Individual Harmonic Components Research Articles

An artificial neural network based approach for harmonic component prediction in a distribution line

With the increasing use of nonlinear devices in both generation and consumption of power, it is essential that we develop accurate and quick control for active filters to suppress harmonics. Time delays between input and output are catastrophic for such filters which rely on real-time operation. Artificial Neural Networks (ANNs) are capable of modeling complex nonlinear systems through adjustments in their learned parameters. Once properly trained, they can produce highly accurate predictions at an instantaneous time frame. Leveraging these qualities, various complex control systems may be replaced or aided by neural networks to provide quick and precise responses. This paper proposes an ANN-based approach for the prediction of individual harmonic components using minimal inputs. By extracting and analyzing the nature of harmonic component magnitudes obtained from the survey of a particular area through real-time measurements, a sequential pattern in their occurrence is observed. Various neural network architectures are trained using the collected data and their performances are evaluated. The best-performing model, whose losses are minimal, is then used to observe the harmonic cancellation for multiple unseen cases through a simplified simulation in hardware-in-the-loop. These neural network structures, which produce instantaneous and accurate outputs, are effective in harmonic filtering.

Effect of rotation speed fluctuation on rotor noise generation: A numerical and experimental study

The practical operations of rotors for unmanned aircraft systems can undergo time-varying rotation speeds due to various uncertainty factors. This work investigates the aeroacoustic effect of the rotor’s rotation speed fluctuation using both numerical and experimental approaches. The measured real-time angular speed signal reveals that a hovering rotor experiences highly deterministic rotation speed variations in one revolution, which are closely related to the motor property. Delayed detached eddy simulations are performed, and the fluctuating rotation speed is realized by controlling the mesh displacement at each time step. The results suggest that significant additional tones are produced at the excitation frequency and neighbour frequencies, even though the amplitudes of the rotation speed fluctuations at the dominant frequencies are much smaller than the mean rotation speed. By comparing the full signal to individual harmonic components, it is found that the phase difference between each mode is unimportant. Therefore, the total aeroacoustic effect can be regarded as a linear superposition of different harmonic components. Aeroacoustic source analysis is also performed to isolate the contribution of various source types and correlate the far-field noise with the near-field source distribution. The results show that the extra tonal noise is mostly dominated by the loading noise, with a weaker contribution from the thickness noise. The agreement between the experiments and the simulations indicates that the rotation speed fluctuation is likely responsible for the generation of middle-frequency tonal noise at harmonics of the blade passing frequency.

3-level inverter based compensator for power quality enhancement using proposed Trianguzoidal PWM technique

In today’s scenario, the integration of a grid-connected load system with a hybrid energy system (HES) is encouraged to improve the reliability of the system. With the stunning rise in nonlinear loads in HES over the last two decades, the power quality (PQ) of the system has emerged as a paramount concern in contemporary times. The power quality problems include the injection of harmonics in the source current, low input power factor, poor voltage regulation, the burden of reactive power, etc. So, to mitigate these power quality problems in a single-phase distribution system, a 3-level Cascade H-bridge (CHB) inverter-based shunt active power filter (SAPF) is employed alongside a proposed Trianguzoidal pulse width modulation (TRZ PWM) strategy. The single-phase distribution system with SAPF is simulated in fixed and dynamic load conditions to check the system’s efficacy. The proposed PWM techniques for SAPF are compared with conventional PWM techniques, i.e., level shift, phase shift, and hybrid PWM techniques. Results indicate satisfactory performance of the proposed PWM techniques, exhibiting low harmonic distortion in source current, well within IEEE 519 limits, and high active filtering efficiency (AFE) compared to conventional PWM methods. Furthermore, this paper provides detailed comparisons of conventional and proposed PWM techniques in the context of active & reactive power supplied or delivered by load, source, and compensator, input power factor, harmonics in source or grid current, AFE, and individual harmonic components concerning fundamental component of source current.

