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The wireless heat transfer (WHT) system is proposed to ensure the reliability and flexibility of the electrical heat tracing for domestic and industrial applications. In this article, the inherent coupling relationship among coil dimension, resistance, distance, and inductance of a WHT system is investigated, which illustrates the intrinsic link between thermal energy and electromagnetic feature of the WHT system under multiple mediums. Besides, the magnitude and distribution of the thermal energy among different coils are analyzed according to equivalent circuits and magnetic coupling mechanisms. For further studying the power distribution characteristic, the power flow model of the multiple coil system is established. On this basis, the uniform thermal energy distribution scheme of the WHT system is proposed to ensure all coils have equal heating power. Moreover, the heating power in the partial compensation condition is also investigated. The result indicates the compensation states of the transmitter coil only affect the magnitude of the heating power. Thus, the transmitter coil compensation states which can be used to adjust the heating capacity of the WHT system. The simulation and experiments are carried out to validate the feasibility of the proposed uniform thermal energy distribution scheme. [ABSTRACT FROM AUTHOR]

The magnetic circuit has been a popular and powerful tool to analyze the magnetic field in electromagnetic devices for a long history. However, in the conventional magnetic circuit there is only one kind of component namely reluctance, which cannot analyze the phase shift or the amplitude attenuation of the alternating flux in electromagnetic devices. In this article, a new physical concept of magnetic-inductance is proposed, based on which the alternating-flux magnetic circuit theory including two kinds of components namely reluctance and magnetic-inductance has been developed. Furthermore, the virtual magnetic power is defined as the analogue of electric power, and the magnetoelectric power law is derived for magnetic circuits. Using the proposed magnetic circuit theory with magnetic-inductance, the relationship between the electric power and the virtual magnetic power is revealed and the long-lasting confusions in previous magnetic circuit methods, i.e., power calculation and phase shifts of magnetic variables, are clarified. By experiments, the magnetic-inductance and the magnetoelectric power law are validated, and their applications in eddy current loss analysis and B-H curve estimation in magnetic materials are demonstrated. [ABSTRACT FROM AUTHOR]

This article proposes a novel dual-three-phase high-power high-speed permanent magnet assisted synchronous reluctance starter generator (PMaSynR SG) for aviation application, which has the characteristics of high efficiency, high power density, high reliability, and excellent antishort-circuit ability. The proposed PMaSynR SG can obtain higher efficiency and power density by embedding permanent magnet in the rotor topology compared with the synchronous reluctance generator, and has better antishort-circuit ability compared with the permanent magnet synchronous starter-generator. Moreover, design of dual-three-phase winding is adopted, which not only reduces the phase current, but also improves the reliability. In this article, the topological structure, characteristics and principle of PMaSynR SG are systematically studied at first. Second, a simplified dq-axis equivalent magnetic circuit model is established, and the expressions of dq-axis inductance and permanent magnet flux linkage are derived on the basis of the basic parameter selection. Then, combined with parameter sensitivity analysis, the influence law of rotor structural parameters on antishort-circuit ability and electromagnetic performance is revealed. Finally, a 40 kW 24 000 r/min PMaSynR SG is designed and manufactured. The simulation and experimental results show that the proposed PMaSynR SG has excellent electromagnetic performance with the power density of 3.1 kW/kg and the efficiency of 94%, while the short-circuit current is only 59% of its rated value. [ABSTRACT FROM AUTHOR]

A circulating power suppression structure for a three-winding-transformer-based converter is proposed in this letter. The equivalent circuit models of the dual-transformer-based and three-winding-transformer-based converter are derived, which illustrates their merits and demerits. With the proposed structure, the drawbacks of these two transformer-type converters can be overcome, and their advantages can be combined. Useless circulating loss in three-winding-transformer can be reduced to mW level and can be omitted. The complex and coupled dual-transformer parameter design problem can be solved. The analysis and performance of the proposed structure are fully validated by experimental results. [ABSTRACT FROM AUTHOR]

In this article, we present the characterization and an experimentally validated electromechanical model of a dual-transduction receiver for electrodynamic wireless power transfer (EWPT) system. This dual-transduction EWPT receiver contains two unimorph-type, series-connected piezoelectric transducers and an electrodynamic transducer within a compact footprint and low-profile design. The receiver makes simultaneous use of both piezoelectric and electrodynamic transducers to generate electrical power while operating at its torsion mode mechanical resonance at ∼744 Hz. The electromechanical system behavior and output performance under low-frequency, magnetic near-fields are analyzed by establishing an equivalent lumped-element equivalent electrical circuit model. A prototype device is fabricated, assembled, characterized, and the experimental results are compared with the model predictions under various excitation and loading conditions. A maximum of 49 μW average power is generated by the prototype under 120 μTrms, which corresponds to 0.54 mW·cm–3 power density and 37 mW·cm–3·mT–2 normalized power density. This chip-sized (0.09 cm3) design offers an innovative and volume-efficient architecture for application in wirelessly charging wearable and implantable medical devices. [ABSTRACT FROM AUTHOR]

In this article, a modified LLC resonant converter with LC antiresonant circuit in parallel branch is proposed. The proposed converter is derived by placing LC antiresonant circuit on parallel branch. In comparison with LLC resonant converter, the equivalent inductance of parallel branch of the proposed converter decreases along with switching frequency within regulating frequency range. This advantageous property contributes for that the turn-off current and circulating conduction loss in the primary side can be reduced at unity voltage conversion ratio due to large impedance of LC antiresonant circuit. Moreover, by optimizing resonant parameters design of parallel branch based on time-domain analysis, the magnetizing current is in close proximity to a sine wave and the conduction loss in the secondary side will be reduced, especially in the light load. A higher voltage conversion ratio can be achieved at low switching frequency due to decreased impedance in parallel branch. In addition, a design flowchart and a design practical case are given to help to implement an efficiency optimization algorithm to decide five resonant design parameters. Finally, a 2 kW 250 V—400 V-input and 48 V-output prototype is built, and the main experimental results are provided to verify the feasibility of the proposed converter and compare with LLC resonant converter. Comparative state-plane trajectories are depicted to compare their characteristics and to verify the model-domain analysis. [ABSTRACT FROM AUTHOR]

