Influence Of Higher Harmonics Research Articles

ОПРЕДЕЛЕНИЕ ПРОГНОЗИРУЕМЫХ ЗНАЧЕНИЙ НЕСИНУСОИДАЛЬНОСТИ НАПРЯЖЕНИЯ НА ОСНОВЕ СТАТИСТИЧЕСКОГО АНАЛИЗА

A significant problem of ensuring the quality of electricity, including the sinusoidal voltage in the distribution grids of energy systems and power supply grids, arose with the growth and use of equipment with a nonlinear load characteristic. Modernization of production and an increase in its energy efficiency are associated with the use of such electrical equipment. In this regard, in the last decade, the problem of the higher harmonics has become one of the important consequences of global innovative development throughout the world and in Russia in particular. However, the creation of conditions for the operation of all electric receivers in a power system with poor quality of electrical energy causes certain difficulties. (Research Purpose) The research purpose is determining the predicted values of non-sinusoidal voltage based on statistical analysis in distribution grids. (Materials and methods) Methods for analyzing non-sinusoidal voltage and finding deviations from established norms are considered. Studies of non-sinusoidal voltage in distribution grids have been carried out, and critical values of indicators and a constant component have been determined. (Results and discussion) Additional losses from the influence of higher harmonics in distribution electrical grids account for about 4 percent of losses at sinusoidal voltage. In the grids of agro-industrial enterprises, as well as in the grids of traction substations, similar losses reach 17 percent. The maximum value for the entire measurement period is taken as the basis for the measurement result of the harmonic component voltage coefficient, since this approach does not take into account one-time emissions, which in the general structure do not affect the operation mode of electrical equipment. Measurements were carried out in all electric grids on the low and medium voltage side in the Irkutsk region, and the paper presents the results of measurements in the southern electric grids of Irkutsk and its suburbs. (Conclusions) Studies have revealed the presence of a constant component of the coefficient of harmonic components and single emissions exceeding the average operating values. The main regularities of the non-sinusoidal voltage coefficient for the measurement period and the effect on the operating modes of electrical equipment connected to distribution grids are determined.

Accurate sub-domain model for magnetic field computation in electrical machines with HTS materials

The primary aim of this study was to develop and validate an accurate sub-domain analytical model to estimate the magnetic field of electric machines with high-temperature superconducting (HTS) excitation and armature windings. The model was developed by utilizing the separation variable and harmonic analysis methods to solve Laplace’s or Poisson’s equations of the vector magnetic potential in two-dimensional polar coordinates. The theoretical derivations of the final analytical equations for the magnetic flux density distribution in the air-gap and in permanent magnets, electromagnetic torque, and no-load back-electromotive force (back-EMF) are explained in detail. Finally, the magnetic vector potential, flux density distribution of each sub-domain, no-load back-EMF, and inductive reactance of the armature winding were solved by considering the critical parameters of the superconducting materials, and the influence of higher harmonics. The finite-element method (FEM) was used to validate the accuracy of the developed analytical method for the investigated HTS generator. The results show the developed analytical method is accurate and time-saving.

EVALUATION OF ADDITIONAL LOSSES AND EFFICIENCY ELECTRICITY CONSUMPTION REGULATION IN LOCAL POWER SUPPLY SYSTEMS


 
 
 Peculiarities of estimation of total energy losses in electric networks and estimation of nature of electricity consumption in local power supply systems (LES) are given. The structure of additional electricity losses in LES in the presence of higher harmonics of current and voltage is carried out, the generalized schedule of instantaneous functions of current i(t), voltage u(t), and power p(t) on components. The offered indicators of an estimation of the performance of criterion of a minimum of losses of the electric power in LES allow to estimate levels of distortion of power processes at consideration both exchange processes, and at the analysis of additional losses of the electric power. The accuracy of measuring the integrated characteristics of energy exchange depending on the available levels of distortion of voltage and current signals is considered. It is shown that in order to take into account the influence of higher harmonics on the total power consumption, it is necessary to determine the change of Frize QFpower as an indicator of additional electricity losses in the presence of non-sinusoidal currents and voltages in at different ratios between the value of current and voltage of the first and higher harmonics. The evaluation of the efficiency of power consumption regulation using the Frize QF power at an arbitrary time interval, as well as the corresponding current distribution into active and reactive components are considered. The peculiarities of increasing the efficiency of power consumption regulation in LES at the cyclic change of generator parameters and load are analysed.
 
