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Although single‐stage inverters are popular for simpler design they face difficulties in shoot‐through mode operation. Insufficient DC voltage regulation and complicated LC network are principal drawbacks of these topologies. A new split source inverter (SSI) can solve problems with single‐stage inverters. In this paper, SSI replaced the voltage source inverter (VSI) of a shunt active power filter (SAPF) which alleviates power quality (PQ) issues in power system. Furthermore, a VSI‐based SAPF faces challenges to maintain consistent voltage across DC‐link capacitor, exactly compensating current generation, and switching loss reduction in inverter. This study examined efficacy of two inverter‐based SAPFs considering a modified synchronous reference frame approach for generating reference current; fuzzy logic controller for regulating DC‐link voltage; and adaptive fuzzy hysteresis current controller for generating switching pulses. Ideal and non‐ideal sources were considered when running the simulations for various load circumstances. The proposed SSI‐based SAPF with an advanced control approach can eradicate source current harmonics to 0.52% and 0.45% under ideal source conditions, and 0.65% and 0.54% under non‐ideal source conditions for non‐linear loads. Similarly, the ripples in the DC‐link voltage are also reduced to 2–3 V for the ideal case and 4–5 V for non‐ideal case. [ABSTRACT FROM AUTHOR]

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ABSTRACT Power quality improvement in grid‐tied solar photovoltaic (PV) system is one of the emergent current research trends. To address the power quality concern, shunt active power filters (SAPF) are widely deployed and researched in grid‐tied PV systems. This paper presents a simplified adaptive transversal (SAT)‐filter control scheme for the two‐stage PV‐SAPF system. The proposed control has the ability to improve different power quality indices. Also, it features faster operation under steady‐state and under dynamic conditions, better dc‐offset rejection ability due to estimation of the accurate fundamental component of the load current. To justify the effectiveness of the proposed control scheme, a thorough comparison is carried out with different conventional and adaptive control schemes. Simulations and extensive experimental analysis are carried out under severe transient conditions such as balanced‐unbalanced supply, sudden load, and irradiation change scenario. [ABSTRACT FROM AUTHOR]

In this paper, a comparison of the emissions of grid-connected converters under grid distortion in the supraharmonic range is performed. The investigated supraharmonic grid distortion is divided into two types, namely odd-integer and even-integer multiples of the grid frequency. It is found that the first distortion type does not affect the emissions of the grid-connected converters, while the second distortion is responsible for the 2N-harmonic emissions that appear in the frequency spectra of the grid-connected converters, which, in turn, interact with the supraharmonic primary emissions of these converters, resulting in additional supraharmonic emissions. To explain this behavior, a mathematical analysis is provided for two types of grid-connected converters with an inverter interface and with a diode bridge rectifier interface. Simulations and experimental studies are performed to verify the main findings of the mathematical analysis. [ABSTRACT FROM AUTHOR]

In this contribution, the time-domain harmonic state estimation is evaluated using the real-time digital simulation, Kalman filter, an optimal measurement algorithm and a physical scaled-down laboratory implementation. This methodology is implemented using MATLAB/Simulink® and runs on RT-LAB® platform in real time. The optimal placement algorithm of measurement devices is used to obtain full observability of the system. This measurement algorithm finds the optimal placement with a limited number of measurement devices, whose measurements may be contaminated with noise. The measurement model is implemented in the physical test power system. Besides, the state estimator assesses the system inputs (internal generator voltages, nonlinear electrical load variables) whose dynamics are totally unknown. The harmonic content of the waveforms is obtained through the fast Fourier transform. The estimated responses in the case studies using the RT-LAB® platform are validated through direct comparison against those obtained in the physical implementation of the electrical power system, obtaining satisfactory results. [ABSTRACT FROM AUTHOR]

In this research, we investigate the power quality of the grid where an Electric Arc Furnace (EAF) with a very high load operates. An Electric Arc Furnace (EAF) is a highly nonlinear load that uses very high and variable currents, causing major power quality issues such as voltage sags, flickers, and harmonic distortions. These disturbances produce electrical grid instability, affect the operation of other equipment, and require strong mitigation measures to reduce their impact. To investigate these issues, data are collected from the Point of Common Coupling where the Electric Arc Furnace is fed. The following three main factors are identified for evaluating power quality: apparent power, active and reactive power, and distorted power. Along with these powers, Total Harmonic Distortion, an important indicator of power quality, is calculated. These data are collected during the full process of producing a complete steel batch. To create a Deep Neural Network that can model and forecast power quality parameters, a network is developed using LSTM layers, Convolutional Layers, and GRU Layers, all of which demonstrate good prediction performance. The results of the prediction models are examined, as well as the primary metrics characterizing the prediction, using the following: MAE, RMSE, R-squared, and sMAPE. Predicting active and reactive power and Total Harmonic Distortion (THD) proves useful for anticipating power quality problems in an Electric Arc Furnace (EAF). By reducing the EAF's impact on the power system, accurate predictions will anticipate and minimize disturbances, optimize energy consumption, and improve grid stability. This research's principal scientific contribution is the development of a hybrid deep neural network that integrates Convolutional Neural Networks (CNNs), Long Short-Term Memory (LSTM), and Gated Recurrent Unit (GRU) layers. This deep neural network was designed to predict power quality metrics, including active power, reactive power, distortion power, and Total Harmonic Distortion (THD). The proposed methodology indicates an important step in improving the accuracy of power quality forecasting for Electric Arc Furnaces (EAFs). The hybrid model's ability for analyzing both time-series data and complex nonlinear patterns improves its predictive accuracy compared to traditional methods. [ABSTRACT FROM AUTHOR]

