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With the rapid development of photovoltaic and fuel cell stacks, high voltage gain converters are urgently demanded. Conventional boost is limited by the exaggerated duty cycle, it is impossible to obtain a high voltage gain while ensuring efficiency. Therefore, a zero-voltage switching (ZVS)-modified SEPIC converter that combines a voltage multiplier cell with traditional SEPIC is proposed in this paper. With detailed parameters design process, this presented converter works at zero voltage switching (ZVS), while obtaining high voltage gain without extremely high duty cycle. Besides, voltage stress is also reduced and low-voltage component with lower parasitic parameters can be used, thus efficiency is maintained. In order to further improve the power density, an integrated inductor scheme is adopted in this paper without changing intrinsic working states of the two inductors. A 36-W prototype is built, and experiments are conducted to verify the advantages of the proposed converter. The efficiency is up to 91.5% at full load. [ABSTRACT FROM AUTHOR]

This paper provides an experimental discussion on a real-time real-power emulator that plays an important role in achieving a total test of medium-voltage, high-power, high-speed induction motor drives. The use of the emulator brings cost and time savings to the test. The test bench including the emulator is characterized by connecting two modular multilevel double-star chopper-cell (DSCC) converters connected in a front-to-front way. This paper designs, builds, and tests a 400- ${\rm V}_{\rm dc}$ , 10-kW downscaled test bench. It mainly consists of the following two identical DSCC converters: 1) one DSCC converter is used as an inverter under test; and 2) the other as a real-time real-power high-fidelity emulator. Experimental waveforms confirm that the emulator can reproduce electrical and mechanical operating performance of the three-phase 200-V, 10-kW, four-pole, 9000-r/min induction motor loaded with a centrifugal compressor. [ABSTRACT FROM AUTHOR]

A high-frequency high voltage gain discontinuous conduction mode coupled-inductor boost LED driver based on planar component is presented in this paper. GaN switch is adopted with lower conducting resistance and higher switching speed. Zero voltage switching (ZVS) is achieved at the same time to reduce high switching loss caused by high switching frequency. Compared with the previous work, the voltage gain is higher and efficiency is higher because of ZVS. This paper focuses on high efficiency; therefore, resonant gate driver is adopted and efficiency is increased by 0.6%. In terms of the coupled-inductor, planar component is used and parameter optimization is also proposed to realize lower loss, including wingding loss and fringing loss caused by the air gap. A 500 kHz 36 W prototype has been designed to demonstrate theoretical analysis. In addition, comparison of drive loss between the resonant gate driver used in this paper and conventional driver implemented by Si8271 is made, revealing advantages of the resonant driver. Obtained efficiency was up to 92.1% at full load. [ABSTRACT FROM AUTHOR]

The use of electronic equipment and other dc-compatible appliances in homes and offices is increasing at a very fast rate, as well as the distributed generation of energy. These two statements will most likely trigger, in a near future, the adoption of district-scale dc grids, connecting dc microgeneration plants and consumers, in an effort to cut the number of conversion steps required to deliver power to dc appliances. DC–DC converters will be fundamental in these systems, allowing the establishment of several voltage levels. The reliability of these converters plays a critical role, ensuring service continuity of the loads connected to them. With the increment of reliability in mind, this paper proposes a simple yet effective open-circuit fault diagnostic method suitable for interleaved dc–dc boost converters, but equally functional for other dc–dc converter topologies. The improvements introduced in this paper greatly simplify the diagnostic action, while making the correct diagnostic of faults independent of the switching duty cycle. Moreover, an alternative reconfiguration scheme is proposed to mitigate the adverse impacts of such faults. To prove the effectiveness of these strategies, a three-phase interleaved boost converter prototype was used in the experiments. [ABSTRACT FROM AUTHOR]

