Showing papers on "Harmonic published in 1995"
08 Oct 1995
TL;DR: In this paper, a synchronous reference frame based controller for a hybrid series active filter system is proposed to provide harmonic damping and the use of simpler and low cost power factor correction capacitors as passive filters.
Abstract: This paper proposes a synchronous reference frame based controller for a hybrid series active filter system. A hybrid series active filter system has been designed, built and installed at Beverly Pump Station in New England Electric utility for 765 kVA adjustable speed drive load to meet IEEE 519 recommended harmonic standards. The series active filter is rated 35 kVA-4% of the load kVA, and is controlled by a synchronous reference frame based controller to act as a harmonic isolator between the supply and load. This paper discusses the basic synchronous reference frame controller structure and addresses its operation under nonunity controller loop gain conditions. Design trade-offs and implementation issues of the synchronous reference frame controller are discussed. Operation of the hybrid series active filter system under off-tuned passive filter conditions and its impact on the performance of the synchronous reference frame based controller is experimentally evaluated. Effectiveness of the series active filter to provide harmonic damping and the use of simpler and low cost power factor correction capacitors as passive filters, is demonstrated by laboratory experimental results. Field installation and laboratory experimental results demonstrate the practical viability of the synchronous reference frame based controller for hybrid series active filter to provide harmonic isolation of nonlinear loads and to comply with IEEE 519 recommended harmonic standards.
322 citations
TL;DR: Experimental results obtained from a 5 kVA prototype confirm the feasibility and the features of the proposed active power filter, which can compensate the reactive power and the current harmonic components of nonlinear loads.
Abstract: The performance and dynamic characteristics of a three-phase active power filter operating with fixed switching frequency is presented and analyzed in this paper. The proposed scheme employs a PWM voltage-source inverter and has two important characteristics. First, it operates with fixed switching frequency, and second, it can compensate the reactive power and the current harmonic components of nonlinear loads. Reactive power compensation is achieved without sensing and computing the reactive component of the load current, thus simplifying the control system. Current harmonic compensation is done in time domain. The principles of operation of the proposed active power filter along with the design criteria of the power and control circuit components are discussed in detail. Finally, experimental results obtained from a 5 kVA prototype confirm the feasibility and the features of the proposed system. >
302 citations
TL;DR: In this paper, a general procedure for constructing phase shifting algorithms that eliminate the effects of nonsinusoidal waveform characteristics is presented. But when the phase shift calibration is inaccurate, these algorithms cannot eliminate the effect of nonsinsooidal characteristics.
Abstract: In phase measurement systems that use phase shifting techniques, phase errors that are due to nonsinusoidal waveforms can be minimized by applying synchronous phase shifting algorithms with more than four samples. However, when the phase shift calibration is inaccurate, these algorithms cannot eliminate the effects of nonsinusoidal characteristics. It is shown that, when a number of samples beyond one period of a waveform such as a fringe pattern are taken, phase errors that are due to the harmonic components of the waveform can be eliminated, even when there exists a constant error in the phase shift interval. A general procedure for constructing phase shifting algorithms that eliminate these errors is derived. It is shown that 2j + 3 samples are necessary for the elimination of the effects of higher harmonic components up to the jth order. As examples, three algorithms are derived, in which the effects of harmonic components of low orders can be eliminated in the presence of a constant error in the phase shift interval.
242 citations
08 Oct 1995
TL;DR: In this paper, it was shown that the position of the zero space vector component within the carrier interval determines the harmonic performance of the modulation strategy, rather than any intrinsic differences between the various methods of calculating the switching instances.
Abstract: Pulse width modulation has been one of the most intensively investigated areas of power electronics for many years, and the number and combination of permutations seem to be endless. However, a general hierarchial consensus appears to have emerged from this work which ranks space vector modulation techniques, regular sampled modulation and sine-triangle modulation strategies in decreasing order of merit based on harmonic performance. However, what has not been clearly identified is why space vector modulation should lead to a reduced harmonic current ripple compared to regular sampled modulation, especially since it is straightforward to show that they produce identical low frequency fundamental components. This paper addresses this issue, by showing how it is the placement of the zero space vector component within the carrier interval that determines the harmonic performance of the modulation strategy, rather than any intrinsic differences between the various methods of calculating the switching instances.
