Due to the increase of Distributed Energy Sources (DER), non-linear and unbalanced loads in the modern Medium-Voltage (MV) grids, concerns about power quality and voltage stiffness are on the rise. To face the aforementioned issues, Active Filter (AF) devices are highly demanded. These devices are based on Voltage Source Converters (VSC). In this perspective, a Single-Delta Bridge-cell Modular Multilevel Converter (SDBC-MMC) seems to be the most adapted VSC topology thanks to its technical and economic advantages. In this paper, a control strategy based on the SDBC-MMC is proposed to compensate for both load reactive power and harmonics, while adopting a simple and efficient control structure. The latter consists in parallelizing the Proportional Integral (PI) Voltage Oriented Control-based (VOC) and the Proportional-Multi Resonant (PMR) control-based. The aim is to regulate the reactive power and partially the harmonics through the commonly used VOC structure, while, the PMR controller will further enhance the compensation of some specific dominating harmonics (5 th , 7 th , 11 th and 13 th ). The PMR regulator is receiving only harmonic signals as an input, and therefore, no interference between both control stages is conceivable when no harmonics are detected. The effectiveness of the proposed control is demonstrated through time domain-simulations in various conditions.

In this study, a complete design of a resonant inductive Wireless Power Transfer (WPT) system for battery-less systems will be presented. The main components of the resonant inductive WPT system are H-bridge inverter, transmitter side coil & compensation capacitor, magnetic core & medium, receiver coil & compensation capacitor and diode rectifier & filter capacitor. In this work, closed loop control mechanism, RF wireless communication, power-up strategy for battery-less receiver side application, loss budget and detailed system description of a series resonant inductive wireless power transfer system will be shown. The design and the proposed methods will be verified with simulations and experimental results.

This paper addresses the comparison of a multi pulse rectifiers which designed with different topologies as star-delta-zigzag connection and their couples (delta-star, delta-delta, star-delta, star-star, zig-zag) for different phase shifting features. It is important because using different transformer pairs with different number of pulses will change the output voltage's total harmonic distortion. The purpose of this work is to compare the possible transformer structures in terms of Total Harmonic Distortion (THD) and power factor value with good voltage regulation. Multi pulse rectifiers with 6-12-18-24-36-pulse will also be added to the comparison work. Simulation results are given to assess the performance of these topologies in terms of power factor and THD. To meet power quality requirement over multi-pulse rectifiers, THD value needs to be lowered, this study compare which transformer configurations and number of pulses give better power quality.

There is a growing interest on the potential use of inductive wireless transfer on modern non-contact rotary systems such as high-speed slip ring applications for aerospace, medical and defense systems. Thus, performance evaluation of inductive Wireless Power Transfer (WPT) for high-speed non-contact slip ring applications where secondary coil is rotating at various speeds is essential. In this work, effects on the current and hence power transmitted through the primary coil depending on the rotation of secondary coil are observed for an inductive WPT system. Harmonic analysis for the primary coil current, analysis of power transmitted and overall system performance at high speeds are observed and new findings which are not present in existing literature are discovered. The effects of rotation in secondary coil on the primary coil current's harmonic content is revealed for the first time in the literature.

In this study, we present a simulation based average modeling approach and a digital current mode controller design for an Output Inductor-less Phase-Shifted Full-Bridge (OIPSFB) DC/DC converter nominally operating in Discontinuous Conduction Mode (DCM). Average current mode control is utilized in the vast majority of Full-Bridge converter applications. One can apply state space averaging method to derive the Continuous Conduction Mode (CCM) system model of these converters because in CCM the system has dynamics closer to linearity. However, for DCM operation, the state space averaging method cannot be used directly because of the nonlinear characteristics due to discontinuous inductor current. In most of the derived average models for DCM, the start-up transition voltage waveform does not reflect the reality. In the model we present in this paper, we set a current limit to average inductor current state with clamping anti-windup. In this way, we obtained a more realistic start-up dynamic for the voltage. Also, to prevent the controller coefficients’ scaling problems in Digital Signal Controller (DSC), we include the real measurement systems’ dynamics in our model and obtained the controller parameters as digital values substituted in DSC. Throughout this paper, we detailed the proposed modeling and digital average current mode controller design approach. We demonstrated the accuracy of our model by comparing simulation results with real system results. Finally, we verified our designed controller on an experimental system.