Power Quality Analysis for Light-Duty Electric Vehicles: A Case Study in Malta

This paper presents a power quality analysis for multiple electric vehicle charging stations of the AC-Level 2 type in a real-life case study. The data was collected with a power quality analyzer that measured the main distribution system feeding nine 7 kW charging stations in a commercial site with light-duty vehicles in Malta, Europe. The relevance of this study to the specific case of Malta is accentuated by the topological challenges of the country; high density of road vehicles, with 18,000 vehicles for each square kilometer; and ambitious targets of reaching carbon neutrality by 2050. Data were collected over six days on an actual charging system with real-life charging patterns. Various results are presented in this paper, including three-phase system voltages and currents, individual harmonic voltage and current components, total harmonic distortion and total current demand distortion. These measurements were compared with standardized thresholds for low-voltage equipment used in public spaces, mainly as stated in IEEE 519-2014.

An artificial neural network based harmonic distortions estimator for grid- connected power converter-based applications

Grid-connected solar Photovoltaic (PV) systems are predicted to cause significant harmonic distortions in today’s power networks due to the increase utilization of power conversion systems widely recognized as harmonic sources. Estimating the actual harmonic emissions of a certain harmonic source can be a challenging task, especially with multiple harmonic sources connected, changes in the system’s characteristic impedance, and the intermittent nature of renewable resources. A method based on an Artificial Neural Network (ANN) system including the location-specific data is proposed in this paper to estimate the actual harmonic distortions of a solar PV inverter. A simple power system is modelled and simulated for different cases to train the ANN system and improve its prediction performance. The method is validated in the IEEE 34-bus test feeder with established harmonic sources, and it has estimated the individual harmonic components with a maximum error of less than 10% and a maximum median of 5.4%.

Active power management of grid-connected PV-PEV using a Hybrid GRFO-ITSA technique

In this manuscript proposed a hybrid Garra Rufa Fish Optimization (GRFO) and Improved Tunicate Swarm Algorithm (ITSA) for improving the power quality of the integrated Photovoltaic (PV) and Plug-in Electric Vehicle (PEV) in Smart Grid (SG) system. The GRFO-ITSA approach is hybrid wrapper of GRFO and ITSA. Commonly it is named as GRFO-ITSA approach. The grid-connected PV-PEV, active power management is performed by the proposed approach. The proposed GRFO approach is used to determine the individual harmonic components and to reduce the recompense currents applied to PVs via PEV converters. The load flow control is performed by ITSA approach, which controls the power among the PVs, and PEVs. Additionally, it satisfies the power demand, and voltage variation. The proposed approach is also to analyze the mutual properties of PVs as well as PEVs on the feeder and transmitting loads, voltage outlines, harmonic alterations of an urban electric power distribution system. Also, the performance of the GRFO-ITSA is implemented on MATLAB site as well as associated with several existing approaches. The GRFO-ITSA have improved the power quality and compensate the harmonics and reactive power of the system. The optimal outcome is obtained by GRFO-ITSA with less computation time.

A Direct Single-Phase to Three-Phase AC/AC Power Converter

The traditional DC-link indirect AC/AC power converters (AC/DC/AC converters) employ two-stage power conversion, which increases the circuit complexity along with gate driving challenges, placing an excessive burden on the processor while implementing complex switching modulation techniques and leads to power conversion losses due to the use of a large amount of controlled power semiconductor switches. On the contrary, the traditional direct AC/AC voltage controllers, as well as frequency changers, suffer from high total harmonic distortion (THD) problems. In this paper, a new single-phase to three-phase AC/AC step-down power converter is proposed, which utilizes a multi-linking transformer and bilateral triode thyristors (TRIACs) as power semiconductor switches. The proposed direct AC/AC power converter employs single-stage power conversion, which mitigates the complexity of two-stage DC-link indirect AC/AC converters and traditional single-stage AC/AC frequency changers. Instead of using high-frequency pulse width modulated gate driving signals, line frequency gate pulses are used to trigger the TRIACs of the proposed AC/AC converter, which not only aids in reducing the power loss of the converter but also mitigates the cost and complexity of gate driver circuits. The proposed AC/AC converter reduces the THD of the output voltage significantly as compared to traditional direct AC/AC frequency changers. The performance of the proposed AC/AC converter is validated against RL and induction motor load in terms of overall THD and individual harmonic components through MATLAB/Simulink environment. A reduced-scale laboratory prototype is built and tested to evaluate the performance of the proposed AC/AC power converter. The experimental and simulation outcomes reveal the feasibility and excellent features of the proposed single-phase to three-phase AC/AC converter topology.

