magnetic interrogation field was proposed, where a magnetic bias was provided along with the magnetic interrogation to promote the target response particularly at even harmonics, throughout the interrogation region.
Abstract: An electromagnetic article detection system of the type wherein a saturable magnetic target generates harmonics of an alternating magnetic interrogation field. A magnetic bias means is provided along with the magnetic interrogation field to promote the production of target response particularly at even harmonics, throughout the interrogation region.


Journal ArticleDOI
Abstract: This paper describes a mathematical model for the simulation of an AC/DC system using direct-phase quantities. This system consists of an AC/DC converter station connected to a synchronous generator at its terminals as well as to an infinite bus-bar through a short transmission line. The proposed model in direct-phase quantities enables the study of the effects of the generated harmonics of the DC transmission on AC systems in general and on the behavior of synchronous machines in particular. The paper describes also a numerical solution using a digital computer for the mathematical model of this AC/DC system. The usefulness and versatility of the computer program are demonstrated by applying it to different AC/DC system configurations. The paper gives results of some studies concerning the effects of the generated harmonics on the behavior of synchronous machines with or without filters in the system.

Journal ArticleDOI
TL;DR: In this paper, the interaction impedance of coupled cavity slow wave structures can be measured by perturbing the resonances of a shorted length of the structure using a dielectric rod.
Abstract: The interaction impedance of coupled cavity slow wave structures can be measured by perturbing the resonances of a shorted length of the structure using a dielectric rod. An analysis of this procedure is presented. The analysis retains radial as well as axial electric fields and all significant space harmonics. The results obtained are easily programmed formulas for calculating total interaction impedance or Pierce impedance using the experimental data.

Journal ArticleDOI
TL;DR: In this article, general expansions in ellipsoidal harmonics are derived for the electrostatic potential and isotropic magnetic shielding outside non-spherical molecules such as adenine and anthracene.
Abstract: General expansions in ellipsoidal harmonics are derived for the electro­static potential and isotropic magnetic shielding outside non-spherical molecules such as adenine and anthracene. The molecular constants in the expansions are identified as simple linear combinations of experimentally accessible electric multipole moments and magnetic susceptibility aniso­tropies. Numerical examples show that the new expansions give better representations of fields outside non-spherical molecules than conventional multipolar expansions based on spherical harmonics.

Patent
25 Jun 1976
TL;DR: In this paper, a regulated DC to AC power converter of the switching type for providing AC power at a selected output frequency, e.g., 50 Hz, is disclosed, which eliminates the need for an inverter transformer, is switched at a switching frequency which is considerably higher than the output frequency.
Abstract: A regulated DC to AC power converter of the switching type for providing AC power at a selected output frequency, e.g., 50 Hz, is disclosed. The converter, which eliminates the need for an inverter transformer, is switched at a switching frequency which is considerably higher than the output frequency, e.g., 10 KHz. Due to the high switching rate the converter filter can be designed with small and lightweight components to provide a desired pass band, which includes the output frequency and harmonics thereof, and provides sufficient attenuation for the switching frequency and its higher harmonics, so as to produce an output with very low ripple or waveform distortion. Due to the high switching frequency the output waveform can be regulated with a response time of a fraction of a cycle. The converter includes a modulator section with a unique arrangement to control the switching of the switches between their On and Off states. In preferred embodiments of the converter the switches are implemented with transistors to form AC power at high power levels. Each switch includes a plurality of relatively inexpensive transistors which are connected in parallel with each transistor drawing only a small portion of the total current through the switch. A novel arrangement is employed to increase switch reliability by preventing its failure even though one or more of its transistors may fail in a short-circuit state. For switches implemented with transistors the extended turn-off time of the transistors, due to their saturated states, is accommodated by controlling the turning On of each switch to occur only after the transistors of the previously turned On switch returned to their Off state.