The effects of harmonics, interharmonics, and subharmonics on low-voltage distribution networks, leading to a deterioration in electrical power quality, have become more evident in recent years. The main harmonic sources are power electronic devices due to their implicit nonlinearity. Interharmonic and subharmonic components are mainly caused by a lack of synchronization between the grid frequency and the switching frequency of the power converters. This can be caused by asynchronous modulated devices, or more commonly by fluctuations in the fundamental grid frequency. Interharmonic currents cause interharmonic voltage distortions that affect grid-synchronized or frequency-dependent systems. The IEC-61000-4-7 proposes a general guide on harmonics, interharmonic measurements, and instrumentation in current supply systems. However, the techniques proposed in the standard are intended for measurement and do not enable a precise identification of the interharmonic components in a signal. This work proposes new definitions for the spectral energy aggrupation to improve signal component detection for the IEC standard. Furthermore, an adaptive Kalman filter algorithm is developed that enables the exact identification in real time of the frequency, amplitude, and phase of these components. The proposed system will become the basis for the implementation of a new range of measurement systems that provide improved accuracy and real-time operation. The work is supported by simulated results analysing various scenarios (including transients after changes in harmonic content in the grid voltage) that demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Induction motors (IMs) are widely used in industrial applications, but harmonic distortion in IM drives can lead to inefficiencies and reduced lifespan. Traditional control strategies and filtering methods have limitations in mitigating lower-order harmonics, particularly the 5th harmonic, which can generate reverse torque and increase overheating risk. Existing solutions often struggle to fully address these issues, especially in high-power applications with dynamic loading conditions. This paper proposes a control strategy to reduce voltage and current harmonics in a Z-source inverter (ZSI)-fed IM drive. The system incorporates an observer-based output feedback robust servomechanism controller, designed using Linear Quadratic Regulator (LQR) and Linear Matrix Inequality (LMI) techniques. It ensures closed-loop stability, precise tracking regulation, and effective disturbance rejection, while also featuring a speed adaptation mechanism for sensorless operation. Simulation results demonstrate significant harmonic mitigation, with the controller achieving 1.01% lower voltage THD and 1.03% lower current THD compared to conventional approaches. This improvement aligns with industry standards and outperforms several existing techniques. The proposed method contributes a comprehensive solution for harmonic mitigation in high-power IM drives, applicable to various industrial applications requiring high-quality power and precise speed control. [ABSTRACT FROM AUTHOR]

Utilizing non-overlap windings has emerged as a favourable choice for minimizing electrical machine manufacturing costs, among other benefits. Nevertheless, it is widely acknowledged that these windings exhibit a notable level of harmonic contents in the resultant magnetomotive force, which can detrimentally impact machine performance, particularly in terms of torque ripple. In the context of wind energy conversion, maintaining low torque ripple is an essential and demanding prerequisite. Medium-speed wind generators present a good trade-off between high energy yield and low gearbox ratios. So far, medium-speed non-overlap winding wound-rotor synchronous generator (WRSG) technologies have been limited to 10/12 and the less common 16/18 pole/slot combinations. In this study, the analysis of a high-pole number combination (24/27 pole/slots) non-overlap WRSG is carried out to theoretically and comparatively predict the electromagnetic and radial force mechanical stress performance analysis with the 16/18 machine with a phase-shifted non-overlap winding (PSW), at 5 MW power level. The study, which is founded on the finite element analysis (FEA) technique, shows that the 24/27 machine exhibits comparable average torque and torque ripple, lower core losses and significantly reduced radial forces compared to the 16/18 PSW-WRSG. However, the 16/18 PSW-WRSG has a 50% reduction in the radial forces compared to the conventional 16/18 non-overlap winding. Experimental vibration analysis of a 3 kW 16/18 WRSG test machine confirms the radial force and vibration reduction in the phase-shifted winding. [ABSTRACT FROM AUTHOR]

The authors present two fast and accurate methodologies for the computation of eddy current losses in the axially laminated rotor of a synchronous reluctance machine. The methodologies are based on different combinations of the finite element method in time and frequency domains with 2D and 3D formulations. First, a comparative study of the 2D and 3D formulations for loss calculation is presented, considering various load angles of the machine to illustrate the problem of eddy‐current losses in this type of machines and its dependence on the load angle. The influence of the iron saturation on the loss calculation is also evaluated in these computations. A novel correction factor based on the computations at two load angles is proposed to convert the losses computed from a 2D model to match those computed from a 3D model. For the sake of generality, investigations are also conducted for various thicknesses of the lamination layers and different machine lengths, and an analytical method to describe the dependency of eddy‐current losses on the load angle of the machine is introduced. Moreover, a simplified method is proposed for modelling eddy currents in the frequency domain and calculating losses in an axially laminated structure based solely on the results of a magnetostatic solution. The results obtained by the simplified model demonstrate excellent agreement with the full 3D magneto‐dynamic simulation. Overall, the findings contribute to understanding and accurately characterising the eddy current losses in axially laminated rotors, offering potential insights for designing and optimising axially laminated synchronous reluctance electric machines. [ABSTRACT FROM AUTHOR]

