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Provides instructions and guidelines to prospective authors who wish to submit manuscripts. [ABSTRACT FROM AUTHOR]

First harmonic analysis (FHA) is arguably the most widely used analytical technique for wireless power transfer (WPT) circuits due to its simplicity. Although FHA can provide closed-form solutions, the existence of rectifier diode forward voltage drop and higher order harmonics, especially the second and third harmonics at variable duty cycle operation, can significantly deteriorate its accuracy. This paper presents an accurate and efficient method called enhanced multiple harmonic analysis (eMHA) for the optimal design and optimal control of WPT systems. The eMHA method considers the nature of nonlinear rectification networks under nonsinusoidal current and reexamines the concept of the equivalent load. As a result, the rectified WPT system is transformed into a series of linear systems with complex load impedances. The steady-state electric quantities can be then explicitly calculated. This enables eMHA to seamlessly work with numerical optimization algorithms to facilitate the automated design and optimization of WPT systems. An example of optimal design and optimal control of a 10 W WPT system is demonstrated. The results obtained by eMHA and FHA are also compared. A prototype of the designed circuit was constructed. The accuracy and effectiveness of eMHA are verified by experimental measurements. This paper is accompanied by a MATLAB-based analytical tool with a graphical user interface demonstrating the effects of circuit variables on electrical quantities and waveforms. [ABSTRACT FROM AUTHOR]

This paper proposes a novel kind of direct-current and alternate-decay-current hybrid integrative magnetization and demagnetization power supplies applied to transformer dc bias treatment based on a nanocomposite magnetic material. First, according to the single-phase transformer structure, one dc bias magnetic compensation mechanism was provided. The dc bias flux in the transformer main core could be eliminated directionally by utilizing the material remanence. Second, for the rapid response characteristic of the magnetic material to an external magnetic field, one positive and negative dc magnetization superimposed decaying ac demagnetization hybrid integrative power supplies based on single-phase rectifier circuit and inverter circuit was designed. In order to accurately control the magnetic field strength by which a good de/-magnetization effect could be achieved, this paper adopts the double-loop control technology of the magnetic field strength and magnetizing current for the nanocomposite magnetic state adjustment. Finally, two 10 kVA transformers and the experiment module of the hybrid integrative power supplies were manufactured and built. Experimental results showed that the integrated power supplies have good de/-magnetization effect and practicability, proving the validity and feasibility of the proposed scheme. [ABSTRACT FROM AUTHOR]

In addition to field-oriented control and direct torque control, the model predictive control (MPC) is another typical control method for permanent-magnet synchronous machine (PMSM) drives. In some critical applications, fault-tolerant controls are usually required. The faults of PMSM drives in this paper are limited as a single-phase open-circuit fault, which may be caused by open circuit or short circuit of one power switch. In the postfault operation, the neutral point of the PMSM is connected to a redundant leg. As is known, MPC is a model-based control method. Since the PMSM has different mathematical models in both normal and postfault operations, two different MPCs (MPC-I and MPC-II) should be, respectively, designed for both normal and postfault operations according to traditional thinking. However, it is first found in this paper that the faulty PMSM drive can be treated as an equivalent healthy PMSM drive, and MPC-I can be shared by both normal and postfault operations without any modification. The major contribution of this paper is to find this fact, and verify it with theoretical analysis and experimental validation. Obviously, this finding will simplify the whole control method of PMSM drives considering single-phase open-circuit fault. [ABSTRACT FROM AUTHOR]

This paper analyzes the influence of phase-locked loop (PLL) on the stability of LCL-type single-phase grid-connected asymmetrical cascaded H-bridge multilevel inverter (ACHMI) with synchronous reference frame proportional-integral (SRF-PI) grid current control under weak grid scenarios. The ACHMI system is composed of power stage circuit and control system, where the control system contains the dual-loop current control strategy established in the hybrid reference frame, the SRF-PLL, and the hybrid modulation method employed to synthesize the multilevel output voltage. The small-signal model of the whole ACHMI system is first established by using a simple step-by-step derivation method, and then, the small-signal analysis method is adopted to linearize the ACHMI, which is then utilized to derive the impedance model of the ACHMI system. Furthermore, an improved impedance stability criterion is derived, which is then employed to analyze the system stability. By using this criterion, the stability of the ACHMI can be evaluated with the variation of the bandwidth of PLL, the output power factor angle of the ACHMI, and the amplitude of the grid current reference signal under weak grid conditions. In this paper, a systematic design procedure for the optimal selection of the PI controller of the PLL is presented, which guarantees the steady-state performance and dynamic response of the ACHMI system. With this design method, the dual-loop current control and PLL can be taken into account simultaneously when analyzing the stability margin of the ACHMI. Finally, the simulation and experimental results from a down-scaled grid-connected ACHMI prototype system are provided to confirm the validity of theoretical analysis. [ABSTRACT FROM AUTHOR]

Power management integrated circuits (PMICs) with on-chip compensation are widely used to power multiple loads in mobile devices with increased power density. However, there are two issues for on-chip compensated PMICs. First, on-chip compensation reconfigurability is required to obtain the appropriate response in various passive components. Second, a converter for a processor requires adaptive voltage positioning (AVP) to reduce the output capacitor size. In this paper, a novel reconfigurable on-chip compensated current-mode buck converter with AVP is proposed to solve the aforementioned issues without requiring high-speed and high-resolution analog-to-digital converter (ADC). A reconfigurable accurate load line control scheme and on-chip compensation are proposed to achieve an accurate load line and AVP in various load lines and passive components. The control scheme, small-signal model, and circuit implementation are illustrated in this paper. The proposed buck converter was implemented into an integrated circuit to verify the analysis. [ABSTRACT FROM AUTHOR]