Impacts of Harmonic Voltage Distortions on the Dynamic Behavior and the PRPD Patterns of Partial Discharges in an Air Cavity Inside a Solid Dielectric Material

The monitoring of partial discharges (PDs) is one of the main methods used worldwide for evaluation and diagnosis of the insulation conditions in equipment powered by medium and high voltages. The occurrence of PDs is usually an indication of the appearance of insulation defects, which over time can compromise the dielectric withstand of the material used, increasing the probability of complete breakdown. In general, laboratory tests for detecting and registering PDs are carried out using purely sinusoidal voltages. However, it is very common for an electrical asset to be subjected at some point in its operating life to voltages distorted by harmonic components. Some studies reported in the literature reveal that harmonic distortions can affect the PDs’ characteristics, nevertheless, the effects of individual harmonic components on PDs still need to be analyzed. In this context, this paper proposes to evaluate the impacts of harmonic voltage distortions on the dynamic behavior and the phase-resolved partial discharge (PRPD) patterns of PDs in an air cavity within a solid dielectric material. For this, a simulation model was implemented, which was used to analyze the effects of applying distorted voltages composed of different harmonic orders (third, fifth, and seventh) and distinct levels of distortion (1%, 3%, 5%, 10%, 15%, and 20%). In addition, the influence of the third harmonic phase angle on PDs is also analyzed. The results extracted from the simulations revealed that the harmonic distortions caused changes in the numbers of PDs per cycle, in the mean apparent charges of the PDs per cycle, and in the PRPD patterns’ characteristics. These changes were very significant for higher distortion levels, which in practice may impair the interpretation of PD measurement records for the diagnosis of the condition of the insulation system.

Calculation of Magnetic Flux Density Harmonics in the Vicinity of Overhead Lines

This paper considers the method for the calculation of magnetic flux density in the vicinity of overhead distribution lines which takes into account the higher current harmonics. This method is based on the Biot–Savart law and the complex image method. The considered method calculates the values of the magnetic flux density for each harmonic component of the current separately at all points of interest (usually lateral profile). In this way, it is possible to determine the contributions of individual harmonic components of the current intensity to the total value of magnetic flux density. Based on the contributions of individual harmonic components, the total (resultant) value of the magnetic flux density at points of interest is determined. Validation of the computational method is carried out by comparison of the results obtained by the considered calculation method with measurement results. Furthermore, the application of the calculation method was demonstrated by calculating magnetic flux density harmonics in the vicinity of two overhead distribution lines of typical phase conductor arrangements.

Анализ и расчет высших гармоник системы электроснабжения завода на основе пакетного вейвлет-преобразования

After analyzing the results of physical tests of the power supply system of the plant, it is found that the values of individual harmonic components exceed the values established by GOST-32144 2013. Based on the data obtained, a simulation model is formed and an analysis of higher harmonics is performed using the packet wavelet transform method. The aim of the work is the analysis and calculation of higher harmonics and additional losses from them in the neutral conductor based on the packet wavelet transform method. The simulation is carried out using the Simulink software package. As a result of the study, it is found that the packet wavelet transform with high accuracy allows to determine the presence of higher harmonics in the power supply system, the efficiency of using the wavelet transform to calculate additional losses in the neutral conductor is shown.

