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Purpose Static converters generate current harmonics in power grids. For numerous studies, analytical frequency modeling is preferred to carry out their harmonic modeling in the context of sizing by optimization. However, a design by optimization has to consider other constraints, e.g. modeling constraints and operating constraints. In this way, this paper aims to focus on applying an analytical frequency modeling on the sizing by optimization of an aircraft electrical power channel.Design/methodology/approach The paper aims to size a multiphysical system by optimization. In this way, the sizing of an aircraft electrical power channel by optimization has been carried out. The models of all the channel components are analytical. Specifically, the frequency model of the power electronics is based on Tran et al. (2016) and is made of equalities and inequalities. Due to this modeling choice, the optimization satisfies hundreds of constraints, such as modeling constraints and static converter operating constraints. Furthermore, transient constraints are only verified after optimization.Findings The difficulty is the modeling of the system by taking into account nonlinear implicit equations having several solutions. A solution is the addition of inequality constraints to the model to guide the implicit solving. Furthermore, this greatly helps the optimization algorithm to find the good operating mode of the static converter, at steady state. This aspect is indispensable to validate the sizing model.Research limitations/implications The number of the configurations per operating period of the static converters is defined a priori and limited.Originality/value The analytical model for the sizing is formulated as a constrained optimization problem. Its solving and the sizing by optimization are carried out by the same optimization algorithm. [ABSTRACT FROM AUTHOR]

Purpose – The aim of the paper is to present the approximation methods of the magnetizing characteristics of the salient pole synchronous machines with the fundamental MMF harmonics. Design/methodology/approach – The energy based approach is used to formulate a set of the functions approximating the magnetic flux linkages versus an equivalent magnetizing current in the circuit model of the synchronous machine. The estimation of the approximation functions parameters is based on the results of the field calculations. Findings – The identification of the approximation functions is effective and significantly simpler on the basis of the magnetic field co-energy function, than on the basis of the magnetic flux linkages. Research limitations/implications – The magnetic field co-energy function determined by FEM is sufficient for simplified calculations of the magnetic parameters occurring in the circuit models of the electrical machines with nonlinear core. Practical implications – The paper provides guidance for the circuit modelling of the multi-pole generators and motors under conditions of magnetic saturation. Originality/value – A paper has succeeded in determining the internal magnetic characteristics of the synchronous machine with a salient pole rotor. [ABSTRACT FROM AUTHOR]

Purpose – Significant amount of harmonics and inter-harmonics are being injected into the power system because of the increasing use of power electronics and large non-linear loads. Therefore, the purpose of this paper is to analyze their contents in real time. Design/methodology/approach – The frequency and phase of an electric power harmonic or inter-harmonic can be estimated by using the discrete spectrum energy center of symmetric windows, the amplitude calculation of an electric power harmonic or inter-harmonic can be calculated by using the Pasival theorem, and their relative estimation error is only decided by the distribution of windows’ energy in the frequency domain, which equals the proportion of the spectrum energy occupied in the side lobe to the whole. Findings – The results of the digital simulation and experimental tests show that the method proposed in this paper has the same measurement precision as and more advantages in computational complexity and burden over other methods, which are based on multipoint interpolation or interpolation polynomial windowed. Originality/value – The method is very suitable to be used to real-time measurement in a single chip DSP micro-processor. [ABSTRACT FROM AUTHOR]

Purpose – Low power devices with switched-mode power supply represent harmonic generating apparatus in widespread use nowadays. The influence of personal computers (PCs), which affect the supply voltage, is considered. Harmonic level due to simultaneous PC operation is quantified by the total harmonic distortion of input current (THDI). The purpose of this paper is to propose a multi-parameter mathematical model for the THDI calculation. The model is convenient for practical engineering application. Design/methodology/approach – The model is derived using the measured and simulated data. The model coefficients are obtained in the least squares sense. Findings – Mathematical modeling of THDI is the least expensive and the most convenient solution for engineering application. The models proposed in the literature have many drawbacks, which motivated the authors to develop a more comprehensive solution. Grid stiffness, capacitance of PC power supply unit and PC cluster size represent the major parameters that affect THDI, and as such they are taken into account in the proposed model. The influence of other existing parameters from both line and load side is also discussed and the reasons for their omitting from the model are explained. The model considers various PC configurations within the cluster and it enables the THDI calculation for an arbitrary PC cluster size. Practical implications – Due to its comprehensiveness and mathematical simplicity, the model is suitable for practical use, and its accuracy is verified through conducted measurements presented in the paper. Originality/value – The proposed model is more comprehensive than the existing ones, and it overcomes their shortcomings. The THDI calculation is simplified to the level of applying basic arithmetic operations only, without jeopardizing the accuracy. The validity of the model is supported by additional measurements carried out in sites characterized by grid conditions quite different from that used for model developing. [ABSTRACT FROM AUTHOR]

