Search

A comprehensive study on the dielectric modulated (DM) drift region for power devices is presented in this paper. The performance of this drift region structure is theoretically analyzed and compared with other two structures: conventional and superjunction. In this paper, a study is focused on switching performance. The C – V relationships during switching are analytically derived, and the depletion widths predicted by the proposed analytical model agree well with simulation in a wide reverse bias region. The switching energy loss is evaluated based on the analytical model and its accuracy is verified by 2-D simulations. An effective depletion charge QD is defined as E\mathrm {loss} / breakdown voltage (BV), from which a figure of merit (FOM) of R\mathrm{\scriptscriptstyle ON,\mathrm {sp}}{}^\ast QD is proposed to compare the performances of these different drift region structures, considering both the conduction and switching losses. The discussions in part I on Si and silicon carbide device structures are extended in part II to include FOMs. It is found that the DM drift region structures show better R\mathrm{\scriptscriptstyle ON,\mathrm {sp}} -BV tradeoffs compared with the conventional structures, but slighter inferior FOMs. However, DM structures are still attractive for applications, where switching loss is less critical than the conduction loss, such as low frequency or soft switching. [ABSTRACT FROM PUBLISHER]

This paper proposes a new isolated single-stage single-switch power-factor-correction (S4 PFC) driver for supplying light-emitting diodes (LEDs) without electrolytic capacitor. In the proposed LED driver, the switch turns on under zero current switching (ZCS) condition. Also, it turns on at a voltage less than its nominal voltage stress, and therefore, the switch capacitive turn-on loss decreases too much extent. The leakage energy is absorbed, so there are no voltage spikes across the switch when the switch turns off. In this paper, operating principles of the proposed driver are discussed, and design considerations are presented. Also, a laboratory prototype for supplying a 21 W/30 V LED module from 220 Vrms/50\,\rm Hz ac mains is implemented, and experimental results are presented to verify the theoretical analysis. [ABSTRACT FROM PUBLISHER]

The predictive control method deals with the prediction of the motor behavior based on a mathematical model of the motor. This model is dependent on the motor parameters. However, these parameters may not match with their actual values due to the measurement error or they may change during the operation of the motor. All these uncertainties and model inexactitude lead to inaccurate prediction of the motor behavior and deteriorate the performance of the predictive algorithm. This paper presents an extension of the predictive current control (PCC) method to improve the prediction accuracy for a permanent-magnet synchronous motor (PMSM). The proposed strategy not only reduces the current ripple but also improves the robustness of the system against parameter uncertainties. Simulation and experimental results that confirm the good performance of the proposed method are presented. [ABSTRACT FROM PUBLISHER]

Important global efforts are underway toward lowering the cost of electric machines for electric and hybrid vehicles by reducing or eliminating the use of rare-earth materials which have been experiencing significant price increases and volatility. Non-permanent-magnet (non-PM) electric machines are a potential solution and are increasingly investigated by researchers worldwide. This paper presents a DC-biased reluctance machine, which is structurally similar to a conventional switched reluctance machine. This type of machine has a DC field winding and an AC three-phase armature winding. It uses a conventional three phase inverter for the armature and an additional auxiliary DC/DC converter for the field winding. This reluctance machine is designed to achieve hybrid vehicle traction requirements of 55 kW peak at 2800 \rmr/min and 30 kW continuous over a speed range going from 2800 to 14 000 \rmr/min. [ABSTRACT FROM PUBLISHER]

In order to provide the ancillary service for smart grid, this paper proposes a modelling and control protocol design approach for the aggregation of heterogeneous thermostatically controlled loads (TCLs). A 2-D state bin is proposed to model the second-order TCL dynamics in a population model. Detailed procedure of calculating the transition probability in the system matrix is provided. In the controller design, a model predictive control (MPC) scheme is proposed to obtain the optimal control actions along the prediction horizon. In addition, implementation of the control signal for adjusting TCLs' statuses are also investigated with practical situations considered. Simulation results reveal the feasibility and efficacy of the proposed modelling and control approach when applied on a large population of TCLs. Some factors that may affect the service performance are also discussed in this paper. [ABSTRACT FROM AUTHOR]

Practical applications of controllers often impose further requirements on the implementation beyond the actual control performance, such as the ability to switch between manual and automatic control or between different control laws or controller parameter settings, known as bumpless transfer. Another common requirement is to limit the control signal in magnitude and/or rate. This paper examines and extends several discrete-time variants of active disturbance rejection control (ADRC), which is increasingly being applied especially in the field of power electronics and drives, in this regard. Detailed guidelines for practical ADRC implementations with these abilities are presented, and all features are being demonstrated with the help of simulation examples. [ABSTRACT FROM PUBLISHER]

This paper presents the analysis of possible transient overvoltages that can be generated during vacuum circuit-breaker (VCB) operation at the connection point of a photovoltaic powerplant. A typical switching event that is related to the VCB concerns energization and de-energization of the unloaded transformer. However, at the typical photovoltaic powerplant, the transformer is fed by an inverter equipped with LC (or LCL) filters that are necessary for limitation of harmonics and ripple in voltage and current. From the point of view of switching operations, the inductance and capacitance of the low-voltage (LV)-side connected filter affect the natural frequency of the transformer, which is reflected by different transient system response during VCB operation. In this paper, laboratory measurement of overvoltages generated during distribution transformer switching by means of VCBs is analyzed. The impact of the LC filter connected at the LV side on the overvoltages suppression was studied. Electromagnetic Transients Program–Alternative Transients Program simulations were conducted in order to verify the possibility of transients elimination by means of the additional series-connected RL choke at the transformer medium-voltage side. [ABSTRACT FROM PUBLISHER]