The volume of magnetic components (transformer and inductor) in a dual active bridge (DAB) converter is a crucial factor determining its power density. This article proposes an orthogonal decoupling magnetic integrated structure (ODMIS) for DAB converter, which aims to reduce the volume of the transformer and inductor. The integrated series inductor and magnetizing inductor do not affect each other in the ODMIS, so the design process of the transformer and inductor can be separated. The condition to realize magnetic circuits decoupling of the transformer and inductor is derived. The loss characteristics of the magnetic core are analyzed, and the optimal decoupling condition to minimize the core loss is also derived. A 400 V/6 kW/20 kHz DAB converter prototype is built to validate the effectiveness of the ODMIS. The measured full-load overall efficiency of the DAB test platform is 97.55%, and the power density of the magnetic integrated components is 10.08 kW/L. Finally, the prototype comparisons between the proposed ODMIS and two existing magnetic integrated structures and discrete magnetic component method are conducted, and the advanced feature of the ODMIS is illustrated. [ABSTRACT FROM AUTHOR]

A key challenge for safe operation of inductive power transfer (IPT) systems is to detect the presence of metal objects (MOs), particularly when a power receiver (Rx) is misaligned from a power transmitter (Tx) during online charging. This letter proposes a metal object detection (MOD) method by monitoring the fifth-order harmonic current of a dual-frequency IPT system driven by a voltage-fed inverter with square-wave output. While power transfer is maintained by tuning at the fundamental frequency, the Tx circuit is tuned simultaneously at the fifth-order frequency to ease the detection of the fifth-order harmonic current for MOD. The Rx circuit is also fully tuned at the fifth-order frequency, but the fifth order current is completely blocked. With the proposed dual-frequency tuning configuration, the presence of MO causes a significant drop in the fifth-order harmonic current at the Tx side, whereas the Rx behaves as an open circuit with no effect on power transfer. Circuit and magnetic field simulation results show the fifth-order harmonic current presents a unique response to the existence of MO, which is in good agreement with practical measurements. Experimental results demonstrate that at a constant 10 W power output, both nonferrous and ferrous MOs within the Tx charging area can be 100% detected, even when the Rx is misaligned by 50% of the Tx coil radius. [ABSTRACT FROM AUTHOR]

An integrated generator–rectifier system is a promising architecture to harvest energy in offshore wind turbines. The system processes the majority of the incoming power using reliable, efficient, and inexpensive passive diodes operating at the generator line frequency. Elimination of capacitors at the diode rectifiers’ output by appropriately phase shifting the voltages of a multiport generator further improves the reliability of the overall architecture. This article creates a generalized framework to evaluate the interactions among different generator ports, diode-bridge rectifiers, and the active rectifier that is used to control the power flow. The framework enables quantifying the effect of integration on the dc bus power ripple and power imbalance among different generator ports. An exemplary winding layout is proposed that ensures theoretically zero interaction between the passive ports, although all the ports are mounted on a magnetic structure. A 10-MW integrated generator–rectifier design and simulation proves the accuracy of the framework using coupled circuit and finite-element simulation. Finally, a laboratory prototype shows the realization of the winding layout. The proposed inductance-matrix-based framework can be used to evaluate other winding layouts to estimate the effect of magnetic coupling on the performance of the system. [ABSTRACT FROM AUTHOR]

In this article, a design of bipolar nonsalient pole (BNSP) transmitter, which originates from motor theory, for high-power EV dynamic wireless power transfer (DWPT) system is proposed. To analyze and evaluate BNSP transmitter in aspect of principle, characteristic, and performance, the existing I-type, S-type, and N-type transmitters in DWPT application are classified as bipolar salient pole (BSP) transmitter, which establishes a reference for comparing. The design parameters and other contrast conditions of BNSP and BSP transmitters are given. Coupling flux and leakage flux of BNSP transmitter are analyzed by comparing the magnetic models and the finite-element models of BNSP and BSP transmitters. Based on the modular design in practical application, the sensitivity of coupling performance to the module gap in BNSP and BSP transmitters is analyzed and compared in simulation. All theoretical results are verified by contrast experiments. The maximum effective mutual inductance of BNSP transmitter is about 31.0% larger than that of BSP transmitter, and the efficiency of the system with output power of 10 kW is 93.5% with BNSP transmitter, about 2.4% higher than that with BSP transmitter. Besides, BNSP transmitter needs 5.9% shorter Litz wire and 53.1% smaller volume of cores, which makes it smaller in size. [ABSTRACT FROM AUTHOR]

The wireless power supply solution has shown great advantages in rail transit applications, such as maglev trains and trams. However, research works on designing the magnetic coupler for wireless charging system in rail applications, which is a crucial problem, are not sufficient. Considering the high power and lightweight requirements, this article selects the coaxial M-shape magnetic coupler with LCL/S compensation for railway applications, which contains the transmitting rail and the receiving coil wound on an M-shape magnetic core. First, analysis was conducted on the requirements for inductance parameters of the magnetic coupler under the circuit constraints, including transmission power, input and output voltages, and component electrical stress, etc. Then, the influence of the geometric parameters of the coil structure and misalignment on its inductance parameters is analyzed. Based on these analysis results, the design method for the M-type magnetic coupler based on the lightweight principal is proposed. The geometric parameters are designed following a certain sequence to minimize the number of iterations and FEM simulation parameter sweeps, making the design procedure suitable for engineering practice. According to the proposed method, the magnetic coupler for a 360 kW wireless charging tram is designed and implemented. Through simulations and experiments, the magnetic coupler is verified to be feasible for the system with light weight. [ABSTRACT FROM AUTHOR]

Circuit models for multiphase coupled inductors are summarized, compared, and unified. Multiwinding magnetic structures are classified into parallel-coupled structures and series-coupled structures. For parallel-coupled structures used for multiphase inductors, the relationships between: 1) inductance-matrix models, 2) extended cantilever models, 3) magnetic-circuit models, 4) multiwinding transformer models, 5) gyrator-capacitor models, and 6) inductance-dual models are examined and discussed. These models represent identical physical relationships in the multiphase coupled inductors, but emphasize different physical aspects and offer distinct design insights. The circuit duality between the series-coupled structure and the parallel-coupled structure is explored. Design equations for interleaved multiphase buck converters based on these models are streamlined and summarized, and a simplified equation showing the relationships between current ripple with and without coupling is presented. The models and design equations are verified through theoretical derivation, SPICE simulation, and experimental measurements. [ABSTRACT FROM AUTHOR]