 

Investigation of complex structure systems based on spectral analysis

The object of research is the process of processing the results of the movement of vibration-absorbing machines in the construction industry. One of the problems in the study of technological vibration machines is the determination of the parameters of the spatial motion of the working bodies of the machine and establishing their compliance with the calculated ones obtained as a result of calculations or numerical simulation. And also when establishing the state of structures under the influence of complex dynamic effects. Difficulties arising in the study of dynamic processes are caused by the determination of the nature and actual values of dissipative forces, the influence of unknown random variables, including interference and imperfections in the measuring technique.The approach proposed in this paper is based on the hypothesis of considering a system of complex structure, has a dynamic effect as a single system with its corresponding dynamic characteristics. The implementation of this approach can be carried out by determining the dynamic parameters of the system with subsequent spectral analysis and the establishment of the main vibration frequencies that are due to external influence, as well as the identification and clear identification of higher harmonics. Recordings of continuous fixation of the vibration process with a known frequency of external influence are used to determine the necessary effective method for presenting the results. Further processing of such results on the basis of the spectral-correlation method makes it possible to determine an effective way to determine the fundamental frequency, to reveal the influence of higher harmonics and extraneous frequencies inherent in the investigated process. The vibration spectra in the linear and logarithmic scales with acceleration and spectral power are considered. According to the research results, it is found that the use of precisely the spectral power of the signal level is an effective method for determining the dynamic process and performing an integral assessment of the overall system.The obtained research results can be used in the study of systems with complex motion with unknown parameters of external influence when performing diagnostics and evaluating the technical condition of technological machines, the vibrations of the supporting and enclosing structures of buildings.

Analytical calculation of the magnetic field in electrical machines with HTS excitation and armature windings

The design of innovative electromechanical systems has been complicated by limited possibilities for improving the characteristics of traditional electrical machines. In this regard, scientists all over the world are researching the prospects to create devices based on high-temperature superconductors (HTS), which will be able to provide higher specific power. This paper presents a technique for calculating the distribution of magnetic fields and the main parameters of an electric machine with HTS field and armature windings and ferromagnetic yokes on the rotor and on the stator. The dependencies obtained in the study are of a general nature and can be used in calculating the parameters of machines of various design schemes. The proposed technique takes into account the critical parameters of the superconductor, the number of pole pairs, the influence of higher harmonics, the number of slots per pole and phase q, and can be extended to the case of an annular armature winding. Using the relationships obtained, the HTS generator was calculated. The result is verified using finite element modeling.

THE DEVELOPMENT OF ELECTRONIC DEVICES FOR MEASURING THE HIGHER HARMONICS FOR SOLAR POWER PLANTS OF ALTERNATING CURRENT OF INDUSTRIAL FREQUENCY

The paper is devoted to the problem of determining the higher harmonics presence in a power network. The paper notes the negative influence of higher harmonics of voltage and current on the power supply system’s elements and communication lines. During the research, a device has been developed to analyze the higher harmonics of the power network. The main element of the device is the Arduino board on the Atmega328p microcontroller. For the correct operation of the device, the corresponding software has been created. The result of modeling of the proposed device operation is a set of harmonic values of the investigated signal in a form suitable for further analysis.

Учет влияния высших гармоник при расчетах потерь мощности и энергии, возникающих в кабельной линии электропередачи, при подключении к сети группы персональных компьютеров

Учет влияния высших гармоник при расчетах потерь мощности и энергии, возникающих в кабельной линии электропередачи, при подключении к сети группы персональных компьютеров

Effect of high speed shear on the non-linear rheological properties of SPI/κ-carrageenan hybrid dispersion and fractal analysis