Purpose - The purpose of this paper is to give a simple, fast and universal inductance calculation approach of slotless-winding machines and comparison of inductances of toroidal, concentrated and helical-winding machines, since these winding types are widely used among low-power PM machines. Design/methodology/approach - Harmonic modeling approach is applied to model the magnetic field of the windings in order to calculate the synchronous inductances. The method is based on distinction between electromagnetic properties of different regions in the machine where each region is represented by its own governing equation describing the magnetic field. The governing equations are obtained from Maxwell's equations by introducing vector potential in order to simplify the calculations. Findings - Results of the inductances of toroidal, concentrated and helical-winding slotless PM machines, which have the same torque and dimensions, obtained by the proposed analytical method are in good agreement with 3D FEM, where the relative difference is smaller than 15 percent. However, the calculation time of the analytical method is significantly less than in 3D FEM: seconds vs hours. Additionally, from the results it is concluded that the toroidal-winding machine has the highest inductance and DC resistance values among considered machines. Helical-winding machine has lowest inductance and DC resistance values. Inductance of concentrated-winding machine is between inductance of helical and toroidal windings; however, DC resistance of the concentrated windings is comparable with resistance toroidal windings. Originality/value - In this paper the inductance calculation based on harmonic modeling approach is extended for toroidal and helical-winding machines which makes the method applicable for most of the slotless machine types. [ABSTRACT FROM AUTHOR]

Purpose - The purpose of this paper is to reduce the torque ripple but not to decrease the average torque of synchronous reluctance machines by using one step or more than two axially laminated rotors with asymmetric flux-barrier. Design/methodology/approach - A 24-slot four-pole synchronous reluctance machine with overlapping windings and asymmetric flux-barrier in the rotor is, first, described and designed by finite element (FE) method for maximizing average torque. The dimensions of asymmetric flux-barrier including the pole span angle and flux-barrier angle will be optimized to minimize the torque ripple and its influence on the average torque is also investigated by FE analysis. The impact of current angle on the average torque and torque ripple are also analysed. The step laminations together with the asymmetric flux-barrier are employed for further torque ripple reduction which can consider the both rotation directions. Findings - The torque ripple of synchronous reluctance machine can be significantly reduced by employing asymmetric flux-barrier but the average torque is not reduced. Research limitations/implications - The purely sinusoidal currents are applied in this analysis and the effects of harmonics in the current on torque ripple are not considered in this application. The 24-slot/four-pole synchronous reluctance machine with single-layer flux-barrier has been employed in this analysis, but this work can be continued to investigate the synchronous reluctance machine with multilayer flux-barrier. This asymmetric flux-barrier can be easily applied to permanent magnet (PM)-assisted synchronous reluctance machine and the interior PM machine with flux-barrier in the rotor, since the space which is used for PM insertion is the same as the SynRM machines. Originality/value - This paper has analysed the torque ripple and average torque of synchronous reluctance machines with asymmetric flux-barrier and step laminations with asymmetric flux-barrier. The torque ripple can be reduced by this flux-barrier arrangement. The difference of this technique with the other techniques such as stator/rotor skew is that the average torque can be improved. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to solve the reactive power adjustment and the overvoltage suppression problems in the extra high voltage (EHV) long distance grid, which often appears transient overvoltage, light load loss and other issues.Design/methodology/approach One 800 kV EHV magnetically saturation controllable reactor (MSCR) used self-power supply control system is designed. The structure and the working mechanism of the novel MSCR are analyzed in detail. Then the control and capacity step adjustment characteristics are obtained by experiments. The harmonic characteristic is studied by theoretical analysis and low voltage test.Findings To solve the problem of harmonics in the working current of nets windings, the fifth and the seventh filers are equipped between the compensation windings and the control system. The effectiveness of the harmonic suppression method is proved by simulation and experiments.Originality/value It proves that the 800 kV EHV MSCR design in this paper can achieve the purpose of the reactive power continuous linear adjustment, and the capacity adjustment is sensitive. After filtering, the harmonics level of the working current meets the standard of the EHV grid. [ABSTRACT FROM AUTHOR]