Summary: Photovoltaic (PV) systems benefit from the cascaded H‐bridge multilevel inverter (CHMLI) topology due to its high flexibility and efficiency. However, PV mismatches in three‐phase grid‐connected systems result in an unbalanced power supply, which leads to an unbalanced grid current. Proportional integral derivative (PID) controllers can be used to control H‐bridge inverters because of their simplicity of tuning as well as their basic structure. However, due to the nonlinearity and high sensitivity of the PID controller, its performance declines as a result of high overshoot, high settling time, and high rise time during significant external disturbances. Moreover, the switching angle of the inverter must be adjusted to provide the required fundamental voltage while reducing harmonic content. In order to address this problem, a control technique with modulation compensation is proposed. The present work offers a two‐degree‐of‐freedom fractional‐order PID controller with an integrated filter (2DOF–FOPID–IF). Moreover, the optimum switching angles are determined for the CHMLI by employing an improved sparrow optimization (ISO) algorithm. To prove the practicality of the suggested technique, simulation, and experimental data are compared with the existing techniques. The proposed technique shows better performance in terms of settling time, overshoot, rise time, and low harmonics. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) systems or simultaneous wireless information and power transfer (SWIPT) systems support multiple charging frequency standards and usually transmit two or more frequencies simultaneously. Multi-frequency sinusoidal pulse width modulation (MF-SPWM) technology can output multiple sine wave frequencies at the same time with only one inverter, which effectively reduces the system size and improves compatibility. However, MF-SPWM and dead-time make the MF-inverter highly nonlinearized, with significant effects on the desired frequencies and the total harmonic distortion (THD) of the multi-frequency output. In this paper, a double Fourier series-based method of harmonic analysis for the dual-frequency inverter (DF-inverter) is proposed, which can accurately calculate the magnitude of each of the harmonics in the output of the DF-inverter taking into account the influence of dead-time. The calculation methods of the minimum pulse width and voltage THD of the DF-inverter are provided. An analysis shows that when the dead-time is less than the minimum pulse width, its influence is negligible. Meanwhile, when the dead-time is slightly larger than the minimum pulse width, there is a trade-off between the desired frequency component and the THD. Experimental results are given and they are consistent with the analytical results of the proposed method, and the error is within 2%. [ABSTRACT FROM AUTHOR]

This paper evaluates the performance of various PWM techniques for a 3-level inverter-based shunt active power filter by statistical parameters. It is well stated in the literature that the uses of power electronics-based devices create several power quality problems, such as poor power factor, harmonics in source current, poor voltage regulation, etc. Shunt active filters effectively alleviate these issues. A 3-level inverter, as a compensator depletes the harmonics in a single-phase grid-tied system. Level-shift, phase-shift, and hybrid PWM techniques generate switching pulses for 3-level inverter operation. These PWM techniques are compared for harmonic distortion at the source current, input power factor, and active filtering efficiency by statistical parameters such as mean squared error, root-mean-squared error, mean absolute deviation, mean absolute percentage error, standard deviation, variance, mean absolute error, and mean relative error. The above statistical parameters have been used to determine the optimum PWM technique for shunt active power filter operation. It is revealed from the results that for the PS PWM technique, the MSE is found to be less, i.e., 0.049441, and also has a low THD, i.e., 1.22% in source current. The behaviour of these PWM schemes is analysed through MATLAB/Simulink 2021b software. This paper contributes extensive information on PWM schemes for 3-level inverter-based compensator. It will help to comprehend various aspects of the power quality of a single-phase distribution system. [ABSTRACT FROM AUTHOR]

Copyright of CT Theory & Applications is the property of Editorial Department of CT Theory & Applications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Artificial intelligence-based optimization algorithm was used to compute the switching angle values. In order to run the inverter with the lowest possible Total Harmonic Distortion (THD) value, it is suggested in this study to use an algorithm such as the Practical Swarm Algorithm (PSA). The multilevel inverter and optimization algorithm were created and simulated in this study using a MATLAB software. A frequency spectrum analysis was also conducted and found to be consistent with the theoretical analysis of the system. To provide practical results, the FPGA generates PWM signals that are appropriate for the inverter switches. On the Spartan-3E Starter set, the suggested control schemes were developed and put it into practice. Xilinx-ISE 12.1i design software and VHDL hardware description language were used to create the FPGA software. The suggested approaches have a number of benefits over conventional digital PWM techniques, including straightforward hardware implementation, minimum scaling of digital circuits, easy digital design, reconfigurable, and flexibility in adaptability. The outcomes of the experiment and the simulation agreed rather well. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents the design of active harmonic current compensator (AHCC) to mitigate the current harmonics generated by supply side for an induction furnace application. Induction furnaces have nonlinear and time-varying properties, resulting in harmonics and voltage/current imbalances. AHCC are high-speed compensators that enhance the performance of induction furnaces and solve power quality issues. The proposed system is designed with modified higher order sliding control (MHOSC) algorithm and extended form of reactive power theory to generate a three-phase reference compensating current. The control method examines the sliding surface parameter uncertainties in order to obtain a controlled direct current (DC) link current when using nonlinear converters. The proposed work compares the performance of proportional integral (PI) tuned sliding mode controllers with emotional tuned intelligent controllers (ETIC). The compensated current reference signal is used to provide switching pulses for AHCC. A major advantage of MHOSC is its ability to endure external disruptions and unpredicted parameter changes, which improves reference current tracking without introducing undesirable oscillations (chattering). Implementation of the proposed control algorithm is validated in MATLAB / Simulink demonstrating that the designed AHCC compensates the harmonic current to an acceptable level (total harmonic distortion of source current is 1.54%) satisfying IEEE 519-2014 standard. [ABSTRACT FROM AUTHOR]