A high step-up dc–dc converter is proposed in this paper. The presented converter benefits from some advantages such as high voltage gain and continuous input current, which makes it suitable for the renewable energy applications. The presented converter is based on the SEPIC converter. However, the converter voltage gain is improved by employing a coupled inductor and two voltage multipliers. A passive clamp circuit is also added to the proposed converter that increases the voltage gain and reduces the voltage stress on the main switch. Thus, a switch with low $R_{{\text{DS(on)}}}$ will be needed that decreases the conduction loss. Besides, the voltage stress on the output diode in the proposed converter is reduced, which alleviates reverse recovery problem. The steady-state analysis of the proposed converter is discussed in this paper. The analysis is verified with experimental results under the output power of 245 W. [ABSTRACT FROM AUTHOR]

Due to the continuous demands for highly reliable and cost-effective power conversion, quantified reliability performances of the power electronics converter are becoming emerging needs. The existing reliability predictions for the power electronics converter mainly focus on the metrics of lifetime, accumulated damage, constant failure rate, or mean time to failure. Nevertheless, the time-varying and probability-distributed characteristics of the reliability are rarely involved. Moreover, in the public literatures, there are few evidences showing that the accuracy of the predicted reliability was experimentally validated. In this paper, a more advanced metric “cumulative distribution function (CDF)” is introduced to predict the reliability performance of the power electronics system based on mission profiles in motor drive application. Furthermore, the accuracy of the predicted reliability metrics is verified through a series of wear-out tests in a converter testing system. It is concluded that the CDF is a very suitable metric to predict the reliability performance of the converter, and it has shown good accuracy with much more reliability information compared to the existing approaches. In this method, the correct stress translation and dedicated strength tests based on mission profiles are two key factors to ensure the efficiency and accuracy of reliability prediction. [ABSTRACT FROM AUTHOR]

This paper presents an improved compact model for a discrete silicon-carbide (SiC) MOSFET. This compact model based on the previous model features a new behavioral model of output characteristics and new nonlinear models of internal capacitors. Simulation with the improved compact model is in better agreement with measurement than that with the previous compact model, as well as transient behavior of the drain–source voltage, the drain current, and the leakage current out of a heatsink. Furthermore, the improved model is useful for constructing the accurate compact model that can reproduce the high-frequency characteristics of the transient waveforms of SiC-MOSFET s. This successful validation indicates that the improved compact model would be a promising tool for a full-simulation-based design system of the power converters using SiC-MOSFETs. [ABSTRACT FROM AUTHOR]

This paper proposes a new power decoupling control method for a direct ac-to-ac converter. The ac-to-ac converter consists of two half-bridge converters, two input filter capacitors, and a series-resonant circuit, which enables it to convert the single-phase line-frequency ac input to the high-frequency ac output directly. The proposed power decoupling control method stores input power pulsation at double the line frequency in the input filter capacitors. Thus, the proposed control method realizes a unity power factor in the line-frequency ac input and a constant amplitude current in the high-frequency ac output without any additional switching device or energy storage element. This paper theoretically discusses the principle and operating performance of the proposed control method and confirms the effectiveness of the proposed control method in experiments using an isolated ac-to-dc converter based on the direct ac-to-ac converter. As a result, the proposed power decoupling control method effectively improved the displacement power factor of the line-frequency ac input current to more than 0.99 and reduced the voltage ripple in the dc load to 4%. [ABSTRACT FROM AUTHOR]

The articles in this special issue focus on the latest achievements of modular multilevel converters regarding the development of new circuit configurations, converter models, modulation strategies, and control schemes. [ABSTRACT FROM AUTHOR]

This paper presents a single-stage converter for a high-bandwidth and high-efficiency envelope amplifier. In the proposed application, due to the high peak-to-average-power ratio, high bandwidth, and the power level requirements, the envelope amplifier has low efficiency. Therefore, many efforts have been made to increase the efficiency of the envelope amplifier. To achieve this improvement, the current ripple cancellation technique is applied in this paper to a synchronous buck converter to cancel the output current ripple and to decrease the switching frequency without a reduction in the large signal bandwidth, for open-loop operation and for the envelope elimination and restoration technique. The advantages of the proposed design are presented and validated experimentally. The transfer function of the output filter of the buck converter with a ripple cancellation circuit has been modeled and compared to measurements, showing a good correspondence. Experimental validation is provided at 4 MHz of switching frequency, for dc and for variable output voltage, applying a sinusoidal reference and a 64-QAM signal. Experimental validation of the efficiency improvement is provided, compared to the equivalent design of the conventional buck converter in terms of the output voltage ripple rejection ratio and large signal bandwidth. [ABSTRACT FROM AUTHOR]

High gain bidirectional dc–dc converter with high efficiency and high power density is a much desired circuit in any converter/inverter system. It is well known that switched capacitor circuits that are variants of the Dickson converter are suitable candidates for such a system. Modular design, absence of external magnetic components, and high efficiency are some of the features that make them suitable candidates. But, the inability to provide fractional and variable voltage gains at high efficiency during normal operation severely limits their application. It also leads to higher voltage stress in the overall system. The aim of this paper is twofold. First, a generalized modular switched capacitor converter, the “(n/m)X converter,” which is a variant of the original Dickson converter is introduced. Using this generalized configuration, the converter can be designed for a required fractional gain. Next, two different methods to enable dynamic variation in gain with high efficiency using the (n/m)X converter are proposed. Detailed analysis, design steps, equivalent circuits, and experimental results for a 1 kW prototype of a variable (4/0.5)X boost converter validate the proposed theory. A peak measured efficiency of over 95% is achieved for the prototype. The design framework and analysis in this paper can be extended to a generic (n/m)X converter. [ABSTRACT FROM AUTHOR]