Purpose – As arc suppression coils (ASCs), magnetically controlled reactors (MCRs) are usually operated in the single-phase mode. Due to the lack of a third order harmonic compensation circuit, the current harmonics are high. The purpose of this paper is to propose a novel structure of MCR and a genetic algorithm (GA) to determine the parameters which will result in minimum total harmonics. Design/methodology/approach – This paper proposes the structure and the working principle of the multi-valve controlled saturable reactor (MCSR). There are several sorts of magnetic valves in the iron cores of the MCSR. The saturation degree of each magnetic valve is different when the same direct component of the magnetic flux is generated in the iron core, therefore current harmonics of different phases emerging, i.e. the total harmonics can be reduced. The magnetization characteristics and the mathematical model of the current harmonics of the MCSR are presented by introducing three parameters. The optimal values of the parameters that result in the smallest total harmonic distortion in the output current are calculated by a GA. Findings – The simulation and experimental results are coincident with the theoretical analyses, which prove the effectiveness of the proposed method on harmonic suppression. Practical implications – The method proposed in this paper can successfully reduce the current harmonics of the conventional MCR, including but not limited to the ASC. A prototype MCSR (540 kVA/10 kV) has been designed and constructed. Originality/value – In this paper, a MCSR is proposed. The mathematical model of the MCSR for harmonic analysis is developed. The optimal parameters that result in the smallest THD in the output current are calculated. The mathematical model can be also used for the harmonic analysis of conventional MCRs. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to present a simple method to analyze the iron loss in the laminated core of power and distribution transformers. Design/methodology/approach – This paper presents a practical method to calculate the no-load loss in the transformer cores. Considering the non-uniformity of the magnetic flux density in the corner areas of the Epstein frames will affect the measurement precision of the Wt-B curves then further affect the core loss calculation in FEM, a dual-Epstein frame method is used to measure the Wt-B curves with the Epstein sample stripes cutting by different angles to the rolling direction. A 2D FEM that considers the type of joints of the core and eddy current effect in the laminations is used to analyze the core loss with multi-angle Wt-B curves. Findings – The impact of lamination thickness, size of gaps and type of joint of the core are considered. Considering the no-load testing conditions, harmonics in the exciting currents are taken into account. Originality/value – Harmonic wave of magnetic flux density in the transformer core is calculated and the core loss in the joint region is calculated by the loss curve measured with dual-Epstein frame. It makes the calculation result of transformer core loss more exactly. [ABSTRACT FROM AUTHOR]

Purpose – In this paper, the aim is to propose a residual-based error estimator to evaluate the numerical error induced by the computation of the electromagnetic systems using a finite element method in the case of the harmonic A-φ formulation. Design/methodology/approach – The residual based error estimator used in this paper verifies the mathematical property of global and local error estimation (reliability and efficiency). Findings – This estimator used is based on the evaluation of quantities weakly verified in the case of harmonic A-φ formulation. Originality/value – In this paper, it is shown that the proposed estimator, based on the mathematical developments, is hardness in the case of the typical applications. [ABSTRACT FROM AUTHOR]