The pump-back test is widely adopted in the industry for characterizing and qualifying high-power converters. One popular pump-back test configuration is to tie the dc links of two converters together and circulate the current through the inductor connected between the ac terminals. In this configuration, one of the converters operates in the voltage mode to generate the virtual grid and the other converter regulates the circulating current, where hysteresis control could be applied. However, the switching characteristics of hysteresis control are unique due to the pulsewidth modulation type voltage being the virtual grid. This paper contributes to analyzing the switching frequency characteristics of the hysteresis control in this pump-back test configuration. The switching frequency tracking phenomenon is revealed and reported in this paper for the first time. Theoretical analysis, simulation validation, and experimental demonstration are provided to support the major conclusions. [ABSTRACT FROM AUTHOR]

This paper provides a theoretical and experimental discussion on a modular multilevel triple-star bridge-cell converter with focus on mitigating the capacitor-voltage fluctuation contained in each bridge cell. A new control method proposed in this paper is characterized by properly superimposing both common-mode voltage and circulating currents in the whole speed range. Moreover, this paper optimizes the amplitude and frequency of the superimposed common-mode voltage on the basis of theoretical analysis, thus resulting in minimizing the voltage fluctuation. The optimized control method makes both voltage fluctuation and cluster-current amplitude smaller than do the existing methods. Experimental waveforms obtained from a three-phase downscaled system using a 370-V, 15-kW, 75-Hz, six-pole, permanent-magnet synchronous motor verify good start-up performance from a standstill to the rated speed, keeping both capacitor-voltage and cluster current within acceptable levels. [ABSTRACT FROM AUTHOR]

The use of power converters is very important in maximizing the power transfer from renewable energy sources such as wind, solar, or even a hydrogen-based fuel cell to the utility grid. An LCL filter is often used to interconnect an inverter to the utility grid in order to filter the harmonics produced by the inverter. Although there is an extensive amount of literature available describing LCL filters, there has been a gap in providing a systematic design methodology. Furthermore, there has been a lack of a state-space mathematical modeling approach that considers practical cases of delta- and wye-connected capacitors showing their effects on possible grounding alternatives. This paper describes a design methodology of an LCL filter for grid-interconnected inverters along with a comprehensive study of how to mitigate harmonics. The procedures and techniques described in this paper may be used in small-scale renewable energy conversion systems and may be also retrofitted for medium- and large-scale grid-connected systems. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a novel ac/dc bridgeless and contactless energy transmission system. The coreless planar transformer and magnetic dipole moment are applied to transmit electrical energy in a noncontact method. In addition, the input ac current of the proposed converter has effective power factor correction. Simultaneously, the primary-side switches have zero-voltage switching, and the secondary-side diodes have zero-current switching. Thus, the power quality and efficiency of the proposed system can be upgraded. Furthermore, the proposed system can increase the transmission distance with the voltage multiplier receiver connected at the rear of the secondary-side coreless planar transformer. Power transmission and circuit operation are described in this paper. Finally, a prototype system is constructed, and its validity has been confirmed with experimental and practical measurements. [ABSTRACT FROM AUTHOR]

A mobile charging system (MCS) for electric vehicles (EVs) is presented in this paper. The proposed MCS has a 2-MWh energy storage capacity for charging five EVs simultaneously with 75-kW individual charging rates. The MCS would be rechargeable from the available power substations (three phase, 480 V) with 375-kW charging rate. The appropriate modular power interface is designed and implemented between the MCS, batteries of the EVs, and the power substations. Experimental validation is presented in this paper to demonstrate the system performance and effectiveness under rapid charging requirements. [ABSTRACT FROM AUTHOR]

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

Many installations in the petrochemical industry routinely require medium-voltage adjustable speed drives (MV ASDs) with long output cables, particularly for offshore applications and land-based well applications. This paper describes the effects of using MV ASDs with long cables. It examines the major issue known as the “standing wave effect,” which may be more prominent at certain cable lengths, as well as the design solutions to ensure proper drive and motor functionality and performance. Examples of this unique phenomenon and the effectiveness of different mitigation measures are presented using simulations and actual data. Simulations are also used to provide a comparison of operating waveforms with two- and multilevel converters. This paper recommends considerations for the installation and/or design of the MV ASD that can be implemented to avoid problems. [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]

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]