This paper presents, initially, a systematic derivation of extended first harmonic approximation (FHA) analysis and, later, a comprehensive time-domain (T-D) analysis to study series–series compensated inductive power transfer (IPT) systems with a diode bridge rectifier. Further, the paper shows that both FHA and T-D methods predict four mutually exclusive and collectively exhaustive modes of operation. Explicit criteria for each operation mode and formulae for mode boundaries are derived and it is concluded that FHA can explain three of four modes. The proposed T-D analysis is capable of describing the quantitative behavior of the system in all four operation modes with closed-form equations for all the mode boundaries. This analysis provides an objective basis to assess the accuracy of FHA predictions under the entire operating conditions. Quantitative comparison of key variables revealed that the FHA results can be unacceptably inaccurate for certain operating points. It is shown that the T-D approach provides a comprehensive design base for series–series compensated IPT without a need to know the load value. The T-D predictions are validated by experiment. A mathematical design calculator tool is also provided to the reader to visualize the mode boundaries, all the waveforms and the numerical results from both methods. [ABSTRACT FROM AUTHOR]

Magnetically coupled impedance-source (MCIS) networks are recently introduced impedance networks intended for various high-boost applications. It employs coupled magnetic in the circuit to achieve higher voltage gain. Various MCIS networks have been proposed in the literature for myriad applications; however, due to effective role of system modeling in the closed-loop controller design, this paper is allocated to small-signal modeling and analysis of MCIS converters. The modeling is performed by means of the circuit averaging and averaged switch technique. A generalized small-signal derivation is demonstrated for pulse width modulation (PWM) MCIS converters and it is shown that the derived transfer functions can simply be applied to Y-source, Γ-source, and T-source impedance networks. Various transfer functions for capacitor voltage, output voltage, magnetizing current, input and output impedance are derived and have been validated through frequency and dynamic responses of computer simulation results. In addition, a comprehensive analysis has been done for all mentioned PWM MCIS converters regarding their circuit parameters. Furthermore, the effect of considering the equivalent series resistances of capacitor and inductor on the stability margin of MCIS converters is revealed in this paper. Finally, in order to validate the derived transfer functions and to consolidate the perfumed analysis, experimental results are presented for all mentioned MCIS converters. [ABSTRACT FROM PUBLISHER]

Operation and analysis of delta-connected ac motor-drive systems under fault-tolerant open-phase mode of operation is introduced in this paper for both scalar- and vector-controlled motor-drive systems. This technique enables the operation of the three-phase motor upon a failure in one of its phases without the need of a special fault-detection algorithm. It is mainly used to significantly mitigate torque pulsations, which are caused by an open-delta configuration in the stator windings. The performance of the fault-tolerant system was verified using a detailed time stepping finite element simulation as well experimental tests for a 5-hp 460-V induction motor-drive system and the results are presented in this paper This paper also compares the operation of this fault-tolerant mode of operation for the cases of scalar-controlled and closed-loop vector-controlled motor-drive systems. [ABSTRACT FROM AUTHOR]

An isolated buck–boost (IBB) converter with a hybrid three-level full-bridge primary-side circuit is proposed to achieve wider voltage range regulation. The primary-side circuit is composed of a three-level leg and a two-level leg. The output voltage of the primary-side circuit is five level (i.e., $\pm V_{{\text{in}}}$ , $\pm V_{{\text{in}}}{\text{/ 2}}$ , and zero), and the secondary-side circuit is a semiactive full-bridge rectifier with two active switches and two diodes. The input voltage of the secondary-side circuit is three level (i.e., $\pm V_{{\text{o}}}$ and zero). Hence, the operation voltage range can be wider than the normal IBB converter's with three voltage levels in the primary-side circuit and secondary-side circuit. This paper focuses on the control strategy allowing the converter to operate in boundary current mode at heavy load and in discontinuous current mode at light load with smooth mode transition. The soft-switching performance and output characteristics of the proposed converter are presented in detail. Compared with the semi-dual active bridge converter, the voltage range is doubled and the peak current of the clamped inductor is decreased. An 800-W prototype with 100–400-V input voltage and 380-V output voltage is built and tested to verify the feasibility of the proposed control strategy. [ABSTRACT FROM AUTHOR]

This paper proposes a generalized design procedure for repetitive current controllers in distorted distribution grids to obtain good disturbance rejection properties and well behaved and robust system dynamics. Different implementation options for repetitive controllers (RCs) are discussed based on an accurate discrete time model. A simple control design is derived, which allows any desirable dynamics to be adjusted by one single parameter. Even a deadbeat design is possible. The impact of model inaccuracies and numerical errors on the dynamic and stability of the system is investigated. It is shown that the RC leads to low damping or even instability at high switching frequencies caused by modeling errors or numerical inaccuracies. Based on the stability analysis, it is discussed how to handle these design challenges, which exist especially for RCs of high order. The proposed control structure and control design concept is verified by simulations and experiments. [ABSTRACT FROM AUTHOR]

Flying-capacitor modular multilevel converter (FC-MMC) overcomes the zero/low-fundamental-frequency operation issues of conventional MMC without injecting common-mode voltage. However, the FC-MMC suffers from high current stress due to the large amplitude of inner high-frequency current. The square-wave design for the inner high-frequency components could effectively reduce the current stress, but the per-phaseLCcircuit (formed by arm inductor and flying capacitor) challenges the square-wave current control. This paper investigates the equivalentLCcircuit in FC-MMC, and proposes a control method to improve the performance of inner current control. Accordingly, the desired square wave is achieved for inner high-frequency current. The current stresses on semiconductor switches and flying capacitor are reduced by around 25% and 45%, respectively. Simulation and experimental results prove the effectiveness of the proposal. [ABSTRACT FROM AUTHOR]