Purpose – The paper aims to explain the investigation of the space vector modulation (SVPWM), in shunt active powers filters (APFs) field, for controlling the generated current. Design/methodology/approach – With the inclusion of the SVPWM control technique, the proposed topology of the two-level shunt active power filter (APF), based on IGBTs, besides its efficiency in harmonics cancellation and power factor correction, contributes in switching power losses reduction. Findings – The paper provides an extended theoretical study and a detailed explanation of the application of the SVPWM on shunt APFs, and demonstrates how power losses can be reduced by limiting the switching process to the two thirds of the pulse duty cycle. Research limitations/implications – Simulation and experimental validations will still be requested as to the accuracy of the model and the applicability to the polluted electrical power systems plants. Practical implications – The paper formulates an easy mathematical method to investigate the SVPWM algorithm with clarification of its various steps. It offers a benefit to people engaged in theoretical and practical research in APFs, inverters, and PWM modulation strategies. Originality/value – Since, there are few studies which clarify the application of the SVPWM on APFs, the paper may help to understand the mathematical implementation of this control strategy both for controlling the APF current and for gating signals generation. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to propose an analytical model for the calculation of forces ripples in bearingless permanent magnet motor.Design/methodology/approach The model is based on a spectral modeling of the forces based on a spectral analysis of the air-gap flux density.Findings The proposed methodology allows the prediction of the ripples of the levitation according the design of the machine and the topology of the winding. It can be used in the design procedure of bearingless motor in order to avoid mechanical resonance of the rotor shaft.Research limitations/implications This model cannot be used for high saturated machines.Originality/value The main originality of this paper consists in the evaluation of the field harmonics according to their sources and the contribution of the different harmonics to the force ripples. This can help the designer to focus on reducing or eliminating only the harmonics of flux density which create the force ripples. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to present the three phase seven-level Z-source neutral point clamped (NPC) inverter with multicarrier pulse-width modulation (PWM) technique. Despite numerous topologies and modulation methods, there is a dire need of developing PWM techniques that can be deployed in multilevel inverters. These inverters decrease the total harmonic distortion and it has a good performance for various electrical power system applications. The proposed inverter is investigated for its performance by executing it in shoot through and non-shoot through modes.Design/methodology/approach The purpose is validated through MATLAB/Simulink software platform for implementing the proposed seven-level Z-source NPC inverter outlined with multicarrier based phase disposition technique. The experimental results are verified using SPARTAN 3E FPGA controller with the same control strategy.Findings The efficiency of the proposed inverter is confirmed in terms of increased and faster conversion in the shoot-through mode. By using PDPWM technique the maximum boost gain is achieved with lower modulation index. High control of DC voltage is obtained with only one DC voltage source and one Z network.Originality/value Three phase multilevel inverters are widely used in improving the output voltage quality and reducing the encountered electromagnetic interference in electronic device or circuitry. They are employed in medium and high –power applications to attain increased power ratings while decreasing the switching losses. The performance results shown in this paper will satisfy the above needs of usage in certain applications and less switching losses. [ABSTRACT FROM AUTHOR]

Purpose – Analytical determination of harmonic components of current in electric circuits containing semiconductor converters with the use of a small parameter method (SPM) in frequency domain. The paper aims to discuss these issues. Design/methodology/approach – A SPM realized in frequency domain was used in the analytical analysis of electric circuits with semiconductor converters. An automated method of formation of orthogonal harmonic components of electrical values on the basis of discrete convolution algorithm was used to provide the possibility of realization of calculation in frequency domain. A nonlinear characteristic of a semiconductor converter was presented by the method of numerical approximation. A numerical structured simulation method was applied to determination of the reference values of current in the analyzed circuit. Laws of theoretical electrical engineering were used for formation of the equations of voltage balance in the circuit with a nonlinear element. Findings – It is shown that application of a SPM with its realization in frequency domain enables significant simplification of the process of the analysis of electric circuits with semiconductor converters in an analytical form and facilitation of calculation automation. Analytical and numerical calculation of a circuit with a diode under active-inductive load demonstrated efficiency and sufficient accuracy of the proposed method. It is shown that increase of the order of approximating polynomial and of the number of the analyzed harmonics provides the improvement of the accuracy of numerical calculations. Practical implications – The results of the work can be used in calculation of electrotechnical devices containing semiconductor appliances and electric devices with nonlinear characteristics. Moreover, the obtained results enable studying the processes of compensation of current higher harmonics in electric networks with a nonlinear load containing semiconductor converters. Originality/value – For the first time it was proposed to apply a SPM with its realization in frequency domain to the analysis of nonlinear electric circuits. The significance of the paper consists in the fact that the offered method makes it possible to carry out both circuit analytical and numerical analysis with the possibility of its automation. [ABSTRACT FROM AUTHOR]

Purpose - The purpose of this paper is to calculate slotting-based eddy currents in permanent magnet excited synchronous machine (PMSM) taking into account axial and circumferential segmentation of magnets. Design/methodology/approach - An analytical approach to calculate eddy current losses in PM caused by slotting harmonics of PMSM is presented. The eddy current reaction field is taken into account as well as axial and circumferential segmentation of the magnets. Findings - The analytical model provides results comparable to 3D-FEM calculations even at high frequencies at reduced computation costs. To generalize the results the magnetic Reynold's number is introduced. Originality/value - Taking into account the axial and circumferential segmentation in the PDE; the approach is much more accurate compared to known approaches; accuracy is comparable to 3D-FEA. [ABSTRACT FROM AUTHOR]

