Core Inductor Research Articles

Robust Current Control of Grid-Tied Inverters Affected by LCL Filter Soft-Saturation

This article provides as contribution a systematic design procedure for robust current control of grid-tied inverters with LCL filters affected by inductor magnetic soft-saturation and also by uncertain grid impedances. The proposed design is based on the following: first, a polytopic time-varying model to describe the effect of the inductances variations; second, a set of linear matrix inequalities to design fixed (robust) state feedback gains, ensuring bounded settling times for the closed-loop transient responses. A less conservative set of linear matrix inequalities is used to certify the procedure. Experimental results from real-time simulations and from a real prototype with commercial powder core inductors show that the proposed procedure can provide superior results than conventional controllers designed not taking into account the soft-saturation. The results with the proposed controller comply with the IEEE 1547 Standard, leading to grid currents with low harmonic content, respecting limits prescribed by this standard even under distorted grid voltages.

Compact MR-compatible DC-DC converter module

The SAFIR collaboration is developing a high rate positron emission tomography insert for a preclinical 7 T magnetic resonance imaging (MRI) device. To meet the desired performance figures, a large number of readout channels (≈15000) and integration of data digitisation into the insert are required. Consequently, the insert will consume about 1.3 kW of input power at low voltages (⩽ 3.3 V). This corresponds to large supply currents of several 100 A, requiring heavy and bulky supply cables. To overcome these problems we developed a compact and MR-compatible DC-DC stepdown converter module. Our converter is based on an air core inductor and is optimised for low electromagnetic emissions. It has an input voltage range from 6 V to 24 V and provides an adjustable output voltage from 1 V almost up to the input voltage. The maximum continuous output current is 6 A. We measured conversion efficiencies between 70% and 87% depending on output load and input voltage. For the operation conditions foreseen (16 V input voltage, 2.4 V output voltage and 3 A output current), we achieved an efficiency of 83.8%. Our tests inside the MRI demonstrated the compatibility between the MRI system and the step-down converters developed. No mutual interference was observed. The signal-to-noise ratio of the MRI remains unaltered, independent of the activity of the step-down converter under any operation condition and no effect on the operation of the DC-DC converter was observed. This successful test of an MR-compatible DC-DC converter creates new opportunities for the power supply of complex hardware inside an MRI. 49 of the DC-DC converters will be used in our SAFIR PET insert, but they can also be used in other applications with high power demand in environments with strong magnetic fields.

Dynamic hysteresis modeling for soft magnetic composites based on isotropic vector play model and Cauer ladder network

PurposeThis paper aims to propose an effective modeling method of dynamic hysteresis properties for soft magnetic composite (SMC) core using an equivalent circuit representation. Because the eddy currents flowing inside iron powder particles should be considered, it is well known that an accurate magnetic field analysis of the SMC core in a wide range of excitation frequency is not easy. To overcome this difficulty, a dynamic hysteresis modeling based on the standard Cauer circuit is investigated.Design/methodology/approachIn the proposed method, the first inductance represents the static magnetic property of the SMC, and the latter part represents the dynamic effect because of the eddy currents. The values of the circuit elements were determined by an optimization method based on symmetric loops measured at several frequencies. To verify the validity of the proposed modeling method, finite-element analyses of a ring core inductor and an alternating current reactor were performed.FindingsBy comparing the simulated and measured magnetic properties, the necessity to consider magnetic hysteresis in the equivalent circuit model is clarified. Furthermore, the frequency-dependent inductances of practical reactors can be obtained from the finite-element analysis combined with the proposed method.Originality/valueThis paper demonstrates the significance of determining the circuit parameters in the equivalent circuit for dynamic hysteresis modeling based on the measured magnetic properties. The effectiveness of the proposed method is verified by comparing frequency-dependent inductances of two kinds of reactors between the simulation and measurement.

Design, Fabrication, and Characterization of Package Embedded Solenoidal Magnetic Core Inductors for High-Efficiency System-In-Package Integrated Voltage Regulators

In this paper, we discuss the design, fabrication, and characterization of package embedded solenoidal inductor using a NiZn ferrite magnetic core material based on the novel fabrication process. The process relies on stencil printing of the magnetic core material along with the photolithography and copper electroplating of the inductor’s traces. The electrical parameters of the fabricated inductors were extracted using a pi-equivalent circuit and showed an average dc resistance of 29 $\text{m}\Omega $ , an inductance of 26 nH, and an ac resistance of $2.62~\Omega $ at 100 MHz, which represents the targeted switching frequency of the system-in-package integrated voltage regulator. The organic substrate parasitic effects were accounted for through the extraction of an average shunt capacitance of 1.2 pF and an average parasitic conductance of 0.12 mS at 100 MHz. The measured 10% saturation current of the inductor was 9.6 A. The electrical parameters of the fabricated inductors were modeled and showed a good agreement with the measured data.