The traditional balance circuit is employed to balance the retired battery string. It will occupy some space for the extra switches, inductors, or/and capacitors of the energy storage system. This letter is trying to share the inductor of the dc–dc converter with the balance system by utilizing the current ripple on the inductor of the multiwinding transformer. The balance circuit does not require additional switches and control logic. The results of dynamic charging conditions show that the circuit is appropriate for balancing the battery string, and the system efficiency with the proposed approach reaches 94.1% at rated 28-W input power. The balance system only increases one diode and one inductor for each cell, which reduces the cost by 60% and 66% separately compared with the traditional resistance equalizer and transformer-based equalizer. [ABSTRACT FROM AUTHOR]

A self-current balancing structure of the dual-transformer-based triple-port active bridge (DT-TAB) converter with the reduced component count is proposed in this article for future sustainable energy system applications. The proposed topology inherits good characteristics of the conventional triple-port active bridge (TAB) with even power sharing in an open loop as a newly added function. It can achieve high power density over the existing TAB converters that possess current-balancing function because the need for an auxiliary magnetic circuit or sophisticated control scheme in equalizing the shared power is eliminated. Besides, the demagnetization and magnetic short-circuit problems associated with the conventional TAB converters that are been eradicated, decoupled power flow management is achieved at all conditions. Moreover, the phase shift between the input H bridges gives an additional control degree of freedom that permits the control of the output power or offers independent control of voltage magnitude during the reverse power flow, thereby extending the system-operating range. The proposed DT-TAB converter has been adapted for the two-port operation. All the power switches achieved zero-voltage-switching turn-on. Finally, the robust operation performances of the proposed DT-TAB converter have been verified by the laboratory prototype assembled and tested up to 1 kW. The experimental results presented at the end are the proof-of-concept. [ABSTRACT FROM AUTHOR]

The input-parallel output-parallel (IPOP) connected converter system allows the use of a low-power converter module for high-power applications. However, mismatches in the IPOP circuit parameters cause uneven current sharing between the constituent modules, which makes the IPOP system unreliable for practical use. Different techniques have been proposed so far; however, they cause an increase in magnetic volume, cost, component count, and complexity of the IPOP system. In this article, a reliable and efficient magnetic integration technique is proposed for the current sharing requirements of the IPOP system based on LLC resonant converter modules. The proposed integrated magnetic current balancing transformer (ICBT) based IPOP LLC resonant converter modules ensures both the input current sharing and output current sharing between constituent LLC modules, under the open-loop condition quite effectively. The proposed ICBT is the resonant inductors of LLC resonant converter modules, coupled to perform the function of current balancing as well as generates enough leakage inductances for resonance operation, simultaneously. Thus, it can reduce the overall magnetic volume and improves power density of the IPOP LLC modules. Moreover, the current sharing performances of the proposed ICBT in both the steady-state and dynamic-state are analyzed based on the magnetic and electrical model. To validate the performance of the proposed ICBT based IPOP two LLC modules, a 2.6-kW hardware prototype was designed, fabricated, and tested successfully. [ABSTRACT FROM AUTHOR]

Timing skew between measurement channels can introduce an unacceptable error in power loss measurement and is difficult to quantify, rendering precise in-situ measurement of magnetic loss essentially unattainable. This article rams the issue head-on by presenting the mathematical model for the timing skew and developing two methods based on the model to realize in-situ direct magnetic loss measurement. The mathematical model is first established to analyze the effects of timing skew on the measured magnetic loss in a dc–dc converter. The first method, called intersection method, illustrates how to unravel the entangled relationship between the actual timing skew and real magnetic loss in the circuit with the aid of the mathematical model. The second method, called derivative method, builds on the intersection method and greatly enhances the accuracy and the repeatability of the loss measurement. Our novel approach for in-situ magnetic loss measurement is verified in simulation and experiment with a conventional dc–dc step-down buck converter under various operating conditions and design parameters. [ABSTRACT FROM AUTHOR]

Suppressing parasitic ringing, unwanted oscillation caused by switching, sufficiently and reliably, is of great importance in wide bandgap semiconductor devices. RC-circuits inserted in parallel with switching devices have been widely used to suppress such parasitic ringing in power electronics circuits due to simple configurations. However, short-circuit current would flow through power lines if capacitors are broken. In this article, we show that parasitic ringing can be damped with an external RLC resonator implemented in parallel to a bus bar. The configuration enables the strong magnetic coupling, which results in high ringing suppression effect. Moreover, the external resonator is designed through analogy with passive parity-time (PT) symmetry. In the range of unbroken phase, ringing energy is distributed effectively to the external resonator, and the damping rate is increased by increasing the loss of the external resonator. Our results represent a significant step toward practical applications of passive PT-symmetry. [ABSTRACT FROM AUTHOR]

This article proposes a half-bridge LLC resonant converter applying a simple circuit with a variable magnetizing inductance scheme for hold-up time requirement. By changing the magnetizing inductance of the main transformer, the proposed converter can satisfy the hold-up time requirement without sacrificing efficiency, featuring small conduction, and turn-off switching losses of the primary switches in the nominal status. In addition, the proposed converter can relieve the burden of the additional components by positioning them on the signal path, and the proposed circuit is self-powered by adding only one additional winding instead of the isolated power supply. Therefore, those of the size and cost of the proposed circuit can be reduced compared to the previous studies. The feasibility of the proposed method was verified with a 350 W prototype converter (56 V/6.25 A), and the improved circuit for the transient mode was also presented. The experimental results validated the theoretical analysis and showed the effectiveness of the proposed converter for high-efficiency applications, especially in light-load conditions. [ABSTRACT FROM AUTHOR]