Abstract Although single‐stage inverters are popular for simpler design they face difficulties in shoot‐through mode operation. Insufficient DC voltage regulation and complicated LC network are principal drawbacks of these topologies. A new split source inverter (SSI) can solve problems with single‐stage inverters. In this paper, SSI replaced the voltage source inverter (VSI) of a shunt active power filter (SAPF) which alleviates power quality (PQ) issues in power system. Furthermore, a VSI‐based SAPF faces challenges to maintain consistent voltage across DC‐link capacitor, exactly compensating current generation, and switching loss reduction in inverter. This study examined efficacy of two inverter‐based SAPFs considering a modified synchronous reference frame approach for generating reference current; fuzzy logic controller for regulating DC‐link voltage; and adaptive fuzzy hysteresis current controller for generating switching pulses. Ideal and non‐ideal sources were considered when running the simulations for various load circumstances. The proposed SSI‐based SAPF with an advanced control approach can eradicate source current harmonics to 0.52% and 0.45% under ideal source conditions, and 0.65% and 0.54% under non‐ideal source conditions for non‐linear loads. Similarly, the ripples in the DC‐link voltage are also reduced to 2–3 V for the ideal case and 4–5 V for non‐ideal case.

Abstract The authors present two fast and accurate methodologies for the computation of eddy current losses in the axially laminated rotor of a synchronous reluctance machine. The methodologies are based on different combinations of the finite element method in time and frequency domains with 2D and 3D formulations. First, a comparative study of the 2D and 3D formulations for loss calculation is presented, considering various load angles of the machine to illustrate the problem of eddy‐current losses in this type of machines and its dependence on the load angle. The influence of the iron saturation on the loss calculation is also evaluated in these computations. A novel correction factor based on the computations at two load angles is proposed to convert the losses computed from a 2D model to match those computed from a 3D model. For the sake of generality, investigations are also conducted for various thicknesses of the lamination layers and different machine lengths, and an analytical method to describe the dependency of eddy‐current losses on the load angle of the machine is introduced. Moreover, a simplified method is proposed for modelling eddy currents in the frequency domain and calculating losses in an axially laminated structure based solely on the results of a magnetostatic solution. The results obtained by the simplified model demonstrate excellent agreement with the full 3D magneto‐dynamic simulation. Overall, the findings contribute to understanding and accurately characterising the eddy current losses in axially laminated rotors, offering potential insights for designing and optimising axially laminated synchronous reluctance electric machines.

Abstract Induction motors (IMs) are widely used in industrial applications, but harmonic distortion in IM drives can lead to inefficiencies and reduced lifespan. Traditional control strategies and filtering methods have limitations in mitigating lower-order harmonics, particularly the 5th harmonic, which can generate reverse torque and increase overheating risk. Existing solutions often struggle to fully address these issues, especially in high-power applications with dynamic loading conditions. This paper proposes a control strategy to reduce voltage and current harmonics in a Z-source inverter (ZSI)-fed IM drive. The system incorporates an observer-based output feedback robust servomechanism controller, designed using Linear Quadratic Regulator (LQR) and Linear Matrix Inequality (LMI) techniques. It ensures closed-loop stability, precise tracking regulation, and effective disturbance rejection, while also featuring a speed adaptation mechanism for sensorless operation. Simulation results demonstrate significant harmonic mitigation, with the controller achieving 1.01% lower voltage THD and 1.03% lower current THD compared to conventional approaches. This improvement aligns with industry standards and outperforms several existing techniques. The proposed method contributes a comprehensive solution for harmonic mitigation in high-power IM drives, applicable to various industrial applications requiring high-quality power and precise speed control.

Many oil fields in the Bohai Oilfield are currently in the stage of high water cut and low recovery. Thus, it is urgent to conduct in-depth research on the potential of these oil fields to maintain stable production. After 20 years of directional well development, Bohai B Oilfield has developed a set of layers with combined production and strong injection, resulting in severe interlayer interference and difficulties in tapping the potential of the remaining oil. Owing to the limited resolution of existing seismic data, it is not possible to identify the reservoir structure inside the braided river composite sand body, including the vertical and horizontal distribution of the interlayer and thin sand body. Therefore, directional well development is currently mainly used. Here, the seismic signal harmonic frequency enhancement technology is proposed, which directly uses the fundamental component of seismic data to predict harmonic and subharmonic information, and then adds it to the original seismic data to expand the high-frequency and low-frequency seismic information, achieving the purpose of frequency enhancement. This method overcomes the limitations of traditional convolutional models, eliminating the need of well information and to estimate seismic wavelets and assume sparse stratigraphic reflection coefficients, thereby reducing the human subjective factors. The research results, verified through dynamic and static information, showed that the seismic signal harmonic frequency enhancement technology can effectively and finely identify the internal structure of braided river sand bodies, help to transform directional wells into horizontal wells for development, avoid interlayer interference, and promote efficient extraction of the remaining oil.

This paper presents a model predictive control (MPC) technique for the control of reactive power flow from a static synchronous compensator (STATCOM) into a weak power system network. The MPC strategy enables the STATCOM to mitigate weak phase voltage magnitudes in a distribution grid. The weak voltage magnitudes usually emanate from large inductive loads connected to the grid’s point of common coupling (PCC). The MPC utilizes a finite control set of voltage vectors to minimize a cost function, which reduces the errors between set references and the corresponding predicted variables. The references in the cost function are set by two outer loop controllers. A time delay compensation strategy is introduced and proposed for selecting the gains of the outer loop controllers. An LC filter was also designed at the STATCOM’s output terminals to confine the harmonics in the injected compensation current to permissible limits. A robust all high pass filter dual second order generalized integrator (AHPF-DSOGI) based phase locked loop (PLL) is developed and proposed for synchronization of the STATCOM into the weak grid. The overall MPC strategy on the STATCOM enables shunt injection of compensation currents at the PCC while mitigating harmonics and consequently improving power quality. The STATCOM effectively regulated the bus voltage when required by switching between the capacitive and inductive modes. Results showing the efficacy of integration of the STATCOM to the grid and robust capabilities of the STATCOM in mitigating voltage swell and dip, as well as harmonics, are presented.