In this research, the effect of shear rate (rotation speed) of high speed shear treatment on the linear and non-linear rheological properties and microstructure of soy protein isolate (SPI)/κ-carrageenan (κ-KARA) hybrid dispersion was studied. It is found that high-speed shear treatment makes the hybrid system more homogeneous in a certain shear rate range (around 6000N) within which the mixing effect is stronger than the shearing effect on the mixed system. However, the elastic (G′) and viscous properties (F′) of the hybrid system increase when the shear rate is above a certain range (over 8000N). The effect of the destruction of the hybrid system structure becomes gradually greater (G’ decrease) than the effect of the mixing, resulting in a decrease of the storage modulus and apparent viscosity. The result of the LAOS test shows that the shear rate only affects the magnitude of the I3/1 peak and does not have a significant effect (p < 0.05) on the peak strain value. In other words, the shear rate only has a significant effect on the influence of higher harmonics. The trend of the Lissajous curve shows that the elasticity of the hybrid system dispersion increases with increasing shear rate. The microstructure and fractal analysis shows that with the increase in the high speed shear rate, the fractal dimension of the mixed system solution increases significantly (p < 0.05), indicating that the degree of chaos of the hybrid system dispersion increases with increasing shear rate.

An experimental study of the operating characteristics of an asynchronous motor with pulse supply

The fundamentals of design procedure of performance data of controlled asynchronous motors (AMs) supplied with pulse voltage are stated in this article. The proposed model is based on a L-shaped equivalent circuit for each of harmonics, on which the curve of applied to a phase voltage is displayed. It is proposed to find the increase of magnetic iron loss caused by hysteresis in proportion to the peak value of the pulse voltage. The influence of PWM voltage on magnetic hysteresis loss is determined by using a coefficient depending on the effective values of fundamental and higher harmonics of the EMF and voltages, as well as the coefficient taking into account the increase of electrical resistance of iron due to the skin effect. In a similar way, it is proposed to take into account magnetic losses in the rotor that are occasioned only by the influence of higher harmonics. It is proposed to determine the increase of resistance and decrease of the inductance of short-circuited rotor of the influence of currents of higher harmonics by the well-known Interelectro methodology. The resulting values of consumption current, power factor, effective power, and consumption power of an asynchronous motor with pulse voltage are calculated taking into account the total effect of currents and voltages of fundamental and higher harmonics. Based on the methodology that we have laid out, a program was written and modeling was carried out of the operational characteristics of an asynchronous motor with a power of 180 W supplied by a PWM inverter with a fundamental frequency of 50 Hz. In addition, the harmonic composition of pulse voltage was obtained by processing the oscillograms taken from phase windings of the motor supplied by the frequency converter. To experimentally check of the proposed model, an experimental plant for loading the asynchronous motor was assembled and the operational characteristics of asynchronous motor with the fundamental harmonic of 50 Hz were determined. The experimental results showed satisfactory convergence with the calculated results that makes it possible to recommend the proposed methodology to evaluate the energy indices of frequencycontrolled asynchronous motors.

REACTIVE POWER COMPENSATOR WITH SMOOTH CONTROL

Reactive power compensation devices are widely used: thyristor-control reactors (TCR) and thyristor-switched capacitors (TSC). The TCR disadvantages are discussed. The TSC disadvantages are: influence of higher harmonics on nonsinusoidal voltage power system, the inability to ensure the smooth regulation. The proposed reactive power compensator consists of series with active filter and capacitors with step switch. Reactive power compensator’s control system is proposed. Hysteretic control of the inverter with current feedback is applied. DC-voltage regulator provides balance of active power. The control system allows overcompensation or undercompensation of reactive power modes. Reactive power distribution regulator performs the redistribution of power between switching capacitors and active filter. Minimization condition of this regulator is active filter’s power. Adjustment properties of reactive power compensator are analyzed. The choice of relations between the capacitors TSC steps to minimize the installed capacity of the active filter and the number of stages in TSC is considered. The approach that makes possible to «isolate» capacitors from harmonic currents and provide smooth control of reactive power is proposed