Today's implantable mechanical circulatory support devices, such as left ventricular assist devices, still rely on a percutaneous driveline, which is a frequent cause of severe infections and which reduces the quality of life for the patients. Inductive power transfer (IPT) is therefore a promising technology to replace the driveline and, hence, reducing the likelihood of an infection. This paper focuses on the series–series compensated IPT system and provides an in-depth comparison of two operating modes, i.e., the operation at resonance and the operation above resonance, and highlights the advantages and disadvantages with respect to the requirements set by the application at hand. In addition, the paper presents the design and the realization of a fully functional transcutaneous energy transfer (TET) implant hardware prototype, which includes the IPT front-end, the control circuit, the backup battery and its charging converter, as well as the communication electronics in a boxed volume of only 10.3 cl. The experimental verification shows that overall dc–dc efficiencies of up to 90% can be achieved for both operating modes when transmitting 25–30 W from the external battery to the implant backup battery, each having a nominal voltage of 14.8 V, using TET coils with 70 mm diameter and 10 mm coil separation distance. [ABSTRACT FROM AUTHOR]

With the development of distributed power generation sources and the widely used dc characterized loads, the dc nanogrid becomes more and more attractive and the converters with three terminal outputs are increasingly studied. Considering the costs, the efficiency, and also the safety, the grounding configuration needs to be addressed when designing the ac–dc converter for a dc nanogrid system. An ac–dc converter with three terminal outputs has been presented for the united grounding configuration based dc nanogrid. Nevertheless, for this type of converters, the output voltages are unbalanced in case of unequal dc loads. This paper proposes a novel buck–boost ac–dc converter with the capacity of output voltages self-balancing by using a coupled inductor. The operation of this converter will be presented in details through analyzing its equivalent circuits. The small signal model of the system in different working modes is given, and the whole system control diagram shows how to balance the dc output voltages. A 220 V/50 Hz/1.5 kW prototype has been developed. Experiments are carried out to verify the effectiveness of the coupled-inductor-based converter. [ABSTRACT FROM AUTHOR]

The three-phase four-wire inverter with split dc-link capacitors can supply unbalanced loads. For the purpose of reducing the filter inductors, a neutral inductor could be introduced into the neutral line. This paper analyzes the operation principle of the three-phase four-wire inverter with split dc-link capacitors when a neutral inductor is introduced. It is illustrated that the neutral inductor can reduce the zero-sequence switching harmonics in the voltages between the phase-leg midpoints and the output neutral point, thus the filter inductors can be reduced. The optimized design of the neutral inductor and filter inductors is proposed with the considerations of the inductor current ripple, the ability of supplying unbalanced loads, and the total energy stored in the inductors. The equivalent circuits of the three-phase four-wire inverter with split dc-link capacitors and neutral inductor is derived in the α–β–0 frame, and the zero-axis voltage regulator is modified to suppress the third-order harmonic in the zero-sequence current caused by the deadtime of the drive signals for the power switches. Finally, the experimental results from a 9-kW prototype are provided to prove the effectiveness of the proposed optimized design of the neutral inductor and filter inductors and the control strategy of the inverter. [ABSTRACT FROM AUTHOR]

The power conditioning interface circuit plays a crucial role in the energy harvesting (EH) capability enhancement in piezoelectric EH (PEH) systems. The principle of most existing synchronized switch circuits for PEH enhancement was summarized under the recently introduced synchronized multiple bias-flip (SMBF) model. The optimal bias-flip strategy derived from SMBF provides valuable insights for future circuit development. Based on such theoretical foundation, this paper implements a new interface circuit called theparallel synchronized triple bias-flip(P-S3BF) for further boosting the harvesting capability beyond the state-of-the-art solutions. By sophisticatedly allocating more bias-flip actions, it makes the best compromise between higher extracted power and lower dissipated power for power conditioning, toward maximum net harvested power. Moreover, the bias voltage reference in P-S3BF is self-contained and self-adaptive. Compared to the other existing solutions involving active voltage manipulations, these two conveniences brought in by P-S3BF are the most significant and necessary features, which facilitate the practical stand-alone implementation of P-S3BF under different periodic vibrations. Experimental result shows that, with the piezoelectric cantilever in use, which vibrates at a constant deflection magnitude, the P-S3BF circuit harvests 24.5% more power than its single bias-flip counterpart, the extensively studied parallel synchronized switch harvesting on inductor; and 287.6% more power than its null bias-flip counterpart, the standard EH bridge rectifier. [ABSTRACT FROM AUTHOR]

Rising power demands in more electrical aircraft (MEA) put power converters for commercial airplanes under increasing pressure to fulfill current harmonic distortion regulations as specified, for example, in DO-160G. Today, the implementation of filters is seen as an effective tool for dealing with harmonics; however, their increased weight and volume are not welcomed in the aerospace industry. This paper proposes a circuit, named forced commutation controlled series capacitor (FCSC-rectifier), which is able to maintain low individual harmonic current levels without the need for filter components. The FCSC-rectifier includes a variable capacitive line reactance that interacts in a controlled manner with the inductive line impedance. The result is that the converter input current is nearly purely sinusoidal with a power factor of almost unity. The FCSC-rectifier is to be used for stand-alone variable-voltage, variable-frequency generation systems and can, therefore, power the full authority digital electronic control system (FADEC) in an MEA. This paper shows that the FCSC-rectifier can maintain a high power factor and acceptable current harmonic levels without the use of filters, despite large voltage and frequency variations. A full description of the circuit modes of operation is presented in this paper together with simulation results showing circuit performance characteristics over a range of voltages and frequencies. Results are experimentally verified using a 1-kW test circuit. [ABSTRACT FROM AUTHOR]

