Seventh Harmonic Research Articles

Low Vibration Control Scheme for Permanent Magnet Motor Based on Resonance Controllers

For an electric locomotive traction motor, it is necessary to maintain relatively low vibration and noise due to the higher design standards. By using effective motor control strategies and implementing current harmonic suppression schemes, motor efficiency and vibration and noise suppression can be effectively improved. This study investigates the current harmonic suppression strategy for permanent magnet synchronous motors by (1) constructing a mathematical model of the permanent magnet motor to explore the sources of low-order harmonics currents such as fifth and seventh harmonics, as well as high-order harmonics at switch frequencies and their multiples, and analyzing the electromagnetic force characteristics generated by the current, and (2) establishing a vector control system for the permanent magnet motor. To suppress the fifth and seventh harmonic components in the current, a resonance controller is constructed, which utilizes the parallel connection of a resonator and PI controller to achieve low-order harmonic suppression. The factors affecting the effectiveness of the resonance controller’s suppression are also analyzed. The experiments are conducted, and the current harmonic suppression scheme constructed in this study can effectively reduce the harmonics in the current, thereby reducing motor vibration and noise.

On‐line dead‐time compensation method for dual three phase PMSM based on adaptive notch filter

For the dual three-phase permanent magnet synchronous motor(dual-PMSM), the deadtime can introduce fifth and seventh current harmonics, and they are only constrained by the small stator leakage impedance, which means even if there are only small fifth and seventh voltage harmonics, the resulting fifth and seventh current harmonics will be very large. The harmonic current will make an increment of the system loss, thus lead to an reduce of the efficiency of the speed control system. This paper proposes a harmonic current suppression strategy for dual-PMSM based on least mean square (LMS) adaptive notch filter. This strategy suppresses the fifth and seventh harmonic currents by introducing four LMS adaptive notch filters in the subspace. The proposed algorithm has good dynamic performance and is insensitive to motor parameters that are offset within a certain range. The effectiveness of proposed method is verified by a set of comparative simulations and experiments.

Self-Amplification of Coherent Energy Modulation in Seeded Free-Electron Lasers.

The spectroscopic techniques for time-resolved fine analysis of matter require coherent x-ray radiation with femtosecond duration and high average brightness. Seeded free-electron lasers (FELs), which use the frequency up-conversion of an external seed laser to improve temporal coherence, are ideal for providing fully coherent soft x-ray pulses. However, it is difficult to operate seeded FELs at a high repetition rate due to the limitations of present state-of-the-art laser systems. Here, we report a novel self-modulation method for enhancing laser-induced energy modulation, thereby significantly reducing the requirement of an external laser system. Driven by this scheme, we experimentally realize high harmonic generation in a seeded FEL using an unprecedentedly small external laser-induced energy modulation. An electron beam with a laser-induced energy modulation as small as 1.8 times the slice energy spread is used for lasing at the seventh harmonic of a 266-nm seed laser in a single-stage high-gain harmonic generation (HGHG) setup and the 30th harmonic of the seed laser in a two-stage HGHG setup. The results mark a major step toward a high-repetition-rate, fully coherent x-ray FEL.

Impact of the Seventh Harmonic Magnitude for an Optimal Control of Five-phase PMSM

In this paper, the impact of the seventh harmonic magnitude for an optimal torque control of 5-phase PMSM is studied. We showed that the machine evolved in two orthogonal frames and can be decomposed into two fictitious machines called respectively main machine, secondary machine. As the two frames are fully decoupled, the torque control of each fictitious machine is done separately. the goal is to maximize the average torque, to minimize the copper losses and to reduce the torque ripples. The main machine is not impacted but in the secondary machine, it is possible to know the variation of the torque ripples and the copper losses by modifying the imposed current references and taking into account the seventh harmonic of the EMF. An itemized analysis of the impact of the EMF seventh harmonic magnitude is done. Simulation results highlight the performances of the torque control strategy under using a robust controller.

An Improved Control Method for Standalone Brushless Doubly Fed Induction Generator Under Unbalanced and Nonlinear Loads Using Dual-Resonant Controller

The brushless doubly fed induction generator in the standalone mode is sensitive to unusual working situations, particularly unbalanced and nonlinear loads. The unbalanced and nonlinear loads can cause significant unbalance and distortion for voltage and current of the power winding (PW). In PW voltage under nonlinear and unbalanced loads, the component of negative sequence represents the unbalance influence, and the fifth and seventh harmonics components represent the nonlinear influence. To address these issues, the dual-resonant controller is employed to reduce the unbalance and nonlinear influences of PW voltage via generating the reference command of control winding voltage, which compensate the negative-sequence component and fifth and seventh harmonic components of PW voltage through the machine-side converter. The experimental and simulation tests are applied to check the effectiveness of the proposed strategy.