Purpose The high computational effort of steady-state simulations limits the optimization of electrical machines. Stationary solvers calculate a fast but less accurate approximation without eddy-currents and hysteresis losses. The harmonic balance approach is known for efficient and accurate simulations of magnetic devices in the frequency domain. But it lacks an efficient method for the motion of the geometry.Design/methodology/approach The high computational effort of steady-state simulations limits the optimization of electrical machines. Stationary solvers calculate a fast but less accurate approximation without eddy-currents and hysteresis losses. The harmonic balance approach is known for efficient and accurate simulations of magnetic devices in the frequency domain. But it lacks an efficient method for the motion of the geometry.Findings The three-phase symmetry reduces the simulated geometry to the sixth part of one pole. The motion transforms to a frequency offset in the angular Fourier series decomposition. The calculation overhead of the Fourier integrals is negligible. The air impedance approximation increases the accuracy and yields a convergence speed of three iterations per decade.Research limitations/implications Only linear materials and two-dimensional geometries are shown for clearness. Researchers are encouraged to adopt recent harmonic balance findings and to evaluate the performance and accuracy of both formulations for larger applications.Practical implications This method offers fast-frequency domain simulations in the optimization process of rotating machines and so an efficient way to treat time-dependent effects such as eddy-currents or voltage-driven coils.Originality/value This paper proposes a new, efficient and accurate method to simulate a rotating machine in the frequency domain. [ABSTRACT FROM AUTHOR]

Purpose With the increasing number of onboard controlled static converters in aeronautics, methods to design lighter configurations are required. This study aims to help the designer sizing optimal electromagnetic compatibility (EMC) filters and, moreover, finding optimal voltage levels and switching frequency, which have a great impact on the design and global mass of such converters.Design/methodology/approach Analytical models for capacitors, inductors and heatsink are settled. Using frequency modeling, EMC can be studied analytically. To deal with frequency and voltages variations, models of perturbations sources are developed. Concerning the problem of surveilling thousands of harmonics to check the whole frequency range of EMC standards in optimization, a strategy that drastically reduces the number of computations and has a good convergence is proposed.Findings The methods settled in the paper allow to optimize a controlled static converter with its EMC filters along with finding optimal switching frequency and voltage levels. A study on a three-phase rectifier reveals the importance of the switching frequency on converter design with EMC filters. A 28 per cent mass reduction is predicted by increasing the switching frequency from 10 to 30 kHz. The designed converters are verified by simulations.Research limitations/implications Investigating the voltage levels along with the switching frequency has not been achieved yet for static controlled converters with EMC constraints. The approach lacks experimental validations, but it is currently ongoing.Originality/value Dealing analytically with the changes of frequency or voltages in an EMC study is a new feature. The possibility to use deterministic algorithm is essential for dealing with the important number of constraints and the numerous interactions between all the parts of the problem, especially EMC. [ABSTRACT FROM AUTHOR]

Purpose This study aims to predict the unstable period-1 orbit (UPO-1) of DC–DC converters and find analytical expressions to describe it.Design/methodology/approach Nonlinear dynamical phenomena of a peak–current–mode controlled direct current–direct current (DC–DC) Boost converter are discussed briefly first. Then fast fourier transform (FFT) analysis of state variables under different dynamic states is provided, and the characteristic of the harmonic content in different states is summarized. Following these, a scientific hypothesis on the harmonic content of the UPO-1 is presented, and the Equivalent Small Parameter method is adopted then, thus analytic-form expressions of the UPO-1 can be derived.Findings According to results of theoretical analysis, numerical simulations and experiments, this paper illustrates that, like stable period-1 orbit, the UPO-1 is also made up of the DC component and harmonics with integer times of switching frequency.Originality/value This work provides an unreported approach for extracting the UPO-1 of DC–DC converters, which is mainly based on predicting the harmonic structure information of the orbit. According to experimental parts of the work, it shows that the stabilizer can be designed easier by using the proposed method. Additionally, from a broader perspective, the results could also have implications in a wide class of forced oscillation systems. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to establish a modified variable coefficient calculation model to analyse the control parameter effect on the iron loss of switched reluctance motor under pulse width modulation (PWM) mode.Design/methodology/approach The finite element model is solved to get the flux density by python language. Due to non-sinusoidal flux density feature and the effect of PWM excitation, the Fourier transform is applied in consideration of harmonic components. To improve the accuracy of iron loss computation, the effect of minor loops is considered by using the rain-flow counting method.Findings When the speed fluctuates around the set speed and the fluctuations are relatively small, it is useful to reduce the iron loss with smaller duty ratio and turn-on angle or greater duty ratio and smaller turn-off angle. The iron loss is less affected by chopping frequency, while the iron loss increases obviously with higher conduction angles. The iron loss under non-energy-returnable-voltage-chop mode is greater than energy-returnable-voltage-chop mode.Originality/value The modified variable coefficient MIEM5 iron loss model is proposed to improve the accuracy of iron loss calculation. Then the control parameters such as duty ratio, chopping frequency, turn on angle and turn off angle are analysed under PWM mode. [ABSTRACT FROM AUTHOR]

