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This paper proposes a resonant switching cell model to analyze and design the single-ended resonant dc–dc converters. The single-ended zero-voltage switching (ZVS) converters such as the Class E converter are efficient for megahertz switching because they feature low turn-on and turn-off switching losses. Also, they use only a ground-referenced switch, allowing a simple gate drive circuit. In this paper, we investigate the single-ended resonant converter with the small input inductance, whereas the conventional Class E converter has a large input inductance. The main contribution of this paper is to propose the resonant switching cell as an analytic model that simplifies the analysis and the design of the resonant dc–dc converters. Furthermore, this paper presents the design method of the resonant switching cell model for minimizing the resonant current magnitude and conduction loss while the converter maintains ZVS property. The experimental results from a 10-MHz GaN-based prototype demonstrate the feasibility and effectiveness of the analysis and design based on the proposed resonant switching cell model. [ABSTRACT FROM AUTHOR]

Three-phase grid-connected inverter modeling depends on the equivalent resistance and inductance between the inverter and the grid. However, these parameters are not fixed during the operation of the inverter and vary with the operating conditions. In this paper, a new globally stable adaptive controller is proposed to estimate these values online and update the controller during its operation. A model reference adaptive system (MRAS) based on two fictitious quantities with no physical significance is utilized, namely $M = v \cdot i^*$ and $N = v^* \times i$ , where $v$ and $i$ are the steady-state values of voltage and current in synchronously rotating frame of reference. Detailed stability analysis of the proposed estimation technique has been presented using a Lyapunov energy function-based approach proving the global stability of the technique. Small-signal modeling and analysis of the proposed scheme has also been presented so as to understand the local dynamics of the system. The guidelines to select the parameter of the proposed MRAS system along with updating the controller are elaborated in this paper. Detailed simulation based on MATLAB/Simulink and PLECS, along with experimental studies through a Texas Instruments TMS320F28377S microcontroller, validates the feasibility of the proposed control architecture. [ABSTRACT FROM AUTHOR]

With the increase in number of VSC based HVDC systems, it is inevitable that there would be interconnections with weak ac grids. The paper presents the analytical basis for identifying coupling in the power loops which is dependent on grid inductance and operating point by utilizing the impedance based modeling technique. The formulation is used to define an inverse-based decoupling outer-loop controller for VSC-HVDC system. The concept is extended to HVDC grids and it is shown that the gains obtained using simple inverse may lead to instability. Robust controller tuning with pole-placement and minimization of $H_\infty$ norm is presented for HVDC grids, which form a restricted feedback system. The results show that the proposed method of decoupling results in effective decoupling of the power loops over a large range of grid inductance values as compared to that with traditional vector control. The system stability is also maintained over a large range of grid inductance values and PLL gains when a sudden variation of parameters is considered. The stability margins can be enhanced by pole-placement. The observations from the small-signal models are confirmed using detailed time-domain simulations. The proposal is expected to be useful in controller design for single VSC as well as HVDC grids, especially, during planing stage. [ABSTRACT FROM AUTHOR]

This paper investigates the contribution of each order inductance harmonic to the torque (both average torque and torque ripple) of multiphase doubly salient synchronous reluctance machines (DS-SRMs). Such machines are similar to switched reluctance machines but supplied with sine wave currents. The investigations in this paper are as follows. First, a general analytical torque model based on Fourier series analysis of inductances has been built for machines with different phase numbers, slot/pole number combinations, and also winding configurations. The instantaneous torque for DS-SRMs with any given phase number can then be accurately predicted. Using such model, contribution of each order inductance harmonic to torque can be investigated separately. It is found that the torque ripple frequency of the DS-SRM only depends on phase number. For example, for an m-phase machine, there will be m $\times $ kth-order torque ripple if mod(mk, 2) = 0, where m is the phase number and k is a natural number. This paper also explains why certain phase numbers inherently produce lower torque ripple than others. The findings in this paper provide a future direction for potential torque ripple reduction methods either from machine design or advanced control. The simulations have been validated by experiments using a six-phase DS-SRMs. [ABSTRACT FROM AUTHOR]

The intelligent estimation method (IEM) is based on approximations which can be described by the configuration and behavioral characteristic of the problem. This paper used the IEM in time domain (IEM-TD) which can be utilized to predict the current distribution and maximum current density. A detailed IEM technique to compute the current distribution over the surface of a rail, current profile around the rail, and maximum current density ( J\max) formula will be presented in this paper. The current distribution is computed for rectangular and circular rails that are shown in color figures. Finally, this paper considers the effect of the rail dimensions and material on these parameters that are shown in several figures. The results of this paper are compared to other published studies and FEM simulation. [ABSTRACT FROM AUTHOR]

This paper deals with a multilevel ac–ac double conversion system that uses the intercell transformer (ICT) for applications which include generating systems and the interfacing of renewable energy sources with the utility grids. Each phase of the proposed configuration is formed through the ICT interleaving operation of two multilevel 5-level E-type legs to achieve the 3-phase 5-level back-to-back E-type converter (3Φ5L BTB E-type converter). The analytical procedure to select the inductance and capacitance values of both the input and output filters is described in the paper. Furthermore, the design and implementation of the input/output ICTs and inductors is discussed. The simulation and the experimental results on the 20-kVA interleaved 3Φ5L BTB E-type converter prototype are presented to validate the proposed analysis. [ABSTRACT FROM AUTHOR]

This paper presents a dc–dc input-parallel output-parallel (IPOP) converter configuration for renewable energy integration with medium-voltage dc grids. A full-bridge zero-current-switching (FB-ZCS) converter with voltage-doubler output is proposed as the fundamental module. To achieve smooth current commutation and ZCS, the leakage inductance of transformer and a resonant capacitor across its secondary are utilized. This resonant capacitor is always charged to its full-rated capacity irrespective of converter loading and requires a dedicated charging interval resulting in duty-cycle loss. For a given leakage inductance, a large resonant capacitor is required for higher current ratings. With a single-centralized converter, these operational and design constraints result in significant duty-cycle loss, restricting the operation range. This paper proposes an IPOP configuration for high-power applications. Phase shedding at reduced loading ensures that individual modules are operated optimally. Input inductance requirement in modules is reduced due to interleaving of the input current. Additionally, voltage stress across converter components and input current ripple are reduced by 50% in the proposed converter modules. Steady-state operation, modeling, current-sharing control, start-up, and shutdown of modules in the IPOP configuration are demonstrated using simulations. Experimental results on a scaled-down prototype are presented to validate its operation. [ABSTRACT FROM AUTHOR]