A Practical Approach for Core Loss Estimation of a High-Current Gapped Inductor in PWM Converters With a User-Friendly Loss Map

Core loss estimation of filter inductors is increasingly important for modeling and optimizing high-frequency, high-efficiency, and high-density pulsewidth modulation (PWM) power electronic converters. However, data provided by inductor core manufacturers are insufficient for core loss estimation in PWM converters, particularly in the case of customized gapped inductors. This paper presents a whole process of characterizing and estimating the core loss of a customized high-current gapped inductor for PWM converters. To excite the inductor for the B–H loop measurement, a test circuit formed by a half-bridge structure is proposed, which has the ability to compensate the asymmetric rectangular voltage on the inductor caused by the device voltage drops. To overcome the other challenges raised by a high excitation current, a refined discontinuous test procedure, triple pulse test, is proposed to reduce the requirements of the high-current test setup (thermal stress, current–time stress for current probes, capacity of dc sources, etc.). For practical purposes, a user-friendly loss map approach is proposed involving only time-domain and electrical variables to replace magnetic variables to enable the straightforward loss mapping process and core loss calculations. Presented experimental results show consistency between the estimated inductor loss and measured values. Overall, the proposed testing approach can be easily implemented on the user's side to develop a loss map of a given inductor. The established core loss map enables the users to accurately and rapidly estimate the core loss of a tested inductor for given PWM waveforms.

Influence of Power Losses in the Inductor Core on Characteristics of Selected DC–DC Converters

The paper presents the results of a computer simulation illustrating the influence of power losses in the core of an inductor based on the characteristics of buck and boost converters. In the computations, the authors’ model of power losses in the core is used. Correctness of this model is verified experimentally for three different magnetic materials. Computations are performed with the use of this model and the Excel software for inductors including cores made of ferrite, powdered iron, and nanocrystalline material in a wide range of load resistance, as well as input voltage of both the considered converters operating at different values of switching frequency. The obtained computation results show that power losses in the inductor core and watt-hour efficiency of converters strongly depend on the material used to make this core, in addition to the input voltage and parameters of the control signal and load resistance of the considered converters. The obtained results of watt-hour efficiency of the considered direct current (DC)–DC converters show that it changes up to 30 times in the considered ranges of the mentioned factors. In turn, in the same operating conditions, values of power losses in the considered cores change from a fraction of a watt to tens of watts. The paper also considers the issue of which material should be used to construct the inductor core in order to obtain the highest value of watt-hour efficiency at selected operation conditions of the considered converters.

Integrated CMOS Switch Buck DC-DC Converter Fabricated in Organic Interposer with Embedded Magnetic Core Inductor

Integrated CMOS Switch Buck DC-DC Converter Fabricated in Organic Interposer with Embedded Magnetic Core Inductor

Novel Motor-Shaped Rotational Inductor for Motor Drive Applications

This paper presents a validation of the novel motor-shaped rotational inductor. To validate the concept, 12 slots 2 poles rotational inductor is tested at different supply frequencies and rotor speeds. Experimental results have shown that the iron losses reduce as the rotor speed increases to the synchronous speed of the stator supply. The performance of the integrated rotational inductor is also compared with traditional EE core inductor in terms of total losses, synchronous inductance, copper resistance, and total harmonic distortion (THD). The total loss-to inductance ratio of the rotational inductor is reduced by 22.5% when rotor is rotating at 18 kRPM and supply frequency is held at 300 Hz. A significant reduction in copper resistance-to-inductance is also noticed when supply frequency is varied from 0 Hz to 20 kHz. Furthermore, the synchronous inductance and voltage and current's %THD of rotational inductor is found to be superior to EE core inductor.

Investigation of Vibration and Acoustic Noise Emission of Powder Core Inductors

In power electronics applications, where the switching frequency is below the audible frequency, the design of magnetic components considering acoustic noise and vibration is as important as designing for efficiency. For the case of the powder core, which is widely used in grid-connected inverters, much research has been conducted in terms of efficiency and core loss. However, there has been limited research dealing with the topic of acoustic noise and vibration. In this paper, Sendust (Fe–Si–Al), MegaFlux (Fe–Si), and HighFlux (Fe–Ni) powder core materials, which have low magnetostriction and low core loss, are analyzed in terms of acoustic noise induced by Maxwell force and magnetostriction. Three types of powder core materials having a rectangular shape are designed for a 4-kW grid-connected inverter. Various building structures, such as rectangular, toroidal, and oval-shaped, for a Sendust core are compared with sound pressure level and efficiency. The effects of the magnetic flux density, Maxwell force, and magnetostriction are analyzed using the finite element method and are verified experimentally. In addition, the experimental results of sound pressure and inductor efficiency are presented according to core materials and building structures.