This paper develops a simplified phasor model for predicting harmonics present at the point of common coupling between a voltage-source power converter and the utility network. It employs the frequency coupling matrix (FCM) modeling technique. The FCM is experimentally determined without requiring access to converter internal details, such as control and output filter parameters, which are generally not available for converters used in distributed generation systems. Experimental measurements are conducted on a commercially available two-stage, three phase, grid-tied photovoltaic inverter to assess the accuracy of experimentally determined FCMs to predict the harmonic behavior of grid-connected converters. This paper considers two grid conditions for the experimental analysis: 1) when the grid is stiff and contains only background voltage harmonics and 2) when the grid contains harmonic grid impedances as well as background voltage harmonics. In all cases, a close match between the results predicted by the FCM approach and experimental measurements is achieved, thus demonstrating the practical viability of using experimentally determined FCM models for harmonic predictions. [ABSTRACT FROM PUBLISHER]

Power electronics is a fast-developing technology within the electrical engineering field. This paper presents the results and experiences gained from applying design-oriented project-based learning to switch-mode power supply design in a power electronics course at the Technical University of Denmark (DTU). Project-based learning (PBL) is known to be a motivating problem-centered teaching method that not only places students at the core of teaching and learning activities but also gives them the ability to transfer their acquired scientific knowledge into industrial practice. Students choose a specification to implement from various power converter application projects, such as a fuel cell power conditioning converter, a light-emitting diode (LED) driver or a battery charger. The students select the topology, design magnetic components, calculate input/output filters and design closed-loop controllers necessary to fulfill the requirements listed in the chosen specification and thus meet the project's goals. This paper presents the course teaching plan and teaching methods, assessment method and student feedback. [ABSTRACT FROM PUBLISHER]

This paper presents an improved dc-link voltage balancing algorithm for a three-level neutral-point-clamped inverter by considering phase current direction. Detailed studies on the effects of change in load current direction on the dc-link capacitor voltages are presented. A maximum value of power factor is numerically derived, above which it affects the capacitor voltage balancing capability. Compared with the previously presented research work, the inputs to the space-vector pulsewidth-modulation block are the three phase currents and the difference between the two capacitor voltages. Depending on the states of the two dc-link capacitor voltages and phase current direction, redundant voltage vector sequences are selected. The selected vectors keep the capacitor voltage deviations within 5% of the total dc-link voltage. Two zero switching vectors (i.e., PPP and NNN) are also removed from all subsectors of the earlier proposed strategy, which one used to produce higher common-mode voltages. Detailed simulation and experimental results are presented in this paper for a 6.0-kW surface permanent-magnet synchronous machine. Both the simulation and experimental results show the required performance of the proposed system. [ABSTRACT FROM AUTHOR]

In this paper, two simple control methods are proposed for improving direct torque control (DTC) with a constant frequency torque controller (CFTC-DTC) in induction machines. The CFTC-DTC was initially introduced to reduce torque ripple and achieve constant switching frequency in inverters. However, when compared to the original DTC, the CFTC-DTC algorithm suffers from slow torque dynamic response owing to the selection of zero-voltage vectors during torque transient. In addition, when the motor operates at low speed, flux droop occurs at sector transitions, which leads to undesirable current distortions. The problem of flux droop occurs because of short-duty voltage cycles and small radial voltage components at low speeds. This paper has two main contributions—to eliminate zero-voltage vectors during torque dynamics in order to establish a fast torque response in the transient state, and to minimize the flux droop at the sector transitions by applying another triangular carrier and modifying the torque output in order to increase the duty voltage cycles at low motor speeds. A detailed analysis of the problems and proposed methods is presented. Experimental results are provided to validate the effectiveness of both proposed methods. [ABSTRACT FROM AUTHOR]

Various methods have been presented in the past to emulate the electrical behavior of modular multilevel converters (MMCs). To meet the demands for the reliability aspect study of MMCs, this paper proposes a viable setup to emulate the thermal behavior and to investigate its feasibility for reliability testing and thermal model validation of the power modules in the MMC. The proposed mission profile emulator has three distinctive features: 1) capable of emulating and measuring the thermal stresses of power modules; 2) capable of implementing practical switching profile as a full-scale MMC; and 3) having significantly reduced requirement for dc power supply compared to existing setups used for electrical studies. Theoretical discussions, and simulations as well as the experimental results are presented to demonstrate the capability of the mission profile emulator both electrically and thermally. Moreover, this paper is accompanied by a video demonstrating how to measure the junction temperature of the power devices using the optical fiber and the thermal camera. [ABSTRACT FROM AUTHOR]

A space vector modulation (SVM) technique of a dual-inverter system for an open-end winding motor drive is described in this paper, where one inverter has a battery power source and the other has an only capacitor across the dc bus. The SVM must be achieved to operate the motor with field-oriented control and simultaneously to control the capacitor voltage at a constant value by using redundant switching states of the dual-inverter system. The control of the capacitor voltage is carried out by selecting a charging or a discharging mode in each redundant switching state, taking the instantaneous motor power factor into account. In addition, it is also required to reduce the error voltage pulses, which are generated in output multilevel voltage waveforms during the dead time. The compensation method of the existing dead-time scheme and the improved SVM sequence to reduce the error voltage vectors are proposed in this paper. The proposed methods are examined through several experimental tests and are confirmed to generate superior output voltage waveforms from the viewpoint of the measured total harmonic distortion and dv/dt. [ABSTRACT FROM AUTHOR]

