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This paper compares the conducted electromagnetic interference (EMI) in Si insulated gate bipolar transistor (IGBT) and silicon carbide (SiC) junction field-effect transistor (JFET) based motor drives. Two inverters, with the SiC and Si transistors, respectively, are built using the same circuit layout and investigated accordingly. Their conducted EMI levels are compared under the conditions of without filter and with traditional common mode (CM) filters. Reasons of the exhibited different noise emissions are analyzed. To verify the discussions, two inverters are tested in the CM. This allows for the identification and analysis of their maximized CM and differential mode (DM) wave shapes. It is shown that the excited parasitic oscillations during the switching transients are magnified more in the SiC JFET inverter, which is the main cause of the noise difference. Lastly, improved filtering solutions are proposed, which effectively suppressed the increased high-frequency noise due to the faster SiC switching speed. [ABSTRACT FROM AUTHOR]

This paper presents the suppression of conducted common-mode (CM) electromagnetic interference (EMI) in an inverter for motor drive with discrete silicon carbide (SiC) JFETs attached on top of the insulated metal substrate (IMS). The EMC performance of the IMS inverter is compared with that of a heat sink inverter in a similar circuit layout. Both are under the same influence of parasitic capacitive couplings between the SiC JFET drains and the substrate base plate. It is found that although the application of conventional CM filters effectively suppresses the emitted noise in the low-frequency (LF) range, the influence of this capacitive coupling results in slight or no improvement in the middle-frequency (MF) and high-frequency (HF) ranges. To deal with this problem, a system CM equivalent circuit model with extracted parasitic parameters is proposed. The model is able to evaluate the filter insertion losses over a broad conducted EMI frequency band, which is essential to achieve an optimized filter design balanced between performance and cost. The presented experimental and calculated results form the step-by-step guideline that effectively suppresses the generated EMI to comply with the standard prescribed by IEC61800-3 C2: Qp. [ABSTRACT FROM PUBLISHER]

Permanent-magnet (PM) machines are considered the most suitable machine type for very high speed applications. Still, due to the growing demand for the ever higher rotational speeds, PM machines are approaching their limits. The focus of this paper is the different factors that lie behind the inherent speed limitations of PM machines. The limits - thermal, elastic, and rotordynamical - are defined, classified, and correlated to basic machine parameters. [ABSTRACT FROM AUTHOR]

First, an electromechanical converter with two mechanical ports and one electrical port (consisting of two concentric machines and two inverters) is considered. This converter works as a continuously variable transmission between the mechanical ports and may, e.g., replace the clutch, gearbox, generator, and starter motor in a motor vehicle. The working principle of this converter is explained. Next, a new converter, the electric variable transmission (EVT), is presented. This converter has similar properties, but is smaller and lighter. The EVT may be seen as built up from two concentric induction machines with a combined relatively thin yoke. Thus, we obtain one electromagnetic device instead of two magnetically separated devices. The working principle of the EVT is explained, and its losses are discussed. [ABSTRACT FROM AUTHOR]

Deals with a study which developed an enhanced version of a method to minimize the amount of permanent-magnet (PM) material required to create a certain flux linkage in the stator winding of a PM machine. Determination of PM volume; Shaping in single-sided surface-mounted machines; Discussion; Conclusion.

Focuses on a study which developed a mathematical expression for the no-load flux linkage in terms of the permanent-magnet (PM) geometry. PM local contribution to flux linkage; Mathematical derivation; Information on instantaneous and average no-load voltage; Method for the shaping of PM.

Presents a study that described the design of an innovative integrated planar passive module for use in a power electronic converter. Comparison of the experimental values with the design; Use of magnetic material; Conductors in the L-C-T structure.

Gives information on a family of soft-switching unity power factor converters with high input power factor and isolated output, with focus on the reduction of conducted electromagnetic interference (EMI). Features of the converters; Identification of six converter topologies that share a zero-voltage-switching (ZVS) phase arm on the input boost converter stage.