Purpose – The aim of this paper is to develop the method of optimal control of the three-phase inverter system for autonomous and power grid operation. The presented method will also allow the cooperation of several inverters creating an autonomous network. This system should also be able to reduce demanded higher harmonics in power voltage according to the list of numbers of these harmonics. In this article the authors describe a system that is used to create a symmetrical three-phase voltage. The supply power is taken from the renewal source. The inverter system as well as cooperation of several such systems to create an autonomous network is under consideration. The generated three-phase voltage should be symmetrical even when the RL load is not symmetrical or else it changes in impulse. Cooperation of the system with the autonomous network is also under consideration. The task is to supply the set current of the basic harmonic to the power grid and possibly to reduce voltage higher harmonics on output terminals of the system. Design/methodology/approach – The method of optimal control for a quadratic objective function was applied. Findings – In the autonomous system the presented method provides a symmetrical three-phase voltage with an unknown unsymmetrical constant or pulsed load. When operating for a power grid the system provides the desired current related to the basic harmonic of the grid voltages. In both cases the demanded higher harmonics of the grid voltages are reduced. Originality/value – Filter of the main harmonic for the power grid voltage was applied. Applied numerical solutions and obtained simulations are also original. [ABSTRACT FROM AUTHOR]

Purpose -- The active power filter with two-level inverter needs a high-rating coupling transformer for high-power applications. This complicates the control and system becomes bulky and expensive. The purpose of this paper is to motivate the use of multilevel inverter as harmonic filter, which eliminates the coupling transformer and allows direct control of the power circuit. The advancement in artificial intelligence (AI) for computation is explored for controller design. Design/methodology/approach -- The proposed scheme has a five-level cascaded H-bridge multilevel inverter (CHBMLI) as a harmonic filter. The control scheme includes one neural network controller and two fuzzy logic-based controllers for harmonic extraction, dc capacitor voltage balancing, and compensating current adjustment, respectively. The topology is modeled in MATLAB/SIMULINK and implemented using dSPACE DS1103 interface for experimentation. Findings -- The exhaustive simulation and experimental results demonstrate the robustness and effectiveness of the proposed topology and controllers for harmonic minimization for RL/RC load and change in load. The comparison between traditional PI controller and proposed AI-based controller is presented. It indicates that the AI-based controller is fast, dynamic, and adaptive to accommodate the changes in load. The total harmonic distortion obtained by applying AI-based controllers are well within the IEEE519 std. limits. Originality/value -- The simulation of high-power, medium-voltage system is presented and a downscaled prototype is designed and developed for implementation. The laboratory module of CHBMLI-based harmonic filter and AI-based controllers modeled in SIMULINK is executed using dSPACE DS1103 interface through real time workshop. [ABSTRACT FROM AUTHOR]

Purpose - The purpose of this paper is to consider both sides of a back-to-back AC-DC-AC interface. Design/methodology/approach - The paper presents a mathematical analysis, simulation, laboratory test in scaled model. Findings - The two main findings comprised concept of control methods for grid AC-DC-AC converter applied in renewable energy sources with variable speed operation under distorted grid. Active filtering functionality in case of non-linear current of a parallel load. Second, a control algorithm dedicated for two-level AC-DC converter applied in industrial networks with high-order harmonics compensation working under hard conditions - balanced and unbalanced voltage dips. Research limitations/implications - The paper shows preliminary results for AC-DC-AC converter and active filter (AF) during voltage dips and for harmonics compensation. Control methods and/or topology should be improved and tested in scale and after at high-power system. Practical implications - Power quality supplied/received to/from the grid can be increased. In case of low-cost system only AF can be applied to existing non-linear receivers. Moreover, in case of full AC-DC-AC converter energy saving and production is possible. Originality/value - Presented control methods give satisfactory results. Paper presents laboratory results for grid and machine side two different power circuits during steady states and transients. Moreover, active filtering operation during voltage dips is presented. [ABSTRACT FROM AUTHOR]