Dual three-phase (DTP) permanent magnet synchronous machines (PMSM) have been utilized in many applications due to their outstanding performance. However, large stator current harmonics limit the further application of the DTP-PMSM due to the low impedance in the harmonic subspace. To solve this problem, this article proposes a current harmonic suppression strategy based on an extended state observer (ESO). A detailed analysis is carried out to demonstrate the disturbance rejection ability and robustness of the proposed method. The theoretical analysis also shows that the ESO strategy outstands the conventional proportional-integral controller and advanced proportional resonance (PR) controller in terms of harmonic reduction. The advantages are verified by simulation and experimental results under different operating conditions. The proposed strategy still works well when considering other factors that may cause harmonic distortion, such as magnetic circuit saturation, saliency ratio, over-modulation of the inverter, the voltage drop caused by electric devices, and dead time. Meanwhile, some limitations are also pointed out. The proposed strategy can also be easily applied to other multiphase PMSM types. [ABSTRACT FROM AUTHOR]

Accurate and real-time capable mathematical models are an essential prerequisite for the design of model-based controller and estimation strategies for electric motors. Magnetic equivalent circuit (MEC) models have proven to be an interesting alternative to classical inductor models that are typically utilized for the controller design. MEC models allow for a systematic inclusion of magnetic saturation and nonfundamental wave behavior of motors, while still having a manageable model complexity. The systematic derivation of the model equations can be rather involved, if in addition to the magnetic circuit of the motor also the electric interconnection is taken into account. For this reason, a modeling framework for electric motors based on MEC models including the electric interconnection is proposed. It makes use of network theory, which allows to systemize and automate major parts of the modeling task. The presented framework can be applied to a wide range of electromagnetic actuators. The feasibility of the proposed framework is demonstrated by the application to the modeling of a PMSM with (turn-to-turn) winding short circuit. A comparison with measurement results shows a high model accuracy of the resulting real-time capable model both for healthy and faulty conditions. [ABSTRACT FROM AUTHOR]

An inverter-fed six-pole radial hybrid magnetic bearing (HMB) has the characteristics of compact structure, high support speed, long service life, and so on. However, using displacement sensors to detect rotor displacements leads to the problems of large volume, high cost, and low reliability. In this article, a self-sensing method using improved particle swarm optimization (IPSO) least square support vector machine (LS-SVM) is proposed, which eliminates the influences of displacement sensors fundamentally. The structure and working principle of six-pole radial HMB are introduced, and the mathematical model of its radial suspension force is deduced according to the equivalent magnetic circuit method. Based on the regression principle of the LS-SVM, the prediction model between the currents in control coils and the rotor displacements is established. Also, the performance parameters of LS-SVM are optimized by the IPSO algorithm, which realizes self-sensing modeling of rotor displacement. The simulation system for self-sensing modeling of rotor displacement for six-pole radial HMB is constructed, and floating experiment, static suspension experiment, dynamic suspension experiment, and disturbance experiment of the rotor are carried out, which verify the robustness and stability of the self-sensing method proposed. [ABSTRACT FROM AUTHOR]

An optimal ampere-turns design for a long-distance dipole-coil-based inductive power transfer (IPT) system for maximum power efficiency is proposed in this article. Assuming that specific requirements, which are the target load power, the physical size of the transmitting (Tx) and receiving (Rx) coils, and the distance between the Tx and Rx coils, are given, quantitative analyses on the optimal ampere-turns of loosely coupled Tx and Rx coils to satisfy the constraints with maximum power efficiency have been conducted in this article. With the proposed design process, the IPT system is expected to be designed and fabricated with minimal cost and time. The maximum experimental error is only 8.8% when the delivery power ranges from 20–200 W in the experiment results, thus demonstrating that the method proposed in this article can suggest a viable design direction of the IPT system. [ABSTRACT FROM AUTHOR]

It is more efficient to employ inductive power transfer (IPT) systems to charge automated guided vehicles (AGVs) than traditional plug-in systems. In order to provide independent and different charging power for the driven system and the control system of AGVs simultaneously, this letter proposes a coaxial dual-receiver structure and a decoupling circuit, which utilizes a passive component connected with two receiving coils to cancel out the mutual inductance between each other. By using this decoupling method, the two receiving coils could be treated as independent receivers without precise placement or additional transformers. First, the decoupling model is analyzed in detail, and the value of the decoupling component is given without any restriction of the ratio of their current. Then, the structure of the dual receiver is designed. Finally, an IPT system with one transmitter and dual receivers is built to verify the feasibility of the proposed method. Experimental results show that when one of the loads varies from 20 to 80 Ω, the voltage fluctuation of the other load is as small as 1.36% with decoupling, whereas 54.46% of voltage fluctuation without decoupling. The results validate that the proposed method is suitable for the application requiring dual independent outputs in the same equipment. [ABSTRACT FROM AUTHOR]

This article presents a new magnetic equivalent circuit (MEC) for a real-time emulation of a 16/10 segmented-rotor switched reluctance motor (SSRM) based on the hardware-in-the-loop (HIL) configuration. The proposed real-time MEC contains the reluctances of slot leakage, air gap, and iron core of the SSRM. To speed up the emulation, a ten-by-ten matrix system is developed for the MEC. A new algorithm is proposed to solve the matrix system to reduce the computation time. To carry out the experiment, the HIL is employed in this article. It can provide a precise and real-time condition for the application of the new method. In the test bench, the field-programmable gate array provides an operating platform to realize the real-time emulation of the MEC model. As verified, the proposed real-time MEC model benefits the real-time emulation and the performance evaluation of the SSRM. The proposed method can be applied to other switched reluctance motors as an efficient way to verify their real-time characteristics with high accuracy and low emulation cost. [ABSTRACT FROM AUTHOR]

A high-stability flat-top pulsed magnetic field (FTPMF) is strongly needed for some scientific studies, such as nuclear magnetic resonance and specific heat measurement. This paper presents a new linear flat-top regulation bypass circuit to generate a high-stability FTPMF based on a battery bank power supply. The bypass circuit consists of insulated-gate bipolar transistors (IGBTs) in parallel that operate in the active region and are free of switch ripples. To achieve precise control of the IGBT current, the influence of the Miller effect and the nonlinearity of the IGBT's transfer characteristic are studied in detail. Then, a dual-feedback loop is designed and analyzed. A prototype consisting of a 1000 V/30 kA battery bank and a bypass circuit of 1700 V/3600 A IGBTs is developed. An FTPMF with a field/duration of 23.370 T/100 ms and a stability of 64.2 ppm has been achieved. [ABSTRACT FROM AUTHOR]