Investigates a novel uninterruptible power supply (UPS) configuration that features low EMI and draws unity power factor without addition of a preregulator. Literature on UPS: Sections of the power circuit; Functions of UPS subconverters; Control of converter's output power; Conclusion.

This paper investigates the diode reverse recovery process and reduction of a half-wave (HW) series Cockcroft–Walton (CW) voltage multiplier based on the steady-state analysis for high-frequency high-voltage (HV) generator applications. The diode reverse recovery process for a multistage voltage multiplier is analyzed after the introduction of steady-state operation. The diode reverse recovery problem is the bottleneck to further increase the circuit operation switching frequency for achieving high power density and short HV pulse rise and decay times. The diode reverse recovery problem is mainly caused by the diodes in the first-stage voltage multiplier. It is suggested that the most effective and economic way to alleviate the diode reverse recovery problem is by employing diodes without reverse recovery such as silicon carbide Schottky diodes in the first stage only. The silicon carbide Schottky diode without reverse recovery needs to be used only in the first stage of the voltage multiplier to effectively mitigate the reverse recovery problems at high frequency. The 300 kHz switching frequency three-stage voltage multiplier circuit hardware prototype experimental results finally validate the analysis. A technology demonstrator of a 300 kHz 8 kW 160 kV HV generator based on the proposed hybrid silicon carbide and silicon diode solution for the HW series CW voltage multiplier is provided finally. [ABSTRACT FROM AUTHOR]

The brushless doubly‐fed induction machine (DFIM) provides an interesting alternative to the commonly applied conventional DFIM in modern multi‐megawatt (MW) wind turbines. This study presents a literature survey on the brushless DFIM. The evolution of the cascaded induction machine into the modern brushless DFIM is discussed, as well as several theories explaining this machines complex operating principles. Nowadays, brushless DFIM research is mainly focused on the development of a commercially competitive brushless DFIM‐based drive for multi‐MW wind turbine applications. An overview of the latest developments in the fields of brushless DFIM modelling, design, and control is provided. Based on this, a qualitative comparison is presented of the brushless DFIM and other well‐established generator systems for wind turbines and the challenges for future research are explored. [ABSTRACT FROM AUTHOR]

Superconducting synchronous generators (SCSGs) are drawing more attention in large direct-drive wind turbine applications. Despite low weight and compactness, the short circuit torque of an SCSG may be too high for wind turbine constructions due to a large magnetic air gap of an SCSG. This paper aims at assessing the effects of armature winding segmentation on reducing the short circuit torque of 10-MW SCSGs. A concept of armature winding segmentation with multiple power electronic converters is presented. Four SCSG designs using different topologies are examined. Results show that armature winding segmentation effectively reduce the short circuit torque in all the four SCSG designs when one segment is shorted at the terminal. [ABSTRACT FROM PUBLISHER]

Abstract: The objective of this paper is to evaluate the feasibility of using claw pole automotive alternator as a generator for small wind turbine and to compare its energy yield and generated electricity cost with commercially available systems. The comparison is based on the energy yield per swept area and cost per energy produced in a low wind speed climate. Concepts such as the selection of suitable turbine parameters and gear ratio were used to achieve good matching of the turbine characteristics with measured alternator performance in order to improve the energy yield from the alternator in battery charging application. The energy yield from the alternator integrated to a 3.9 m diameter turbine is comparable with many commercially available turbines. The generated electricity cost of a commercially available turbine can be reduced by more than a factor of 2 by replacing its generator with our proposed alternator. The alternator-based turbine system is therefore a low cost solution aimed at making wind energy available to areas where the current cost of wind technology makes it prohibitive. [Copyright &y& Elsevier]