Purpose - The purpose of this paper is to present a method for analyzing higher magnetic force harmonics in electrical machines based on electromagnetic finite element simulation. Design/methodology/approach - Sampling of air gap field solution data allows for a Fourier decomposition of magnetic forces and flux densities. A two-dimensional convolution gives insight into the spectral decomposition of forces responsible for acoustic noise, vibration and higher torque harmonics. Findings - The proposed approach seems especially suitable for synchronous machine models. The influence of magnetic circuit design parameters that are difficult to calculate analytically on the harmonic air gap content can be analyzed and the spectral force decomposition illustrated by means of space vectors. Originality/value - The approach is generalized to the convolution and analysis of arbitrarily sampled two-dimensional data in this paper. [ABSTRACT FROM AUTHOR]

The article presents a research study on an analytical method for predicting iron loss in magnetic lamination in pulse width modulation (PWM) converter supply. It states that the method considers harmonics that coexist with direct current (DC)-bias field, non-linearity of ferromagnetic, and deformed flux. It says that the method also focus on effect of DC-bias field with the static hysteresis and classical eddy current losses. It says that the method shows that iron losses come from harmonics.

Purpose - The purpose of the paper is to show the application of the fixed-point method with the T, F-F formulation to get the steady-state solution of the quasi-static Maxwell's equations with non-linear material properties and periodic excitations. Design/methodology/approach - The fixed-point method is used to solve the problem arising from the non-linear material properties. The harmonic balance principle and a time periodic technique give the periodic solution in all non-linear iterations. The optimal parameter of the fixed-point method is investigated to accelerate its convergence speed. Findings - The Galerkin equations of the DC part are found to be different from those of the higher harmonics. The optimal parameter of the fixed-point method is determined. Originality/value - The establishment of the Galerkin equations of the DC part is a new result. The method is first used to solve three-dimensional problems with the T, F-F formulation. [ABSTRACT FROM AUTHOR]

Purpose - The aim of this paper is to estimate the iron losses for an induction machine in the healthy case taking the slotting effect into account and to study the effect of an inter-turn short-circuit on these losses. Theoretical results are then compared with experimental ones. Design/methodology/approach - A simple analytical model of iron losses allows one to calculate and to appreciate the contribution of the slotting effect on induction machine iron losses without and with an inter-turn stator short-circuit. This semi-analytical approach is based on the iron stator and rotor flux density repartition which is deduced from the air-gap flux density. Findings - The iron losses are not only due to the fundamental air-gap flux density, but also to the slotting harmonics. In fact, the slotting effect generates harmonic flux density waves with very low magnitudes but with high-angular velocities, leading to non-negligible harmonic iron dynamic losses which have similar values on both the stator and the rotor. The inter-turn short-circuit generates an iron losses and a slotting harmonic contribution increase. Research limitations/implications - Experimental measurements give the total iron losses. They do not allow separating the fundamental and the slotting harmonics contribution. Practical implications - The knowledge of the iron losses behaviour in the healthy machine taking into account the slotting effect is important to optimize the design. The fault contribution on these losses allows one to estimate the damage which can be engendered by the fault. Originality/value - Generally, iron losses studies and calculations are performed numerically using finite element software. The analytical approach can be interesting because it allows one to make faster calculations and to analyze the influence of the machine geometric parameters. [ABSTRACT FROM AUTHOR]

Purpose - The purpose of this paper is to present a coupled finite element (FE) - reluctance network model for a hybrid step motor. Design/methodology/approach - The equivalent permeances of the air-gap are determined by 2D nonlinear FE computations. The results of the 2D model are used in a 3D analytical model. A spectral decomposition and a nonlinear fitting of the amplitudes of the permeance harmonics are performed to account for both saturation and high order harmonic effects. The nonlinear resolution of the circuit equations is performed with an iterative process. The performances are determined by using the principle of virtual works. Findings - The method is validated with a 2D FE computation and then applied to a 3D hybrid step motor. Originality/value - The proposed method enables fast and efficient computations of the performances of hybrid stepping motor. [ABSTRACT FROM AUTHOR]

The article presents a study on the optimum regulation of cascaded multi-level inverters' (direct current) DC sources. It presents a new notion in choosing the values of the DC source voltages in cascaded multi-level inverters for the output voltage total harmonic distortion (THD) improvement. The study indicates that applying the introduced concept results in significant improvement in the harmonic minimization and extension of the inverter's operating range.