In this paper, a new dc–dc high voltage gain converter with low-voltage stresses on switches and diodes is proposed. Even though, in the topology of the proposed converter there are not any coupled inductors and transformer utilized, the voltage conversion ratio of the proposed converter is considerable in comparison to its conventional types. Also, two switches of the proposed converter provide longer charge time for two inductors which make the proposed converter capable of providing high voltage gain without preselecting extremely large duty cycles. In addition, the number of power circuit components of the proposed structure are few and the voltage stresses on semiconductor elements are low. In this paper, theoretical analysis of the proposed converter for each operating mode is presented and the voltage gain, voltage and average current stresses of elements, maximum input current ripple, efficiency and equations of critical inductances are calculated. Moreover, to verify the capability of the proposed converter, it is comprehensively compared with other similar recently presented high voltage gain boost converters. Finally, an approximately 12 V/380 V and 520-W prototype of the proposed converter is implemented in laboratory to demonstrate its practical performance, then, the experimental results reconfirm each other and theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper presents bidirectional grid-connected modular multilevel converters (MMC) with direct digital control and division-summation processes to achieve power-injection and rectification functions. A direct digital control is developed to track current references, regulate dc-bus voltage and cell voltage, and balance the upper and lower dc-bus voltages. It can accommodate wide filter-inductance variation and take care of source voltage harmonics to achieve tight current tracking and low distortion output current. Based on the power-balance principle, the commands of arm currents can be determined directly. In this paper, the MMC configuration is introduced first, and then the control laws for current tracking and voltage regulation are derived in detail. Experimental and simulated results obtained from two 50 kW MMCs operated in power-injection and rectification modes have verified the analysis and discussion. [ABSTRACT FROM AUTHOR]

This paper presents a new configuration of high gain (HG) single ended primary inductor converter (SEPIC) with a ripple-free input current to maximize the efficiency of the PV panel for standalone water pumping system (WPS). The ripple eliminating circuit combined with the HG SEPIC converter to achieve reduced ripples in photovoltaic (PV) current is independent to the duty cycle control and hence, it can be easily integrated to the main power circuit of configuration. This circuit does not need any active switches, control, or drive circuit for its execution. The ripple eliminating circuit yields a complete removal of the electrolytic capacitor connected across the PV array and significantly reduces the inductance of the HG SEPIC converter. It also improves the response and power density of the dc–dc converter. The large gain of dc–dc converter enables the use of low-voltage PV panel and minimizes the partial shading and parasitic capacitance effects on PV array source. Due to the substantial compatibility between natural characteristics of switched reluctance motor (SRM) drive and WPS, a four-phase SRM drive is utilized in the proposed scheme. In addition, a single current sensor based maximum power point tracking technique is utilized in the proposed system, which helps to reduce the cost and improve the accuracy of the overall system. Analytical, simulated, and experimental results of the developed system are presented to demonstrate the performance of the system. [ABSTRACT FROM AUTHOR]

The operating principle of the clamp circuits like clamping diodes and flying capacitor in three-level LLC converter is different from other three-level converters, because the mean value of the resonant tank current is always zero and pulse-frequency modulation control is generally used instead of pulsewidth modulation control. And the converter with only the clamping diodes or flying capacitor is difficult to realize voltage balance. In this paper, the characteristics of the three-level LLC converter with single clamp circuit are first analyzed. Then, the operation principle of the hybrid-clamped circuit under the unbalanced voltages on input capacitors is described with the mode analysis, based on which the mechanism for voltage autobalance is elaborated and the effects of two clamp circuits are derived. Then, the design of the clamping diodes and the flying capacitor is also involved. Finally, a three-level LLC converter prototype is built and the experimental results verify the validity of the theoretical analysis and design. [ABSTRACT FROM AUTHOR]

Unipolar-pulsewidth modulation (UP-PWM) inverter takes advantages of high power efficiency and small output chokes which is widely used in the industry. However, UP-PWM inverters cannot be used in parallel operation due to a current unbalance problem. This paper studies the current unbalance problem of paralleled UP-PWM inverters with common dc bus and ac bus. First, the problem of unbalanced inductor current is defined and analyzed. Second, a technique to eliminate unbalanced currents is proposed. The proposed current balancing technique only requires one more current sensor in an inverter module rather than changing converter topology or modulation method, which makes it possible to apply UP-PWM inverters in parallel-operation while keeping the advantages of unipolar switching. The proposed current balancing method is verified by both simulation and hardware experiment. Experimental verification is performed on two 1 kW, 400 V input, and 120 V/60 Hz output prototypes, which shows a good agreement to the analytical study. [ABSTRACT FROM AUTHOR]

There currently exists a mature literature on modeling the aggregate load of a distribution feeder by making use of measurements at its feeder-head at substation. The primary application of such feeder-aggregated load models is in sub-transmission or transmission system analysis. However, there is a growing need in practice also to model each individual load across the feeder. If available, such individual load models have applications in power distribution system analysis, e.g., to better integrate distributed energy resources or to improve power quality and reliability. Motivated by this observation, in this paper, we propose a new method for individual load modeling in power distribution systems. It works by using the measurements only at the feeder-head. It takes an innovative approach to analyzing the load switching events across the distribution feeder itself, instead of or in addition to relying on upstream voltage events that are commonly used in feeder-aggregated load modeling. By tracking the downstream load switching events, the proposed method can make a robust estimation of the ZIP load model parameters for all individual loads. The proposed method is examined on small illustrative test-feeders as well as the IEEE 33-bus test system under various operating scenarios. The adverse impact of errors in measurements and system parameters are also investigated on the performance of the developed load modeling method. [ABSTRACT FROM AUTHOR]

This paper is concerned with quasi-synchronization of delayed memristive neural networks (MNNs) with switching jumps mismatches via aperiodically intermittent control. The issue is presented for three reasons: 1) the existing controllers for synchronization may be too complicated and not economical; 2) under the influence of switching jumps mismatches, synchronization of MNNs may fail to achieve; and 3) matrix measure method is less conservative but cannot be applied directly to synchronization of MNNs. To overcome these difficulties, the concept of asynchronously switching time interval is proposed to describe the phenomenon when the drive-response MNNs switch their connection weights asynchronously. Then, aperiodically intermittent control is designed and quasi-synchronization analysis is carried out based on a combined method that compromises the merits of interval matrix method and matrix measure method. A quasi-synchronization criterion, expressed in terms of the mixture of ${p}$ -norm and matrix measure of the memristive connection weights, is established. Meanwhile, the fundamental reason for the failure of complete synchronization is revealed. Moreover, an explicit expression of the error level is obtained and the design of the controller under a predetermined error level is presented. The obtained results in this paper reduce the conservativeness and provide a novel insight into the research of synchronization of MNNs. [ABSTRACT FROM AUTHOR]