Magnetostriction and the Influence of Higher Harmonics in the Magnetic Field

Knowing the effect of the higher harmonics of the magnetic field on the magnetostrictive behavior of electrical steel is highly beneficial for the noise aspects. In this work, the effect of a third harmonic with a variety of amplitudes and phase delays is extensively studied. Magnetostriction measurements are performed on samples of grain-oriented and nonoriented electrical steel under sinusoidal excitations with a third harmonic component and are compared with those of a purely sinusoidal excitation. The frequency spectrum of the measured data, where the second and the fourth harmonic are the most significant ones are then calculated. The measured data show that only knowing the amplitude of the third harmonic is not sufficient to estimate the variations of the magnetostriction. In fact the phase delay of such third harmonic can significantly alter the results. The measurements are carried out on two grain-oriented and two nonoriented samples under a magnetization with a fundamental of 1.3 T and 50 Hz, from which the following conclusions are drawn. Increasing the phase delay of a 8% third harmonic ratio from 0° to 180° delay, causes a variation up to 55% of the 100 Hz component for the two nonoriented materials. In the case of grain-oriented materials, up to 50% change is obtained. The measured data of the 200 Hz components show an increase, as well. However, since their values are far lower than the 100 Hz component, their effect is considerably smaller on the magnetostrictive behavior. These results are highly important for the noise of electrical machines and transformers, due to the magnetostriction phenomenon.

Design of a Computer Code “HPFCODE” To Evaluate the Influence of the Harmonics in the Electrical Networks

This paper aims to present the design of a computer code (HPFCODE), for calculate a power flow and power losses in power systems under the influence of harmonics, using the GUI in MATLAB. After described the program was run for two networks IEEE 6 nodes and IEEE 14 nodes. The power flow by Newton-Raphson method was calculated as the losses of active and reactive power in the lines, respectively, where the loads are linear and nonlinear (Static Var Compensator(SVC), Thyristor controlled Reactor(TCR), and Unified Power Flow Controller ((UPFC)), The results were almost consistent and show the influence of higher harmonics on power losses in electrical networks. DOI: http://dx.doi.org/10.11591/ijece.v2i5.1465 Full Text: PDF

Influence of High Harmonics of Magnetic Fields on Trapped Magnetic Fluxes in HTS Bulk

Abstract Various kinds of HTS bulk motors are proposed and have been developed. Generally, those motors are driven by semiconductor inverters and currents fed to the armature windings contain high harmonics. Therefore, the bulks are exposed to high harmonics magnetic fields and AC losses are produced in the bulks. The AC losses deteriorate the efficiency of the motors and cause temperature rise of the bulks which decrease the trapped magnetic fluxes of the bulks. Usually, electro-magnetic shielding devices are inserted between the bulks and armature windings. However, the shielding devices degrade compactness of the motors. Therefore, it is important to have knowledge of the influence of the high harmonics magnetic fields on the AC losses and trapped magnetic fluxes of the bulk for optimum design of the shielding devices. In this work, the authors experimentally study the influence of high harmonics magnetic fields.

Investigations on Neutronic Decoupling Phenomenon in Large Nuclear Reactors

Abstract Characteristic size (size of core expressed in terms of neutron migration length) of a nuclear reactor has been used as a simple thumb rule to assess the degree of neutronic coupling the reactor core. In the present paper, neutronic decoupling phenomena of reactor cores is studied using a sophisticated technique, called eigenvalue separation (EVS). A large eigenvalue separation reflects a distant higher harmonic and ensures neutronic coupling in respective neutron flux mode of the core. The EVS analysis technique has been used to optimize core geometry of pressurized water reactors, i.e., Height to Diameter (H/D) ratio of the reactor has been optimized to minimize the deep influence of higher harmonics on the stability. The study brings out that a typical H/D rat io beyond 1.3 should be avoided in large sized cores to maximize core neutronic coupling and hence the stability of the reactor.