Deadbeat predictive current control (DPCC) can predict motor behavior based on SPMSM model. However, during the operation of motor system, motor parameters (such as stator inductance and flux linkage) vary frequently according to different working conditions, which may lead to controller parameter mismatch, causing current harmonic content to increase and efficiency to decrease. In order to solve these problems caused by parameter variation, first, this paper proposes a current prediction error model by considering uncertainties of model parameters. Second, stator inductance and flux linkage are decoupled based on current prediction error model, which can reduce the interaction between parameters. Finally, the Kalman Filter (KF) algorithm is presented to filter the decoupled parameters. It is shown that the stator inductance and flux linkage can be identified accurately and the complexity of computation can be simplified. The traditional DPCC method, Extended Kalman Filter (EKF) based DPCC method and the proposed DPCC method are comparatively analyzed in this paper. Simulation and experiment indicate that the proposed parameter decoupling identification method can effectively reduce current harmonic content, current fluctuation and current tracking errors caused by parameter mismatch. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the direct- and quadrature-axis inductances for linear tubular actuators with permanent magnet arrays, highlighting and featuring how they are affected by the end effects. A semi-analytical and an experimental analysis are performed to prove the influence of end effects on self- and mutual inductances. The synchronous parameters, i.e., d - and q -axis inductances of the actuator, are determined using a semi-analytical method and an experimental method. Once the synchronous parameters are all identified, high performance control methods (such as direct force control and vector control) may be implemented. [ABSTRACT FROM AUTHOR]

In this paper, extremely subwavelength evanescent Bessel beam launchers are designed, simulated, and experimentally tested to generate nondiffracting beams. The launching apertures consist of several concentric coils strategically positioned to spatially filter the fields of a single actively fed radiating coil. The geometrical properties of each coil element of the aperture were obtained through a procedure based on the orthogonal matching pursuit algorithm in order to maximize the quality of the launched beam while minimizing manufacturing complexity. Two apertures with outer diameters of 64 and 48 mm were fabricated and the generated field distributions were measured at the operating frequencies of 13.66 and 13.86 MHz, respectively. Desired and measured field distributions exhibited correlations above 0.9 even as the distance from the aperture was increased, demonstrating the ability of the apertures to approximate the field distribution and harmonic content of a Bessel beam. This paper furthers the study and practical implementation of Bessel beams and other types of beams in extremely subwavelength applications such as focusing, wireless power transfer, magnetic stimulation, and microwave ablation. [ABSTRACT FROM PUBLISHER]

Reluctance coilgun (RCG) is a special coilgun which uses solid ferromagnetic material instead of induction coil as projectile. RCG has shown great advantages and potential in the application of antiterrorism weaponry due to its simplicity, reliability, and excellent controllability. As a compact lightweight pulsed-power supply (PPS), the compensated pulsed alternator (Compulsator) will play a key role in promoting this kind of electromagnetic weapon into practical applications. Focused on a specific RCG which has conductive rails and brushes, this paper deduced the electromagnetic force analytical formula by using the virtual displacement principle and researched the feasibility of the electromagnetic launch design scheme which uses compulsator as the PPS of the RCG system by co-simulation method. Finally, this paper finished tests of the system by taking advantages of a small demonstrative RCG and a scale-model prototype of the compulsator. The results indicate that the design scheme is completely feasible. [ABSTRACT FROM PUBLISHER]

This paper investigates the effects of the dynamic properties of a photovoltaic generator (PVG) on the stability of a grid-connected current-source inverter (CSI)-based photovoltaic system and presents a simple yet effective active compensator to ensure system stability. A detailed equivalent model of the PVG that considers the dynamic resistance, diffusion capacitance, series inductance, and dc cable resistance and inductance is used, and the effects of these parameters are assessed. It has been found that when the PVG operates in the constant-current region (CCR), the phase margin becomes negative in the control-to-input dynamics, which alters the stability of the dc-link current control. The change in the system dynamics when the operating point of the PVG shifts from the constant-voltage region (CVR) to CCR is verified through a detailed small-signal state-space model of the complete system. Furthermore, an active compensator is proposed to ensure stable dc-link current control operation at all operating points of the PVG. The influence of different control parameters on the integrated system dynamics is examined to determine the range of the control parameters required for stable operation. The performance of the proposed system under utility-grid fault, grid voltage parameter variation, weak grid, and changes in insolation level is also evaluated. Detailed nonlinear time-domain simulation results, using a typical utility-scale CSI-based PV system, validate the analytical results and the effectiveness of the proposed active stabilization under different operating conditions. [ABSTRACT FROM AUTHOR]

This paper presents a literature review on magnetically-controlled devices, variable inductors (VI), and variable transformers (VT), and their applications to lighting gears for discharge lamps and/or LED lamps. These current-controlled devices are mainly characterized by nonlinear and non-uniform saturation of the magnetic core. The paper describes the fundamentals and basic operating principle of such devices and provides an overview of existing patents. These patents refer the devices, VIs or VTs, as useful or industrially applicable. Some present one or more claims regarding the construction of the device and behavioral characteristic; others refer to specific applications, such as voltage regulation or universal ballast operation. Afterwards, the paper focuses on the review of specific techniques and circuits taking advantage of the presence of a controlled inductance value, by covering recent applications regarding discharge and solid-state lamp drivers. These applications will show how these multi-winding devices, typically not considered due to their low efficiency, may fulfill an important role and add features to state-of-the-art lamp drivers. [ABSTRACT FROM AUTHOR]