Solid state transformer (SST) integrated hybrid dc–ac microgrid (HMG) has wide operating capabilities in presence of dc–ac loads, renewable energy resources, and energy storage. This paper proposes control strategies for localized control of zonal hybrid microgrid, enabled by the SST and centralized energy storage devices (ESD) integrated using dual active bridge (DAB) converter. The control of DAB dc–dc converter is modified for zero circulating power flow (ZCPF) operation in both SST and ESD. Power management and coordination control used in this paper ensures the power supply reliability of the zonal HMG integrated through the SST. Microgrid system, along with its proposed controllers, provides a stabilized low-voltage dc and ac network ports, in both grid feeding and forming modes. The performance of the configured HMG system is evaluated under various power management scenarios using the MATLAB software platform. Further, the SST architecture, with its proposed controller, is tested on FPGA-based hardware platform. [ABSTRACT FROM AUTHOR]

This paper presents a novel integrated-stage light-emitting diode (LED) driver based on Flyback and resonant converters. The Flyback converter realizes power factor correction in the discontinuous conduction mode. The resonant converter is operated as a dc–dc converter to support the LED loads. Moreover, the resonant converter can clearly decrease the drain–source voltage of the active switch and exhibits zero-voltage-switch characteristics. Therefore, a cost-effective MOSFET can be chosen as the main control component that can decrease the cost of the whole system. Compared to a single-active-switch converter (such as Class-E converter), the number of passive components in the resonant converter can be limited to four. Therefore, the power density of the system can be improved drastically. In this paper, a 100-W prototype is presented under the experimental condition to validate the proposed integrated-stage LED driver. [ABSTRACT FROM AUTHOR]

The new continuous fast terminal sliding mode control (CFTSMC) is adopted in this paper for the speed regulation of permanent magnet synchronous motor drive applications. The CFTSMC method has a capability to converge the error faster, provide higher tracking accuracy and robust against the load disturbances. However, the CFTSMC method needs high switching gain during the strong disturbances, which introduces the chattering and steady state variation to the system. To address these issues, a composite CFTSMC technique based on the extended state observer (ESO) is proposed in this paper. The ESO is used to estimate the system disturbances for feed-forward compensation. The ESO-based CFTSMC method needs smaller switching gain than the CFTSMC method. Moreover, the ESO-based CFTSMC method has a strong robustness against load disturbances, better convergence rate, and better tracking accuracy than the CFTSMC and conventional continuous sliding mode control method. The superiority of the proposed control method is verified by the Lyapunov function and confirmed by the simulation and experimental results. [ABSTRACT FROM AUTHOR]

Tile-based viewport-adaptive streaming methods have been used in delivering omnidirectional video for virtual reality applications. In these methods, the 360° video is encoded in multiple quality versions by using the motion constrained tile set (MCTS) technique. A set of high-quality and low-quality tiles, corresponding to viewport and non-viewport areas, respectively, are selected and transmitted to the user. However, these methods require frequent intra random access points to ensure seamless viewport switching capability, very high decoding complexity, or a multi-layer coding scheme. The frequent intra random access points include very high bitrate in viewport switching points. The high decoding complexity and multi-layer decoder requirements are not aligned with the omnidirectional media format (OMAF) standard. Such requirements make these methods sub-optimal or impractical for streaming the omnidirectional video. This paper studies the current tile-based solutions for delivering the omnidirectional content. Moreover, the OMAF-compliant shared coded picture (SCP)-based scheme is proposed in this paper for streaming the omnidirectional video. The core concept of the SCP-based method is to manipulate the switching point pictures in a way that the frequent intra-coded pictures are no longer required for the viewport switching operations between different quality versions of the content. The experiments illustrated that the SCP-based method outperforms the MCTS-based method on average by 11% to 14% in terms of streaming bitrate reduction with only 4% extra decoding complexity. [ABSTRACT FROM AUTHOR]

This paper investigates a Vienna rectifier as a charger for series-connected battery packs. Focusing on carrier-based pulsewidth modulation (CBPWM), the ripple current flowing through the neutral point (NP) results in the voltage oscillation if the loads are resistive. To reduce the ripple of average NP current with mitigated distortion under balanced and unbalanced dc-link voltages conditions, a novel CBPWM with segmented component injection scheme (SCIS) is proposed in this paper. After dc component injection, continuous intervals for optimized component injection and clamping intervals for compensation component injection are identified. Optimized components are calculated originally based on unbalanced factor to make the average NP current zero-size in one switching period. Moreover, unique compensation components generate suitable NP current to shape the sinusoidal input currents according to the circuit analysis. In consequence, the SCIS not only keeps the input current with low-harmonic distortion, but also minimizes the oscillation of dc-link voltage under balanced and unbalanced conditions. In addition, the value of the NP current during the clamping intervals is analyzed under various operating conditions. The effectiveness and the performance of the proposed SCIS are verified by simulation and experiments. [ABSTRACT FROM AUTHOR]

This paper presents an interleaved boost converter with a bifold Dickson voltage multiplier suitable for interfacing low-voltage renewable energy sources to high-voltage distribution buses and other applications that require a high-voltage-gain conversion ratio. The proposed converter was constructed from two stages: an interleaved boost stage, which contains two inductors operated by two low-side active switches, and a voltage multiplier cell (VMC) stage, which mainly consists of diodes and capacitors to increase the overall voltage gain. The proposed converter offers a high-voltage-gain ratio with low voltage stress on the semiconductor switches as well as the passive components. This allows the selection of efficient and compact components. Moreover, the required inductance that ensures operation in the continuous conduction mode (CCM) is lower than the one in the conventional interleaved boost converter. The distinction of the proposed converter is that the inductors’ currents are equal, regardless of the number of VMCs. Equal sharing of interleaved boost-stage currents reduces the conduction loss in the active switches as well as the inductors and thus improves the overall efficiency, as the conduction power loss is a quadratic function. In this paper, the theory of operation and steady-state analysis of the proposed converter are illustrated and verified by simulation results. A $\text{200-W}$ hardware prototype was implemented to convert a $\text{20-V}$ input source to a $\text{400-V}$ dc load and validate both the theory and the simulation. [ABSTRACT FROM AUTHOR]