Superior soft magnetic properties and mechanical strength in nanocomposites employing a double-percolating microstructure

Innovative methods for producing soft magnetic materials, such as inductor cores, are highly sought to achieve desirable microstructures, pursuant to excellent magnetic, mechanical and chemical properties. Here, silicone resin and nano-sized LBSCA glass (NG), prepared by a sol-gel method, were introduced to a nanocrystalline FeSiBNbCu ferromagnetic phase to produce soft magnetic composites (SMCs) by applying liquid-phase sintering-related spark plasma sintering (SPS). This novel strategy contributed to form a dense and uniform double-percolating microstructure in the SMCs with the co-doping of 1.0 wt % silicone resin (SR) and 0.6 wt % NG, which not only remarkably improved magnetic flux density (∼1.39 T), effectively permeability (∼237.0 at 1 kHz) and Vickers hardness (∼7.1 GPa), but also lowered coercivity (∼7.9 A/m) and core loss (∼120 W/m3 at 20 mT and 1 kHz, ∼2774.6 kW/m3 at 60 mT and 50 kHz). A group of additives have been designed and doped into the SMC and systematically studied to compare and understand the behaviors behind these outstanding results. The evolution of phase components and microstructure of the SMCs with different additives has been revealed and correlated with their performances.

A 10 kW Solar-Powered Bidirectional EV Charger Compatible With Chademo and COMBO

Charging electric vehicles (EVs) from photovoltaic panels (PV) provides a sustainable future for transportation. This paper presents the development of a 10 kW EV charger that can be powered from both a PV array and the three-phase ac grid. The goal is to realize a high power density and high-efficiency three-port power converter that integrates the EV, PV, and grid and meets the Chademo and combined charging standard/Combo EV charging standards. The EV port is designed to be isolated and bidirectional, so that both charging and vehicle-to-grid can be implemented. As PV and EV are both dc by nature, the converter uses a central dc link to exchange power between the EV and PV, thereby increasing efficiency. The use of silicon carbide devices and powdered alloy core inductors enables high switching frequency and power density. The closed-loop control allows four different power flows: ${\text{PV}\rightarrow \text{EV}, \text{EV}\rightarrow }$ grid, grid ${\rightarrow \text{EV}}$ , and ${\text{PV}\rightarrow }$ grid. Hence, the converter operates as a PV inverter, a bidirectional EV charger, and a combination of both. A 10 kW prototype has been successfully tested, and its experimental waveforms and measured efficiency are presented. It has three times the power density and higher partial and peak load efficiency when compared to existing solutions.

Photosensitive Glass-Ceramics for Heterogeneous Integration

The push for heterogeneous integration requires very unique material properties with respect to processing, material constants, and integration capabilities with other materials (such as copper, II...

Current Ripple Analysis and Controller Design for Grid-Connected Converters Considering the Soft-Saturation Nature of the Powder Cores

The powder-core-based inductor has a wide inductance variation due to the soft-saturation nature when subjected to varying load current. Under such a condition, the current ripple is influenced, and the conventional inductor design principle may be inaccurate. Besides, the voltage of the inductor is distorted. Also, the bandwidth of the controller is hard to determine. In this paper, the current ripple under the condition of wide inductance variation is analyzed, and its change rule is revealed; then, a new inductance design principle is proposed. The harmonic components for the three-phase converter with the powder core inductor are investigated, and the harmonic characteristic of the input current is analyzed. According to the current harmonic characteristic, the resonance controllers are introduced to eliminate harmonics, and the quality of the current is improved. Besides, the bandwidth of the controller is found to vary with the output power. Then, a compensation method is proposed to eliminate the influence of inductance variation on the bandwidth. The experimental results verify the analysis.

Optimal Design of High-Power Modular Multilevel Active Front-End Converter Using an Innovative Analytical Model

Optimal design and selection of arm inductances have been as a challenging subject in the field of modular multilevel converter (MMC). The average steady-state model is generally used as the analytical circuit model that neglects the switching frequency and harmonic values. Also, most of the researchers neglect the saturation effect of inductor core to simplify the analytical model. Contrary to the transformers, choosing the maximum flux density of inductance core is a sensitive issue, in order to design and minimize the inductors. Increasing the flux density reduces the inductor size, but getting close to the saturation region might alter the performance of the converter. This paper presents a systematic optimization approach to minimize high-power MMCs with saturable arm inductance considering technical, thermal, and manufacturing constraints. An accurate steady-state analytical model of MMC converter has been proposed and verified. A combination of converter circuit model and inductance electromagnetic model is employed to find the optimal arm inductances and capacitor values. The effect of nonideal inductance core on converter outputs has been investigated. A dimensioning model of inductor consisting of electromagnetic and thermal models is presented. To compute the optimal inductor size, a novel hybrid optimization loop is proposed including the analytical model of the converter and the inductor in which circuit, electromagnetic, and thermal properties are taken into consideration. In order to increase the accuracy of the dimensioning model, an internal verification loop is employed to verify and correct the analytical model using finite-element analysis. The proposed optimization loop aims to find the minimum inductor size considering technical and manufacturing constraints. Finally, the converter mass sensitivity of MMC converter versus some important constraints, such as temperature rise and capacitor ripple, has been investigated.