This paper presents a three-port three-phase current-fed dc–dc converter with high-frequency isolation and bidirectional power flow. Port I is fed by a battery bank, port II employs a set of photovoltaic modules, and port III is connected to a dc link. The topology uses three single-phase H-bridge cells in the primary side and a three-phase H-bridge converter in the secondary one. High-frequency isolation is ensured by three single-phase transformers connected in an open delta-wye configuration. The theoretical analysis is performed considering the fundamental component of the voltage across the transformers. Maximum power point tracking, the battery current, and the power flow between the primary and secondary sides are controlled by the use of variable duty cycle technique in the primary side and the use of phase-shift technique between the primary and secondary bridges. In order to validate the study, experimental results of the proposed system considering the dc rated voltages as 48 V/96 V/380 V for Ports I/II/III, respectively, and rated power of 3.5 kW are carried out. [ABSTRACT FROM AUTHOR]

A dv/dt filter is useful to mitigate the deleterious effects of voltage pulses with high edge rates, such as voltage overshoot and ringing in motor drive systems, which can cause premature motor failure. With the introduction of wide-bandgap semiconductor drives, these issues will become more pronounced. This paper introduces a new type of dv/dt filter where the inductor, capacitor, and damping resistor are integrated into the output bus bar or cable of a silicon carbide (SiC) inverter. This integrated filter may be smaller, lighter, and cheaper to construct than filters built from discrete components. An analytical model of the integrated dv/dt filter is developed, and this model is used to design output filters for a 460 V AC, three-phase SiC motor drive. Prototype filters are constructed and tested with a SiC inverter connected to a 460 Vrms, 30-HP induction motor, and experimental results demonstrate output waveforms that match the analytical model and meet the National Electrical Manufacturers Association (NEMA) MG 1 Part 31 requirements for inverter-rated motors. Finally, the voltage waveforms and losses of the prototype-integrated filter are compared with several other mitigation options, demonstrating that the integrated filters meet the NEMA specification at a fraction of the mass and volume of the discrete component solution without sacrificing efficiency. [ABSTRACT FROM AUTHOR]

Nonlinear inductors have wide applications in dc/dc converters. The multiwindow multipermeability nonlinear inductor based on low-temperature co-fired ceramic (LTCC) technology has been proven to have a gradually changing wide-range inductance value curve while requiring no extra dc bias, which makes them suitable in various high-efficiency dc/dc converters. This paper focuses on the design of such a multiwindow multipermeability inductor based on an innovative module. Currently, the design of the LTCC inductors requires complicated simulation when coupling matrices among all the windows are taken into consideration. A simplified model for calculating the inductance value is proposed in this paper to reduce complexity. In the proposed model, the complicated inductance simulation is simplified to calculating inductance of three basic units in a nine-window inductor. By simulating the nine-window inductor, inductance of a rectangle-shaped inductor with any number of evenly distributed windows on it can be calculated. Based on the proposed model, the design guideline of the nonlinear inductor is also summarized. A 16-window two-permeability prototype is presented to demonstrate the design process according to the new model. The complete simulation and the test results are also provided to verify the model. The proposed model correlates with the simulation results very well. [ABSTRACT FROM PUBLISHER]

This paper describes a new method for the online parameter estimation of an induction heating system. Simulations and experiments are presented in order to measure its impedance matrix for more exact control in closed loop. In previous papers, various parameter identification methods including offline methods were introduced and compared for current inverters. It has been demonstrated that parameter identification is necessary to achieve good control of the inductor currents. A “pseudoenergy” method for a simple and fast implementation is compared to a classical “ $V/I$ with phase shift” method. They are experienced on a reduced-power three-phase coupled resonant system supplied with voltage inverters with satisfying results. [ABSTRACT FROM PUBLISHER]

A dual active bridge (DAB) converter promises high power density. The highest power transfer can be achieved by phase shift modulation inside the zero-voltage switching boundaries. This paper analyzes the transients of DAB commutation. Although commutation has been previously analyzed for DAB with the linear turn-off snubbers, in today's industries, the output capacitors of the switches are utilized as the snubberless approach. The presence of these time-variant capacitors leads to nonlinear equations. This paper applies a piecewise linear model for analyzing the commutation of the ac-link current into the switches. The study is inspired by practical experiments, and the results are experimentally verified. [ABSTRACT FROM PUBLISHER]