Marx generator using all-solid-state devices has been studied for many years. Higher parameters are always the demand for new applications. Traditional all-solid-state Marx generator can output high voltage due to its series topology, but the current is always limited by the switch. In this paper, a stage-stage paralleled topology of Marx generator for high current has been proposed. Topology structure and driving mode comparison for current balance have been analyzed. The paralleled driving mode for the current balance and the shaping waveform has been proposed. For experiment, a four-stage-four-paralleled Marx generator with metal–oxide–semiconductor field-effect transistors (MOSFETs) has been constructed with output pulses 2.2 kV, 730 A (depending on the load), rise time of 31 ns, fall time of 56 ns, and adjustable pulsewidth from 400 to 800 ns. [ABSTRACT FROM AUTHOR]

This paper describes a study on the high-voltage compact solid-state pulsed-power modulator for parallel reactor operation. The current capacity of the pulsed modulator has been improved to drive multiple reactors in parallel. The pulse discharge switch uses the IXYK120N120C3 (1200 V/120 A) insulated-gate bipolar transistor for a high current output. The gate driver has been improved according to the characteristics of the replaced switch. The output specifications of the modified pulsed-power modulator are a maximum output voltage of 40 kV, a maximum output current of 300 A, a pulsewidth ranging from 1.5 to $5~\mu \text{s}$ , a maximum repetition rate of 3 kHz, and an average power of 13 kW. The modulator has the dimensions of $450 \times 475 \times 600$ mm3, a maximum peak power of 12 MW, and a maximum power density of 93 kW/L. A resistive load experiment and a plasma reactor parallel drive test were performed. Four parallel reactors were driven using one modulator. In addition, a 50% reduction in the concentration of toluene was obtained through the experiment of the toluene gas treatment using only parallel plasma reactors. [ABSTRACT FROM AUTHOR]

Switching behavior analysis is an indispensable step for evaluating the steady-state performance of a bidirectional dc–dc converter and a prerequisite for soft-switching modulation design. For dual-bridge series resonant dc–dc converters (DBSRCs), the commonly used fundamental harmonic approximation (FHA) does not usually provide predictions accurate enough for reliable analysis and design. This paper discloses the exact closed-form solution for the zero-voltage switching (ZVS) operation conditions of DBSRCs for the most general case, in which all modulation quantities—i.e., phase shift, duty cycles, and switching frequency—are included. The proposed approach relies on a geometrical analysis of the converter state-plane trajectory, and allows us to analytically predict the ZVS or hard-switching state of any switch and for any given converter operating point. By inherently capturing the effects of all tank harmonics, the model disclosed in this paper shows higher accuracy than the conventional FHA-based approach, and translates into a practical tool for ZVS prediction and optimization at the converter design stage. Based on the derived analytical results, switching behavior of DBSRCs with minimum rms current trajectory (MCT) modulation is investigated, and an effective design choice of resonant-to-switching frequency ratio is presented, which contributes to reduced switching losses and enhanced efficiency. Furthermore, a variable frequency modulation scheme is formulated, achieving ZVS operation of all transistors over a wide input/output voltage range and efficiency improvement versus MCT technique. The analysis and conclusions are validated via extensive experimental tests on a 700 W DBSRC prototype. [ABSTRACT FROM AUTHOR]

In low-power applications of photovoltaic (PV) systems, the transformerless grid-connected inverters have been preferred to increase the efficiency and reduce the cost, size, and power losses when they are compared to the ones with the transformer. A transformerless single-phase inverter topology with a single dc-link capacitor for the grid-connected PV systems is proposed in this paper. The proposed inverter has been simulated by using a cooperation process of the MATLAB and SPICE package programs and it has been implemented for experimental verification. The proposed inverter reduces the high-frequency common-mode leakage current caused by parasitic capacitances of PV panels, whereas it is controlled with the unipolar sinusoidal pulsewidth modulation. Also, the results show that the common-mode voltage remains constant. The efficiency of the proposed inverter has been compared to that of the most common topologies having the dc-link decoupling during the zero voltage states. This paper is accompanied by a video file demonstrating the power loss distribution in the inverter. [ABSTRACT FROM AUTHOR]

Electrically excited synchronous machines have shown potential to be an alternative to permanent magnet synchronous machines in electromobility and wind power applications. High-frequency wireless power transferring technology enables a compact design of brushless exciters for the machine. In this paper, a dynamic model of high-frequency brushless exciters is proposed for the purposes of operating condition monitoring and excitation control. The modeling is done by using arithmetic and differential equations as well as considering different operation modes of the system. The operation modes are defined based on the physical behaviors of the excitation circuit. Experiments are performed to verify the model with variations of different circuit parameters. Furthermore, parameter sensitivity study, component parameter selection, and loss analysis are conducted to demonstrate the effectiveness of the model. The model is therefore proposed as an effective tool to assist the design and optimization of the brushless excitation system. [ABSTRACT FROM AUTHOR]

One of the recent trends in power electronics field is to achieve high efficiency and compact size by using wide bandgap power devices such as silicon carbide (SiC) or gallium nitride switches. This paper compares the efficiency, the motor terminal voltage quality (dv/dt), and the common mode current of the SiC-based variable frequency drives (VFDs) according to the inverter topologies with and without the output filters. For this purpose, both the 2-level (2L) and 3-level (3L) topologies with SiC devices are built and tested. Here, the well-known 2L half-bridge inverter is compared with the well-known 3L T-type neutral point clamped inverter. A dv/dt filter and a sine wave filter have been discussed to satisfy the National Electrical Manufacturers Association standards as well. The experiments have been carried out with a 380-V/60-Hz, 3.7-kW induction motor and the custom designed power stages. Additionally, the experiments with both a 3-m and a 50-m cable length between the VFD and the induction motor are performed and reported. [ABSTRACT FROM AUTHOR]