Lightning strikes in substations may result in extremely uneven ground potential distribution, which will threaten the safety and stability of equipment in substation. However, the main parameters for evaluating the performance of grounding grids are grounding resistance and impulse impedance, and little attention is paid to the distribution of the transient ground potential differences. In addition, when measuring the impulse impedance of a grounding grid, the length of the current leads should be very large, which requires a high-capacity impulse generator to suppress the influence of lead inductance on current waveform. In this paper, a test method is proposed for the transient characteristics of grounding grid with the current-return point located in the same grid. The feasibility of the method is illustrated by analyzing the ground impedance between the current injection point and the return point, longitudinal current of the grounding conductor, transient ground potential rise and transient ground potential difference. The effects of parameters such as soil resistivity, lightning waveform, size of the grounding grid, spacing and materials of the grid conductor are discussed to demonstrate that the method can be applied to most substations. Finally, the practicality of the method is verified by experiments in a 220 kVsubstation. [ABSTRACT FROM AUTHOR]

Solid-state transformers (SST) are emerging technologies to replace the conventional low-frequency main transformer (MTR) in railway vehicles. In order to isolate the load side from the AC 25 kV high-voltage (HV) side and to reduce the whole size of the SST, HV insulation and high-frequency transformers should be used in DC/DC converters. Furthermore, due to the severe constraint of installation space and difficulty of heat dissipation management in the bottom of railway vehicles, high-power density and minimum transformer loss should be considered. To satisfy such design requirements of the proposed SST for railway vehicles, high efficiency integrated transformers, which inherently have leakage inductance, are proposed for dual-active-bridge (DAB) converters in this paper. In order to obtain appropriate equivalent leakage inductance for the DAB converters, a calculation methodology for the leakage inductance has been introduced and verified by simulation. Two separated winding structures in the center-core are adopted to improve the core loss, and appropriate winding turns with 60 kV HV insulation capability are selected, according to the proposed design procedure of the integrated transformers. In order to compare the proposed transformers with the conventional transformer having additional inductors and to verify the major characteristics of the transformers, two 125 kW proposed transformers and conventional transformers have been built and evaluated by an 250 kW SST module, operating at 10 kHz switching frequency. Under a 125 kW full-load condition, 99.7% transformer efficiency was obtained by the proposed integrated transformers, which are 4.7% smaller and 7.0% lighter than the conventional transformer. As a result, 26°C maximum temperature improvement has been obtained and 60k V HV insulation capability has been satisfied by the proposed integrated transformers. [ABSTRACT FROM AUTHOR]

The Roebel bar conventional design of large AC machines uses the classical strand-slot inductance model (CSSIM). Suitable alternatives are missing as the CSSIM is favored for its inherent simplicity based on the ideally permeable iron core hypothesis. However, saturated armature slots can lead to high variations of the slot inductance, where the CSSIM cannot represent this precisely. An accurate prediction of the strand inductances is crucial when optimizing the transpositions of large Roebel bars to be competitive on efficiency and low measurement tolerances. This fact is crucial in under-roebeling, having less than a 360-degree transposition over the active part. In the end, the goal is to compensate the winding overhang parasitic field with the slot-parasitic field. This paper proposes a differential strand-slot inductance model (DSSIM) based on the concept of differential inductance (DI). It is compatible with a circuital lumped-element model (LEM) that considers the strand topology, geometrical dimensions, saturation level, and small-scale effects. Numerical simulations showcase the performance improvement of the DSSIM against known models. Finally, a 20-strand prototype of a slot model with actual Robel bar strands corresponding to a simplified bar cross-section in a large AC machine’s slot demonstrates the presented DSSIM’s precision. [ABSTRACT FROM AUTHOR]

In this paper, a new pilot protection scheme for AC line connected to LCC-HVDC inverter based on composite-mode model is proposed. First, taking commutation failure into consideration, 1-mode and 2-mode equivalent instantaneous models of inverter in different operating conditions are built. Second, according to the equivalent instantaneous inductances of inverter in different combinations of operating conditions, the equivalent models of inverter are summarized into 4 operation states. Then, the 1-mode and 2-mode equivalent models are combined to establish the composite-mode model of AC/DC hybrid system. And then, using multi-time section information, the instantaneous inductances of backside composite-mode model are calculated. Thus, protection criterion is constructed on the difference between composite-mode models of in-zone faults and that of out-of-zone faults for fault locating. Finally, RT-LAB simulation tests show that, the proposed method offers high sensitivity and reliability, unaffected by commutation failure. [ABSTRACT FROM AUTHOR]

This paper presents the analyses on the self-sustained oscillation of superjunction MOSFET intrinsic diode. At first, the characteristics of the self-sustained oscillation for the superjunction MOSFET intrinsic diode are identified by the double-pulse switching test. The test results show that the self-sustained oscillation with significant self-amplification phenomenon can be triggered during the reverse recovery transient of superjunction MOSFET intrinsic diode. Based on the Sentaurus TCAD simulation, the self-sustained oscillation is reproduced. The simulation results reveal the root cause of the self-sustained oscillation. Due to the snappy reverse recovery of superjunction MOSFET intrinsic diode, the steep slope of diode snap off current can generate high voltage across the common source inductance, which drives the gate–source voltage and turns on the high-side MOSFET. The unexpected MOSFET turn-on can, in return, enhance the steepness of the current slope when the diode snap off. This leads to a positive feedback process and self-sustained oscillation is generated. In the end, based on the theoretical analyses and experimental results, the necessary methods that can suppress the oscillation are presented. [ABSTRACT FROM AUTHOR]

The challenging demands of pulsed electron beam devices (such as the GESA device) with respect to their pulsed power supply have led to the development of a new semiconductor-based Marx generator. At a maximum output voltage of 120 kV and 600-A pulse current for a duration of up to 100 $\mu \text{S}$ , stepwise arbitrary output waveforms are desired. A fast rise time of the generator is achieved by using fast switching circuitry, low inductance capacitors, and a low inductance stage arrangement. For low jitter triggering of all stages and efficient signal transmission, the generator uses an optical bus system for communication. Due to the inherent dynamic load characteristics of the GESA device, the generator features a fast overcurrent protection scheme. This paper presents selected design aspects of the generator and their validation in a small-scale assembly able of delivering up to 8 kV at 600-A load current. [ABSTRACT FROM AUTHOR]