SiC devices are gaining acceptance in the motor drive industry. This paper compares the power loss and efficiency between two options that can be used with SiC-based variablefrequency drives (VFDs). In the first option, the SiC VFD is equipped with an output sine-wave filter with carrier frequency at 50 kHz. A $dv/dt$ filter is used for the second option with the carrier frequency reduced to 8 kHz. Both options are compared with a standard Si insulated-gate bipolar transistor (IGBT) VFD operating at a carrier frequency of 8 kHz with no output filter. The focus of this paper is to present different filtering options for SiC VFDs. The $dv/dt$ filter is designed to meet the same specification as that of the standard Si IGBT VFD with no output filter, so as to present a fair comparison between a standard Si IGBT VFD and the next-generation SiC VFD. Results using a 460-V 11-kW system show that the SiC VFD with an output sine-wave filter has a lower efficiency compared with SiC VFD with a $dv/dt$ filter. Influence of the various filtering options on leakage current in the motor drive system has also been studied, and the results are presented in this paper. [ABSTRACT FROM PUBLISHER]

This paper provides a theoretical and experimental discussion on ac-inductors design for a modular multilevel triple-star bridge-cells (TSBC) converter, or shortly a TSBC converter. This converter requires multiple ac inductors for controlling nine cluster currents. This paper proposes three three-legged, six-winding, “interzigzag” inductors for the TSBC converter. Since each leg of the individual inductor has two windings, the three inductors have 18 windings in total. The wire leads are zigzagged among the three inductors. This unique structure of the “interzigzag” windings leads to the following feature: Both three-phase supply and motor currents produce no magnetic flux in each of the nine legs. This feature makes each inductor smaller in size and lighter in weight. A specially-designed downscaled motor-drive system rated at 400 V and 15 kW is constructed and tested to confirm the validity of a design of the proposed inductors, as well as to verify transient motor-drive performance during four-quadrant operation. [ABSTRACT FROM AUTHOR]

Dielectric barrier discharge (DBD) is the most efficient way used in industry for ozone generation. In the last decades, many papers were published on such DBD-based ozone generators. Several geometric configurations can be used to generate ozone. They can be classified into two types depending on the discharge form: volume DBD, which is the common one in ozone industry, and surface DBD. Many studies have been conducted to analyze the ozone generation efficiency of both reactors to get maximum ozone production with the lowest possible power consumption. The aim of this paper is to carry out an experimental analysis of a patent-pending new reactor, of hybrid configuration, in which occur simultaneously a volume and a surface DBD. The hybrid reactor comprises a ground stainless steel cylindrical electrode, within which is placed a glass tube separated by an interval of 1 mm in which the volume DBD occurs. A second mesh stainless steel electrode connected to the high voltage is placed inside the glass tube wherein the surface discharge occurs. The obtained results showed a clear superiority of the hybrid reactor compared with both volume and surface DBD in terms of the ozone concentration. The difference in the ozone concentration reaches up to 50% compared with the volume DBD and 30% compared with the surface DBD. [ABSTRACT FROM PUBLISHER]

This paper first presents an adaptive switching frequency modulation that optimizes the efficiency of the cascaded buck-boost (CBB) converter. Such bidirectional dc–dc CBB topology is typically deployed in PV-battery-device systems. A precise loss-model that accounts for component nonlinearities is developed to determine power-loss distribution. According to the loss model, optimal switching frequencies are selected that correspond to the lowest total loss in both the buck and the boost modes of the operation. Then, a small volume low-profile planar-nanocrystalline inductor is designed to further increase efficiency and power density. Finite element analysis method is used to evaluate the inductor design. A digital control system is designed to periodically adjust the optimal switching frequencies to modulate the pulsewidth modulation duty cycle and to take into account any load and line regulations. The objective of this paper is to achieve ultra-high efficiency (over 99%) for a well-known CBB converter. A 100 W CBB converter prototype was built to verify the proposed algorithm and designed nanocrystalline inductor. A California Energy Commission weighted efficiency of 98.87% with a peak efficiency of 99.31% was achieved for the buck mode and 98.58% with a peak efficiency of 99.25% was achieved for the boost mode, both at nominal voltage. Also, a power density of 3.67 kW/L was reported. [ABSTRACT FROM AUTHOR]