In this paper, a new vibration reduction control of the switched reluctance machine (SRM) is proposed, which takes into consideration the undesirable effects of the torque ripple. The control approach aims to reduce the variation of the sum of radial forces while optimizing the control parameters of the machine to achieve the torque ripple minimization. Thus, a reference current adapter is used in order to handle the tradeoff between the vibration reduction and the torque ripple reduction. It produces an auto-tuning reference current that limits the variation of the torque and of the total radial force. The effectiveness of the proposed control strategy is proved by simulation and experimental results. Comparisons with conventional control methods investigating vibrations, noise, and torque ripple are provided, which show the advantages of the control approach based on an auto-tuning reference current. [ABSTRACT FROM AUTHOR]

The supply-side current of an inverter-fed induction motor (IM) is easily accessible and less affected by noises than the motor stator current. This paper proposes a novel sensorless speed estimation method for an IM using the spectrum of the supply-side current. However, due to the influence of fundamental supply frequency, it is difficult to carry out the speed detection straight from the supply-side current signal. In this paper, an analytic model for characterizing the supply-side current of an inverter-fed IM using the modulation theory and the switching function concept is developed. Then, the Hilbert transform is applied to extract the speed harmonic component from the supply-side current. Finally, an interpolated Goertzel algorithm is put forward to enhance the estimation precision of IM speed. The performance of the proposed sensorless speed estimation method is proved by the speed estimation results obtained from hardware experiments of an IM fed by an inverter under different load conditions. [ABSTRACT FROM AUTHOR]

With the rapid growth of voltage source converter based high-voltage direct current (VSC-HVdc)-integrated offshore wind farms, wind turbines (WTs), and VSC stations are required to provide frequency regulation to maintain the onshore system frequency stability. However, after a temporary power increase during the initial period of a disturbance, WTs and VSC stations must reduce their output power to restore their own initial operating states. If there is no other power injection to offset the corresponding power shortage, a significant second frequency drop (SFD) may occur. To address this issue, this paper proposes an adaptive frequency regulation method with grid-friendly restoration. Different frequency regulation strategies are designed to adaptively use the releasable kinetic energy in WTs or the electrostatic energy in VSC stations according to their own real-time operating status. In addition, a system-level grid-friendly coordination is proposed to use the persistent energy reserves of WTs with a deloading strategy to increase the instantaneous power injection and avoid a significant SFD while other WTs or VSC stations restore their operating states. The quantitative calculation and switching mechanism of the additional power injections of deloading WTs are highlighted, and the effectiveness of the proposed method is verified in a case study. [ABSTRACT FROM AUTHOR]

This paper considers the global stabilization problem via sampled-data control for a class of switched nonlinear systems meanwhile taking into account asynchronous switching. First of all, a state feedback sampled-data controller is constructed by backstepping design method. Then, a relationship between the sampling period and the average dwell time is derived, which can guarantee that the closed-loop system is globally asymptotically stable. Finally, two simulation examples are presented to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a single-inductor dual-output (SIDO) dc–dc converter is proposed. The significant feature of the proposed converter is feeding a constant power load in low-voltage side (LVS) port, where even feeding a variable load at LVS does not have any cross regulation to high-voltage side port with the desired approximation. Magnificently, both merits are obtained in open-loop manner, which is an outstanding characteristic in comparison with that of the existed converters. In this paper, soft commutation and soft switching of switches and diodes are investigated along with the aforementioned main novelty. Moreover, detailed theoretical analyses of the proposed SIDO dc–dc converter in continuous conduction mode are presented besides the comparisons with some other structures. Finally, theoretical analyses are verified through a 1500 W experimental prototype results. [ABSTRACT FROM AUTHOR]

In this paper, a series-capacitor-based interleaving buck power factor correction (PFC) converter is proposed, the intermediate energy storage capacitance of which is operated at discontinuous capacitor voltage mode (DCVM), and automatic power factor (PF) correction for this converter is obtained. Moreover, the voltage across the series capacitor of the proposed PFC converter is clamped at the input voltage, and thus peak voltage stress existed in the traditional DCVM buck PFC could be relieved. By effectively regulating the charge/discharge time for the series capacitor, ultrahigh step-down conversion ratio of the proposed converter is achieved, the conversion ratio of which is independent of the duty cycle and only related to the switching frequency and circuit parameters. Therefore, high PF can be obtained due to very narrow deadtime of the input current. Meanwhile, the proposed PFC converter can realize the soft turn-on of part power switch and soft turn-off of part power diodes. In addition, comparing with the traditional discontinuous inductor current mode PFC, the input current of the proposed PFC converter is continuous so that the peak value and root-mean-square value of input current can be reduced. The operational principle, performance analysis, and parameter design principle are given in this paper. The analysis results show that the PF and total harmonic distortion are also independent of the duty cycle. Finally, a 220-Vac input, 60 W/15 V output experimental prototype is built to verify the validity of the theoretical analysis. [ABSTRACT FROM AUTHOR]