This paper proposes a receiver circuit for inductive ear-to-ear communication. Its input resonance structure, an LCR front-end, is optimized for both a data transmission rate of 100 kbit/s and maximum voltage excess. Following an analytical study, the optimal quality factor $Q_{\text {LCR}}$ is found to be 12.8. Subsequent amplification of ON-OFF keyed bits is performed with a four-stage JFET amplifier, introducing a total amplification of 68.6 dB at a sensitivity of $31.6~\mu \text{V}$. Each stage is implemented in common-source JFET topology containing a current source in its drain path instead of the conventional drain resistor. This modification allows for a per-stage increase in voltage amplification by a factor of 1.87, avoiding extra quiescent current (detailed circuit theory is added). A hardware realization for signal demodulation reconstructs the baseband signal. In combination with a dedicated transmitter, a Hartley Oscillator, the inductive ear-to-ear transmission system demonstrates a reliable functionality over a distance of 18 cm. Operation is possible with a standard 1.5 V battery cell requiring low currents on a discrete benchtop prototype [transmitter: 0.8 mA; receiver: 4.0 mA]. Applying a carrier frequency of 3.175 MHz, the system is fully compliant with ITU regulation 5.115. [ABSTRACT FROM AUTHOR]

In this paper, an analytical torque ripple model for interior permanent magnet synchronous machine (IPMSM) is introduced at first, which can be used to estimate the torque ripple. Then, the inductance variation due to magnetic saturation is analyzed through experimental investigations, which demonstrates that magnetic saturation has a great influence on the inductances, and hence the torque ripple minimization performance. Thus, this paper proposes an online parameter identification approach to estimate the inductances and incorporates them into the torque ripple minimization. The proposed parameter identification approach can estimate the dq-axis inductances accurately such that it brings significant torque ripple minimization improvement for IPMSMs. Numerical and experimental investigations have been conducted to validate the proposed approach based on a laboratory IPMSM. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study on current loop auto-tuning for self-commissioning of sensorless interior permanent magnet synchronous machine (IPMSM) drives. Well-tuned current controllers are essential for both high-performance operation and self-commissioning procedure. However, current controller design parameters, i.e., $L_{d}$ and $L_{q}$ , are not known at the beginning of the self-commissioning procedure where their estimation also has unique challenges. For example, an initial rotor position to determine the actual d- and q-axes is not known. Also, feedback controllers cannot be used in the estimation because they are not tuned yet. As a solution, this paper proposes a method to estimate the spatial inductance map by spatially scanning the motor via sinusoidal voltage injection in a controlled manner. Then it uses the estimated inductance values to tune the current controllers. The proposed method identifies $L_{d}$ and $L_{q}$ values using open-loop voltage injection without needing actual d- and q-axis positions. The whole procedure takes around a second. Practical considerations such as an automatic selection of the injection voltage, and digital control and dead-time effects are carefully addressed. The findings are experimentally verified on a 3-phase IPMSM drive. Furthermore, its applicability to different motor types is also demonstrated. [ABSTRACT FROM AUTHOR]

It is quite often to utilize the transformer leakage inductance in the resonant tank of the LLC resonant converter to allow for a drastic reduction in the converter cost, weight, size, and volume. The effects of the secondary leakage inductance on the operation of the LLC resonant converter are not well discussed in the relevant literature, and it is the purpose of this paper to give an insight into these effects. The contribution of this paper lies in the following: first, highlighting that it is not always an accurate assumption to consider that the values of the primary and secondary leakage inductance are identical, specifically in asymmetric magnetic core structures. Second, it has been disclosed that the well-known coupling factor (k12) cannot properly express the unequalized leakage inductance distribution in the proposed asymmetric transformer. Therefore, the authors bring the primary coupling factor (k1) and secondary coupling factor (k2) into practice to appropriately express the unequalized leakage distribution on the primary and secondary windings, which can be controlled by the allocation of the relevant winding with respect to the air gap, utilizing the noise absorber, and changing the distance between the winding. Several transformer prototypes had been built and experimentally tested to validate these hypotheses. Third, it has been observed that the transformer voltage gain and efficiency can be improved when the transformer leakage inductance is concentrated on the secondary side to avoid the voltage drop inflicted by the relatively large value of the magnetizing current $(i_{m})$ , especially at the light load condition. Fourth, it has been reported that in a transformer structure with a concentrated value of leakage on the secondary side would decrease the resonant tank input impedance, vertically widen the voltage–gain curve of the converter, and eventually increase the frequency control bandwidth with respect to the load variation. Transformer prototypes had been constructed and tested in a 390 V/12 V–220 W LLC resonant converter to evaluate the proposed analysis. [ABSTRACT FROM AUTHOR]

This paper proposes the theoretical framework and the consequent application of the input–output feedback linearization (FL) control technique to linear induction motors (LIMs). LIM, additionally to rotating induction motor, presents other strong nonlinearities caused by the dynamic end effects, leading to a space-vector dynamic model with time-varying inductance and resistance terms and a braking force term. This paper, starting from a recently developed dynamic model of the LIM taking into consideration its end effects, defines a FL technique suited for LIMs, since it inherently considers its dynamic end effects. Additionally, it proposes a technique for the on-line estimation of the inductor resistance, based on model reference adaptive system (MRAS) on-line estimator; it has been exploited for adapting on-line the FL control action versus inductor resistance variations leading to undesirable steady-state tracking errors. The stability of the proposed MRAS on-line estimator has been proven theoretically, adopting the Popov's criterion for hyperstability. The proposed approach has been validated experimentally on a suitably developed test setup, under both no load and loaded conditions. It has been compared firstly with the simplest control structure, which is the scalar $V/f$ control, secondly under the same closed-loop bandwidths of the flux and speed systems, with the industrial standard in terms of high-performance control technique, i.e., field-oriented control. [ABSTRACT FROM AUTHOR]