Single-phase ac light-emitting diode (LED) lamps require long-lifespan and high-efficiency ac–dc power converters for power factor correction (PFC) and current regulation. In such converters, the inherent double-line-frequency ripple power from the ac source is isolated from the load by large electrolytic capacitors (E-caps) or E-cap-less active circuits to improve reliability and lifespan. This paper presents an ac–dc LED driver with an additional active rectifier and a unidirectional auxiliary circuit for ripple power isolation. As compared with other similar designs, the proposed LED driver operates with reduced redundant power processing and a lower voltage on the storage capacitor, and the additional active circuits include fewer power components. The prototype with small polymer-hybrid capacitors and ceramic capacitors is separately tested in the experiment. [ABSTRACT FROM AUTHOR]

This paper presents a detailed analysis of short-circuit current behavior during interturn short-circuit faults in permanent magnet synchronous machines (PMSMs) by considering the short-circuit contact resistance. For this purpose, an finite element analysis (FEA)-based equivalent circuit model is developed to understand the circulating current behavior in the shorted turns. Various fault resistance and number of shorted turn combinations are examined at different torque and speed levels. To include saturation due to high fault currents, the inductance matrix of faulty machine is created in FEA environment and incorporated into the equivalent circuit model as four-dimensional lookup tables. In order to take loop responses into account, the model is controlled through field oriented control (FOC) with closed speed and current loops. An experimental setup is built to verify the simulation results using a PMSM with several winding taps. It is shown that the experimental results and the simulations are quite consistent with each other. The findings from this study are essential to predict fault severity, develop mitigation techniques and determine the safe operating area for faulty machines. [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]

A transmission line emulator has been developed to flexibly represent interconnected ac lines under normal operating conditions in a voltage-source-converter-based power system emulation platform. As the most serious short-circuit fault condition, the three-phase short-circuit fault emulation is essential for power system studies. This paper proposes a model to realize a three-phase short-circuit fault emulation at different locations along a single transmission line or one of several parallel-connected transmission lines. At the same time, a combination method is proposed to eliminate the undesired transients caused by the current reference step changes while switching between the fault state and the normal state. Experiment results verify the developed transmission line three-phase short-circuit fault emulation capability. [ABSTRACT FROM AUTHOR]

Transistor models have been playing a key role in designing efficient power converters. As the operating frequency of the converters becomes higher, transistor models need to represent physical device behavior accurately. This paper proposes a comprehensive surface-potential-based model of silicon carbide (SiC) power MOSFETs that realizes accurate circuit simulations. Whereas conventional simulation models are based on empirical formulas, the proposed model is constructed in a surface-potential-based framework by considering the physical structure and behavior of vertical power SiC MOSFETs. The proposed model represents both I–V and C–V characteristics from weak inversion to the high-power region. In addition, the proposed model calculates the channel mobility degradation due to SiC/SiO $_2$ interface traps, which significantly affects the circuit performance. Through experiments using a commercial SiC power MOSFET, excellent agreements are obtained between measurement and simulation in I–V and C–V characteristics at various temperatures for wide power ranges up to 1 kW. The transient behavior of a double-pulse tester is also well reproduced within a timing error of 12.6 ns even under the high temperature. [ABSTRACT FROM AUTHOR]

Multiple coupled inductors are used in power electronics to improve the dynamic cross regulation and to reduce mass and volume, mainly in high performance application, such as space or defense, where manufacturing cost is not the main driver. These elements can be modeled with its inductance matrix which is a symmetric and positive semidefinite matrix. The inductance matrix eases circuit analysis, many known circuital models are directly related to it and it can be used in SPICE simulation via its coupling coefficient component, which can be identified as the normalized matrix of the inductance matrix. Therefore, a precise and correct measurement technique of the inductance matrix or coupling coefficient matrix is needed. This paper analyzes different measuring techniques described in the technical literature and proposes a new method to measure the coupling coefficient or inductance matrix of tight coupled or dissimilar turns’ number windings, where other methods fail. A discussion follows, to know the influence of parasitic elements in the accuracy of the new proposed method called resonance (RE) method. The paper adds three experimental examples to verify the theoretical study and concludes that the RE method provides correct values of the coupling coefficient $k$ of tight coupled or dissimilar turns’ number windings compared to other measurement techniques. [ABSTRACT FROM AUTHOR]

This paper introduces a new bidirectional single-phase inverter topology. The proposed topology has three ports: a dc port, an ac port, and a ripple port. The ac and dc ports are bidirectional to support rectifier or inverter operation. A small inductor, which is of alternating current, exchanges power between different ports of the single-phase system. The proposed topology is capable of accomplishing voltage step-up or step-down, suppressing the ripple power, and performing inversion or rectification operation in one stage of power conversion. The proposed configuration offers an active decoupling function, which not only eliminates the double-frequency ripple power at the dc port but also achieves minimum capacitance requirements to minimize the size of the decoupling capacitor. This facilitates the use of a very small thin-film capacitor, which offers a much longer life-cycle and higher reliability compared with a bulky electrolytic capacitor. A control approach is also developed to regulate the dc-port and ac-port currents and manage the ripple power through proper distribution of power between each port. Moreover, a very small capacitor can be placed in parallel with the inductor to reinforce the proposed configuration with soft-switching operation, which enhances the overall efficiency and minimizes the voltage stress over the semiconductor devices. This converter is capable of accommodating an arbitrary number of dc or single-phase ac sources and/or loads configuring a multiple-input multiple-output inverter without introducing any additional passive elements or sacrificing the performance of the inverter. The primary focus of this paper is dc-to-ac conversion mode of operation, in spite of the fact that it can easily be configured to serve as a rectifier. Experimental and simulation results are presented to validate the operation of the proposed topology and its control strategy. [ABSTRACT FROM AUTHOR]