Introduction. With the increasing complexity of power systems and the integration of diverse energy sources, issues such as voltage sags, swells, and signal distortions have emerged as critical challenges. These power quality problems can result in equipment malfunction, production downtime, and financial losses for industries, as well as inconvenience and potential damage to electrical appliances in households. There is an urgent need for enhanced system efficiency. Methods. This objective is effectively achieved through the utilization of the newly proposed power theory, which is rooted in solar photovoltaic (PV) control, in conjunction with the Unified Power Quality Conditioner (UPQC). Purpose. The proposed method incorporates a modified synchronous reference frame scheme, coupled with a phase-locked loop mechanism. This control strategy enables the UPQC to effectively mitigate power quality issues. Novelty. PV-UPQC is utilized to uphold power integrity in the presence of diverse current and voltage distortions. This device, known as a multi-objective power conditioning apparatus, serves the purpose of maintaining power quality. PV-UPQC incorporates both a shunt and series voltage source converter, which are interconnected through a shared DC-link. Additionally, the PV system is interconnected at the DC-link of the UPQC in order to supply power to the load. Results. In this study, a novel approach is presented for controlling the UPQC, aiming to address power quality concerns such as unbalanced grid voltage and harmonic distortions and enabling us to control active and reactive power. References 16, tables 2, figures 15.

Abstract—Based on the data of several spaced magnetic stations, the spectrum of geomagnetic variations is studied in the range of periods from two to 40 years. Special attention is paid to spectral features in the supposed range of action of intraterrestrial processes that cause geomagnetic jerks. It is shown that the detected spectral peak in the vicinity of the period of 6.5 years aligns with the previously revealed recurrence pattern of jerks with a period of three to four years; however, this peak is absent in the spectrum of solar activity. The possible wave mechanisms of the occurrence of jerks and their 6-year quasi-periodicity caused by known types of magnetohydrodynamic waves in the liquid core of the Earth, are considered, and it is shown that they are not sufficiently convincing in reproducing observations of jerks. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Summary The aim of this paper is to present a methodology for solving а dynamic electric circuit with nonlinear hysteretic inductor without the use of hysteresis model or equivalent circuits. A consideration of nonlinear and hysteretic behaviour of the magnetic core under quasistatic conditions is based on applying harmonics interpolation method (HIM) to the measured magnetising field strength waveforms. A dynamic behaviour of the magnetic core is considered through the application of the statistical theory of losses (STL). A considered electric circuit consists of AC voltage source connected in series with shunt resistor, additional linear resistor and inductor, as well as a nonlinear hysteretic inductor. The solution for electric current of the circuit is obtained by solving equation derived from Kirchhoff's laws through a series of successive iterations. Coupling of electric and magnetic part of the circuit is obtained from fundamental laws of electromagnetism. Methodology is validated for four cases of the considered electric circuit — without additional elements, with one additional or both additional elements, for sinusoidal voltage source amplitudes of 2, 4, 6, 8 and 9 V and frequency of 50 Hz. Validation is repeated for frequencies of 100, 200 and 300 Hz while keeping the ratio of the amplitude to frequency constant. Detailed theoretical approach and methodology, comparisons between measured and calculated results, as well as adequate discussion are presented. [ABSTRACT FROM AUTHOR]

In this scientific paper, we have considered a method for determining the complex reflection coefficient based on spectral analysis of the output voltage of a parametric microwave converter. [ABSTRACT FROM AUTHOR]

Conversion of DC power into AC power at medium and high level utilize Multilevel-inverter (MLI) because of many advantages of MLI over conventional inverters. The MLI converter topologies have gained a huge attraction towards various applications like photovoltaic and even electric vehicles (EVs). This article represents a new switched capacitor topology (SC-MLI). The proposed SC-MLI contains ten power electronic switches and has a boosting capability with the help of one capacitor. It also uses two input DC sources and has a voltage gain of 1.4. Also, the capacitor is self-balancing and switches have less stress as compared to other configurations. Selective Harmonic Elimination (SHE) technique is employed for the generation of eleven levels. A comparison is also made with the recently developed MLI topologies based on different parameters. Finally, a hardware prototype is developed to check the feasibility of the proposed MLI in the laboratory and satisfactory results have been presented. [ABSTRACT FROM AUTHOR]

Recent studies have proved the usability of the nonlinear S0 lamb mode without satisfying the phase velocity matching criteria, and the possibility to extend its application to varying thickness plates. Based on that, this work proposes an experimental study of the inspection of macro scale localized defects with a size smaller than the used wavelength, via the second and third harmonics generation. Results were obtained on verifying their cumulative effect with varying the defect's width and also on finding that the third harmonic is better suited for larger scale inspection using the nonlinear lamb waves, and identifying the propagating modes in the plates using the wavelet transform. [ABSTRACT FROM AUTHOR]