230 citations
TL;DR: This method is useful for shunt active power filters and is capable to eliminate harmonics, compensate power factor, and correct unbalance problems simultaneously, and has the ability to slow-down sudden transient changes in the load.
Abstract: The effectiveness of an active power filter depends basically on three characteristics: (a) the modulation method used; (b) the design characteristics of the PWM modulator; and (c) the method implemented to generate the reference template. For the last characteristic there are many methods, most of them complicated and hence difficult to implement and adjust. In this paper, a new method, which has simplicity at its main characteristic, is presented. The method is based on "sample and hold" circuits, synchronized with the peak value of the phase-to-neutral mains voltage. This method is useful for shunt active power filters and is capable to eliminate harmonics, compensate power factor, and correct unbalance problems simultaneously. It also has the ability to slow-down sudden transient changes in the load. Experimental results, with the reference template obtained with the method, are presented in the paper.
197 citations
TL;DR: In this article, the authors proposed a new methodology for the calculation of the nonsinusoidal periodic steady state in power systems with nonlinear and time-varying components, including the network and part of the loads.
Abstract: The basic principles of an efficient new methodology for the calculation of the nonsinusoidal periodic steady state in power systems with nonlinear and time-varying components are described. All linear parts, including the network and part of the loads, are represented in the frequency domain, while nonlinear and time-varying components, mainly loads, are represented in the time domain. This hybrid process is iterative, with periodic, nonsinusoidal, bus voltages as inputs for both frequency domain solutions and time domain simulations: a current mismatch is calculated at each bus and used to update the voltages until convergence is reached. Thus the process, but not the solution, is decoupled for the individual harmonics. Its efficiency is enhanced by the use of Newton type algorithms for fast convergence to the periodic steady state in the time domain simulations. Potential applications of this methodology are in the computation of harmonic power flow and in the steady state initialization needed in the calculation of electromagnetic transients. >
181 citations
05 Mar 1995
TL;DR: In this paper, a new family of single-stage isolated power-factor-corrected power supplies with fast regulation of the output voltage is introduced, and the most important design issues, including all of the following: storage-capacitor voltage, dual-range and wide-range operation, device RMS currents, and line harmonic currents.
Abstract: The paper introduces a new family of single-stage isolated power-factor-corrected power supplies with fast regulation of the output voltage, and discusses the most-important design issues, including all of the following: storage-capacitor voltage, dual-range and wide-range operation, device RMS currents, and line harmonic currents. In addition to the theoretical analyses, experimental data are also provided. >
167 citations
TL;DR: In this article, a hybrid filter topology and its control to prevent harmonic currents from entering the power system is presented, and the proposed topology enables practical implementation of active harmonic current filters.
Abstract: Use of nonlinear loads and devices in power systems is expected to grow rapidly. Examples are thyristor-controlled inductors for FACTS, converters for HVDC transmission and large adjustable speed drives. All of these loads inject harmonic currents into the power system. A novel hybrid filter topology and its control, to prevent such harmonic currents from entering the power system, are presented in this paper. Analysis shows that in the proposed filter, the power electronic converter, required to generate harmonic currents for compensation, has a rating of only 9% when compared to the converter rating in an active filter and approximately one-half of that in a series-hybrid filter discussed in the literature. The proposed topology enables practical implementation of active harmonic current filters. The control of this filter under transient conditions such as start-up and during steady state is demonstrated by means of simulations. Results from a scaled-down hardware prototype are presented to verify the simulations. >
165 citations
TL;DR: A new real-time detecting method based on adaptive interference canceling theory for harmonic and reactive currents that is useful for dynamic compensation equipment such as active power filters, static VAr compensators, etc.
Abstract: The conventional detecting methods for power system harmonic and reactive currents have various limitations. Based on adaptive interference canceling theory, a new adaptive detecting method for harmonic and reactive currents is presented, the corresponding detection system is developed, and experiments are performed which verify the feasibility of the method proposed. The new real-time detecting method is useful for dynamic compensation equipment such as active power filters, static VAr compensators, etc. >
161 citations
TL;DR: In this paper, a technique of parallel connection of power devices by using current sharing reactors for pulsewidth modulated (PWM) inverters is reported, which not only increases the current capacity but also decreases the output harmonic contents.