Torque enhancement of dual three‐phase PMSM by harmonic injection

The torque enhancement of the dual three-phase permanent magnet synchronous machine (DT-PMSM) drive system by full exploitation of flux-linkage and current harmonics is comparatively studied in this study. The torque capability of DT-PMSM is previously evaluated with strategies of harmonics utilisation, i.e. strategy 1 of third harmonic utilisation and strategy 2 of fifth and seventh harmonic utilisation, which can extend the torque capability by 18.2 and 9.0%, respectively. However, the full exploitation of harmonics including third, fifth, and seventh harmonics in the dual three-phase system is not addressed. In this study, the strategy 3 of third, fifth, and seventh harmonic utilisation is also included. Its corresponding harmonic current control is proposed and the average torque and harmonic torque are analysed in detail. Based on a test rig with existing prototype DT-PMSM, the torque with strategy 3 is increased up to 26.5%, which is superior to the previous strategies.

ANALISIS KUALITAS DAYA PADA SUPLAI DAYA LISTRIK PT. SOSRO


 
 
 
 In more than ten years, quality of electricity has growed from clearness to be an principal issue. One heavy problems from quality of power is harmonic distortion and its consequences. Particularly, the increasing of penetration of loads bases on power electronics (non-linear load) what creates a harmonic distortion in AC power systems. Then, quality of electricity becomes principal issue for utility and its consumer and both swiftly adopts philosophy and proposes limits in new international standard (IEC, EN, BS, IEEE). As consequence the equipments of power conditioning (converter) will become more important for electrical utility and its consumer. From the results with the data logger recording at PT SOSRO distribution feeder system found that there are several current and voltage harmonics are significant in the load and hence the supply side. Fifth and the seventh Harmonic are heaviest harmonic components in the current load. Installation of passive filters will be one solution to overcome the issue with the current harmonics. The recomendation proposed will be submitted to management for consideration PT SOSRO factory in determining which type of passive filter will be used.
 
 
 

Harmonic generation in solids with direct fiber laser pumping.

High harmonic generation in solids presents the possibility for bringing attosecond techniques to semiconductors and a simple source for frequency comb spectroscopy in the vacuum ultraviolet. We generate up to the seventh harmonic of a Tm fiber laser by focusing in silicon or zinc oxide. The harmonics are strong and stable, with no indication of material damage. Calculations show the potential for generating nineteenth harmonic photons at 12 eV photons of energy.

Measurement of harmonic distortion and Skewness of stator current of induction motor at crawling in Clarke plane

This study deals with measurement of harmonic distortion and Skewness of stator current in Clarke plane at crawling of induction motor. Three-phase current signals have been transformed into Clarke plane. Dominancy of seventh harmonic is observed by assessing maxima and minima of stator current Concordia in Clarke plane. Specific reference signals having sinusoidal nature and different frequencies are defined and then areas covered by the real system data with the reference signal have been determined, wherefrom individual contributions of fundamental waveform and harmonic components are measured separately and total harmonic distortion factors are determined. Then wavelet decomposition of stator current is done in Clarke plane, wherefrom, signals are assessed with the help of Skewness of approximate coefficient in Clarke plane. Significant differences are noted between those parameters found during crawling and that of normal condition which may be useful in detection of such fault.

All solid-state 1917 nm deep-UV light source by seventh harmonic generation of an 888 nm pumped, Q-switched 1342 nm Nd:YVO_4 laser with excellent beam quality

In this paper we report on the realization of a deep-UV light source using the 1.3 μm transition of neodymium as pumping wavelength. The 191.7 nm radiation was obtained by generating the seventh harmonic of a high-power Q-switched 1342 nm Nd:YVO4 laser. A cesium lithium borate crystal was used for sum frequency mixing of the sixth harmonic and the fundamental. With a total of four conversion stages, up to 240 mW were achieved, with excellent beam quality at 155 mW (M2 < 1.7) and 190 mW (M2 < 1.9).

Design and magnetic measurements of bi-harmonic undulators for free electron laser

In this paper we describe the design and measurement studies of table top bi-harmonic undulators for higher harmonic lasing in FEL. The bi-harmonic undulator are fabricated by placing shims at suitable locations in the undulator gap of a six period planar undulator. An analytical formula is given for the shim counting and positioning along the length of the undulator and field integrals from the Hall probe data are presented for the third, fifth, seventh and ninth harmonic of the bi-harmonic undulator.

High-order harmonic generation of picosecond laser radiation in carbon-containing plasmas

A study of the high-order harmonic generation of picosecond laser radiation in the carbon-containing plasmas is reported. The materials studied for plasma formation were the graphite, glassy carbon, pyrographite, boron carbide, silicon carbide, and pencil lead. We show that picosecond pulses (t=38&#x2009;&#x2009;ps) can be efficiently converted in the short wavelength range using the laser-produced plasmas. We also demonstrate the resonance-induced enhancement of the seventh harmonic of Nd:YAG laser (152&#xA0;nm), which few times exceeded the intensity of the fifth harmonic.