Introduction. With the increasing complexity of power systems and the integration of diverse energy sources, issues such as voltage sags, swells, and signal distortions have emerged as critical challenges. These power quality problems can result in equipment malfunction, production downtime, and financial losses for industries, as well as inconvenience and potential damage to electrical appliances in households. There is an urgent need for enhanced system efficiency. Methods. This objective is effectively achieved through the utilization of the newly proposed power theory, which is rooted in solar photovoltaic (PV) control, in conjunction with the Unified Power Quality Conditioner (UPQC). Purpose. The proposed method incorporates a modified synchronous reference frame scheme, coupled with a phase-locked loop mechanism. This control strategy enables the UPQC to effectively mitigate power quality issues. Novelty. PV-UPQC is utilized to uphold power integrity in the presence of diverse current and voltage distortions. This device, known as a multi-objective power conditioning apparatus, serves the purpose of maintaining power quality. PV-UPQC incorporates both a shunt and series voltage source converter, which are interconnected through a shared DC-link. Additionally, the PV system is interconnected at the DC-link of the UPQC in order to supply power to the load. Results. In this study, a novel approach is presented for controlling the UPQC, aiming to address power quality concerns such as unbalanced grid voltage and harmonic distortions and enabling us to control active and reactive power. References 16, tables 2, figures 15. [ABSTRACT FROM AUTHOR]

The present study provides an evidence for the generation of harmonics of magnetosonic waves in the Martian magnetosheath region. The wave signatures are manifested in the magnetic field measurements recorded by the fluxgate magnetometer instrument onboard the Mars Atmosphere and Volatile Evolution missioN (MAVEN) spacecraft in the dawn sector around 5–10 LT at an altitude of 4,000–6,000 kms. The wave that is observed continuously from 19.1 to 20.7 UT below the proton cyclotron frequency (fci ≈ 46 mHz) is identified as fundamental mode of the magnetosonic wave. Whereas harmonics of the magnetosonic wave are observed during 19.7–20.3 UT at frequencies that are multiple of fci. The ambient solar wind proton density and plasma flow velocity are found to vary with a fundamental mode frequency of 46 mHz. It is noticed that the fundamental mode is mainly associated with the left‐hand (LH), and higher frequency harmonics are associated with the right‐hand (RH) circular polarizations. A clear difference in the polarization and ellipticity is noticed during the time of occurrence of harmonics. The magnetosonic wave harmonics are found to propagate in the quasi‐perpendicular directions to the ambient magnetic field. The results of linear theory and Particle‐In‐Cell simulation performed here are in agreement with the observations. The present study provides a conclusive evidence for the occurrence of harmonics of magnetosonic wave in the close vicinity of the magnetosheath region of the unmagnetized planet Mars. Plain Language Summary: Mars is an unmagnetized planet. The solar wind particles that bombard Mars continuously, are responsible for the loss of its atmosphere. This scenario is opposite to that of the Earth, as its strong intrinsic magnetic field forms a protective shield around the planet, called the magnetosphere. Various electrostatic/electromagnetic waves are often generated in the Earth's magnetosphere, which are potential candidates for controlling the transfer of energy and momentum from one region to another. In case of Mars, it possesses a weakly induced magnetosphere, which is dynamic due to its continuous interactions with solar wind. The field measurements from the MAVEN spacecraft can be used to understand plasma waves in the vicinity of Mars. Here, we report the first observations of the harmonics of magnetosonic wave in the Martian magnetosheath region. The magnetosonic waves are low‐frequency compressive waves driven by the ions in the presence of magnetic field. These waves are known to play a role in the particle heating process in the Earth's magnetosphere. Therefore, its observation in the Martian plasma environment is of interest to the scientific community to understand their role in plasma heating in the Martian ionosphere‐magnetosphere system. Key Points: Harmonics of Magnetosonic wave are observed in the Martian magnetosphere in dawn sector (5–10 LT)Magnetosonic harmonics dominantly have right‐handed polarizationAmbient proton density and velocity found to vary with fundamental mode frequency of 46 mHz [ABSTRACT FROM AUTHOR]

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This paper demonstrates an enhancement of power quality for a photovoltaic (PV) system connected to the grid with a hybrid energy storage system (HESS). The proposed system utilizes a ramp-rate control (RRC) strategy to limit severe fluctuations in the PV power output. Battery storage is integrated to store surplus energy generated by the PV system and is used for continuous power application. A high-power density device, known as a supercapacitor (SC), is employed to mitigate transient fluctuations in the battery. The proposed system facilitates smooth PV power generation, stabilizes the DC bus voltage (VDC), and eliminates source current harmonics induced by non-linear loads. The Shunt Active Power Filter (SAPF) discussed in this paper serves two primary purposes. Firstly, it acts as a reactive power buffer, smoothing out fluctuations and reducing current harmonic distortions. Secondly, it enables active power injection into the grid, utilizing a specific renewable solar PV source. The efficiency of the modeled compensation system is demonstrated by the sinusoidal shape of the current and the compensation of reactive power (RPC). The targeted system showcases the effectiveness of the current setup by exhibiting low total harmonic distortion (THD). The multifunctional features of the proposed system were implemented using the MATLAB/Simulink software, and the results were validated using an OP5700 Hardware-in-the-Loop (HIL) test bench. This integration of distributed power generation capabilities not only enhances the overall power quality but also improves the efficient utilization of renewable energy resources (RESs). [ABSTRACT FROM AUTHOR]

AC/DC converters, controlled by pulse width modulation (PWM) and used as power factor correction (PFC), is considered one of the main contributors to emissions in the range 2 kHz–150 kHz, recently known as the supraharmonic (SH) range. This study looks at the impact of SH grid distortion on the LF (<2 kHz) and HF (>2 kHz) emission of an AC/DC converter. The PFC boost converter is used as a particular case for validation of the results. It is observed that the AC/DC converters emit additional LF interharmonics and subharmonics when the grid voltage contains interharmonic components in the SH range. A mathematical analysis is provided to study and assess the interference between the SH in the background distortion and the AC/DC converters. Experimental studies are then performed for a PFC boost setup based on dSPACE MicroLabBox for the purposes of validating the mathematical analysis. [ABSTRACT FROM AUTHOR]