In this paper, we explore the challenges of implementing resonant converters using silicon carbide (SiC) power devices at high frequency: namely, the issue of high parasitic inductance packages and the ability to drive and enhance the mosfet at these frequencies. Although power circuit designers have many alternative device technologies to choose from, such as silicon and gallium nitride materials, SiC devices have several advantageous attributes especially in high power applications. As a solution, we study the device performance and parasitics of SiC mosfets in different packaging schemes. We further offer a solution to the challenges of driving SiC devices by demonstrating a multiresonant gate driver and use this scheme to drive an SiC mosfet at 30 MHz and a SiC JFET at 13.56 MHz in a class-E inverter, achieving 85.7 $\%$ drain efficiency for the mosfet and 93.8 $\%$ for the JFET. [ABSTRACT FROM AUTHOR]

Thanks to the advantages of high power density and the capacity of bidirectional power transfer, the CLLC resonant converter is widely used in the hybrid ac–dc microgrid as a dc transformer to interlink the ac and dc bus. Since the voltages of ac and dc bus are controlled by the energy management system, the CLLC resonant converter operates under open-loop condition, which means the switching frequency and duty cycle are fixed. As a result, in the hybrid ac–dc microgrid applications, for the CLLC converter, the main concern is not the voltage regulation but the conversion efficiency. This paper focuses on the total power loss optimization and the magnetic design of the CLLC resonant converter based on artificial intelligence (AI) algorithm. In order to optimize the total power loss, an AI algorithm-based two-stage optimal design method is proposed. In the first stage, the total power loss, including the driving loss, turn-off loss, conduction loss of the switches, the power loss of the resonant capacitances, and copper and core loss of the transformer are optimized by the proposed AI algorithm, GA+PSO, and the optimal parameters, including the leakage inductances (Lr1 and Lr2), magnetizing inductance (Lm), and resonant capacitances (Cr1 and Cr2) are derived. In the second stage, the optimal leakage inductances and magnetizing inductance are realized by setting proper distance between the primary winding and the secondary winding (dw), and the thickness of the air gap (da). As for the magnetic design, in this paper, the leakage inductances of a planar transformer are used as the resonant inductances. The equations of dw and da to achieve the optimal leakage inductances and magnetizing inductance are derived. Both the proposed optimal design method and the equations of dw and da are validated by simulations and experiments. [ABSTRACT FROM AUTHOR]

This paper proposes an improved design methodology of the double-sided LC-compensated capacitive power transfer (CPT) system considering the inductance detuning. Compared to the perfect-resonant scenario, this paper shows that the inductance detuning has the benefit to achieve the soft-switching condition for the CPT system, and the output current and internal voltage stresses can also be maintained within the desired range. The contributions of this paper are summarized in three parts. First, it analyzes the impacts of the inductance variations on the system frequency property, including the input current, output current, and internal capacitor voltage stresses. Second, it proposes three principles to detune the inductances as the methodology to design a CPT system. Third, a prototype is implemented, which achieves 368.5 W power transfer across a 400 mm × 400 mm × 4 mm glass layer with 91.8% dc–dc efficiency. Experimental results validate that the proposed design principles are satisfied, showing that the output current is within the desired range, the input soft-switching condition is achieved, and the internal voltage stresses are within the safety limit. Moreover, the efficiency and frequency properties are also validated by the experimental results, showing a wide power range of the high-efficiency operation (higher than 90%) and a wide frequency bandwidth of the soft-switching operation (from 0.96 to 1.12 MHz). [ABSTRACT FROM AUTHOR]

The brushless doubly fed reluctance machine (BDFRM) with a multibarrier rotor has shown great promise in applications where high reliability and low maintenance cost are required, such as offshore wind turbines. This paper presents a systematic analytical analysis and performance characterization of the BDFRM with a multibarrier rotor. First, the airgap magnetomotive force distributions under both open circuit and loaded condition are detailed, based on which a more practical rule than the widely accepted |p1 − p2|≠1 is derived to effectively avoid the unbalanced magnetic pull in such machines. Analytical formulas different from those for slip-ring doubly fed induction machines are then obtained to estimate inductance parameters for circuit modeling and control purposes. Design equations for initial sizing and torque density comparison are also developed, with achievable torque density discussed. Both finite-element analysis and experimental tests are conducted to validate the effectiveness of the presented analysis. [ABSTRACT FROM AUTHOR]

Fractional slot concentrated winding (FSCW) permanent magnet synchronous machines (PMSMs) have been a research hotspot over the past few decades. Recently, the magnetic gearing effect in FSCW PMSMs is revealed along with its gear ratio, which is a function of slot/pole number combination. At the design stage of FSCW PMSMs, one of the key issues is the selection of the slot/pole number combination. This paper shows that the gear ratio can contribute to a proper slot/pole number selection in any multiphase FSCW PMSMs by acting as a unified index for a quick overall performance comparison. In this paper, first, the magnetic gearing effect in FSCW PMSMs is explained and the gear ratio is further discussed. The advantages of adopting gear ratio as the overall performance index over other indices are revealed. The influence of the gear ratio on the winding factor, torque output, cogging torque, inductance, and rotor losses of three- and six-phase FSCW PMSMs is analyzed and validated by experiments, thus proving the analyses. [ABSTRACT FROM AUTHOR]