As the reliability of semiconductors in power electronics converters has great importance for industrial systems, it should also be taken into consideration for pulsed power applications, one of the most electrically stressful conditions for power semiconductors. Power semiconductors in pulsed power applications are usually subject to overloaded conditions. Therefore, commonly used mean time to failure analysis methods does not give accurate results. In this paper, different reliability analysis methods for press-pack semiconductors are inspected and compared. The most suitable method is chosen and a reliability analysis approach is given specifically to pulsed power applications with the aid of Finite Element Method (FEM) analysis tools. Some assumptions are made to simplify the reliability analysis and explained with FEM. Results are compared with field data and other methods.

Electron beam melting has been used recently in additive manufacturing by various researchers. In those electron beam melting applications, the electron energy can be 60 to 100 keV, the beam current can be around 10 mA to 100 mA, and the beam spot size can be as small as 200 µm according to electron energy and beam current. Those parameters can result in very high beam power densities. The diagnostics of this powerful beam can be quite a problematic issue. As the electron beam current required for the application is quite similar to DC current, fast undestructive current measurement techniques for current beam profile and beam position are very limited in performance. Therefore, some destructive techniques to measure current and other beam properties are essential. As part of the beam di-agnostics for electron beam melting application for additive manufacturing, the authors proposed a complete beam diagnostics system to measure the electron gun's capabilities and associate electromagnetic lens systems. The following properties have been diagnosed as part of this research work: i) Beam Current, ii) Beam Spot size for enlarged and focused beams, iii) Scanning velocity of the de-flected beam, iv) Profile of the beam. The authors proposed methods to measure focused beam spot size and deflected beam scanning velocity using Secondary Emission Grid Sensors. Moreover, the authors proposed a new technique to measure beam profile using consecutively placed several copper plates with beam guiding holes of various diameters. The proposed beam profile measurement method effectively determines the useful beam radius for metal powder melting properties specifically to additive manufacturing applications.

Estimating the core losses of magnetic materials is crucial for the electrical, thermal, and mechanical modeling of modern power electronic converters. Thus, there have been a number of methods proposed in the literature to estimate core losses. However, none of the existing works have introduced a method to estimate the core losses for arbitrary flux density waveforms by making use of manufacturer provided loss calculation parameters with a memory efficient algorithm. In this paper, existing core loss estimation methods are reviewed and a novel method is proposed to estimate the core losses under arbitrary voltage excitation by a modification of the improved Generalized Steinmetz Equation (iGSE) algorithm. The novel method is referred to as the Recursive Improved Generalized Steinmetz Equation (RiGSE) and its performance is experimentally verified for arbitrary flux density waveforms. The experimental verification of the proposed core loss estimating method is the only known example in the existing literature in terms of the evaluation of arbitrary flux density waveforms.

Large power transformers (LPTs) are critical components affecting grid resiliency in high-intensity, low probability events. Hybrid transformers (HTs), consisting of standard transformers integrated with series-connected fractionally-rated converters, have been proposed to improve the resiliency and functionality of LPTs. However, when integrating with relatively less reliable power electronics, it is critical not to impact the reliability of otherwise highly reliable passive transformers. Simultaneously, the power electronics must be protected from system transients such as high fault currents (1020 kA in 13 kV applications). This paper proposes a Fail-Normal Switch (FNS), which will be an integral part of the transformer and bypasses the power electronics to retain the basic transformer functionality in the case of system or converter faults. The FNS consists of a combination of anti-parallel SCRs and a normally closed mechanical switch. The FNS is a fully autonomous unit embedded with local intelligence, making it unaffected by the converter controller failures. In addition to the capability of handling high fault currents with a sub-cycle response, various failure modes under practical scenarios, such as control power failure, communication failure, SCR gate drive failure, and the corresponding failure handling methods using a multi-layered protection scheme, are presented. An FNS prototype to be used with a 24 kV, 5 MVA HT is built and tested experimentally for reliable operation under various failure modes.

ASELSAN Inc. has been conducting experimental research on electromagnetic ( EM) launch technologies since 2014. First-generation 1-MJ and second-generation 3.25-MJ pulsed power supplies (PPSs) were built and tested with 25 mm x 25 mm square bore EM Launcher-1 (i.e., Elektromanyetik Firlatma Yolu- 1: EMFY-1) EM Launcher at an open area test range by ASELSAN. In 2018, ASELSAN built an EM launch laboratory to perform experiments up to 2-MJ muzzle energy. The stored energy of the second-generation PPSs will be increased to 8 MJ, and the new 50 mm x 50 mm square bore EMFY-2 and 50 mm x 75 mm rectangular bore EMFY-3 EM launchers will be used. We present the ASELSAN EM Launch Laboratory and the results of the first EMFY-2 EMlauncher shoot fed by 3.25-MJ PPS at the laboratory.