The double-sided LCC topology provides a highly efficient compensation method for electric vehicle (EV) wireless charging systems. However, the two compensated coils occupy a large volume. In order to address the volume increase as well as to be compatible with unipolar coil structures, which are widely applied in EV wireless charging systems, an integration method is introduced in this paper. Aspect ratios of the compensated coils are studied to minimize the respective coupling effect. With the proposed integration method, the extra coupling coefficients are either eliminated or decreased to a negligible level. A wireless charging system with the proposed integration method is built and the experimental results show that the system resonates at 85 kHz and delivers 3.09 kW with a dc–dc efficiency of 95.49% at an air gap of 150 mm. Furthermore, a comparison with the integration method into bipolar coil structures is presented and the results demonstrate that the system with the proposed integration method is more immune to front-to-rear and vertical misalignments. [ABSTRACT FROM AUTHOR]

An important feature of an inductive power transfer (IPT) system is its power transfer efficiency and capability can be significantly affected by the load and the magnetic coupling variations. Therefore, identifying the load and the mutual inductance is essential to improve the system performance. This paper proposes a load and mutual inductance identification method for IPT systems with parallel-compensated power pickups based only on the information detected from the primary side. The proposed method can be implemented for primary resonant circuits whether they are series or parallel tuned, or with a hybrid compensation, such as an LCL configuration. An identification model is established according to the steady-state characteristics of the system. Identification results are obtained based on mathematical derivations and analyses. The proposed identification method is realized without any extra communication or control, and both the simulation and experimental results have verified its feasibility. [ABSTRACT FROM AUTHOR]

The phase-shifted full-bridge (PSFB) converter with synchronous rectifier (SR) is one of the most attractive dc–dc converters for the server power supply due to its high power capability and small secondary ripple current with the output inductor. Moreover, it can more reduce the secondary conduction loss by using parallel-connected mosfets in SR. However, due to large input capacitance of the parallel-connected mosfets in SR, the PSFB converter has large SR gate driving loss, which particularly degrades the light load efficiency. Thus, in this paper, one additional resistor is added to the conventional SR gate driving circuit to recycle the gate driving energy. As a result, the proposed circuit can improve the light load efficiency of the PSFB converter without operation mode change, additional controls, and complex circuits. The most advantage of the proposed circuit is that it is very simple and available to any other SR gate driver IC. The validity of the proposed circuit is confirmed by experimental results from a prototype with 340–400 V input and 12 V/66.66 A output. [ABSTRACT FROM AUTHOR]

LCL filters are commonly used to connect voltage-sourced converters (VSCs) to the grid. This type of filter is cheaper than a single inductor for the same current total harmonic distortion (THD), but it generates resonance problems if no active or passive damping method is applied. Active damping methods are becoming popular in the literature because they improve efficiency, but they are sometimes difficult to implement and additional measurements are required. This paper proposes an active damping method for VSCs connected to weak grids, which is based on making the open-loop phase zero at the resonance frequency. It will be shown that this strategy provides adequate damping of oscillations and that it can be achieved in two different ways: at the design stage (if the design constraints make it possible) or with an all-pass filter in series with the current controller. Two methods to design the all-pass filter are proposed. Also, the proposed active damping technique is compared with three alternatives already proposed in the literature. All the control algorithms are verified by simulation and in a 15-kW prototype of a three-phase VSC connected to a configurable weak grid via an LCL filter. [ABSTRACT FROM AUTHOR]

Z-Source inverters have recently been proposed as an alternative power conversion concept as they have both voltage buck and boost capabilities. These inverters use a unique impedance network, coupled between the power source and converter circuit, to provide both voltage buck and boost properties, which cannot be achieved with conventional voltage-source and current-source inverters. To facilitate understanding of Z-source inverter modulation, this paper presents a detailed analysis, showing how various conventional pulse-width modulation strategies can be modified to switch a voltage-type Z-source inverter either continuously or discontinuously, while retaining all the unique harmonic performance features of these conventional modulation strategies. This paper starts by analyzing the modulation requirements of a single-phase H-bridge Z-source inverter, and subsequently extends the analysis to cover the more complex three-phase-leg and four-phase-leg Z-source inverters, with carrier-based implementation reference equations derived for all the inverters. The theoretical and modulation concepts presented have been verified both in simulation and experimentally. [ABSTRACT FROM AUTHOR]

Transient voltage unbalance is the major problem that limits the application of series-connected IGBTs in highvoltage and high-power converters. Asynchronous gate delay causes series-connected IGBTs not to turn-on and turn-off at the same time resulting in severely unbalanced voltage sharing. An active voltage balancing control technique is proposed in this paper to solve the asynchronous gate delay problem. By sampling the feedback signal caused by unbalanced voltage sharing, the microcontroller generates a time delay for the gate driver to compensate the asynchronous gate delay. The most vital part of active voltage balancing control, the status feedback circuit, is also discussed in detail in this paper. The function of the status feedback circuit and the effect of active voltage balancing control are verified in a two series-connected HV-IGBTs platform in rated operation (5 kV bus voltage and 600 A load current). [ABSTRACT FROM AUTHOR]