Reduced switch active phase converters (APC) are cost-effective solutions for running three-phase loads from single-phase grids. This paper proposes a novel auxiliary-capacitor-based APC (AC-APC) for this application. The combination of the topological location of the auxiliary capacitor and the control of the AC-APC reduces current stress on the semiconductor devices. In this paper, a selection criterion for the optimal auxiliary capacitor value is formulated to reduce the device currents in such a way that the overall efficiency is enhanced. This paper presents a comparative analysis of converter volt-ampere (VA) rating and device power loss for conventional H-bridge active front-end and inverter-based topology, APC, and AC-APC. To evaluate the efficacy of the proposed AC-APC, an experimental study is conducted on the APC and the AC-APC feeding a 3-hp three-phase induction motor. At a full load of $\text{2.5}\,\text{kW}$ and $\text{0.8 } \text{power factor}$ , the measured maximum efficiency of the AC-APC is $2\%$ higher than that of the APC. Analytical evaluation of converter currents and device power loss are in close agreement with experimental observations. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel real-time multiple-input multiple-output (MIMO) channel sounder for the 28 GHz band. Until now, most investigations of the directional characteristics of millimeter-wave channels have used mechanically rotating horn antennas. In contrast, the sounder presented here is based on a phased array structure that performs fast electronic steering of the beams in the horizontal and vertical domains. This approach drastically shortens the measurement times for measurements that are directionally resolved both at the transmitter (TX) and the receiver (RX), and the measurement time per location is reduced from minutes or hours to milliseconds. This not only enables measurement of more TX–RX locations for a better statistical validity but also allows to perform directional analysis in dynamic environments. The sounder also has high phase stability, which, in conjunction with the short measurement time, leads to a low phase drift between TX and RX. This in turn enables phase-coherent sounding of all beam pairs even when TX and RX have no cabled connection for synchronization, and thus avoids any delay ambiguity. Furthermore, the phase stability over time enables complex RX waveform averaging to improve the signal-to-noise ratio during high path loss measurements. The paper discusses the system design as well as the measurements performed for verification of the sounder performance. Furthermore, we present sample results from double directional measurements in dynamic environments. [ABSTRACT FROM AUTHOR]

This paper describes a dc-link voltage control method of a single-phase back-to-back cascaded H-bridge inverter (SBCI) for a medium-voltage motor drive system. The main advantage of the SBCI topology over the conventional regenerative cascaded H-bridge topology with a three-phase active front-end (AFE) is a simple system structure, which is composed of an input transformer, a power cell, a current sensor, etc. However, the challenging points of the SBCI are larger voltage ripple in the dc-link capacitor and imbalance of dc-link voltages of each phase. The asymmetric dc-link voltage of each power cells could cause unstable operation such as over-modulation due to the lack of the dc-link voltage of a particular phase and result in over-voltage or under-voltage faults. In this paper, the control strategy of the dc-link voltage for the SBCI that uses the negative-sequence voltage of the converter is described. The proposed control method is verified with a computer simulation whose target is a 6.6-kV–1.25-MW medium-voltage drive system. Also, through the experimental setup with the prototype SBCI whose power rating is 16.2 kVA, the dc-link voltage of each AFE has been controlled within a 0.5% error of its reference value at the full load. [ABSTRACT FROM AUTHOR]

This paper describes the design of a high-efficiency energy management system for low-power, low-voltage energy harvesting powered wireless sensor systems. With typical voltages of less than 1 V and power levels lower than 1 mW, there are significant challenges when applying energy harvesting sources to supply pulsed power levels of up to 120 mW at voltage levels of 1.8–4 V as required by wireless sensor loads. The proposed approach integrates energy storage elements within a voltage step-up circuit to produce a new high-efficiency energy management circuit that converts the energy produced by a low-power, low-voltage source into a series of high power pulses. An optimized switched supercapacitor energy buffer circuit including a self-powered control circuit is proposed. Efficiencies of up to 91% are shown for an indoor solar cell source with a power level of 0.5 mW, supplying an equivalent wireless sensor with pulsed power levels of 10–120 mW. This is significantly higher than 83% achieved for the dc–dc stage of the existing best solution under the same source conditions, but requires an additional conversion step to provide high power pulses. [ABSTRACT FROM AUTHOR]

This paper studies the high power density bidirectional dc–dc converter with interleaving, soft-switching, and near critical conduction mode (near-CRM) operation. Systematic design and control methods are proposed to enhance the effectiveness of passive currents balancing between multiple interleaved phases without using individual phase current feedbacks. This paper first analyzes the zero voltage turn-on operation, including the turn-off energy diversion by the added snubber capacitor and the turn-off resonance models. Second, the intrinsic inverse co-relation between the phase current deviation and the resulting effective duty cycles variation is quantitatively formulated and modeled as a closed-loop mechanism that balances the currents passively. Then, the design constraints of the system parameters including the snubber capacitance, dead time, and valley currents of the near-CRM mode are formulated to guarantee the effectiveness of counteracting the current unbalance. Finally, a variable switching frequency control is proposed to actively control the valley current and maintain the current balancing effectiveness throughout the operating range. An IGBT-based 20-kW three-phase interleaved prototype with the maximum efficiency of 99.1% is constructed to verify the proposed design and control methods. [ABSTRACT FROM AUTHOR]

This paper presents a generalized analysis of the Class-E power amplifier (PA) with a shunt capacitance and a shunt filter, leading to a revelation of a unique design flexibility that can be exploited either to extend the maximum operating frequency of the PA or to allow the use of larger active devices with higher power handling capability. The proposed PA fulfills zero voltage switching (ZVS) and zero voltage derivative switching (ZVDS) conditions, resulting in a theoretical dc-to-RF efficiency of 100%. Explicit design equations for the load-network parameters are derived, and the analytical results are confirmed by harmonic-balance simulations. Two PA prototypes were constructed with one designed at low frequency and the other at high frequency. The first PA, which employs a MOSFET and a lumped-element load-network, delivered a peak drain efficiency $(\!D\!E)$ of 93.3% and a peak output power of 37 dBm at 1 MHz. The second PA, which employs a GaN HEMT and a transmission-line (TL) load-network to provide the drain of the transistor with the required load impedances at the fundamental frequency as well as even and odd harmonic frequencies, delivered a peak $D\!E$ of 90.2% and a peak output power of 39.8 dBm at 1.37 GHz. [ABSTRACT FROM AUTHOR]