Abstract: A technique of parallel connection of power devices by using current sharing reactors for pulsewidth modulated (PWM) inverters is reported in this paper. The proposed technique not only increases the current capacity but also decreases the output harmonic contents. The output voltage waveforms of the proposed inverter have certain voltage levels during their half cycles, thus it is anticipated that it will be difficult to analyze the output waveforms. For such waveforms, a frequency analysis approach is described, whose results are verified by experiments. >
156 citations
TL;DR: In this article, the response of the earth to a moment tensor point source is evaluated in the frequency domain for both spheroidal and toroidal motion by numerical integration of the appropriate system of ordinary differential equations with source term and summation over vector spherical harmonics.
Abstract: SUMMARY
We present a new method to calculate complete synthetic seismograms for a spherically symmetric earth model which uses neither eigenfrequencies and eigenfunctions nor an earth-flattening transformation. The response of the earth to a moment tensor point source is evaluated in the frequency domain for both spheroidal and toroidal motion by numerical integration of the appropriate system of ordinary differential equations with source term and summation over vector spherical harmonics. Attenuation is included by using complex elastic moduli. Owing to the discrete sampling of the response in the frequency domain, the numerical effort is proportional to the length of the desired time series for a fixed maximum frequency. This makes the method much more efficient than normal-mode calculations for higher frequency applications, where often seismogram lengths of 20 to 40 min are sufficient. Since the angular degree of the spherical harmonics provide a natural discretization in the wavenumber domain, spatial aliasing is unimportant. Time aliasing is suppressed by evaluating the response at complex frequencies with constant imaginary part.
We have compared synthetic seismograms obtained by the new method with normal-mode seismograms up to a frequency of 20 mHz and achieve excellent agreement for all three components. The accuracy of the method is further corroborated by comparisons with real data up to a frequency of 200 mHz. We tested the numerical scheme up to frequencies of 1 Hz and harmonic degrees of 12 000 and did not find any numerical instabilities. Incidentally, the approach sheds some light on how normal modes make up body waves.
TL;DR: In this article, a scaling law of the amplitude oscillating with the fundamental frequency corresponding to the maximum of the global mode is found to agree with the Landau model in a range of Reynolds Re numbers larger than in previous studies, and the position of the maximum amplitude of the fundamental modes scales as (Re−Rec)−1/2.
Abstract: Numerical simulations of wake flow behind an equilateral triangular obstacle are presented. The form of global modes and their dependence on the Reynolds number found in this study are in accordance with recent experimental results of Goujon–Durand et al. [Phys. Rev. E 50, 308 (1994)]. A scaling law of the amplitude oscillating with the fundamental frequency corresponding to the maximum of the global mode is found to agree with the Landau model in a range of Reynolds Re numbers larger than in previous studies. The position of the maximum amplitude of the fundamental modes scales as (Re−Rec)−1/2. The amplitude of the second harmonic of the longitudinal component of the velocity as well as the correction to the mean flow have different critical behavior than the velocity components oscillating with fundamental frequency. During linear growth the position of the maximum of the global modes is constant and moves only in the nonlinear regime. The effects of the blockage and the boundary conditions on the side ...
TL;DR: In this article, a method for ultrasonic harmonic imaging is disclosed, which uses microbubbles particularly selected for their properties of reradiating ultrasound energy at frequencies other than the exciting frequency.
Abstract: A method for ultrasonic harmonic imaging is disclosed, which uses microbubbles particularly selected for their properties of reradiating ultrasound energy at frequencies other than the exciting frequency.
TL;DR: The Harmonic Domain this paper is a general frame of reference for power system analysis in the steady state which models the coupling between phases and between harmonics, and illustrates its potential applications in a small power system with multiple nonlinearities.
Abstract: The Harmonic Domain is a general frame of reference for power system analysis in the steady state which models the coupling between phases and between harmonics. In this frame of reference the nonlinear components, converted into harmonic Norton equivalents, are combined with the rest of the system and solved iteratively by the Newton-Raphson technique. This paper describes the structure of the new domain and illustrates its potential applications in a small power system with multiple nonlinearities. >
TL;DR: In this article, the second harmonic generation (SHG) microscope was used to obtain two-dimensional images of ferroelectric domain structure using the inhomogeneous distribution of the quadratic nonlinear optical constant.