Bidirectional inductive power transfer (BD-IPT) systems facilitate wireless grid integration of electric vehicles to offer vehicle-to-grid (V2G) services. This paper presents a novel push–pull parallel resonant converter-based BD-IPT system to provide a more efficient and cost-effective solution to wireless V2G technologies. The proposed system integrates the functionality of bulky passive elements into a double-D type magnetic coupler to achieve high power density. A phase-delay control technique is proposed to reduce the startup transients as well as to regulate bidirectional power flow between the primary and secondary sides of the push–pull converters. A zero-voltage switching zone is identified to maintain safe operation of the system. Both the operating principles and control philosophy of the converters are described, and a detailed mathematical analysis is presented. The effectiveness of the proposed system is verified by building a 3.3-kW prototype system. The experimental results show that the peak power transfer efficiency reaches 96.5%, and the efficiency remains high under a wide range of operating conditions. [ABSTRACT FROM AUTHOR]

To predict the dynamic performance or realize advanced control for switched reluctance machines (SRMs), knowledge of the flux-linkage characteristics is essential. These characteristics can be determined by a magnetic equivalent circuit (MEC), a finite-element method (FEM), or measurements. The MEC and FEM results are usually not accurate, while results from measurements are accurate, but very expensive and time-consuming. In this paper, a new calibration strategy is proposed to quickly obtain flux-linkage characteristics with low effort. First, flux-linkage samples at aligned and unaligned positions are obtained from fast measurement. Then, a reluctance calibration strategy is utilized to calibrate the airgap and iron reluctance parameters with measurement values. The calibration results are compared with complete measurement results, and good agreements can be found, which verifies the feasibility and accuracy of the proposed strategy. Furthermore, a simulation model is built in MATLAB with the calibration results, and dynamic performances at different speeds and control strategies are simulated and compared with experiments for further validation. In addition, the applicability of the proposed method to the variation of some parameters, such as material, airgap, and winding placement, and different topologies is discussed as well. The presented strategy can serve as a low-effort way to obtain accurate flux-linkage characteristics of SRMs. [ABSTRACT FROM AUTHOR]

This paper presents the circuit design and magnetic integration of push–pull class-E inverters for wireless power transfer (WPT) up to megahertz. The design criterion for achieving zero-voltage switching (ZVS) of a class-E inverter with coupled windings is derived mathematically. The approaches of magnetic integration for push–pull class-E inverters are analyzed and compared. Then, a new magnetic structure with hybrid magnetic materials is proposed to build the integrated inductors with either coupled windings or uncoupled windings. A 3-MHz WPT system is built to verify the analysis. The detailed comparison of the class-E inverters with magnetic integration is presented in terms of switch voltage, efficiency, harmonic currents, and thermal distribution. In the optimized design example, the switches keep ZVS over the entire load range without using any closed-loop control. The system efficiency reaches 87.1% at 350-W output power. [ABSTRACT FROM AUTHOR]

A magnetic integration method of single- and multi-stage electromagnetic interference (EMI) filters is presented. Common-mode and differential-mode inductors are integrated into a single magnetic core unit to significantly reduce the filter volume. A 500-W silicon carbon (SiC) single-phase inverter is used as an experimental platform. The magnetic integration model is designed, and the magnetic circuit analysis is conducted in a simulation to ensure that the core will not reach magnetic saturation under full-load conditions. The feasibility of the proposed method is verified by an EMI test in a simulation and an experiment. Compared with a traditional discrete passive EMI filter, the proposed integrated EMI filters can reduce 40% of the total volume and 69% of the inductor volume in an integrated single-stage EMI filter with satisfactory EMI suppression ability. Although the weight of integrated inductor of integrated multi-stage EMI filter (IMSEF) has 23.8% increment, the IMSEF shows a better EMI suppression ability and 4.6% inductor volume reduction. [ABSTRACT FROM AUTHOR]

Powder cores have been gaining much attention as one of the attractive magnetic cores used in power converters due to their superior features such as high saturation flux density and their capability to suppress fringing flux due to the distributed airgaps. However, powder cores have a unique feature that the relative permeability of the magnetic core varies depending on the magnetic field intensity. The comprehensive modeling of variable relative permeability, design method of powder cores, and computer simulation methods are not well discussed in the relevant literature. This paper proposes a novel modeling, magnetic design method, and simulation technique considering dc superimposition characteristics of powder cores. The modeling method relies on a simple novel model equation representing the behavior of the variable relative permeability under the dc current superimposition condition, which is helpful to evaluate the performance of powder cores and to properly design various magnetic components. In this evaluation, five different magnetic powder cores are used to show the accuracy and properness of the proposed method. Theoretical analysis has been presented and the effectiveness of the proposed methods has been evaluated through simulation and experimental tests. [ABSTRACT FROM AUTHOR]

This paper presents a new low cost, non-invasive, and isolated current sensing technique for the grid-tied photovoltaic (PV) flyback microinverter. This is accomplished by using the flyback transformer itself as a current sensor, achieved by introducing a tertiary winding to the flyback transformer. The mathematical integration of the tertiary winding's open circuit voltage through a ground-clamped-integrator results in the sensing of the magnetizing current. Since the magnetizing current is a combination of both primary and secondary current, control of both grid current and maximum power point tracking (MPPT) is implemented by sensing only the magnetizing current. This allows the PV, primary, secondary, and the grid current loops to be free of any invasive current sensors. Moreover, controlling the magnetizing current provides an alternative solution to an inherent problem with continuous conduction mode (CCM), the control complexity. Linear ramping and de-ramping of the magnetizing current allows for a set–reset hysteresis control to be implemented, resulting in CCM control simplicity that is akin to the boundary and discontinuous conduction mode. A grid-tied microinverter prototype is presented for verification, achieving the following experimental result: 1.9% grid current THD, 0.9988 power factor, above 99% static MPPT efficiency and dynamic efficiency of 98.50%. [ABSTRACT FROM AUTHOR]