Stochastic computing (SC) is a promising technology that can be used for low-cost hardware designs. However, SC suffers from its long latency. Although parallel processing can efficiently shorten the latency, duplicated stochastic number generators (SNGs) are necessary, which cause substantial hardware overhead. This paper proposes a scalable SNG based on the spin-Hall-effect (SHE), which is capable of generating multiple independent stochastic streams simultaneously. The design takes advantages of the efficient charge-to-spin conversion from the Spin-Hall material and the intrinsic stochasticity of nanomagnets. Compared to previous spintronic SNGs, the SHE-SNG can reduce the area by $1.6\times -7.8\times $ and the power by $4.9\times -13\times $ while increasing the degree of parallelism from 1 to 16. Compared to CMOS-based SNGs, the proposed SNG obtained $24\times -120\times $ and $53\times $ reduction in terms of area and power, respectively. Finally, three benchmarks were implemented, and the results indicate that SC implementations with the proposed SHE-SNG can achieve $1.2\times -29\times $ reduction of hardware resources compared to implementations with previous CMOS- and spintronic-based designs while scaling the degree of parallelism from 1 to 64. [ABSTRACT FROM AUTHOR]

This paper presents a novel insulated gate bipolar transistor (IGBT) behavioral model on the field programmable gate array (FPGA), which is suitable for the real-time simulation of fast transients in power electronics circuits. In this model, the static and dynamic behaviors of the IGBT switch are described and modeled separately. The static IGBT model is represented by the saturation region of output characteristic and is a part of the circuit network model. The dynamic IGBT model is combined with the static one to describe the fast switching transient behaviors by using the IGBT equivalent circuit model. The presented dynamic model in this paper does not involve any iterative solving algorithm and can be designed with highly pipelined structures on FPGA. Therefore, the IGBT switching transient waveforms can be generated precisely with a 5 ns resolution. The proposed model is tested with two cases—a four-phase floating interleaved boost converter and a three-phase five-level modular multilevel converter. The effectiveness and accuracy of the model are validated by comparing the real-time simulation results with offline simulation software. [ABSTRACT FROM AUTHOR]

High-speed train systems have proven to be very flexible and attractive systems that can be developed under various circumstances and in different contexts and cultures. As a result, high-speed trains are widely deployed around the world. Providing more reliable and higher data rate communication services for high-speed trains has become one of the most urgent challenges. With vast amounts of spectrum available, the millimeter wave (mmWave) system is able to provide transmission rates of several gigabits per second for high-speed trains. At the same time, mmWave communication also suffers from high attenuation; thus, higher energy efficiency should be considered. This paper proposes an energy-efficient power-control scheme of train–ground mmWave communication for high-speed trains. Considering a beam switching method for efficient beam alignment, we first establish the position-prediction model, realistic direction antenna model, and receive power model. And, then we allocate the transmission power rationally by using the power minimization algorithm while ensuring the total amount of transmission data. Based on this, this paper also develops a hybrid optimization scheme and finds the limit of total energy consumption when the number of segments goes to infinity. Using simulation with various system parameters and taking velocity estimation error into account, we demonstrate the superior performance of our schemes. [ABSTRACT FROM AUTHOR]

A quench protection switch (QPS) is indispensable to protect the magnet coils from the damage of quench in a superconducting Tokamak. In this paper, a QPS based on artificial current zero is involved. The vacuum circuit breaker (VCB), which is driven by a high-speed electromagnetic repulsion mechanism, is used as the main circuit breaker (MCB). Two kinds of commercial vacuum interrupters (VIs), which have contacts generating axial magnetic field (AMF) and transverse magnetic field (TMF), respectively, are applied. The breaking current with an amplitude of 10~25 kA is generated by an LC oscillating circuit. The countercurrent with frequency in the range of 500–3000 Hz is provided by a commutation branch. The interruption performance of the two kinds of VIs under different breaking current and countercurrent frequencies is investigated. The experimental results indicate that the differences in interruption performance under the two types of contacts are increasing with larger frequencies of countercurrents. [ABSTRACT FROM AUTHOR]

In a cognitive radio network (CRN), two nodes have a rendezvous when they tune to the same channel simultaneously. Providing rendezvous guarantee between any pair of nodes is essential because a rendezvous is necessary for communication. Some existing works claim that rendezvous guarantee can be provided by using a dedicated common control channel to negotiate the channel being used. A serious problem of these mechanisms is that a globally available channel may not exist. Some channel hopping protocols try to provide a rendezvous guarantee without using a common control channel. However, these solutions may suffer from a poor number of rendezvous or uneven channel utilization. In this paper, we propose a novel distributed channel hopping protocol: Quorum and Latin square channel hopping (QLCH). The QLCH scheme efficiently provides rendezvous guarantee by utilizing the concept of quorum systems and Latin squares. The former is utilized to guarantee balanced rendezvous among nodes, whereas the latter is adopted to share the rendezvous among channels. QLCH efficiently provides fast rendezvous guarantee and can cooperate with other channel hopping protocols to enhance network throughput. Analytical and simulation results verify the improvement of QLCH. For example, when there are 30 flows using 11 channels in a CRN, the achieved time to rendezvous of QLCH is 9.84 times lower than that of the existing protocol SYNC-ETCH, whereas the achieved network throughput of QLCH is 362% higher than that of the existing protocol, i.e., Quorum-based channel hopping (L-QCH). [ABSTRACT FROM PUBLISHER]

This paper discusses the ability of a SAR to create high-resolution images with high sensitivity in a stripmap configuration. Since geometric resolution is driven by the effective azimuth beamwidth of the antenna, it compares beam spoiling methods to beam switching methods with particular attention to the achieved SNR. It also formulates the effects of element mutual coupling on the SNR. Further, since existing systems may not be able to switch beams at a rate equivalent to the PRF, this paper also discusses a method to process beam switched data collected in a burst configuration, showing that SNR and the presence of grating lobes trade against each other as the number of pulses per burst increases. Finally, this paper investigates improvements to signal quality offered by using a multichannel system, with elements aligned in the flight direction, over a single channel system. [ABSTRACT FROM PUBLISHER]