Journal ArticleDOI
TL;DR: The measured third harmonic power output from a paramagnetically doped superconductor in a strong microwave field has been found to vary with temperature as (1-t)/sup -1//, as predicted by Gor'kov and Eliashberg's theory for concentrations close to critical as mentioned in this paper.
Abstract: The measured third harmonic power output from a paramagnetically doped superconductor in a strong microwave field has been found to vary with temperature as (1-t)/sup -1/, as predicted by Gor'kov and Eliashberg's theory for concentrations close to critical and Eliashberg's theory for the dilute alloy. The magnitude of the order-parameter relaxation time deduced from the measured power is consistent with a model constructed from these two theories. (AIP)

Patent
14 Jun 1976
TL;DR: A power supply circuit having a crystal controlled solid state oscillator induction coupled to a dual transistor circuit so as to eliminate second harmonics in a coil connected to a power supply in completing the circuit, and coil further having a resonance circuit there around.
Abstract: A power supply circuit having a crystal controlled solid state oscillator induction coupled to a dual transistor circuit so as to eliminate second harmonics in a coil connected thereto and to a power supply in completing the circuit, and coil further having a resonance circuit therearound. Such power supply being suitable for driving a plasma gas envelope.

Journal ArticleDOI
TL;DR: In this paper, an analysis is made of the extent of residual 6-pulse harmonics due to the imperfect balance of 12pulse bridge operation, and a basis for specifying certain design tolerances is provided.
Abstract: In substituting a degree of imbalance between the phase impedances of HVdc converter transformers for the usual assumption of equal impedances, the generated ac harmonics are modified and triplen (non-characteristic) harmonics are produced. They are analysed and assessed; and are not expected to be serious provided due attention is paid to impedance balancing. Certain normal harmonics for 6-pulse operation are ideally eliminated by 12-pulse operation. An analysis is made of the extent of residual 6-pulse harmonics due to the imperfect balance of 12-pulse bridge operation. The paper provides a basis for specifying certain design tolerances.

Journal ArticleDOI
TL;DR: Comparison of measured harmonics to the predictions of two phenomenological models suggest the presence of complex nonlinear transformations in the peripheral auditory system.
Abstract: Discharges in cochlear nerve fibers evoked by low frequency phase-locked sinusoidal acoustic stimuli are synchronized to the stimulus waveform. Excitation and suppression regions of single units were explored using a stimulus composed of either a fixed intensity test tone at the characteristic frequency, a variable intensity interfering tone with a simple integer frequency relation to the characteristic frequency, or both. Compound period histograms were constructed from period histograms in response to normal and reversed polarity stimuli. Discharge patterns were characterized by Fourier components of the histogram envelopes. The two stimulus frequencies constituted the principal harmonics in the histogram envelopes and their combination accounted for observed rate changes. Suppression of the test tone harmonic as a function of interfering tone intensity was always seen; rate suppression was not. The harmonic was typically suppressed by 20–30 dB compared to the value for the test tone alone and often reached the 40–60 dB resolution limit of the experiment. Suppression plots were nearly linear on a power scale with an average slope of-0.8. The onset of suppression occurred for an interfering tone 9 dB greater on average than the test tone intensity. Information transfer through the peripheral system was described by the ratio of the principal harmonic amplitudes versus the ratio of the intensities of the two stimulus tones. These plots were nearly linear on a power scale with an average slope of 0.9. Neither the onset of suppression nor the slopes of the harmonic plots displayed strong dependence on characteristic frequency or interfering tone frequency. These features of harmonic behavior, however, are closely related to system nonlinearity. Comparison of measured harmonics to the predictions of two phenomenological models suggest the presence of complex nonlinear transformations in the peripheral auditory system.

Journal ArticleDOI
TL;DR: In this article, an efficiency of 3% was obtained in the generation of the second harmonic of nonmonochromatic neodymium laser radiation in an LiIO3 crystal.
Abstract: An efficiency of ~3% was obtained in generation of the second harmonic of nonmonochromatic neodymium laser radiation in an LiIO3 crystal. The laser was operated under free-oscillation conditions and the dispersion of phase matching was compensated by a diffraction grating. An investigation was made of the angular and spectral characteristics of the harmonic radiation. It was found that compensation of the phase-matching dispersion widened the harmonic spectrum from 0.2–0.3 nm to half the width of the laser spectrum.