Определение потерь в стали бесконтактного двигателя постоянного тока с использованием линейной аппроксимации импульсов напряжения

Analysis of iron loss of a BLDC motor is of particular interest at the design stage or when researching methods to improve energy efficiency. Most of the existing methods for determining losses in steel are based on the analysis of losses for individual harmonic components of induction with their subsequent summation. However, the application of these methods for various forms of voltage obtained at the output of the converter is incorrect due to the non-linearity of magnetic circuits. This paper proposes a method for determining steel losses of BLDC motor using a linear approximation of voltage pulses, which makes it possible to take into account the influence of the voltage shape on the magnitude of magnetic induction directly, without expansion into a Fourier series. The dependences of steel losses on the switching frequency for various values of the duty cycle, and on the rise time of voltage pulses are obtained. Comparison of the simulation results of the 5 kW BLDC Motor with the experimental data of the idling mode given by the manufacturer proved the adequacy of the considered method.

Квазистатический "уход" маятника при возмущении точки подвеса высокочастотной полигармонической вибрацией с некратными частотами

The paper dwells upon the dynamic behavior of a 2d pendulum under polyharmonic vibration. The study shows that the angles between the vertical coordinate axis and the directions of the individual harmonic components effects are generally different. Relying on the well-known approach, we solved the problem in two approximations. The movement of the pendulum contains two components: the "low-frequency" component and the "high-frequency" one. As the frequencies are not multiple, the movement is essentially an aperiodic process. Hence, when deriving the basic relations, it is impossible to use an effective method of averaging the solution within a period of fast oscillations. Dividing the solution by the frequencies of oscillations, we obtained an equation describing the slow motion and an approximate formula based on it for determining the pendulum quasi-static displacement, i.e., the "drift effect". The result is generalized by taking energy dissipation into account. Findings of research show that near the quasi-static position of the pendulum, loss of stability is possible as a result of parametric resonance at the combination frequencies of the external action. The paper gives an example in which an approximate solution is compared with an exact numerical simulation and shows the results of this comparison

DEVELOPMENT OF AN ALGORITHM FOR CREATING A THREE-DIMENSIONAL GRAPH OF THE TOTAL HARMONIC OF VOLTAGE COMPONENTS RATIO

In the power supply system of industrial enterprises with low installed capacity, a battery of cosine capacitors is used as reactive power compensation devices in most cases. However, in certain modes of operation in such a network due to the presence of electrical receivers, which generate the highest harmonics, there may be resonance phenomena. Therefore, in such a network you should know both the presence of harmonic components and their percentage.
 
 It is known that according to GOST 32144-2013 it is necessary to take into account not only the individual harmonic components of the voltage of about 40 harmonics, but also the total ratio of these components. For this reason, the calculation of this parameter in the power supply system of consumers is an urgent task.
 
 In this paper the principle of structure of the three-dimensional graph of the total factor of harmonic components of voltage is revealed. The arguments for the dependence of this factor on the most important parameters of the electrical network, such as system short-circuit power, capacitor bank, load consumption are given.
 
 The authors have developed an algorithm for creating a three-dimensional graph of the total harmonic voltage components coefficient with the disclosure of the principles of its construction. As an example, the paper presents graphical dependencies: kU = f(SКZ , QBK ); kU = f(SКZ , PNG ); kU = f(QBK , PNG).

Development of a relay-vector control system for a multi-phase semiconductor converter of electric energy