Magnetic Integration of LTL Filter With Two LC-Traps for Grid-Connected Power Converters

High-order inductor-traps-inductor (LTL) filters recently attracted a lot of research attentions in grid-connected converter applications due to their excellent harmonic attenuation ability, low cost, volume, and weight. However, more magnetic cores for trap inductors are required compared to conventional inductor-capacitor-inductor (LCL) filters. In order to further reduce the volume and weight of output power filter, this paper proposes a magnetic integrated LTL filter with two LC -traps. On the basis of conventional integrated LCL filters, the proposed method introduces a coupling winding wound on the central-limb of an EE-type magnetic core, and two equivalent trap inductors are introduced by the magnetic coupling between different windings. A step-by-step design guideline of the proposed magnetic integration method and the parameters design of LTL filters are also presented. The feasibility and effectiveness of the proposed method are finally verified by the experimental results.

Thermal Performance Modeling of Foil Conductor Concentrated Windings in Electric Machines

While the use of foil windings in transformers and air core inductors is not uncommon, their use in electric machines is just emerging. Although prototype realizations have been reported in the literature, a definitive analysis of their thermal performance is necessary to evaluate their potential for broad applications. This paper is devoted to presenting a comprehensive model for evaluating their thermal performance including loss modeling and temperature rise prediction in realistic designs. An overview of foil windings in electric machines and their advantages in improved fill factor is presented, along with experimental results that compare the ac losses and temperature distribution under identical steady-state operating conditions with a prototype round conductor coil and foil conductor coil. A lumped parameter thermal model that predicts the heat transfer behavior of the foil conductor coil is presented along with supporting experimental results.

Finite element modeling of nanoscale-enabled microinductors for power electronics

Abstract

Robust Lightning Indirect Effect Protection in Avionic Diagnostics: Combining Inductive Blocking Devices With Metal Oxide Varistors

The combination of iron core inductors and metal oxide varistors has been modeled and experimentally characterized to propose a robust protection system for indirect lightning effects in avionic environment. In particular, a numerical procedure to design transient limiters with high current rating, low clamping voltage, and low degradation rate is presented and described in detail. The protection systems are modeled using a circuital approach based on the diffusion equation, which is implemented in a finite difference time domain scheme. Two different modeling approaches to represent the nonlinearity and the hysteretic behavior of an iron core inductor are presented and discussed. Simulation results are verified by pin injection tests following the specific standards for avionic diagnostics.

High-frequency Magnetic Properties of [Fe80Ni20-O/SiO2]n Multilayer Film Served as Magnetic Core of Solenoid Inductor

In this study, we report the significant enhancement of high-frequency performance of solenoid inductors incorporated [Fe80Ni20-O/SiO2]n magnetic multilayer film prepared by magnetron sputtering as magnetic core over their air-core counterparts. The integrated solenoid inductor with multilayered magnetic core revealed excellent high-frequency performance in a wide operation frequency range of 0-4 GHz, and acquired a peak inductance density of 72 nH/mm2. Compared to their air-core solenoid inductors with equivalent geometry, there were more than 35-fold enhancement for inductance and 24-fold enhancement for peak quality factor of the 21-turn integrated solenoid inductor with multilayered magnetic core operating at 1.5 GHz. The results indicated that the multilayer magnetic core had promising prospect for applications in GHz frequency electromagnetic devices.

Design of a coil geometry for generating magnetic field to evaluate biological effects at 85 kHz

AbstractIn recent years, the use of induction‐heating systems has increased and wireless power transmission (WPT) systems have been discussed. These applications are installed close to a human body. Therefore, it is important to discuss the effects of alternating magnetic fields and to evaluate electromagnetic interference. This paper discusses the design procedure of a magnetic field generator to evaluate the electromagnetic interference at 85 kHz that is being studied in WPT systems for EV and HEV. The magnetic field generator presented in this paper consists of a single‐phase inverter circuit that uses SiC‐MOSFETs and an air–core inductor that is used as the coil for generating a magnetic field. In particular, this paper shows that the coil used for generating magnetic field needs to reduce the winding voltage to generate higher magnetic flux. In addition, this paper presents the design procedure of the proposed coil structure that can satisfy some limited conditions. The experimental results of the proposed system rated at 82 kHz and 100 A are presented.