Journal ArticleDOI
TL;DR: In this paper, the discrete eigenvalue problem associated with the one-speed azimuthal Fourier harmonics in plane geometry is discussed and an explicit expression, well suited to numerical evaluation, is given for the dispersion function.
Abstract: The discrete eigenvalue problem associated with the one-speed azimuthal Fourier harmonics in plane geometry is discussed. An explicit expression, well- suited to numerical evaluation, is given for the dispersion function, and the reality and maximum number of discrete eigenvalues are demonstrated. From numerical examples, it is found that quite often there are no discrete eigenvalues, particularly for the higher harmonics. (auth)

Journal ArticleDOI
TL;DR: In this article, the nonlinear interaction of a single particle with an electromagnetic wave at a cyclotron harmonic was studied and the cases of a coherent wave particle interaction and of an incoherent interaction were treated.
Abstract: The nonlinear interaction of a single particle with an electromagnetic wave at a cyclotron harmonic is studied. Emphasis is on the large wavelength limit (fast wave). The cases of a coherent wave particle interaction and of an incoherent interaction are treated. In both cases explicit expressions for the temporal evolution of the particle perpendicular energy distribution function are presented. The heating is efficient at the first two harmonics. The formation of a suprathermic tail is predicted at the second and higher harmonics.

Journal ArticleDOI
TL;DR: In this paper, a singular perturbation analysis of the interaction of the fundamental plane wave progressing in the direction of the sinusoidally varying permittivity of an unbounded medium with the first four space harmonics progressing in a reverse direction is carried out.
Abstract: A singular perturbation analysis of the interaction of the fundamental plane wave progressing in the direction of the sinusoidally varying permittivity of an unbounded medium with the first four space harmonics progressing in the reverse direction is carried out. The periodic inhomogeneity introduces self and mutual interaction phenomena. The self interaction, in general, produces a phase shift and causes the mutual interaction to occur for frequencies higher than those predicted by the Bragg condition. The mutual interaction introduces a complex change in the wavenumber resulting in the interacting waves becoming evanescent. Analytical expressions for the frequency shift and the other wave characteristics in the interaction region are deduced. With the increase in the order of the interaction, the frequency shift becomes a more dominant effect than the wave evanescence.

Journal ArticleDOI
TL;DR: In this article, an analysis of the excitation of the ordinary mode propagating perpendicular to an external magnetic field in a plasma with low β∥ is performed for plasma in which in addition to the thermal electrons there is a hot anisotropic electron component.
Abstract: The excitation of the ordinary mode propagating perpendicular to an external magnetic field in a plasma with low β∥ is discussed. The analysis is performed for plasma in which in addition to the thermal electrons there is a hot anisotropic electron component. Relativistic effects are taken into account in the stability analysis. Both a ring distribution and a loss cone distribution are used to model the hot electron species. For the ring distribution typical growth rates are larger than that for the case of the loss cone distribution. Excitation of the ordinary mode is found at numerous harmonics of the cyclotron frequency for the ring distribution, however, the loss cone distribution is found to give instability primarily at the fundamental harmonic.

Patent
10 Sep 1976
TL;DR: In this paper, current transformers are utilized to combine the outputs of two 30° phase shifted inverters to produce a three phase output which is low in fifth and seventh harmonics.
Abstract: Current transformers are utilized to combine the outputs of two 30° phase shifted inverters to produce a three phase output which is low in fifth and seventh harmonics. The arrangement utilizes transformers having volt-ampere ratings which are very low compared to the power output of the inverters. The circuit may also be used to convert a three phase input to a multi-phase full wave rectified output without reflecting high fifth and seventh harmonics back into the line.

Patent
29 Dec 1976
TL;DR: In this article, a method for transmitting information with a desired bandwidth while suppressing interference due to harmonics of a system-wide signal, by transmitting each bit of information as a pair of spaced rectangular envelope modulation pulses having a time interval there between essentially equal to the reciprocal of the difference between the frequencies of a carrier and of adjacent harmonics, is proposed.
Abstract: A method for transmitting information with a desired bandwidth while suppressing interference due to harmonics of a system-wide signal, by transmitting each bit of information as a pair of spaced rectangular envelope modulation pulses having a time interval therebetween essentially equal to the reciprocal of the difference between the frequencies of a carrier and of adjacent harmonics of the undesired system-wide signal A sequential plurality of double-pulse modulating waveforms can be transmitted for reception by a receiving means having a like plurality of demodulators each synchronized and sequentially enabled only when one of the pair of modulating pulses are present A novel double-pulse demodulator means, capable of essentially rejecting undesirable harmonics in a system utilizing a data carrier modulated to be interlaced between sequential harmonics of a system-wide signal, and novel means for synchronous gating thereof, are disclosed