In this paper, a current controller for a parallel operation of inverters is described. When inverters operate in parallel, it is a well-known fact that the inverter current is composed of the average current (AVC) and the zero-sequence circulating current (henceforth ZSCC), which inevitably flows between inverters under the parallel operation. Considering this, previous studies concentrated on reducing ZSCC. However, in this paper, it is found that the inverter current has another component, a differential current, in addition to the two components of AVC and ZSCC. Based on these three decomposed current components, three equivalent circuits are derived from n-paralleled inverters. To minimize the differential current and improve the regulation performance of the total output phase current, a decomposed current control scheme is proposed from equivalent circuit models. The proposed algorithm is applied to a system consisting of three paralleled two-level inverters with small shared inductance whose dc links are connected in common. Additionally, synchronous pulsewidth modulation is employed as the PWM method for each inverter. The proposed current controller is compared with two conventional current controllers, one where each inverter controls its own currents and the other where only AVC is controlled. Through experiments, it is shown that these conventional controllers have limitations and the proposed current controller overcomes these limitations. The effectiveness and feasibility of the proposed control scheme are verified through experimental results. Especially, both theoretical analysis and experiment results verify that the proposed method is robust with regard to parameter errors. [ABSTRACT FROM AUTHOR]

This paper presents the methodology and validation of high-frequency (HF) transformer simulations, which take into account the frequency dependence of the winding resistances and inductances. The parameters’ frequency dependence is approximated by curve fitting of the values computed by the finite element method (FEM) simulations in the frequency domain. After inverse Fourier transformation into the time domain, the convolution integrals are solved efficiently by the trapezoidal integration rule. The simulation results are validated using measurement data. [ABSTRACT FROM AUTHOR]

In the linear transformer driver system, the capacitor needs to satisfy the requirement of long life time and low inherent inductance. The inherent inductance of the capacitor plays an important role in limiting the rise time and peak current of the LTD output pulse, therefore, the volume of the capacitor should be as small as possible to reduce the inductance. Since the paper?s permittivity is larger than the film?s and the breakdown strength of film is larger than that of the paper, we adopt oil immersed paper-film mixed dielectric as the capacitor dielectric structure to take advantage of the combined properties of the two different dielectric films. In this paper, based on the result of the simulation, the electrode structure was optimized and a capacitor was designed with a capacitance of 100 nF and an inherent inductance of less than 140 nH. According to results of the experiment, the capacitor inherent inductance satisfies the expected requirement. The typical failure can be classified into two main modes: (1) insulation erosion at the pressure-contact taps and (2) foil edge breakdown, both resulting in short circuit failure. Based on the typical failure modes found from the dissection of failed capacitors, an improved design is presented. [ABSTRACT FROM AUTHOR]

In order to design a permanent magnet synchronous motor (PMSM), the inductance must be computed. In this paper, the flux concentrating PMSM (FCPMSM) is introduced. Calculating the inductance is difficult because of the complex structure of the rotor. Because the rib and the bridge consist of an iron core, they have nonlinear characteristics. In order to obtain the effective value of the inductance, nonlinear characteristics must be considered in a magnetic equivalent circuit (MEC). In this paper, to calculate the inductance of an FCPMSM, the relative permeance of the rotor was analyzed. Then, the dq-axis MEC, including the nonlinear magnetic reluctance, was created using the flux line. Finally, we verified the validity of the proposed inductance calculation method by comparing the results between the finite-element method and the proposed method. [ABSTRACT FROM AUTHOR]

A novel broadband bandpass frequency-selective surface (FSS) designed for fifth generation (5G) EMI shielding is proposed in this paper. This new design employs the vertical vias into the 2-D periodic arrays, and such a single 2.5-D periodic layer of via-based structure is demonstrated to produce a highly stable angular response up to 60° for both TE and TM polarizations. By cascading two layers of such 2.5-D periodic arrays, the proposed FSS is able to obtain a broad passband as well as the wide out-of-band rejection. Moreover, it has a quite sharp band edge between the passband and the specified stopband. A corresponding equivalent circuit model (ECM) is further developed for better analysis of the operating principle. Finally, a prototype working at the center frequency of around 28 GHz is fabricated and measured. The main novelty of this paper is introducing the 2.5-D concept into designing a wideband FSS, and further reduce the unit size as well as improve the angular stability. Favorable agreement is achieved among the 3-D full-wave simulation, ECM and measurement. All these results demonstrate that the proposed FSS is a good candidate for 5G EMI shielding. [ABSTRACT FROM PUBLISHER]

In this paper, we describe a current generator which consists of the Marx, the current-limited resistors, and the output port and can produce a double-exponential current waveform with the 3 kA, the rise time 10 ns, the pulsewidth 100 ns following the requirement of the IEC 61000-4-25 standard, while the effective impedance of the tested systems does not exceed 2 Ω. A new cavity of Marx is constructed by 12 steel rods which help assembly work more convenient; moreover, the current waveform has less disturbed signal. Because of using the cavity, the charging, trigger, and grounded circuits can be installed out of the Marx. Meanwhile, the cantilever insulated support of Marx also is used. The methods above can help make a compact current generator with a low inductance which can be beneficial to research the electromagnetic coupling laws of system circuit ports and chips. [ABSTRACT FROM AUTHOR]

A novel rectifying circuit topology is proposed for converting electromagnetic pulse waves (PWs), that are collected by a wideband antenna, into dc voltage. The typical incident signal considered in this paper consists of 10-ns pulses modulated around 2.4 GHz with a repetition period of 100 ns. The proposed rectifying circuit topology comprises a double-current architecture with inductances that collect the energy during the pulse delivery as well as an output capacitance that maintains the dc output voltage between the pulses. Experimental results show that the efficiency of the rectifier reaches 64% for a mean available incident power of 4 dBm. Similar performances are achieved when a wideband antenna is combined with the rectifier in order to realize a rectenna. By increasing the repetition period of the incident PWs to 400 ns, the rectifier still operates with an efficiency of 52% for a mean available incident pulse power of −8 dBm. Finally, the proposed PW rectenna is tested for a wireless energy transmission application in a low- $Q$ cavity. The time reversal technique is applied to focus PWs around the desired rectenna. Results show that the rectenna is still efficient when noisy PW is handled. [ABSTRACT FROM PUBLISHER]