A system of relay-vector control of current in the circuit of a polyphase electric machine has been developed. For this, on the basis of the analysis of electromagnetic processes in a multiphase semiconductor converter of electrical energy, its discrete mathematical model was created, which takes into account the redistribution of electromagnetic energy by individual spatial harmonic components, depending on the number of phases. Using this mathematical model, a method for relay control of spatial harmonic components of the input current of the converter in the “tube” has been developed. The formation of polyharmonic currents in each of the phases, conjugated in shape and phase with the voltage supplying the converter at each control period, is carried out by means of the optimal voltage vector of the semiconductor switch. To select the optimal control action, the objective function of the minimum deviation of the projections of the base voltage vectors of the semiconductor switch for the j-th combination of the state of the keys from the calculated control action determined by the mathematical model is used. An objective function of this type allows one to take into account different values of the amplitudes of the base voltage vectors of the semiconductor switch in the transformed orthogonal coordinate systems. In this case, there is no need to predict changes in the instantaneous values of the input current for one or two periods ahead, which is ensured by a decrease in the number of iterations to determine the optimal control action. To check the developed provisions, a simulation model of a nine-phase semiconductor converter of electrical energy with a relay vector control system was created. The results of the study of the model confirmed the adequacy of the developed technical solutions, the use of which will ensure the most complete realization of the own advantages of a multiphase electric machine in order to generally improve the weight, size and energy indicators of the autonomous power supply system.

Spectral Analysis of Torsional Vibrations Measured by Optical Sensors, as a Method for Diagnosing Injector Nozzle Coking in Marine Diesel Engines.

The study aimed to verify whether it is possible to diagnose the coking of a marine diesel engine injector nozzle by performing a spectral analysis of the crankshaft’s torsional vibrations. The measurements were taken using laser heads, clocked at 16 MHz. The reasons for selecting this type of optical sensors are described as well. The tests were carried out under laboratory conditions, using a test stand with a Sulzer 3AL 25/3 engine, operating under a load created by a Domel GD8 500–50/3 electric generator. A unique method is presented in the paper, which enables the measuring and calculation of torsional vibrations of engine crankshafts. The method was developed at the Chair of Marine Power Plants at the Maritime University of Gdynia. It has been proven that the distribution of differences in the values of individual harmonic components depends on the location of a defective injector nozzle in the cylinder.

Photovoltaic and Plug-in Electric Vehicle for Smart Grid Power Quality Enhancement

The optimization of energy quality applied to the intelligent power network recently assumes to be the principal challenges for the next-generation smart grid. The main goal of this study is to investigate a control strategy implemented in grid-connected photovoltaic (PV) installation converters and plug-in electric vehicle (PEV) for active power management, grid frequency controlling and nonlinear (NL) loads polluted current compensation. This approach is generally composed of two parts: The first one consists of "Neuronal NL loads currents identification system" which plays an important role for identifying in real time, with high precision, each individual harmonic component of the measured line currents and then deducing the references compensation currents applied to PVs and PEVs converters. The second one is the "Grid frequency control algorithm." The purpose of this part is to control the power flow exchanging between the PVs, PEVs and the electrical network to achieve the smoothness of the smart grid daily power demand ensuring, consequently, the flattening of the grid frequency variation.

METHODOLOGY OF DETERMINATION OF THE OF MULTIFREQUENCY MAGNETIC FIELD LEVEL AT WELDER`S WORKING ZONE

The purpose of this work is to develop a methodology for determination of the total level of multifrequency magnetic field (MF) at the working area of welder by studying the dependences of the magnetizing force of its individual harmonic components to the electrical characteristics of the MF source and welding modes. The study was carried out at a wide frequency range of the MF action for the researching of dependences to MF technological parameters of the contact welding machine and the distance to it. An induction magnetic field sensor and a digital recording oscilloscope with a fast Fourier transform function were used for experimental studies of MF magnetizing force and their spectral ranges. Based on the analysis of the obtained MF oscillograms and spectrograms, the shape and magnitude of the MF magnetizing force signals in different frequency ranges were established. Since it is impossible to quantify the overall level for a multifrequency MF with taking into account all the harmonic components of the MF simultaneously, the generalized magnetic field level indicator (MFI) was proposed, which became the basis for its use as a methodology for the assessment of MF impact on human body. The use of the proposed methodology allowed to establish that it is generated MF with harmonic components in the frequency ranges 5-50 and 50-1000 Hz at working area under contact spot welding, which may exceed their maximum allowed levels, leading to the respective increase of MFI level. It was established that any changes in the mode of contact spot welding, compared to the mode of welding with one batch of full-phase pulses of welding current, lead to the increase in MFI with exceeding of maximum allowed level at a distance of 800-1000 mm from the axis of contact welding machine electrodes; modelling of the front and trailing edges of the pulse lead to the reduction of MFI level, while increasing the angle of phase control of the heating mode leads to the increase of MFI level. The proposed methodology can be applied as universal both for hygienic assessment of the electromagnetic environment during arc welding and for other electrical equipment. The developed methodology gives possibility to assess the overall impact of multifrequency MF on human body. It is based on the known laws of electrodynamics using a new generalized indicator - magnetic field level indicator MFI.