Abstract: By using the second harmonic generation (SHG) microscope, which we have recently developed, two‐dimensional images of ferroelectric domain structure were successfully obtained by exploiting the inhomogeneous distribution of the quadratic nonlinear optical constant in specimens 90° domain structure of BaTiO3 was observed with intensity contrast of the second harmonic wave A periodically inverted antiparallel domain in LiTaO3 was also observed This fact indicates that the SHG microscope provides a new method of observing antiparallel ferroelectric domain structure in a nondestructive way, which is especially important for characterizing the quasiphase matched devices for compact blue light lasers
21 Feb 1995
TL;DR: In this article, an analysis and design method of the output LC filter of single-phase PWM inverters is presented, where analytical expressions for the total harmonics of the inductor current and capacitor voltage of the LC filter are derived.
Abstract: In this paper, an analysis and design method of the output LC filter of single-phase PWM inverters is presented. At first, the analytical expressions for the total harmonics of the inductor current and capacitor voltage of the LC filter are derived. As the unique values of the parameters of the LC filter cannot be specified based on the total harmonic of the capacitor voltage alone an additional criterion based on the minimum reactive power of the LC filter is used to specify these parameters. Experimental results are included to verify the derived expressions. >
TL;DR: Experimental studies of high-order harmonic generation in rare-gas-like Na+ and K+ ions created in a laser-produced plasma and the harmonics generated with a short- pulse, high-power, titanium-sapphire laser operating at 794 nm show that the cutoff in the harmonic spectra at high orders may be due to ionization-induced defocusing of the fundamental laser beam.
Abstract: We describe experimental studies of high-order harmonic generation in rare-gas-like Na+ and K+ ions. The ions were created in a laser-produced plasma and the harmonics were generated with a short- pulse, high-power, titanium-sapphire laser operating at 794 nm. The highest harmonic order observed was the 27th {29. 4 nm), while much higher harmonic orders were observed in a jet of neutral Ne gas un- der similar conditions. Pronounced ring structures were observed in the harmonic far-field distribution and these structures varied with focusing condition. The cutoff in the harmonic spectra at high orders may be due to ionization-induced defocusing of the fundamental laser beam. Calculations illustrating how this effect reduces the peak intensity obtained in the plasma compared with the intensity obtained in the Ne gas are presented.
08 Oct 1995
TL;DR: In this article, an active damping function can be realized by feedback control of an LC filter connected to the AC side of the rectifier, which does not require any additional components in the main circuits, permitting a simple circuit configuration.
Abstract: A new control method for current-type pulse-width modulation (PWM) rectifiers which can provide active damping function is presented. This damping function is effective only on the harmonic components of AC input current selectively. Thus steady-state waveform distortion and transient oscillation of the input current are reduced by the active damping effects. The active damping function can be realized by feedback control of an LC filter connected to the AC side of the rectifier, and it does not require any additional components in the main circuits, permitting a simple circuit configuration. The control system of the proposed PWM rectifier is analyzed by using a simple block diagram developed in the present paper. From the analytical results, the influence of the circuit parameters and control delay on the active damping effects and the stability of the operation are clarified to establish the design method. To confirm the effectiveness of the active damping function, some results of basic experiments are included. As an example of application of the active damping function, the proposed rectifier is applied to reduce the harmonic currents generated by conventional rectifiers operating in parallel with the proposed rectifier. Some experimental results in this application are also included.
09 May 1995
TL;DR: A method is developed for designing broadband beamformers with highly frequency-invariant behavior, yielding systems with efficient log-periodic transducer structures and plane wave responses which deviate from the desired response by less than 1% of the peak mainlobe response.
Abstract: A method is developed for designing broadband beamformers with highly frequency-invariant behavior. The method combines harmonic nesting with filter-and-sum beamforming, yielding systems with efficient log-periodic transducer structures and plane wave responses which deviate from the desired response by less than 1% of the peak mainlobe response. In particular, null locations are very constant with frequency, allowing the nulling of directional broadband interference. A digital implementation covering audio frequencies (500-7200 Hz) is built and demonstrates results in good agreement with simulations, yielding deviations under 5% of peak response.