One of the perspective directions in high-energy-density physics is the creation of powerful electro physical facilities capable to form megampere current pulses with short front. This paper presents test results of the device based on five-element disk magnetocumulative generator DMCG480 and an explosive current opening switch. The current pulse of 15 MA with characteristic rise time of \sim 0.8~\mu \texts was obtained in the equivalent multiwire array load of 17 nH at circuit breaking with the current of 32 MA. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to analyze and investigate the influence of temperature variation on the characteristics and performance of interior permanent magnet (IPM) machines. The impact of temperature variation on the materials of IPM machines is discussed to show the sources of performance variation. The flux linkages, torque output capability, and inductance variation as functions of the temperature are analyzed and discussed. This paper also shows the influence of temperature variation on key IPM machines performance including constant torque curves, voltage limit ellipses, maximum torque per ampere trajectories, and torque–speed curves. Experimental results of a traction IPM machine verified the analysis and theory. The results and trends shown in this paper set a foundation for developing control algorithm, which takes the temperature effects into consideration, especially in the applications where operating temperature varies significantly. [ABSTRACT FROM AUTHOR]

The pulse transformer is used in many applications to provide high-voltage pulses. In order to obtain high and narrow output pulses, it is necessary to reduce the leakage inductance of the pulse transformer. The circuit of a high-voltage power supply is analyzed and simulated to study the effect of the leakage inductance on the pulse waveform. Afterwards, the winding structure is analyzed. Three transformer models were built based on the asymmetric parallel winding, the traditional parallel winding, and the taper winding. Their leakage inductances and parasitic capacitances are calculated and compared. The 3-D finite element simulation is adopted to compute the leakage inductance precisely. The simulation results demonstrate that the asymmetric parallel winding in this paper reduces the leakage inductance effectively with small parasitic capacitances. In addition, using the asymmetric parallel winding, a pulse transformer prototype is manufactured and tested. The experimental results verify the accuracy of the simulation method and the feasibility of the asymmetric parallel winding. [ABSTRACT FROM PUBLISHER]

This paper presents a design approach to an interior permanent magnetic synchronous motor (IPMSM) for the compressor of a hybrid electric vehicle operated in a 42-V battery system. The approach is to estimate the range of inductance and back-EMF to satisfy the required efficiency of IPMSM. Then, the preliminary geometry satisfying the region is decided by PM type, current density, fill factor, and so on. Last, the detailed design with optimization is performed to consider magnetic saturation and reduce cogging torque and torque ripple. At this time, the simulation results are obtained by finite element analysis and in consideration of operating temperature. In the end, the validity of the design process presented in this paper is verified by test. [ABSTRACT FROM AUTHOR]

The brushless excitation structure characteristics of the aviation wound-rotor synchronous starter/generator (WRSSG) put forward the requirement on the brushless exciter (BE) model that both the stator and rotor windings can be interfaced with the external circuit directly. In this paper, a double-side variable-parameter voltage-behind-reactance (DS-VP-VBR) model of the BE considering magnetic saturation was established firstly to realize the direct connection between the stator and rotor windings with external circuits. Then, a double-side constant-parameter VBR (DS-CP-VBR) model with completely decoupled RL circuit was developed through the algebraic transformation and numerical approximation from the DS-VP-VBR model. In order to further improve the model accuracy, the leakage inductance variation of the stator and rotor windings were also considered. Computer studies under steady-state and transient operating conditions verified the validity and accuracy of the proposed BE DS-VBR models. [ABSTRACT FROM AUTHOR]

In this paper, the mathematical model of a novel 12-stator-pole/10-rotor-tooth doubly-fed flux-switching permanent magnet (DF-FSPM) machine employing 3-phase stator winding and 5-phase rotor winding is established and analyzed. Firstly, the stator and rotor winding inductance waveforms are analyzed in stator reference frame and modeled as the functions of rotor position considering major harmonic contents. Then, the inductances are transformed from the stator reference frame into the rotor reference frame using two Park transformation matrices, all of which become constants after the transformation. Thereafter, the voltage equation, power equation, torque equation are derived step by step. It shows that the magnetic coupling between stator and rotor windings causes the phase voltages to be affected by both stator and rotor currents. However, the reluctance torque and the torque produced by the magnetic coupling between stator and rotor windings are negligible. Further, the flux weakening capability of the machine is predicted from the voltage and torque equations. The power factors are analytically calculated and compared with the finite-element analysis, which indicates that both the stator and rotor of DF-FSPM machine exhibit high power factors. Finally, experimental validation is carried out on a prototype machine. [ABSTRACT FROM AUTHOR]

In this paper, asymmetric underlap double-gate (AUDG) MOSFET is studied to analyze the influence of high- k spacer on the intrinsic device parameters. The AUDG-MOSFET architecture offers better device performance, particularly, drain-induced barrier lowering in contrast to the conventional double-gate (DG)-MOSFET. However, the ON current and the distributed resistances for the device increase considerably. The analysis of the device presented here shows that the detrimental effects of the device can be effectively eliminated using high- k spacers. To evaluate the device performance and to study the improvement associated with the use of high- k spacers, different intrinsic parameters are analyzed. These parameters include transconductance ( , transconductance generation factor ( g_{m} / I_{d}) , intrinsic gain ( gmro) , intrinsic capacitance ( Cgd , Cgs) , resistance ( Rgd , Rgs) , transport delay ( \tau m) , inductance ( Lsd) , cutoff frequency ( fT\!) , and the maximum frequency of oscillation ( fmax) , gain bandwidth product, and inverter delay. [ABSTRACT FROM AUTHOR]

This paper introduces a three-phase reversible transformer model for the study of low-frequency transients. The model topology is obtained from the direct application of the principle of duality by drawing basic circuit elements on top of the transformer frame. The model parameters are obtained from terminal and physical size measurements as well as the characteristics of the iron core. The implementation of the model is based on standard drag-and-drop circuit elements available in electric circuit simulation programs. The model is validated with inrush current and normal open circuit laboratory measurements. The main advantage of this model is that the parameters remain the same for the simulation of different operating conditions from all terminals. This is true for transients involving deep saturation, normal loading operation, or open circuit. [ABSTRACT FROM AUTHOR]