Using X-ray topography, the distributions of deformations in the volume of two types of AT-cut quartz resonators of different sizes were obtained on laboratory and synchrotron X-ray sources. The comparison of X-ray topography data and the amplitude–frequency characteristics of the resonators was used to establish a correlation between the deformation patterns and the features of oscillatory processes for the operating modes and their harmonics, as well as for parasitic modes. A connection between vibrations at parasitic modes and their harmonics, which manifest themselves in an amplitude inhomogeneity, and the topology of the resonators has been found. The applied significance of the obtained results for the development and optimization of new designs of piezoelectric elements and the development of their manufacturing technology is pointed out. [ABSTRACT FROM AUTHOR]

In the increasingly complex and dynamic electrical power system, forecasting harmonics is key to developing and ensuring a clean power supply. The traditional methods have achieved some degree of success. However, they often fail to forecast complex and dynamic harmonics, highlighting the serious need to improve the forecasting performance. Precise forecasting of electrical power system harmonics is challenging and demanding, owing to the increased frequency with harmonic noise. The occurrence of harmonics is stochastic in nature; it has taken a long time for the development of dependable and efficient models. Several machine learning and statistical methods have produced positive results with minimal errors. To improve the prognostic accuracy of the power supply system, this study proposes an organic hybrid combination of a convolutional neural network (CNN) and bidirectional long short-term memory (BiLSTM) with the attention mechanism (AM) method (CNN-BiLSTM-AM) to forecast load harmonics. CNN models intricate non-linear systems with multi-dimensionality aspects. LSTM performs better when dealing with exploding gradients in time series data. Bi-LSTM has two LSTM layers: one layer processes data in the onward direction and the other in the regressive direction. Bi-LSTM uses both preceding and subsequent data, and as a result, it has better performance compared to RNN and LSTM. AM's purpose is to make desired features outstanding. The CNN-BiLSTM-AM method performed better than the other five methods, with a prediction accuracy of 92.366% and a root mean square error (RMSE) of 0.000000222. [ABSTRACT FROM AUTHOR]

Summary: Multilevel inverters (MLIs) are widely used in various sectors of power electronics. Some major benefits of using MLI are the high‐quality voltage output, harmonic reduction, and efficiency. However, MLIs also bear a range of disadvantages including an excessive number of components, high total standing voltage (TSV), and complicated control scheme. Thus, a novel cross‐switched neutral point clamped (CSNPC) nine‐level inverter is proposed. Many of the suggested MLIs use a large number of DC supplies and additional switches that are not fully utilized and generate high power loss. However, the proposed MLI topology has a smaller number of power electronic switches and DC supplies, leading to higher energy efficiency. Moreover, a simplified high frequency modulation technique, named hysteresis‐band‐based discontinuous pulse width modulation (DPWM) is devised to control the proposed MLI. This modulation scheme has effectively minimized capacitor voltage imbalance. Furthermore, the designed structure is extendable to a modular MLI, without any additional H‐bridge circuit. To verify its benefits over other recent similar types of MLIs, a thorough comparison is presented for the number of components and power losses. The proposed MLI has showed 95.54% efficiency, and the modular CSNPC can achieve a total harmonic distortion (THD) of 6.43%. [ABSTRACT FROM AUTHOR]

Many distribution system operators are installing PQ monitoring systems in their medium-voltage networks. Installation of PQ monitors in all the nodes of the network is uneconomical, and power quality monitors are rather expensive. Therefore, the optimal placement of PQ monitors has to be found, while minimising cost and maximising observability. Researches published so far have presented PQ placement algorithms, but only from the aspect of one PQ disturbance (either dips or harmonics). In this paper, an algorithm for PQ monitor placement is presented, and its novelty is that it is the first research work accounting for several key PQ disturbances at once: harmonics, flicker, unbalance and dips. The chosen PQ disturbances are also modelled using novel modelling techniques, with the PQ disturbance behaviour modelled for a longer time period of one week or month. PQ disturbance behaviour is modelled for a real study case, where known real network topology, customer structure and measurements are used to develop a model validated by PQ measurements. Obtained synthetic PQ data, which are validated by PQ measurements, are used to optimise the PQ monitor locations. To choose the optimal PQ monitor locations, multiple linear regression was used, with the coefficient of determination R2 being the selection criterion. The results show that only two PQ monitors are necessary to monitor the analysed large real medium-voltage distribution grid, with high confidence. The methodology is straightforward and relatively easy to apply, and can be implemented for other medium-voltage distribution networks. [ABSTRACT FROM AUTHOR]

In the realm of electrical engineering, standards play a pivotal role in ensuring the quality and reliability of electrical systems. This paper conducts a comprehensive comparative analysis of the Institute of Electrical and Electronics Engineers (IEEE), International Electrotechnical Commission (IEC), and European Committee for Electrotechnical Standardization (CENELEC) standards, with a particular focus on power quality engineering. Specifically, it focused on key parameters such as the K-factor, the factor K, the Harmonic Loss Factor FHL and the unbalanced factor. By elucidating the differences and similarities between these standards, this study aims to provide insights into their respective impacts on electrical infrastructure, guiding engineering practices, and facilitating global trade. Understanding the regional applicability and industry impact of IEEE, IEC, and CENELEC standards is essential for engineers, manufacturers, and policymakers to navigate the complexities of electrical quality engineering in a diverse and interconnected world. [ABSTRACT FROM AUTHOR]