This paper presents a new dc/ac inverter for low-power applications (i.e., high-voltage, low-current applications), which offers soft switching of the power semiconductors and low output current ripple. In the proposed power circuitry, a novel ripple steering approach is used that can provide soft switching for the power semiconductors and significantly attenuate the high-frequency current ripple of the inverter. The proposed ripple steering technique utilizes the switching frequency and the duty cycle in order to perform the aforementioned tasks. Basically, the ripple steering technique steers the energy of the ripple to the output capacitances of the power semiconductors in order to provide the soft-switching condition. Theoretical analysis, simulation results, and experimental results verify the feasibility of the proposed technique and demonstrate the superior performance of the proposed inverter. [ABSTRACT FROM AUTHOR]

An LLC resonant converter would have light-load voltage regulation problems due to the effect of parasitic capacitances in a high-frequency range. In this paper, an energy feedback control method is proposed to improve the light-load regulation capacity by using synchronous rectifiers (SRs). The SR bridges are controlled ahead of the primary inverter bridges to deliver the energy from load to source, reducing the output voltage independent of the load. Then the desired voltage can be achieved even in no-load conditions by regulating the operation time of the energy feedback mode. The gain, voltage ripple, and efficiency performances of the proposed control method are discussed based on the precise analysis and an accurate model of the converter. Moreover, the light-load operations of the LLC resonant converter are analyzed deriving the critical load condition. Finally, the proposed control method is verified by the experiments of a 12 V/8 A LLC resonant converter prototype. [ABSTRACT FROM AUTHOR]

To improve misalignment tolerance for an inductive power transfer (IPT) system, a third-coil is employed to reversely connect with the primary coil of the loosely coupled transformer (LCT) in series. The LCT with a third-coil (LCT-TC) not only can improve the misalignment performance in x- and y-directions, but also does not affect the inherent output characteristics (such as constant current or voltage output) of original compensation topologies. In addition, the proposed approach can keep the IPT system operating with relatively high efficiency against misalignment. Then, a detailed design method of LCT-TC is presented. Finally, a double-side LCC-compensated IPT system is chosen as an example to verify the feasibility of proposed LCT-TC. A 3.4-kW prototype is constructed, and experimental results show that the proposed method has a good misalignment performance. The LCC-LCC IPT system with LCT-TC can retain 96% of the well-aligned power at 40% misalignment, and the end-to-end (dc–dc) overall system efficiency is at least 92%. Besides, the fluctuation of the output current is [–2%, 5%] while the load varies from 15 to 34 Ω within 40% misalignment. [ABSTRACT FROM AUTHOR]

This paper presents the three-phase custom power active transformer (CPAT), characterized by the integration of power electronics in a transformer to facilitate grid services. Such integration enables step-up/step-down transformation between primary and secondary as well as shunt and series compensation services to the power system through a single transformer. The CPAT can empower the grid with flexible ac transmission system and power quality services such as power flow control, reactive power compensation, active filter, and voltage regulation through a single monolithic transformer. In this paper, designs of the three-phase CPAT are realized and analyzed based on their equivalent magnetic circuit as well as their structure requirements and constraints. Simulation analysis of the three-phase CPAT clarifies its capability to actively regulate power flow between the primary and secondary windings as well as achieve grid harmonic current compensation. Moreover, through real-time simulations and an experimental prototype, the merits and performance of the three-phase CPAT were further validated. [ABSTRACT FROM AUTHOR]

Cascaded H-Bridge converters in medium-voltage (MV) applications have all the dc link capacitors supplied from external source through a multiwinding phase-shift transformer. This type of transformers has a complex winding geometry, which leads to unbalanced leakage flux paths. The unbalance affects the dynamic behavior of the converters. This work proposes a modeling approach, which realistically captures the unbalance in the leakage flux path of phase-shift transformers, using permeance magnetic circuit. The model can be seamlessly integrated into system-level simulation of power electronic circuits. Taking advantage of the repetitive structure of the windings, the model requires very limited number of parameters, which can be easily obtained from the geometry data together with only a few experimental tests. The fidelity of the model is experimentally confirmed on a phase-shift transformer from a commercial MV drive system. [ABSTRACT FROM AUTHOR]

Magnetic pulse compressors, based on magnetic switches, are considered as competitive candidates for high-voltage pulse generation. It is generally believed that the lack of operating-parameter tunability of these devices is currently one of the crucial factors limiting their applications. In this paper, an adjustable high-power magnetic pulse compressor, which is deemed as the key component of a power supply system, is investigated theoretically and experimentally. Dominant parameters of the compressor, including the compression ratio, the saturation time, and the peak voltage, can be regulated, which is beneficial for widening the application areas of power supply systems. Specifically, the prepulse of the magnetic pulse compressor is studied as one of the key parameters. A two-stage magnetic pulse compressor was then setup and when the charging time of the primary source was alternated between 19 and 25 μs, pulses with rise-time of 1 μs were achieved with good repeatability. This in turn verified the tunable capacity of the device. When applied in a solid-state high-voltage pulse generator, the pulse compressor successfully enabled the generation of intense electron-beam with peak power over 5 GW, peak voltage of 380 kV, pulse width over 170 ns, and repetitive rate of 20 Hz. The device has been successfully used for research on plasma science and for driving the sources of high-power microwaves where the requirements on the device often vary substantially. In the latter application, based on the high reliability of the solid-state pulse generator, optical diagnosis has been conducted of the plasma expansion characteristics of the magnetically insulated coaxial diodes cathode, in order to analysis the mechanism of the pulse shortening phenomenon. Experimental results show reasonable agreements with the analyses. [ABSTRACT FROM AUTHOR]