The article discusses a study on the application of an analytical acoustic and electromagnetic model of a pulse-width modulation (PWM) controlled induction machines to a fractional-slot winding machine. The stator and rotor currents were calculated using multilayer single-phase equivalent circuit, and air-gap radial flux density was computed using winding functions formalism. It discusses the effects of winding space harmonics and PWM time harmonics on noise spectrum.

Purpose - This paper aims to present the prototype of a 140?kVA shunt active power filter (APF) for current harmonics and fundamental reactive power compensation of a 200?kW induction heating system. Design/methodology/approach - Design issues of the power components, of the switching ripple filter and of the digital control are addressed and discussed. The APF control algorithm has been implemented on the 16-bit, fixed-point, TMS320LF2407?A DSP controller. The current control is based on proportional-sinusoidal signal integrators with good performance in current harmonic elimination and power factor compensation. Findings - The experimental tests, performed in real industrial environment for a 200?kW induction heating plant, show that the performance goals are fulfilled. Practical implications - The sinusoidal signal integrators (for consistency with the other plural forms of acronyms) of the current controller are implemented in the rotating reference frame aligned with the voltage vector at the point of common connection. This allows the compensation of two harmonics with a single SSI, thus halving the computational effort of the DSP. Originality/value - In industrial induction heating, the need for harmonic and reactive power compensation lasts a few seconds per minute, making passive solutions not suitable. The presented APF is a valid solution for this application, where only a few tailored implementations are available on the market. [ABSTRACT FROM AUTHOR]

Purpose - The paper proposes to deal with the problems concerning the N-phase (N+1)-wire system with sinusoidal voltage sources and nonlinear loads. In the model of the N-phase voltage source the inner impedance has been included. The problem of the optimization of working conditions of the system is a minimization of RMS value of its line currents as well as their distortions caused by nonlinear loads. Design/methodology/approach - The solution of this problem is based on the frequency domain. It is obtained by means of Lagrange's multipliers and the suitable measurement experiment. Findings - After optimization source currents are sinusoidal with minimized RMS values. After connection of the designed compensator to the system under research the phase currents are equal to determined active currents. Research limitations/implications - This method can be used for some classes of nonlinear loads, i.e. for systems with inertialess (non-reactive) elements, which consume the active power of the basic harmonic of the voltage source and where the currents of the system are periodical. The mentioned power is an additional constraint of the presented minimization. Practical implications - The working point of the system can be obtained by means of the compensator LC, RLC or (RLC,-R). It will always be a linear one and its structure consists of two components: elements with parameters determined for the basic harmonic and the filter for elimination of the higher harmonics caused by nonlinear loads. Originality/value - The presented method has been generalized for N-phase (N+1)-wire systems. [ABSTRACT FROM AUTHOR]

Purpose - The paper aims to provide an approach to actively decrease the radiation of acoustic noise in synchronous machines. Design/methodology/approach - Splitting regular three-phase windings of synchronous machines into two independent three-phase systems allows for an active influence of the current waveform if both winding systems are mutually displaced against each other. The harmonics content of each phase-current varies due to the mutual inductive coupling with participating currents of both systems. Therefore, the ensuing force-density distribution on the stator teeth varies accordingly. Resulting structure dynamics and furthermore the radiation of relevant harmonics of the acoustic noise are based on the mechanical excitation of considered force-density distributions. Findings - Configurations of mutual displacement of phase windings of both winding systems with significant decrease of mechanical deformation and emitted acoustic noise are found. Simulation methods to entirely describe and prove the behavior described are developed. Research limitations/implications - The proposed approach is developed for a particular synchronous machine. Other machine types are conceivable for analysis in the same manner. Tools need to be adapted. Universal and reliable statements regarding acoustic behavior depend on the mechanical restraint of the machine and may therefore vary. Practical implications - Active force-density distribution is used for the noise reduction of alternators in vehicle applications. Additionally, wind-power generators are considered for the application of split stator winding systems to actively counteract inhomogeneous force distributions on the rotor, evoked by stalling of the propeller blades during pole passing. Originality/value - Active force-density modification by stator winding modifications allows for the decrease of noise radiation of electrical machines with rotating-field windings. Innovative simulation methods developed may now replace prototyping partially. [ABSTRACT FROM AUTHOR]