Double-sided cooling based on planar packaging method features better thermal performance than traditional single-sided cooling based on wire bonds. However, this method still faces thermal and electrical challenges in multichip SiC power modules. Specifically, one is severe thermal coupling among parallel bare dies, and the other is unbalanced current sharing due to unreasonable layout design. This article aims to explore the potentials of SiC power devices in power module, which are higher current capability and reliability. The proposed packaging method is called interleaved planar packaging and can get rid of the optimizing contradiction between thermal and electrical performance. In this packaging method, there are two functional units: interleaved switch unit and current commutator structure. Benefited from the two units’ electromagnetic and thermal decoupling effects, the interleaved power module features low loop inductance, balanced current, low coupling thermal resistance, and even thermal distributions. A 1200 V 3.25 mΩ half-bridge SiC power module based on interleaved planar packaging is fabricated and tested to verify this method's superiority. [ABSTRACT FROM AUTHOR]

This paper presents a new component within the flexible ac-transmission system (FACTS) family, called distributed power-flow controller (DPFC). The DPFC is derived from the unified power-flow controller (UPFC). The DPFC can be considered as a UPFC with an eliminated common dc link. The active power exchange between the shunt and series converters, which is through the common dc link in the UPFC, is now through the transmission lines at the third-harmonic frequency. The DPFC employs the distributed FACTS (D-FACTS) concept, which is to use multiple small-size single-phase converters instead of the one large-size three-phase series converter in the UPFC. The large number of series converters provides redundancy, thereby increasing the system reliability. As the D-FACTS converters are single-phase and floating with respect to the ground, there is no high-voltage isolation required between the phases. Accordingly, the cost of the DPFC system is lower than the UPFC. The DPFC has the same control capability as the UPFC, which comprises the adjustment of the line impedance, the transmission angle, and the bus voltage. The principle and analysis of the DPFC are presented in this paper and the corresponding experimental results that are carried out on a scaled prototype are also shown. [ABSTRACT FROM PUBLISHER]

Fault current limiters (FCLs) are expected to play an important role in the protection of future power grids. Inductive FCLs are particularly interesting due to their inherent reaction to a fault, but are not commercialized because of a too large amount of magnetic material and an induced overvoltage across dc windings. This paper introduces a new three-phase FCL with a common core and trifilar windings. With the new FCL topology, the phase windings are placed on a single core, resulting in significant reduction of the amount of required magnetic material. Furthermore, the phase windings are wound simultaneously, so that the flux coupling between the phases is increased considerably. It cancels out the magnetic field and reduces the FCL normal impedance significantly. The dc windings are used only to compensate for possible asymmetry in the system currents. Consequently, the number of dc turns and the induced overvoltage are considerably decreased. Testing of a scaled-down FCL lab prototype made it possible to verify the FE simulation results and demonstrated the principle of operation of the new topology. Experimental and simulation results matched very well. [ABSTRACT FROM PUBLISHER]

Diesel generators in small electricity grids are mostly not used in a very efficient way. The reason for this is twofold. First of all, the efficiency of a diesel generator is dependent on the ratio determined by the average power divided by the peak power of the generator. The smaller this ratio is, the lower the efficiency. Furthermore, some loads can regenerate energy. In small grids, this energy is mostly not needed elsewhere and should be dissipated. A solution solving both problems previously mentioned is using an energy storage device in the system. This storage can be used for peak shaving and storing regenerated energy. This paper focuses on a generator-set with energy storage. Six different power management strategies are discussed. Calculation of the costs shows that adding an energy storage device lowers the cost for all methods. Verification with simulation and experiments has been carried out. [ABSTRACT FROM AUTHOR]

Doubly fed induction generator (DFIG) still shares a large part in today's wind power market. It provides the benefits of variable speed operation cost-effectively, and can control its active and reactive power independently. Crowbar protection is often adopted to protect the rotor-side voltage source converter (VSC) from transient overcurrent during grid voltage dip. But under unbalanced grid voltage condition, the severe problems are not the transient overcurrent, but the electric torque pulsation and dc volt- age ripple in the back-to-back VSCs. This paper develops dynamic models in MATLAB/Simulink, validates it through experiments, investigates the behavior of DFIG during unbalanced grid voltage condition, and proposes new controllers in separated positive and negative sequence. Methods to separate positive and negative sequence components in real time are also developed, and their responses to unsymmetrical voltage dip are compared. Simulation results prove that the separated positive and negative sequence controllers limit the torque pulsation and dc voltage ripple effectively. [ABSTRACT FROM AUTHOR]