Evidence of High Harmonics from Echo-Enabled Harmonic Generation for Seeding X-Ray Free Electron Lasers

Echo-enabled harmonic generation free electron lasers hold great promise for the generation of fully coherent radiation in x-ray wavelengths. Here we report the first evidence of high harmonics from the echo-enabled harmonic generation technique in the realistic scenario where the laser energy modulation is comparable to the beam slice energy spread. In this experiment, coherent radiation at the seventh harmonic of the second seed laser is generated when the energy modulation amplitude is about 2-3 times the slice energy spread. The experiment confirms the underlying physics of echo-enabled harmonic generation and may have a strong impact on emerging seeded x-ray free electron lasers that are capable of generating laserlike x rays which will advance many areas of science.

Design and simulation of a ∼390 GHz seventh harmonic gyrotron using a large orbit electron beam

A ∼390 GHz harmonic gyrotron based on a cusp electron gun has been designed and numerically modelled. The gyrotron operates at the seventh harmonic of the electron cyclotron frequency with the beam interacting with a TE71 waveguide mode. Theoretical as well as numerical simulation results using the 3D particle-in-cell code MAGIC are presented. The cusp gun generated an axis-encircling, annular shaped electron beam of energy 40 keV, current 1.5 A with a velocity ratio α of 3. Smooth cylindrical waveguides have been studied as the interaction cavities and their cavity Q optimized for 390 GHz operation. In the simulations ∼600 W of output power at the design frequency has been demonstrated.

Coherent detection of nonlinear nanomechanical motion using a stroboscopic downconversion technique

A method is presented that overcomes bandwidth limitations arising in a fiber-optic setup transducing mechanical motion. The reflected light from a sample incorporating a nanomechanical resonator is analyzed. Modulating the incoming laser intensity at a suitably chosen frequency, the mechanically induced oscillation of the reflected light is coherently downconverted to a frequency within the detection bandwidth. Additionally, based on the mechanical nonlinear response, the optical signal can be quantitatively converted into displacement, yielding a sensitivity of 7 pm/Hz at optical power levels of 20 μW. We detect and image mechanical modes up to the seventh harmonic of the fundamental mode at 7.7 MHz.

Efficient harmonic microbunching in a 7th-order inverse-free-electron laser interaction

We have shown that a seventh-order inverse-free-electron laser (IFEL) interaction, where the radiation frequency is the seventh harmonic of the fundamental resonant frequency, can microbunch a beam of relativistic electrons inside an undulator. Using coherent transition radiation (CTR) emitted by the bunched 12.3 MeV beam as a diagnostic, strong microbunching of the beam is inferred from the observation of CTR at the first, second, and third harmonics of the seed $10\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ radiation. Three-dimensional IFEL simulations show that the observed harmonic ratios can be explained only if transverse spatial distribution of the steepened bunched beam is taken into account.

AC susceptibility harmonic response in YBCO single crystals with different oxygen contents

We measured up to the seventh harmonic response of the complex ac susceptibility ( χ n ′−j χ″ n ; n=1–7) vs. temperature, in YB 2C 3O x single crystals with different oxygen contents (6.5⩽ x⩽7). The ac field was applied in presence of an external dc field both parallel to the c-axis of the crystals. We show evidence that deoxygenation leads to a reduction of bulk pinning strength evidenced by a decrease in the value of the third, fifth and seventh harmonics. We compare our measurements with a numerical model that includes effects of flux creep and sample geometry where the activation barrier depends explicitly on temperature.

A digital control system for the iodine stabilized He–Ne laser

A digital control system has been developed for the iodine stabilized He–Ne laser. The system is based on a digital signal processor and a general purpose microprocessor. The hardware is briefly described. The algorithms used for laser frequency locking are presented and new methods which are made possible by this system are discussed. An improved way of locking the laser to the fifth or seventh harmonic of the modulation frequency has been implemented digitally.

Unmodulated CO 2 laser stabilized by means of Stark and photoacoustic spectroscopy

A high-power CO 2 laser (9P(34)) for use in optically pumping a CH 3OH laser (70.5 μm) has been stabilized in the vicinity of the center of the CH 3OH saturated absorption line by means of photoacoustic spectroscopy (PAS). The stabilized pump laser beam is unmodulated because the PAS signal for stabilization was obtained by modulating the Stark field in the external PAS cell filled with CH 3OH molecules at low pressure. The unmodulated effect is to eliminate the spectrum spread due to the frequency modulation, and is demonstrated in the frequency mixing between the seventh harmonic of the CH 3OH laser and a CO 2 laser at 10.2 μm. The frequency stability has been estimated quantitatively with reference to a CO 2 laser stabilized on the Lamb dip of 4.3 μm fluorescence.

Absorption profile of the seventh harmonic of the CH stretch in liquid benzene

We report the measurement of the absorption profile of the seventh harmonic of the C—H stretch in liquid benzene by a pulsed dye laser opto-acoustic technique. The absorption peaks at 18808 cm −1 (5316 A), with a peak absorption coefficient being 4.5 × 10 −4] cm −1. The asymmetrical absorption profile has a full width at half maximum of 317 cm[su−1 . The systematic trends of the series of harmonic absorption lineshapes in benzene, in the liquid, and in the vapor phase, are discussed.