In this paper, a position estimation method is proposed to accurately measure the rotor position of a switched reluctance motor equipped with embedded sensing coils under both unsaturated and saturated conditions. This method effectively solves three key problems existing in traditional methods based on embedded sensing coils, which are the mutual induced voltage effect, the main magnetic circuit saturation effect, and low accuracy of the rotational speed estimation in near-zero-speed regions. To address the first problem, the sensing coils are connected into a special designed structure. Then, the sensing coil inductance, which varies with the rotor position, is encoded by some voltage signals. After that, a novel hybrid harmonic filtering algorithm based on a delay filter and a coordinate transformation is proposed to remove the dc, even harmonic, and 3nth harmonic components of the demodulated voltage signals, according to which the rotor position can be estimated continuously and accurately. By applying this hybrid harmonic filter, the main magnetic circuit saturation effect on the position estimation has been indirectly avoided. To solve the third problem, a starting algorithm based on the voltage thresholds is proposed, and a rotational speed estimation method is developed. Detailed experimental results are provided to verify the validity of the proposed methods. [ABSTRACT FROM AUTHOR]

Ferrite materials are widely used for magnetic cores in power electronic converters. The hysteresis effect of the material leads to power loss and harmonic distortion. In order to predict the behavior of the magnetic component in the system environment during the design phase, accurate system-level time-domain simulation is desired. This paper proposes an approach to model the frequency-independent magnetic hysteresis effect of ferrite core materials in magnetic circuits based on the permeance–capacitance analogy. The model is able to accurately reproduce the per-cycle energy loss and equivalent permeability of the hysteresis loops under excitation in a wide range of amplitudes. [ABSTRACT FROM AUTHOR]

This paper proposes a hybrid electronic and magnetic structure named a variable-inverter-rectifier-transformer (VIRT) that enables a transformer with fractional and reconfigurable effective turns ratios (e.g., 12:0.5, 12:2/3, 12:1, and 12:2). This functionality is valuable in converters with wide operating voltage ranges and high step-up/down, as it offers a means to reduce the turns count and copper loss within the transformer while also facilitating voltage doubling and quadrupling. These properties are especially beneficial for miniaturizing the transformer stage in many power electronics applications, such as universal serial bus wall chargers. We introduce the principle of operation of the structure and present models for its magnetic and electrical behavior. The instance of VIRT described in this paper comprises four half-bridge switching cells distributed around a planar magnetic core and connected to two “half-turns” wound through that core. By controlling the operating modes of the half-bridge cells, we gain control over the flux paths and current paths used in the transformer, and this hybridization enables fractional and reconfigurable effective turns ratios. An experimental prototype integrates the VIRT with a stacked-bridge LLC converter to accommodate a widely varying input (120–380 \textV\text{dc}) and output (5–20 \textV\text{dc}), and VIRT is shown to be highly beneficial in keeping efficiency high over this wide output voltage range. [ABSTRACT FROM AUTHOR]

This paper presents a generalized power-decoupling control scheme using a multiport isolated bidirectional converter for a multilevel inverter, which has multiple dc links inside. In the proposed method, a single power-decoupling capacitor is needed for all the dc links in the multilevel inverter cell. First, a prototype of the power-decoupling concept of individual H-bridge cells in the multilevel inverter is proposed, using a separate power-decoupling circuit. Then, a more advanced one-step power-decoupling method is proposed. The lifetime and reliability of the multilevel inverter is improved as film capacitors replace the large capacitance electrolyte capacitors. A multi-input ports/single output voltage-fed dual half-bridge converter (MDHB) is used for the power-decoupling circuit. A steady-state analysis for the peak and root mean square of the MDHB current is carried out for the loss breakdown. The currents are functions of the switching frequency, phase shift, leakage inductance, turn ratio, and output voltage, which make the multiport transformer design complex. A design methodology is proposed, which takes into account the design of the copper and core losses as functions of the switching frequency and number of turns. Furthermore, a special winding method for the input port is illustrated to obtain identical leakage inductances for the uniform current distribution in the multiport transformer. The proposed MDHB employs a current-sensorless power-decoupling control that contributes to the spontaneous ripple rejection of all the dc links without individual link current information, as well as to the cost and size reduction. Hence, the ripple-rejection controller is independent of the control configuration of the multilevel inverter, and also available for universal applications of various inverter topologies. Since the primary-input ports of MDHB share a single magnetic core for interfacing the ripple power to the unified secondary ripple capacitor, the controller design becomes difficult in considering the dynamic interaction among the ports, along with the average-voltage control loop design. In this paper, the dynamic analysis and controller design procedure of the circuit is also presented. The power decoupling is achieved even when the ripple frequency is other than the double frequency of the inverter output, since the single-pole transfer function of the small-signal model of the MDHB allows sufficient phase margin, along with high bandwidth. The proposed power-decoupling method for the multilevel inverter is validated with the help of simulation and 1.2-kW hardware prototype experimental results. [ABSTRACT FROM AUTHOR]

10 kV integrated gate-commutated thyristor (IGCT) has been recently developed and has the potential to push wind turbine systems to higher power and voltage rating. Converters employing IGCTs need snubber and over-voltage protection circuit to limit the rate of current's rising and peak over voltage across IGCT during turn-on and -off state, respectively. The conventional resistor-capacitor-diode (RCD) snubber which is used in such power converter dissipates a significant amount of power. In order to reduce the amount of energy lost by the conventional RCD snubber, this paper proposes flyback-type snubber. Flyback-type snubber not only meets all of the IGCTs characteristics during on- and off-state but also significantly saves the power loss. The proposed flyback-type snubber can save up to 73% of the loss in conventional di/dt snubber circuit according to the PLECS magnetic simulation of three-level neutral point clamped grid side converter. The experiments are performed using IGCT stack. Flyback transformer yields the effectiveness of the proposed snubber in wind turbine systems. [ABSTRACT FROM PUBLISHER]

Recently, a magnetic pad called the tripolar pad (TPP) has been introduced for inductive power transfer (IPT) systems. This paper evaluates the effective coupling factor and leakage magnetic field of a 20-kW IPT system that uses a combination of TPP and circular pad (CP) topologies over a range of lateral displacements. The results show that the effective coupling factor and the leakage magnetic field of the TPP–TPP system are substantially better when the secondary is displaced away from ideal alignment. Leakage magnetic field is reduced up to 43% compared to the CP–CP system at the worst-case misalignment, which is due to the ability of the TPP–TPP system to generate and capture different types of magnetic field shapes. Simulation methods for both the TPP and CP are validated in the laboratory using a 2-kW system operating at 85 kHz. [ABSTRACT FROM PUBLISHER]