In this paper, the possibility of reaching high power densities in multikilowatt dc-dc converters with galvanic isolation is demonstrated and the main design issues are discussed. The is- sues related to converter topology, transformer design, and thermal management are addressed, and new conceptual solutions are pro- posed. Implementing zero-voltage-switching quasi-zero-current. switching topology, optimized transformer design with leakage layer, and thermal management based on conduction enhanced by heat pipes at critical places resulted in very high power density and efficiency. The power density reached by the converter prototype is 11.13 kW/L with water cooling and 6.6 kW/L with air cooling. In the same time, the measured efficiency exceeded 97% in a broad load range. The new design concepts are demonstrated on a 50-kW converter prototype that was successfully tested at full-load conditions. [ABSTRACT FROM AUTHOR]

At a workshop held on the Aeolian Islands in Sicily during May 2004 a group of academic and industry engineers from all over the world discussed the medium- and long-term future of power electronics and its applications in specific areas. The following main issues were identified and discussed. • The demand is not for power electronic solutions but for system integration of electronic power processing. A more multidisciplinary approach is needed. • We will witness a proliferation of energy storage in systems. The technology is in place and the improvement in system performance makes it worthwhile. • A large penetration of power electronics into power systems will happen within the next 25-30 years. The main transmission grid will not be affected. The power electronics development will be in distributed generation and in the loads. • The success of the integrated starter/generator (ISG), hybrid, or electric cars depends on political decisions more than on technological advances. However, the success of a recent Japanese hybrid car and the cost of oil could trigger the critical momentum for large-scale use of power electronics in automotive applications. • We are moving toward standardized power supply building blocks for computers and other applications. The main push is for lower cost, and production technology becomes the important issue. • Demands for improved performance in a diversity of applications will stimulate R&D in power electronics in the future. Intelligent control and energy management will come easily. Thermal and passive component integration is equally important and will require attention. [ABSTRACT FROM AUTHOR]

Presents a study which formulated an expression for the no-load flux linkage in permanent-magnet machines. Information on the contribution of magnet elements to the no-load flux; Discussion of the magnet shaping in short-pole-pitch machines; Conclusion.

In this paper, a coupled-inductor-based LCC resonant converter with the primary-parallel–secondary-series (PPSS) configuration is proposed to achieve output-voltage sharing ability for HV generator applications. The PPSS configuration of the LCC resonant converter with the voltage multipliers is introduced to achieve high output-voltage and increase the output-power level. However, the variations of the magnetizing inductance, leakage inductance, and winding capacitance of the HV transformer and voltage multiplier impact on the output-voltage sharing performance. Subsequently, the resonant inductors in the primary side of the conventional LCC resonant converters with the PPSS configuration are coupled to achieve the output-voltage sharing without any additional circuits and control efforts. Furthermore, an analytical equivalent circuit model considering the magnetizing inductor of the HV transformer is derived to analyze the output-voltage sharing ability. Moreover, the design method for the coupled inductors considering the output-voltage sharing performance affected by the leakage inductance of the coupled inductors is presented. Finally, the output-voltage sharing performance of the proposed coupled-inductor-based LCC resonant converter with the PPSS configuration is validated by the experimental results of a 50-V input, 5-kV output 100-W prototype. The prototype experimental results show that the unbalance voltage degree decreases from 67.7% to 8.5% with the utilization of the coupled inductor. [ABSTRACT FROM AUTHOR]