Astigmatism is a type of aberration in beam optics which causes asymmetry in transverse coordinates. This asymmetric beam often shows an elliptical profile instead of circular, which may cause differences between the major and minor ellipse axes diameters and ellipse azimuth angle. In this research work, a novel astigmatism correction system is proposed for electron accelerators with a minimum number of electromagnetic lenses. An adaptive quadrupole lens is designed by coaxially locating two quadrupoles 45 degrees apart from each other. The focusing and defocusing axes and the azimuth angle of the resultant adaptive quadrupole are determined adaptively by the vector sum of created magnetic fields of two coaxially located quadrupoles. The adaptive quadrupole lens is placed on the common focal point of two solenoids as part of an expander lens. In this way, the focal points of the major and minor axes of an elliptical beam are slightly changed from the common focal point of the expander. This act helps to increase the minor axis diameter of the electron beam while decreasing the major one, resulting in a circular profile. Both a 2D beam trajectory model in MATLAB and a 3D Particle Accelerator simulation with Computer Simulation Technology (CST) tool show that the proposed method successfully corrects the astigmatism having any elliptical parameters for a sample electron beam.

Here, a novel harmonic suppression performance criterion, namely suppression factor (SF), is suggested for the wide-frequency power filtering equipment. Performances of single-tuned passive filter, combination of passive filters tuned to various frequencies, shunt active power filter (APF), and a shunt hybrid active power filter (HAPF) topologies have been evaluated considering their SF values over a defined frequency range. Moreover, effect of the control method for the active filtering equipment on SF values is also analysed by comparing both theoretical and the experimental results. The frequency range of harmonics to be suppressed is chosen using the field measurements of Induction melting furnace (IMF) load, one of the most problematic loads in terms of interharmonics, and a field implemented HAPF system is used for the experimental verifications.

This paper proposes a design methodology for an active power filter (APF) system to suppress the second harmonic subgroup injected by an AC electric arc furnace (EAF) to the utility grid. The APF system is composed of identical parallel units connected to the utility grid via a specially-designed coupling transformer. Each APF converter is a three-phase three-wire two-level voltage source converter (VSC). The number of parallel APF units, coupling transformer MVA rating, and turns ratio are optimized in the view of the ratings of commercially-available high voltage (HV) IGBTs. In this research work, line current waveforms sampled at 25.6-kS/s on the medium voltage (MV) side of a 65-MVA EAF transformer are then used to extract the second harmonic subgroup, 95-, 100-, and 105-Hz current components, by multiple synchronous reference frame (MSRF) analysis, which was previously proposed to decompose EAF current interharmonics and harmonics in real-time. By summing up this digital data of the second harmonic subgroup, the reference current signal for the APF system is produced in real-time. A detailed model of the APF system is then run on EMTDC/PSCAD to follow the produced reference current signal according to hysteresis band control philosophy. The simulation results show that the proposed APF system can successfully suppress the second harmonic subgroup of an AC EAF.

Although hysteresis band current control is an easy to implement and robust control method for industrial power electronics converters, it has also some disadvantages like variable and high switching frequency causing high switching losses. In this study, a novel adaptive fuzzy hysteresis band current control system is proposed by making use of fuzzy expressions of both hybrid active power filter (HAPF) current and integral of its harmonic components to reduce the switching losses of three-phase three-wire two-level HAPF. To reach this aim, a relation between switching frequency and integral of filter current harmonic components is formulised and used for defining a fuzzy hysteresis band. Moreover, the magnitude of the instantaneous current switched is also correlated to the switching losses; in this way, its fuzzy expression is also used for defining hysteresis band. Those fuzzy expressions are then utilised to constitute a dynamically changing hysteresis bandwidth. The proposed control system is finally optimised using EMTDC/PSCAD simulation environment and implemented in the field. The implemented HAPF system has been shown to successfully suppress all the interharmonic and harmonic current components produced by a steel melting facility occupying three induction melting furnaces and it has provided around 9% reduction in overall losses.