INFLUENCE OF THE THICKNESS OF THE BACK WALL OF A WOODEN ORGAN PIPE AND THE AIR PRESSURE IN THE WIND CHEST ON ITS SOUND PROPERTIES

The paper presents the results of the study of the influence of the back wall thickness of an organ pipe made of resonant spruce wood and the air pressure in the wind chest on its frequency spectrum. A wooden organ pipe with a replaceable back wall was used in the experiment. The wooden plate used for the back wall had an initial thickness of 7 mm. The plate was gradually thinned in 1 mm decrements to a thickness of 1 mm. For each plate thickness, the frequency spectrum was scanned at four different air pressures, namely 588 Pa, 716 Pa, 814 Pa and 941 Pa. The results of the experiment showed that at a given back wall thickness, the fundamental tone frequency increases with increasing air pressure. The decrease in the back wall thickness was manifested by a decrease in the fundamental frequency. At an air pressure of 716 Pa, the intensity of the fundamental as well as the second harmonic component of the pipe acoustic spectrum increased slightly at all wall thicknesses. With increasing air pressure, the intensity of higher harmonic frequencies also increased. The decrease in the back wall thickness of the wooden organ pipe had only a minimal effect on the intensity of the individual harmonic components of the frequency spectrum. Changing the thickness of the back wall of a wooden organ pipe will not significantly affect its final sound.

Development of a vector control system of the semiconductor converter, which will provide a polyharmonic operating mode of a polyphase electric machine

A system for vector control of current in the circuit of a polyphase electric machine has been developed. For this, on the basis of the analysis of electromagnetic processes in a multiphase semiconductor converter of electrical energy, its discrete mathematical model was created, which takes into account the redistribution of electromagnetic energy by individual spatial harmonic components depending on the number of phases. Using this mathematical model and the scheme of injection of higher current harmonics, which provides a polyharmonic mode of operation of a semiconductor converter, a method for independent control of the spatial harmonic components of the input current of the converter has been developed. The formation in each of the phases of polyharmonic currents, conjugated in shape and phase with the voltage supplying the converter, is carried out by means of control actions in the form of voltage vectors of a semiconductor switch, the implementation of which is carried out by the method of multiphase space-vector modulation. To check the developed provisions, a simulation model of a nine-phase semiconductor converter of electrical energy with a vector control system was created. The results of the study of the model confirmed the adequacy of the developed technical solutions, the use of which will ensure the most complete realization of the own advantages of a multiphase electric machine in order to generally improve the weight, size and energy indicators of the autonomous power supply system.

Stability analysis of roundness profiles of drawn tubes

The geometric accuracy is significant property of the product. For semi-finished products, this accuracy may also affect the accuracy of the final product (the resulting mechanical component). Geometric accuracy (inaccuracy) can be transmitted from one operation to the next in production - technological heredity arises. It is, therefore, essential to analyze the deviations on the produced areas and take measures to ensure that the negative effect of one operation was not transferred to the next operation. It is insufficient to analyze only the numerical values of the measured deviations. It is necessary to directly analyze the measured profiles in the field of macro geometry. The paper presents a stability analysis of roundness profiles measured on the drawn tube. The analysis uses knowledge from harmonic analysis and from the Fourier series. The measured roundness profiles are divided into individual harmonic components. Arithmetic means of amplitudes of individual harmonic components are moni-tored. There were analyzed parameters determining the stability of the profile - standard deviations.