This paper presents an in-depth critical discussion and derivation of a detailed small-signal analysis of the phase-shifted full-bridge (PSFB) converter. Circuit parasitics, resonant inductance, and transformer turns ratio have all been taken into account in the evaluation of this topology's open-loop control-to-output, line-to-output, and load-to-output transfer functions. Accordingly, the significant impact of losses and resonant inductance on the converter's transfer functions is highlighted. The enhanced dynamic model proposed in this paper enables the correct design of the converter compensator, including the effect of parasitics on the dynamic behavior of the PSFB converter. Detailed experimental results for a real-life 36 V-to-14 V/10 A PSFB industrial application show excellent agreement with the predictions from the model proposed herein. [ABSTRACT FROM AUTHOR]

This paper presents a single-phase to three-phase power conversion system with parallel rectifier and series inverter to cope with single-phase to three-phase asymmetry. Such converter guarantees both reduction in the input current processed by rectifier circuit and reduction of the output voltage processed by the inverter circuit. It is worth mentioning that, in spite of proposing a topology with features not yet observed on the technical literature, this paper presents a comprehensive model of the proposed converter, modulation strategy, and a general comparison with the conventional configuration. Simulated and experimental results are also presented. [ABSTRACT FROM AUTHOR]

This paper investigates the open-circuit faults of switching devices in the three-level T-Type inverter and proposes a new tolerant control method. The three-phase current and variation of the neutral-point voltage are detected to determine the fault switch. A carrier-based pulse width modulation is developed to tolerate switch fault by transiting from three-level to two-level switching. This makes the modulation scheme easier to be implemented compared to space vector modulation. For the neutral-point fault, the fault phase is operated by two-level modulation to produce the same rating voltage. On the other hand, the inverter is able to produce balanced voltage with reduced rating by keeping the phase of half-bridge fault to the neutral-point voltage. The neutral-point voltage is also able to be balanced by using two-level modulation since it does not contribute the neutral-point current. The performance and effectiveness of the proposed tolerant control are verified by a laboratory build. [ABSTRACT FROM AUTHOR]

This paper proposes a dual-coupled LCC-compen-sated inductive power transfer system with a compact magnetic coupler to improve misalignment performance. In the magnetic coupler, the main coils form the first coupling, and compensation inductors are integrated with the main coils to form a second coupling. In the design presented in this paper, the main coils are unipolar and the compensation inductors are in a Double D structure. The fundamental harmonics approximation method is used to analyze the circuit, and the couplings between the main coils and compensation inductors are considered to determine the net power flow. In misalignment cases, it is shown that the coupling between the compensation inductors, and the cross couplings between the compensation inductors and main coils, contribute to increasing the system power. A 3.5 kW prototype is designed and implemented to validate the proposed dual-coupled system. The primary coil size is \text450 mm\times \text450 mm, and the secondary coil size is \text300 mm\times \text300 mm. Experimental results show that the proposed dual-coupled system can significantly improve the misalignment performance, and retains at least 56.8% and 82.6% of the well-aligned power at 150 mm misalignment in the x- and y-directions, respectively. [ABSTRACT FROM PUBLISHER]

This paper presents a general space vector modulation (SVM) method for the modular multilevel converter (MMC). Compared with earlier modulation methods, the proposed SVM method not only utilizes the maximum level number (i.e., $2n+ 1$, where $n$ is the number of submodules in the upper or lower arm of each phase) of output phase voltages, but also leads to an optimized control performance in terms of capacitor voltage balancing, circulating current suppression, and common-mode voltage reduction. The maximum level number is achieved by introducing a new equivalent circuit of the MMC, and the optimized control is obtained by selecting the optimal redundant switching states. Since the computational burden of the SVM scheme is independent of the voltage level number, the proposed method is well suited to the MMC with any number of submodules. Simulation and experimental results are presented to validate the proposed method. [ABSTRACT FROM PUBLISHER]

High-order filters (HO-filters) such as LCL-LC-filters have recently drawn attention to their small size and better attenuation to switching harmonics than LCL -filters for three-phase inverter grid interfaces. Hybrid damping that combines passive damping and active damping is an effective method to suppress HO-filter resonances. However, due to the high-order characteristic of the system, the tuning procedure for the parameters of hybrid damping is complicated. Hence, an equivalent circuit analysis method is proposed in this paper to accurately simplify the model of the HO-filter. Based on this, a systematic step-by-step design method for HO-filter-type grid-connected inverters with hybrid damping has been proposed. The passive losses, effects of equivalent series resistances (ESRs) and robustness against grid impedance variation have been studied. Compared with existing design procedures, the proposed method makes the hybrid damping more reliable by locating appropriate position for closed-loop resonant poles. Experimental results verify the proposed systematic design procedure. [ABSTRACT FROM AUTHOR]

In this paper, we present a technique to characterize common mode chokes at high frequencies that only requires a measurement, which can be performed with a spectrum analyzer with the tracking generator. This technique is based upon a theoretical modal analysis of the common mode choke as a four-ports device. This analysis demonstrates that the transmission coefficient measured for one of the windings of the common mode choke, while the other winding is open circuited will always show two minimums, which are associated with resonances involving currents flowing, respectively, in common mode and in differential mode in the common mode choke. Therefore, the response at high frequencies of the common mode choke to both a common mode and a differential mode stimulus can be foreseen from the measurement of this transmission coefficient. Moreover, from the analytical expressions obtained for the frequencies of resonance of the common mode choke in that configuration, we develop a method for obtaining the capacitive, resistive, and inductive parameters of a circuit model of the common mode choke. To validate the proposed technique different commercial common mode chokes have been measured and the predicted performance of the model has been compared with measured responses. We have verified that in all the cases the measured transmission coefficient exhibits the resonant behavior predicted by the theoretical analysis. We have checked that in most cases the method designed for extracting the high-frequency parameters of the circuit model of the common mode choke yields an accurate model of the device up to frequencies as high as 30–50 MHz. An exception are common mode chokes made of materials with an extreme variation of their properties with regards to frequency, such as nanocrystalline materials. [ABSTRACT FROM AUTHOR]