ASELSAN Inc. has been conducting experimental research on electromagnetic launchers since 2014. A 1 MJ Pulsed Power Supply (PPS) and 25 mm × 25 mm square bore 3 meters EMFY-1 Electromagnetic Launcher have been built at ASELSAN. This paper represents results of the first experiments of EMFY-1 Electromagnetic Launcher with 1 MJ PPS and c-type aluminum armature. The pulse currents of the PPS modules are measured by Rogowski current probes. The muzzle voltage of the launcher is measured to analyze the contact quality between armature and the rails. The velocity of the projectile is calculated from the B-dot probes' outputs.

This paper describes the design and field implementation of a hybrid active power filter (HAPF) system to suppress time-varying interharmonics injected into the grid by medium-frequency coreless induction melting furnaces (IMFs). In a sample steel melt shop, variable-frequency load-resonant inverters of works coils are supplied from the medium-voltage grid via 12- and 24-pulse thyristor rectifiers. The cross-modulation phenomenon in ac-dc-ac link of the medium-frequency coreless IMF installations produces interharmonics and characteristic and uncharacteristic harmonics in the grid-side line current waveforms. Furthermore, frequencies of dominant interharmonics are migrating in time inside a frequency window as the operating frequency of the load-resonant inverter varies in wide range during a melting cycle. The HAPF system developed for this application consists of nine HAPF units operating in parallel in current control mode and is connected to the grid via a coupling transformer. Current control is achieved by extracting high-order fixed frequency characteristic harmonic components from the reference current signal and defining a fixed hysteresis band for each HAPF unit. The input LC filter of the HAPF system is optimized in the design stage by taking into account the frequency range of prominent interharmonics. Theoretical findings are verified in a sample steel melt shop by extensive field measurements. Field test results have shown that the developed HAPF system suppresses successfully the dominant time-varying interharmonics and harmonics in the frequency range from 250 to 650 Hz.

Current tracking performance of hysteresis current control depends on some parameters such as coupling impedance, sampling time, execution time, and dc link voltage. In this paper, hysteresis band control method for a three-phase three-wire two-level Hybrid Active Power Filter (HAPF) converter coupled with series LC filter is formulized. The effect of both sampling frequency and execution time on current tracking performance is investigated. In order to enhance the current tracking performance of a sample HAPF system working in the field, its field data is analyzed and an EMTDC/PSCAD simulation environment is formed to represent the actual system in the field. The simulation environment is designed so that the sampling frequency and execution time models can be easily modified in order to observe their effect on current tracking performance. The simulation results show consistent results with the theoretical findings that the increase in sampling frequency and the reduction on execution time significantly improves the reference tracking performance. It is reached in this paper that the use of more powerful processor and increase in sampling frequency for the HAPF system working in the field are necessary for better current tracking performance.

Using generalized building blocks for the design of power electronics converters is advantageous in terms of scalability, modularity, power density, and reliability. For the control of those power electronic converters composed of Power Electronics Building Blocks (PEBBs), an easily scalable and modular control system should also be integrated. In this paper, a hierarchical control system architecture is proposed for the first time for a modular Hybrid Active Power Filter (HAPF) system in order to suppress interharmonics, which their magnitudes and frequencies change dynamically in time, produced by Induction Melting Furnace (IMF). The proposed control system architecture is successfully implemented in the field on a 2.7-MVA modular HAPF system for a steel melting facility equipped with three IMFs. The performance of the HAPF system and the proposed control architecture is verified by the intensive field tests. The overall system has been working successfully in a steel melting facility since March, 2013.

This paper describes a hybrid system for the mitigation of power quality (PQ) problems of medium-frequency coreless induction steel-melting furnaces. The hybrid system is composed of passive shunt-detuned filters and a hybrid active power filter (HAPF). Since the single-phase load-resonant thyristor inverter of the work coil operates at variable frequency and supplied from a multipulse thyristor rectifier, interharmonic current components, due to cross-modulation phenomenon across ac-dc-ac link, appear in supply lines. The frequencies of these interharmonics are migrating in time over a wide range, and they interact with passive shunt LC filters and other power-system components resulting in harmful effects on the overall system. Reactive power compensation of medium-frequency coreless induction steel-melting furnace is achieved by passive shunt-detuned filter banks, thus avoiding the amplification risk of interharmonic current components. Interharmonics are satisfactorily suppressed by a HAPF with K control strategy. The performance of controller is improved by modifying the conventional K control strategy and adding feedforward control loops for dominant characteristic harmonics. The resulting hybrid system is operating in a steel-melt shop successfully since March 2013.