In this paper, a unified equivalent circuit model which can simplify the design and analysis of a family of high-voltage (HV) generation architectures based on the series–parallel (LCC) resonant converter is proposed. First, four HV generation architectures are reviewed in terms of the modularization level of HV transformers and rectifiers. Next, the steady-state, unified equivalent resistor and capacitor (RC) model that can be easily embedded into the resonant tank to replace the complex HV transformers and rectifiers is derived. The generic model can be applied to the HV generators with different architectures, different voltage multiplier topologies, stage, and polarities number. Further analysis of the power factor of the resonant tank, the voltage gain of HV generators, and electrical stresses of power components is achieved with the derived equivalent circuit model. The analysis reveals the inherent circuit properties among HV generators with different configurations. Subsequently, a comprehensive design methodology considering the power factor, conduction angle, and quality factor is presented, which leads to low electrical stresses on the components and high efficiency. Furthermore, the parameter selection constraint based on the power factor, conduction angle, and quality factor is derived, which can ensure the effective design outputs. Finally, the proposed unified equivalent model and comprehensive design methodology are validated by the experimental results of a 250 V input, 20 kV output 500 W HV generator hardware prototype with distributed transformers and voltage multipliers. [ABSTRACT FROM AUTHOR]

This paper aims at assessing the potential of partially superconducting generators for 10 MW direct-drive wind turbines by investigating their performance for a very wide range of excitation currents. Performance indicators such as shear stress and efficiency and other generator characteristics are compared for 12 different generator topologies. To be sufficiently attractive, superconducting generators must have significant advantages over permanent magnet direct-drive generators, which typically have shear stresses of the order of 53 kPa and efficiencies of 96%. Therefore, we investigate what excitation is required to obtain a doubled shear stress and an efficiency of 98%. To achieve this, the different topologies require a range of excitation from 200 to 550 kAt (ampere-turns) with a low armature current density of 2 A/mm$^2$ . The more iron that is used in the core of these topologies, the easier they achieve this performance. By examining the maximum magnetic flux density at the location of the superconducting field winding, feasible superconductors can be chosen according to their engineering current density capabilities. It is found that high- and low-temperature superconductors can meet the performance criteria for many of the topologies. MgB $_2$ superconductors are feasible for the fully iron-cored topology with salient poles but need cooling down to 10 K. [ABSTRACT FROM PUBLISHER]

This paper describes the behavior of voltage weak DC distribution systems. These systems have relatively small system capacitance. The size of system capacitance, which stores energy, has a considerable effect on the value of fault currents, control complexity, and system reliability. A number of potential definitions of voltage weak DC distribution systems are proposed. These definitions address the main characteristics of voltage weak systems. A small signal model of a general voltage weak DC distribution system is developed in order to observe sufficient conditions for system stability. This is achieved by analyzing the dominant poles. The source converters are modeled as droop-controlled current sources in parallel with their respective terminal capacitors. As constant power loads have incremental negative impedances, which affect the system stability, especially, in voltage weak system, ideal constant power loads with their terminal capacitors are included in the small signal model. A three-node voltage weak DC distribution grid is analyzed, as a case study, by implementing the developed small signal model. The effects on system stability by the values of system capacitance, cable inductance, and cable resistance are investigated using dominant pole placement. Likewise, the influence of proportional-integral regulators and droop coefficients of source converters on the stability of the system is examined. Finally, the three node DC distribution grid is developed in MATLAB/Simulink in order to demonstrate the influence of small capacitance on system stability. Moreover, effect of the rate of change of constant power loads on the system stability is simulated. These results are further compared and verified on a voltage weak DC experimental test bench with a 350 VDC bus voltage. [ABSTRACT FROM AUTHOR]

This paper deals with a generic methodology to evaluate the magnetic parameters of contactless power transfer systems. Neumann's integral has been used to create a matrix method that can model the magnetics of single coils (circle, square, rectangle). The principle of superposition has been utilized to extend the theory to multi-coil geometries, such as double circular, double rectangle and double rectangle quadrature. Numerical and experimental validation has been performed to validate the analytical models developed. A rigorous application of the analysis has been carried out to study misalignment and hence the efficacy of various geometries to misalignment tolerance. The comparison of single-coil and multi-coil inductive power transfer systems (MCIPT) considering coupling variation with misalignment, power transferred and maximum efficiency is carried out. [ABSTRACT FROM AUTHOR]

Provides information on a study which investigated the theoretical calculation of losses in a planar inductor under load. Development of the loss model; Thermal measurements in planar inductors; Application of finite element method in calculating loss measurements.