Compared to the dual-active-bridge converter, the dual-bridge series resonant converter (DBSRC) can widen soft-switching range. To further widen the soft-switching range and improve the circuit performance, a new DBSRC with dual tank based on DBSRC is proposed in this paper. This new converter features two resonant tanks and a tapped transformer, and it can perform better than the DBSRC by optimized tap coefficient x of the tapped transformer. Its operation principle, voltage gain, the soft-switching characteristics, and output power are analyzed in detail, and compared with the DBSRC. Results show that the proposed dual-tank topology has presented higher voltage gain, wider soft-switching region, and larger output power than the traditional DBSRC when the tap-coefficient x is selected reasonably. At last, a 1-kW prototype is built; experimental results verify the feasibility and advantages of the proposed dual-tank converter. [ABSTRACT FROM PUBLISHER]

Grid impedance and the output impedance of grid-connected inverter are important parameters for the operation of grid-connected systems, such as solar, wind, and other distributed-generation resource systems. The impedance mismatch between the grid and the interfacing circuit often generates harmonic resonances that lead to reduced power quality and even instability. Since the impedances usually vary over time as a function of many parameters, online measurements are required for stability assessment and adaptive control of the inverters. Several methods have been proposed for quick, accurate measurements of impedances, but the use of multiple-input multiple-output (MIMO) identification techniques have not been considered. Applying the MIMO techniques, different components of the inverter output impedance or grid impedance can be simultaneously measured during a single measurement cycle. Therefore, the operating conditions of the system can be kept constant during the measurements, and the overall measurement time is significantly reduced. This paper shows the use of orthogonal binary sequences to simultaneously measure the “d” and “q” components of grid-connected inverter output impedance and/or grid impedance. Experimental results based on a three-phase grid-connected inverter are presented and used to demonstrate the effectiveness of the proposed methods. [ABSTRACT FROM PUBLISHER]

Instead of bulky electrolytic capacitors, active power decoupling circuit can be introduced to a single-phase converter for diverting second harmonic ripple away from its dc source or load. One possible circuit consists of a half-bridge and two capacitors in series for forming a dc-split capacitor, instead of the usual single dc-link capacitor bank. Methods for regulating this power decoupler have earlier been developed, but almost always with equal capacitances assumed for forming the dc-split capacitor, even though it is not realistic in practice. The assumption should, hence, be evaluated more thoroughly, especially when it is shown in the paper that even a slight mismatch can render the power decoupling scheme ineffective and the IEEE 1547 standard to be breached. A more robust compensation scheme is, thus, needed for the dc-split capacitor circuit, as proposed and tested experimentally in the paper. [ABSTRACT FROM AUTHOR]

This paper presents a transformerless bipolar dc–dc converter based on series-connected submodules. It is intended for transforming dc voltage and managing power flow for medium/high-voltage dc grids. The dc–dc converter is composed of positive-pole and negative-pole subsystems, each of which consists of six arms/branches. Every two arms and one branch are constructed into a T-type circuit with the outer terminals interface to primary- and secondary-side dc buses. The two T-type circuits in one subsystem are connected in parallel to transmit power between primary and secondary sides. The transformerless structure (none bulky coupled inductors as well) solves the challengeable insulation and cooling issues of the extremely high-power magnetics in prior arts, while not sacrificing the power efficiency and system reliability. A $ \pm $ 10-kV 2-MW simulation model performed in MATLAB/Simulink verifies the feasibility of the bipolar dc–dc converter. Experimental results obtained from a laboratory setup also confirm the validation of the proposal. [ABSTRACT FROM AUTHOR]

A high stability flat-top pulsed magnetic field has both high field strength and high field stability simultaneously, which can be used for the high precision scientific experiments. In this paper, we present such a high stability flat-top pulsed magnetic field facility developed in the Wuhan National High Magnetic Field Center. A passive bypass circuit is developed to regulate current up to tens of thousands amperes, as well as a 25 T/200 ms flat-top pulsed magnetic field with a ripple of 250 ppm (0.025%). The main circuit scheme of the facility as well as the preliminary experimental results will be presented in this paper. [ABSTRACT FROM AUTHOR]

Switch fault diagnosis is an important design aspect for pulse width modulation (PWM) dc-dc power converters. It can prevent power converters from further damage, and also make preparations for remedial actions. In this paper, a fast switch fault diagnostic method is proposed for PWM dc-dc converters operating in continuous conduction mode. The proposed method utilizes the magnetic component (inductor or transformer) voltage for fault diagnosis. Based on the real-time voltage measurement and switch gate-driver signals, characteristics of switch open-circuit faults and short-circuit faults are rapidly extracted, and thus, switch faults can be quickly detected. The magnetic component voltage can be measured by an auxiliary winding in the magnetic core, and gate-driver signals can be easily got from the control circuit. Moreover, the fault detection can be implemented by a low-cost logical hardware circuit, and this circuit can be integrated into the control circuit. The fault diagnosis principle, design considerations, and implementation are discussed in this paper. Experiments are conducted to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]