18 Jun 1995
TL;DR: In this paper, a hybrid series active filter system has been designed, built and installed at Beverly Pump Station in New England Electric Power Company utility for 765 kVA, 480 V adjustable speed drive load to comply with IEEE 519 recommended harmonic standards.
Abstract: A hybrid series active filter system has been designed, built and installed at Beverly Pump Station in New England Electric Power Company utility for 765 kVA, 480 V adjustable speed drive load to comply with IEEE 519 recommended harmonic standards. The series active filter has a small rating-35 kVA which is 4% of the load kVA-and is controlled by a synchronous reference frame (SRF) based controller. The hybrid series active filter system is controlled to act as a "harmonic isolator" between the supply and load. This paper discusses the SRF controller implementation issues, design considerations of the series coupling transformer and protection issues of the small rating series active filter inverter. Operation of the series active filter under off-tuned passive filter conditions is investigated. The effectiveness of the series active filter to provide harmonic damping and the use of simpler and low cost passive filter structures such as power factor correction capacitors is demonstrated by laboratory experimental results. Field installation results demonstrate the practical and economic viability of hybrid series active filter systems for harmonic compensation of large nonlinear loads to comply with IEEE 519 recommended harmonic standards. >
TL;DR: To decide whether identification is aided primarily by selecting the target vowel on the basis of its harmonic structure ("harmonic enhancement") or removing the interfering vowels on theBased on results, harmonic enhancement and harmonic cancellation are interpreted.
Abstract: The improvement of identification accuracy of concurrent vowels with differences in fundamental frequency (ΔF0) is usually attributed to mechanisms that exploit harmonic structure. To decide whether identification is aided primarily by selecting the target vowel on the basis of its harmonic structure (‘‘harmonic enhancement’’) or removing the interfering vowel on the basis of its harmonic structure (‘‘harmonic cancellation’’), pairs of synthetic vowels, each of which was either harmonic or inharmonic, were presented to listeners for identification. Responses for each vowel were scored according to the vowel’s harmonicity and that of the vowel that accompanied it. For a given target, identification was better by about 3% for a harmonic ground unless the target was also harmonic with the same F0. This supports the cancellation hypothesis. Identification was worse for harmonic than for inharmonic targets by 3%–8%. This does not support the enhancement hypothesis. When both vowels were harmonic, identificatio...
TL;DR: The asymptotic covariance matrix and bias of the estimators of dsω(t)/dts, s = 0,1,2,…, m − 1, are obtained for the frequency with bounded m-derivative and the estimator is shown to be strongly consistent and Gaussian for a polynomial frequency.
TL;DR: Cyclic statistics and higher order spectra-based approaches are shown to yield the same frequency estimates and linear or nonlinear cumulant-based algorithms to identify ARMA model parameters for the noises.
Abstract: The problem of concern here is parameter estimation of harmonics in the presence of multiplicative and additive noise. Cyclic statistics are employed to estimate the frequencies and phases, after which the time series is demodulated and cumulants of the noise processes are estimated. The latter are then supplied to linear or nonlinear cumulant-based algorithms to identify ARMA model parameters for the noises. Cyclic statistics and higher order spectra-based approaches are shown to yield the same frequency estimates. Simulation examples illustrate the algorithms. >
TL;DR: In this article, the authors examined various scenarios for controlling high-order harmonic generation with combinations of laser fields and showed that the phase shifts of all harmonics linearly depend on the dc field strength.
Abstract: Using solutions of the time-dependent Schr\"odinger equation for the ${\mathrm{H}}_{2}^{+}$ molecular ion, we examine various scenarios for controlling high-order harmonic generation with combinations of laser fields. It is found that (i) the harmonic generation ``plateau'' can be modified by combining a laser field with its third harmonic field, (ii) even harmonics are controllable using the combination of a laser field and a weaker second harmonic field, and (iii) the phases of high-order harmonics in a strong driving field can also be changed by additional fields. In particular, when a weak dc electric field is applied, we prove that the phase shifts of all harmonics linearly depend on the dc field strength. In addition, when an ultrastrong static magnetic field is applied collinearly with the driving laser polarization, harmonic generation efficiency is enhanced and higher harmonics beyond the usual ``cutoff'' are generated as a result of the squeezing of the transversely spreading electron wave packets. The enhancement is a confirmation of the electron-ion recollision mechanism for high-order harmonic generation.