Nonlinear three-mode interactions in a developing mixing layer

A formulation based on the integral energy method is presented for the nonlinear interaction problem between three large-scale coherent modes in a developing, laminar, free shear layer. Both binary and three-mode nonlinear, modal energy and phase interactions are included. The modal evolution and the development of the mean flow are very sensitive to the initial energy contents and phases of the participating modes. A strong nonlinear coupling of the modal phase variations with the variations of the modal energies is shown to exist and is responsible for the rapid reversal of the intermodal energy interactions in favor of the occasionally declining mode. This nonlinear mechanism preserves the higher frequency modes far downstream and is shown to contribute to the appearance of mean flow contraction observed in experiments through local collective return of energy to the mean by all modes. Depending on initial conditions, our results support the arguments of R. A. Petersen and R. C. Clough [“The influence of higher harmonics on vortex pairing in an axisymmetric mixing layer,” J. Fluid Mech. 239, 81 (1992)] and M. R. Hajj, R. W. Miksad, and E. J. Powers [“Subharmonic growth by parametric resonance,” ibid. 236, 35 (1992)] according to which three-mode resonances are more efficient than the binary ones. Two cases relevant to situations where the first and second subharmonics of the most amplified mode are forced involving the 3/2 harmonic and 2/3 subharmonic, respectively, are examined. Comparisons of the calculations with experimental results indicate good qualitative agreement.

Jump phenomena of current in piezoelectric-ceramic vibrators under high power conditions

In order to investigate the origin of current-jump phenomenon when piezoelectric-ceramic vibrators were driven at high power levels, the influence of higher harmonics due to the ferroelectric nonlinearity on the jump phenomenon was studied. Using the equivalent circuit equation including a higher harmonic term, the theoretical calculation was performed. Since the calculated values of current under jump phenomena agree well with the measured ones, the jump phenomenon is due to the higher harmonics caused by ferroelectric nonlinearity. It was also found that the strain jump phenomenon appears when the jump of current occurs around the resonance frequency.

Influence of higher harmonics on Poincaré maps derived from current self-oscillations in a semiconductor superlattice

The effect of higher harmonics on the shape of Poincar\'e maps (first return maps) derived from current self-oscillations has been investigated in a semiconductor superlattice system driven by a dc + ac voltage bias. In addition to the intrinsic fundamental frequency, a number of higher harmonics with comparable amplitude are observed. The current oscillation traces are simulated according to the power spectra in order to determine the effect of the higher harmonics on the Poincar\'e maps. The calculated Poincar\'e maps for quasiperiodic oscillations as well as frequency locking are clearly distorted by the presence of the higher harmonics. The shape of the distorted Poincar\'e maps agrees with the experimentally observed ones. The calculation also reveals that the phase shift between the different frequency components of the current has an important effect on the shape of the Poincar\'e maps.

Shape-asymmetry of the diffraction efficiency in Bi12TiO20 crystals: the simultaneous influence of absorption and higher harmonics

Studying moving holographic gratings in a Bi12TiO20 crystal with an applied external field, we have observed the appearance of a “shape-asymmetry” in the diffraction efficiency as a function of frequency detuning. The effect is mainly absorption-induced; for large modulation depth it is further enhanced by the influence of higher harmonics.

Periodic response and stability of hysteretic oscillators

Difficulties encountered in the study of the response of hysteretic systems under periodic force lie in the multivalued nature of the constitutive relationship. In this paper, some of these difficulties are circumvented by assuming an incremental formulation which results in an ordinary nonlinear problem with single-valued functions, though with an enlargement of the phase space. Consideration is given only to periodic oscillations that are found through the harmonic-balance method with many components; there thus ensues a system of algebraic equations that is solved numerically. Stability is studied by the linearized Poincar´ map determined via numerical integration. A simple hysteretic oscillator, that presents degrading and non-degrading behaviour, is considered. The results clearly show that the influence of higher harmonics is far from negligible. While non-degrading oscillators reveal stable behaviour over all the frequency range, in the degrading case there is instability that allows either saddle-...

Accurate solutions and stability criterion for periodic oscillations in hysteretic systems

The study of the periodic response of hysteretic oscillators is reduced to that of nonlinear elastic oscillators by assuming an incremental formulation for the constitutive relationship. The harmonic balance method with many components allows for accurate periodic solution computation. The Floquet theory can be used to check stability. Developed equations are applied to the study of frequency response curves of a hysteretic oscillator that, although simple, shows both degrading and non degrading behaviour. The results reported clearly show the shortcomings of traditional methods; the influence of higher harmonics is far from negligible.