Fuzzy-based control systems have demonstrated a remarkable ability to control nonlinear processes, a characteristic commonly observed in power systems, particularly in the context of power quality enhancement. Despite this, an updated and comprehensive literature review on the applications of fuzzy logic in the domain of power quality control has been lacking. To address this gap, this study critically examines published research on the effective and efficient use of fuzzy logic in resolving quality issues within power systems. Data sources included the Web of Science and academic journal databases, followed by an evaluation of target articles based on predefined criteria. The information was then classified into seven categories, including control system type, features of the fuzzy logic controller, fuzzy logic inference strategy, power quality issue, control device, implementation methodology (efficacy testing), and efficiency improvement. Our study revealed that fuzzy-based control systems have evolved from simple type-1 fuzzy controllers to advanced control systems (type-2 fuzzy and hybrid) capable of effectively addressing complex power quality issues. We believe that the insights gained from this study will be useful to both experienced and inexperienced researchers and industry engineers seeking to leverage fuzzy logic to enhance power quality control. [ABSTRACT FROM AUTHOR]

The Unified Power Quality Conditioner (UPQC) is a promising solution for mitigating multiple Power Quality(PQ) issues in distribution systems, including harmonics, poor power factor, voltage sag/swell and voltage imbalance. The conventional Sliding Mode Controller (SMC) in UPQCs suffers from wide switching frequency variations, chattering problems, and inherent active and reactive power coupling. This study proposes a nonlinear control method, Sliding Mode-based Direct Power Control (SMC-DPC), for the simultaneous regulation of the shunt and series compensators in a UPQC. By optimizing voltage vector selection based on real-time power errors, the proposed method effectively mitigates chattering, and reduces switching frequency variations, and ensures precise tracking of instantaneous active and reactive powers even in the presence of coupling effects. The proposed approach simplifies the system design and improves steady state and dynamic power tracking. The simulation results in MATLAB Simulink® on a 20 kVA system demonstrate that the proposed method achieves a source current THD of 1.52%, compared to 2.31% for conventional SMC and 5.11% for linear controller. Furthermore, the method is robust to grid parameter variations and demonstrates satisfactory performance in both strong and weak grids. In weak grids, the proposed method reduces the line losses by 13.71% and 14.54% compared to SMC and linear controller respectively. The reported results comply with international standards such as IEEE-519 and IEC 61000-3-12, confirming effectiveness of SMC-DPC for enhancing PQ in distribution system.

The increase in the penetration of inverter based renewable energy resources comes with several challenges. For one, the power quality can be cited as an issue due to the impact of the electronic devices in the grid voltage profile, which can cause harmonic disturbances and then affect all other installations nearby. Considering the issue previously described,} this paper analyzes the effects of grid voltage harmonic disturbances in the operation of a grid-connected Voltage Source Converter (VSC) with current control in the stationary reference frame. A mathematical model is derived and validated both through simulations and experiments in order to associate the voltage harmonic magnitude disturbance with the respective current harmonic magnitude response from the grid-connected VSC. The model is also utilized to tune paralleled resonant controllers to mitigate the effect. Furthermore, the results and analyses highlight not only the effectiveness but also the limitations from the proposal.

The rapid growth of renewable energy, particularly wind energy, has significantly contributed to global electricity generation, with global renewable energy capacity reaching an all-time high of 3870 gigawatts (GW) in 2023. However, ensuring high power quality for grid integration remains crucial for wind energy's role as a leading source in the energy transition. This necessitates the development of advanced Wind Energy Conversion Systems (WECS) capable of regulating current, voltage, and frequency to ensure power quality. This work proposes a novel predictive control strategy for multilevel inverters in WECS to achieve a total harmonic distortion (THD) below 5% in the generated electrical power. The proposed predictive control algorithm is presented and implemented in a WECS simulation with a multilevel inverter. The performance of the proposed system is evaluated through simulations using MATLAB/SIMULINK. Our results demonstrate that the predictive control approach outperforms traditional controllers for multilevel inverters in terms of output voltage, harmonic reduction, execution time, and overall WECS control.

The use of electronic load controllers (ELCrs) is widely adopted in pico hydropower systems to maintain output power supplied to the consumer load, regardless of changes in consumer demand. This is due to the absence of moving mechanical parts, affordability, prevention of the hammer effect in pipes, and being more efficient than the governor systems. However, implementing existing ELCrs in a pico hydropower system can pose challenges related to power quality, efficiency, or costs. In this paper, a fuzzy PI-based single-switch bidirectional AC chopper electronic load controller (FP-SSBAC ELCr) is proposed. This configuration reduces the number of insulated gate bipolar transistors (IGBTs) from two, typically found in the conventional bidirectional AC choppers, to one per phase, resulting in cost reduction. A hybrid controller, comprising fuzzy and PI controllers, is designed to quickly maintain a constant output voltage and frequency when consumer load abruptly changes. The gains of the PI controller are updated by the fuzzy logic controller based on the voltage error and its derivative. The proposed model is simulated in MATLAB/Simulink and validated experimentally under sudden changes in consumer load. The results achieved with the FP-SSBAC ELCr demonstrate improved dynamic performance without overshoot compared to PI-based ELCrs. The highest recorded voltage and current total harmonic distortions (THDs) are 2.8 % and 2.1 %, respectively, meeting the IEEE 519 standard. Therefore, the proposed model has the potential to enhance performance and efficiency and can be implemented cost-effectively in pico hydropower systems.