24 Apr 1995
TL;DR: An analysis is presented of the harmonic output of a Volterra kernel when excited with a multiharmonic signal, which lays the basis for the design of such signals, and a range of new periodic signals are defined.
Abstract: The frequency-domain measurement of the Volterra kernels of a nonlinear system using periodic multisine signals is now a practical possibility. An analysis is presented of the harmonic output of a Volterra kernel when excited with a multiharmonic signal, which lays the basis for the design of such signals. This is followed by a review of previous work in this area, after which a range of new periodic signals is defined. The minimization of the signal crest factors is then examined, along with the practical problems associated with their application. Practical results are presented which illustrate the application of the signals to testing a reference nonlinear circuit and a servo motor system.
TL;DR: In this article, a dual frequency probe using a multilayer ceramic is proposed for simultaneously obtaining a high resolution B mode and a high sensitivity Doppler mode image, which consists of two layers in which the poling directions are opposite and the individual thicknesses are different.
Abstract: A dual frequency probe using a multilayer ceramic is proposed for simultaneously obtaining a high resolution B mode and a high sensitivity Doppler mode image. This ceramic consists of two layers in which the poling directions are opposite and the individual thicknesses are different. It is possible to control the values of relative electromechanical coupling factors in the fundamental and the second harmonic by changing the thickness ratio. A thickness ratio of 1:0.7 was decided from computer simulation based on the Mason's model. A sufficient resolution has been shown from the fact that the intima of the carotid artery could be distinguished by an actually fabricated probe with dual frequencies of 3.75 and 7.5 MHz. Also, the sensitivity of this probe in the Doppler mode at 5 cm depth from the surface has been improved as much as 5 dB over that of a conventional one. >
TL;DR: An experimental study of the generation of second-harmonic light in a one-dimensional periodic structure truncated by the introduction of a defect in the central period observed an enhancement of the nonlinear interaction in the vicinity of the defect when the second- Harmonic wave was excited for modes within the forbidden zone or stop band.
Abstract: Electromagnetic mode selection in periodic dielectric materials may be used to obtain sharp optical features such as suppression and enhancement of the radiation of oscillating dipoles. Periodic dielectric materials may be studied by means of the photonic band gap (PBG) theory.1 In the framework of this theory, we present an experimental study of the second harmonic (SH) generation from a slab of nonlinear molecules embedded in a 1-dimensional periodic dielectric structure truncated by the introduction of a defect in the central period.
06 Nov 1995
TL;DR: In this paper, a static power convertor active power filter based on a DSP controller with enhanced performance of current control is presented, where a novel predictive current control method is introduced to compensate the phase error of harmonic components due to discrete sampling.
Abstract: This paper presents a static power convertor active power filter based on a DSP controller with enhanced performance of current control. A novel predictive current control method is introduced to compensate the phase error of harmonic components due to discrete sampling. With a close coordination between the reference current prediction, PWM pattern generation, and control timing, high performance control is achieved. Experimental results show that the developed system gives satisfactory performances in its harmonic/reactive power compensation.
TL;DR: The results for the defocusing and the blueshifts of the harmonic spectra observed show that the generation of a higher-order harmonic requires a higher intensity in time and space.
Abstract: We present systematic experimental studies of high-order harmonic generation in He and Ne that have been performed with an intense, femtosecond Ti:sapphire laser at intensities in the tunneling regime, where special attention is concentrated on the strong-field effect. A broad plateau is formed in the harmonic distribution that includes harmonic peaks at low and high orders and the observed highest orders (shortest wavelengths) are the 103rd (7.6 nm) for He and 95th (8.2 nm) for Ne. The laser-ellipticity-dependent harmonics observed suggest different generation processes for the low orders below and around the atomic ionization limit and for the high orders in and above the plateau region. The medium ionization is found to induce strong self-defocusing of the incident laser beam, and its effects on the harmonic generation are studied. The results for the defocusing and the blueshifts of the harmonic spectra observed show that the generation of a higher-order harmonic requires a higher intensity in time and space. The theoretically predicted harmonic cutoff is demonstrated to agree well with experiment when we take into account the interaction intensity limited in the ionizing medium. The characteristic harmonic behaviors observed are discussed based on the interaction intensity and the propagation effect in the medium.