This paper presents an overview and techno-economic feasibility study of solid-state fault current limiters (SSFCL) for low-voltage residential and commercial applications. An SSFCL is proposed to be installed upstream inside a conventional panelboard or load center. The simulation results demonstrate the effectiveness of utilizing SSFCL for residential houses and commercial buildings and the advantages of fast fault current limiting and great reduction of fault energy. Some physical design considerations are made for installing an SSFCL including their fault-current-limiting inductors inside a panelboard or load center. The proposed SSFCL solution potentially has best overall benefits compared to the conventional mechanical solution and other solid-state-based solutions. [ABSTRACT FROM AUTHOR]

This paper introduces a three-phase grid-connected inverter for commercial-scale photovoltaic systems. The circuit topology combines an ac-inductor-less active bridge with a parallel-connected pulsewidth modulation inverter acting as an instantaneous reactive power compensator. The active bridge, called a 120° conduction inverter, operates at a switching frequency equal to the grid frequency and outputs a 120° rectangular current, while the compensator eliminates the harmonic currents included in the rectangular current. The main advantage of this strategy is the reduction in size of the required ac inductor by a factor of 4, as well as the reduction of power losses in the switching devices. The theoretical analysis clearly shows that the compensator can synthesize a sinusoidal output current by controlling only instantaneous reactive power, thus eliminating the need for electrolytic capacitors. A 5-kW experimental setup validates the operating principle and the control method of the proposed inverter and exhibits an inverter efficiency as high as 99.2% with Si superjunction mosfets. [ABSTRACT FROM AUTHOR]

Multioutput converters with single input source are currently studied as an alternative to conventional dc–dc topologies in order to improve power density in low-power multiload applications. This paper reviews three different ways in which a boost topology can be customized to supply multiple outputs. The first way uses a charge-sharing approach using individual switches to distribute inductor energy to different capacitors. The second method of creating a multiport converter (MPC) combines two converters with similar front end to generate two outputs using only one controlled switch. Using this method, a boost converter can be combined with single–ended primary–inductor converter (SEPIC), Cuk, and current source converter topologies. The third method uses time multiplexing of switches to produce two regulated ports and is referred to as switched-boost action. This method uses relatively less number of switches and allows regulation and control of all the outputs. Practical utility of switched-boost action based MPC is reported in this paper. This switched-boost MPC is applied to a renewable power converter system to interface a solar panel, a battery, and home loads to produce a 12-V and a 48-V bus. The 12-V bus is interfaced to battery and capable of optimally charging the battery in constant current–constant voltage (CC-CV) mode. The converter is demonstrated to operate with solar panel as it supplies a 12-V battery and a 48-V load bus. When the solar power is not available, the converter automatically goes into a mode in which the 12-V battery supplies the loads on the 48-V bus. [ABSTRACT FROM AUTHOR]

Many research works report the use of LCL filters for grid-interfaced PV systems. Indiscreet selection of passive LCL filter parameters may result in poor filtering and increased power losses. LCL filter parameter selection is critical to get a good performance and at the same time ensure that losses and costs stay low. This paper proposes a novel approach to design the LCL filter for a grid-interfaced PV system. A cost-based minimization approach on a cost per joule basis for each of the filter elements is explored to obtain the optimal filter design. Simulation results for a 10-kVA grid-connected inverter with an LCL filter are presented in order to verify the efficacy of the proposed design. The impact of designed filter parameters on the ripple current is also discussed in this paper. The total inductance of the LCL filter is varied and filter parameter values which give lowest cost is identified while meeting harmonic standard requirements and the fundamental voltage drop across the filter. Finally, the proposed design is also experimentally validated via a hardware prototype. Results validate the design method in terms of the harmonic attenuation and total harmonic distortion. [ABSTRACT FROM AUTHOR]