This paper presents a new transformer, i.e., the custom power active transformer (CPAT) which integrates both series and shunt power conditioning through power electronics into a single transformer. This is achieved through a distinct design of the magnetic circuit and auxiliary windings of the transformer. In this paper, a single-phase CPAT is proposed as well as a preface into its extension to multiphase systems. Through its magnetic equivalent circuit model, several design considerations and control limitations are revealed in the paper. Analysis of the resulting CPAT structure shows some prospects in material saving as well as size and cost reduction when compared to the traditional multitransformer-based configuration. In this paper, the proposed single-phase CPAT is utilized in a distribution system application, where the control architecture is designed to attenuate voltage and current distortions at both the load and the grid side, respectively. Performance and effectiveness of the proposed CPAT are evaluated through simulation and experiments. [ABSTRACT FROM PUBLISHER]

In this paper, a type of low-frequency integrated ac inductor without inductance coupling is proposed for differential rectifiers/inverters. The objective is to increase the power density of these converters by replacing their two bulky and low-frequency ac inductors with the proposed integrated ac inductor, which is much more compact. The principles of the proposed magnetic integration approach and the optimization procedures are explained in detail. An integrated inductor with 34.9% reduction in volume as compared to its discrete-inductor counterpart is designed and tested via simulations using the software Maxwell. Three integrated inductor prototypes with a core volume reduction of up to 30.9% are constructed in the laboratory and are applied to a buck differential rectifier for experimental verification. Their performance in terms of coupling effect, thermal temperature, power efficiency, and system switching frequency is examined. [ABSTRACT FROM AUTHOR]

Inductive power transfer (IPT) converters are resonant converters that attain optimal energy efficiencies for a certain load range. To achieve maximum efficiency, it is common to cascade the IPT converter with front-side and load-side dc/dc converters. The two dc/dc converters are normally controlled cooperatively for the requirements of output regulation and maximum efficiency tracking using a control technique based on perturbation and observation, which is inevitably slow in response. In this paper, a decoupled control technique is developed. The load-side dc/dc converter is solely responsible for output regulation, while the front-side converter is responsible for impedance-matching of the IPT converter by controlling its input-to-output voltage ratio. The controls are linear and therefore fast. DC and small-signal transfer functions are derived for designing the control parameters. The performances of fast regulation and high efficiency of the IPT converter system are verified using a prototype system. [ABSTRACT FROM AUTHOR]

The high-frequency sideband current harmonics are the inherent concomitants of applying sinusoidal pulse width modulation (SPWM) in permanent-magnet synchronous machine drives. Abundant spatial interharmonic magnetic field components in fractional-slot concentrated-winding (FSCW) interior permanent-magnet synchronous machine (IPMSM) render it very susceptible to electromagnetic radial vibration. In this paper, a universal analytical interharmonic model of magnetic field in FSCW IPMSMs is proposed, and further, it is employed to develop the sideband radial force density model of SPWM. Both comprehensive finite-element analysis (FEA) simulations and experimental tests are carried out to underpin the validity of the analytical models. The close agreements between the analytical, FEA, and experimental results have revealed that the proposed analytical approaches can deliver accurate sideband current and vibration predictions with minimum computational efforts and suffice for fast preliminary assessments. In addition, the validated analytical models can offer detailed and insightful revelations of various factors that affect the corresponding sideband vibration components. [ABSTRACT FROM PUBLISHER]

High power density and high efficiency in dc/dc converters are required in various applications such as the automotive application. Interleaved multiphase circuits with integrated magnetic components can fulfill these requirements because passive components occupying significant space in power converters can be downsized without high-switching frequency driving of power devices. However, dc-biased magnetization is a drawback of integrated magnetic components because of unbalanced inductor average currents. This imbalance arises from the tolerance among the phase components. To overcome this problem, inductor average current control is implemented in interleaved multiphase dc/dc converters. Nevertheless, the imbalance cannot be completely eliminated because the current sensors inserted into each phase have gain errors. The purpose of this paper is to present a magnetic design method to improve the immunity to unbalanced currents. A comprehensive analysis is carried out with two main objectives: to prevent magnetic saturation, which may arise due to the current unbalance and to downsize the magnetic components by selecting the optimal coupling coefficient taking into consideration the maximum permissible percentage of unbalanced currents. Simulation case studies are presented to support the analysis. Finally, a 1-kW prototype of the interleaved boost converter is built to validate the accuracy of the design method. [ABSTRACT FROM PUBLISHER]

This paper presents a power electronics design for the piezoelectric actuators of an insect-scale flapping-wing robot, the RoboBee. The proposed design outputs four high-voltage drive signals tailored for the two bimorph actuators of the RoboBee in an alternating drive configuration. It utilizes fully integrated drive stage circuits with a novel highside gate driver to save chip area and meet the strict mass constraint of the RoboBee. Compared with previous integrated designs, it also boosts efficiency in delivering energy to the actuators and recovering unused energy by applying three power saving techniques, dynamic common mode adjustment, envelope tracking, and charge sharing. Using this design to energize four 15 nF capacitor loads with a 200 V and 100 Hz drive signal and tracking the control commands recorded from an actual flight experiment for the robot, we measure an average power consumption of 290 mW. [ABSTRACT FROM PUBLISHER]

In order to substantially improve multiphase interleaved bidirectional buck/boost converter's (IBC) current ripples and efficiency, this paper proposes a more symmetric four-phase inverse coupled inductor (ICI) structure and its comprehensive design solution. First, this paper presents a more symmetric four-phase ICI structure which has the advantages of larger inductance values and more symmetric inductance parameters comparing to existing four-phase ICI of similar volume. Second, this paper presents the four-phase ICI's two magnetic circuit analytical models, the four-phase ICI's inductance calculation results from the two models are verified with Maxwell 3-D simulation and experiments. Third, this paper presents the four-phase ICI's comprehensive design solution with the two models and Maxwell 3-D piecewise linear transient simulation. Finally, the advantages of the four-phase ICI are verified with experiments. When the four-phase ICI is used in multiphase IBC, the IBC will have smaller current ripples, more symmetric phase current waveforms, lower output voltage ripple, and higher efficiency both in buck and boost modes. [ABSTRACT FROM PUBLISHER]