The pulsed high-power supplies in this paper employs a homopolar inductor alternator (HIA) as the motor/generator integrated energy storage pulsed alternator. Lumped parameter design equations are developed, which is used to establish the mathematical model of the HIA, and the analytic calculation method of inductance matrix is derived. Prototype flywheel energy storage was built, and the basic structure of HIA is analyzed by using finite-element method (FEM). This paper proposes a simplified equivalent 2-D salient-pole synchronous generator model to simplify the 3-D FEM of HIA and investigates the motor control method of HIA based on the simplified 2-D equivalent model. The experiments were conducted for speed up to 8000 rpm and the six-step inverter drive strategy presented in this paper achieves the motor/generator integrated control on inductor energy storage pulsed alternator (IESPA). Most experimental results were in line with designed value. [ABSTRACT FROM PUBLISHER]

The spoke-type permanent magnet synchronous motor (PMSM) is a motor built using nonrare earth elements, which feature low flux density. It has a flux concentrated structure of permanent magnet arrangement to improve power density. Further, the torque in the spoke-type PMSM is composed of a magnetic torque component from the permanent magnets and a reluctance torque arising from the inductance difference between the $d$ - and $q$ -axis. This paper analyzed the $d$ - and $q$ -axes inductances that affect the reluctance torque depending on the magnitude of the applied current and the current phase angle of the spoke-type PMSM at base speed. We also derived the variation of the $d$ - and $q$ - axis inductances, which is shown at the operation speed region. Accordingly, the variation of the current phase angle for generating the maximum output power is analyzed. Based on the above results, we predicted the variation in the driving mode of the spoke-type PMSM, and subsequently verified the prediction experimentally. [ABSTRACT FROM AUTHOR]

Analytic modeling techniques of a double-sided interior permanent-magnet flat linear brushless motor (IPM-FLBM) with slot-phase shift and alternate teeth windings are proposed in this paper. Since the buried-type IPM-FLBM with the slot-phase shift and alternate teeth windings is fairly new compared with conventional linear motors, little research has been previously done in modeling and analysis. The analytic models presented in this paper provide the effective and reliable methods for this new type of linear motor. For this purpose, a simplified magnetic equivalent circuit and superposed winding function are investigated. A variable winding function is newly developed in order to evaluate the inductances of the salient motor with the alternate teeth windings. All analytic models are verified with 3-D finite-element analyses (FEAs) step by step. The steady-state thrust force is modeled using a classical closed-form solution for linear brushless ac motors. The static end-effect and cogging forces for the ripple force evaluation are investigated using FEA. The validities for performance parameters are demonstrated experimentally. [ABSTRACT FROM PUBLISHER]

The paper addresses an optimization-based reference calculation method for Modular Multilevel Converters (MMC) operating in normal and constrained situations (when the converter needs to prioritize its quantities as it has reached voltage or current limitations, e.g. during system faults). The optimization problem prioritizes to satisfy the external AC active and reactive current set-points demanded by the grid operator through the corresponding grid code. If the operator demands are fulfilled, it uses the available MMC degrees of freedom to minimize the arm inductance losses. Otherwise, if the operator demanded AC set-points cannot be accomplished, the optimization attempts to minimize the error prioritizing between either AC active or reactive currents. The optimization problem constraints are imposed through a steady-state model considering simultaneously the external and internal AC and DC magnitudes of the converter. The steady-state model also includes the voltage variation in the equivalent arm capacitors (considering the ripple). Then, the imposed limitations are the maximum allowed grid and arm currents, the maximum allowed arm voltages and the sub-module capacitor maximum voltages. The paper presents a detailed formulation of the optimization problem and applies it to several case studies where it is shown that the presented approach can be potentially used to obtain the MMC references both in normal and fault conditions. [ABSTRACT FROM AUTHOR]

A variable-switching constant-sampling frequency critical soft switching model predictive control (VSCS-MPC) method is proposed in this paper to improve the dynamic behavior, efficiency and power density of the DC/DC power converters. Firstly, this paper analyzes the boundary constraints of critical soft switching that are derived with the key parameters of the interlock time and threshold current for typical SiC and GaN devices. Then, the VSCS-MPC method is proposed for synchronous DC/DC converter. Both the current source load and resistive load converters are validated with the proposed MPC method. VSCS-MPC includes two controlling parts. First is the frequency controller to maintain the critical soft switching operation by adjusting the switching frequency based on the pre-defined boundary conditions with a constant sampling frequency. A discretized frequency controller is developed to improve the stability of the system by maintaining a fixed sampling frequency. Second part is the model predictive controller to track the output voltage/current and maintain critical soft switching during dynamic periods. The explicit optimization and oversampling methods are applied in the MPC controller to meet the high frequency demand. A large current ripple ($\triangle i_L$ $\ge$ 200 %) is introduced to achieve the critical soft switching and reduce the inductance. The switching losses are decreased by the frequency controller and the critical soft switching is maintained especially in dynamic periods due to the fast response of MPC. [ABSTRACT FROM AUTHOR]

Weak grids are gaining considerable attention since power generation resources are remote from constant power loads (CPLs), which results in low-frequency/harmonic oscillation. Meanwhile, due to the play, and plug demand of modern power system, the line inductance of weak grids often changes, which is also regarded as the variation regarding short circuit ratio (SCR). Based on this, the conventional impedance-based stability operation point assessment approaches should be expanded into stability domain assessment approach considering the line inductance variation. Therefore, the stability-oriented line inductance stability domain assessment approach for weak grids with CPLs is proposed in this paper. Firstly, the source impedance matrix of weak grid, and load admittance matrix of CPLs are separately built. Secondly, an improved stability forbidden domain criterion is proposed through related mapping transformation process, which has lower conservatism than two previous improved stability criteria. Thirdly, the improved stability forbidden domain criterion is switched into the condition that the intermediate matrices are Hurwitz. Meanwhile, the line inductance stability domain is directly obtained through these intermediate matrices, and guardian map theory. Finally, the simulation, and experiment results illustrate that the proposed approach has less conservatism, and high efficiency. [ABSTRACT FROM AUTHOR]