This paper presents a study of the losses in the integrated buck–flyback converter (IBFC) used as high-power-factor LED driver. The aim of the study is to investigate the possibilities of increasing the efficiency of the IBFC converter. The procedure of the improvement is done by obtaining the equations of the current through each component in terms of converter parameters. The current is found in an average value or rms value, depending on the type of the parasitic component, whether it is modeled by a parasitic forward voltage source or by a parasitic resistance, respectively. Using these equations and the parasitic model, the losses of each element of the converter are estimated. This paper proposes a technique to increase the efficiency of the IBFC by redesigning the converter parameters. Furthermore, this paper presents a case of study with a step-by-step efficiency enhancement process of an existing driver. The driver is operating under universal input conditions, and 38 V output, supplying an LED luminary of 26.5 W. The new design shows an improvement of the efficiency from 82% in the old design to 89% in the proposed one. Moreover, the new design shows an improvement in the power factor and the THD and a 50% reduction in the output current ripple. Furthermore, a reduction in the number of components has been achieved, as it is found by the analysis that by adjusting the converter parameters, one diode can be removed. Finally, the presented methodology is explained in detail so that it can easily be applied to other dc–dc converters. [ABSTRACT FROM AUTHOR]

This paper proposes a zero-voltage ride-through (ZVRT) method and an LCL filter design method to meet the fault ride-through (FRT) requirements for a single-phase grid-connected inverter with a minimized LCL filter. A high inverter output current overshoot occurs at a grid voltage sag and a grid voltage recovery, when a low-inductance LCL filter design is employed in order to minimize the filter volume. In order to suppress the current overshoot, a high-speed gate-block operation and the design method of the minimized LCL filter are proposed. In particular, the filter design considers the delay time in the gate-block operation in order to clarify the reduction limitation of the inductance in the LCL filter. As a result, the maximum inverter output current overshoot is suppressed to 146% by the high-speed gate-block operation and the designed LCL filter, where the impedances of an interconnected inductor and a filter inductor are 1.0% and 0.78% of the inverter normalized impedance, respectively. Therefore, it is possible to meet the FRT requirements with the proposed ZVRT method even with the minimized LCL filter. [ABSTRACT FROM AUTHOR]

A breaker-less shipboard medium-voltage dc (MVDC) system is gaining more attention recently due to its advantage in dealing with a dc fault by using switched-mode power modules and disconnectors. The specific power module investigated in this paper is the power conversion module (PCM) that transforms power from a MVDC to a low-voltage dc (LVDC) bus. The PCM plays an important role in a system-level fault management. The recently emerging isolated modular multilevel dc/dc converter and the widely used dual active bridge converter are promising solutions for PCM applications. The control algorithms including fault protection strategy for both topologies have been developed and presented in this paper. The MVDC side fault and LVDC side fault of each topology has been analyzed and evaluated. The simulation and experimental results are provided to demonstrate the fault protection features of two topologies in a breaker-less dc system. [ABSTRACT FROM AUTHOR]

This paper presents theoretical and experimental discussions on a practical speed-sensorless start-up method for an induction motor driven by a modular multilevel cascade inverter based on double-star chopper cells (MMCI-DSCC) from standstill to middle speed. This motor drive is suitable, particularly for a large-capacity fan- or blower-like load. The load torque is proportional to a square of the motor mechanical speed. The start-up method is characterized by combining capacitor-voltage control with motor-speed control. The motor-speed control with the minimal stator current plays a crucial role in eliminating a speed sensor from the drive system and in reducing an ac-voltage fluctuation occurring across each dc capacitor. Experimental results obtained from the 400-V 15-kW downscaled system with no speed sensor verify that the motor-speed control proposed for the DSCC-based drive system can enhance the start-up torque by a factor of three under the same ac-voltage fluctuation. Several start-up waveforms show stable performance from standstill to middle speed with different load torques. [ABSTRACT FROM AUTHOR]

This paper provides an intensive discussion on analysis, simulation, and experiment of a back-to-back (BTB) systemunifying two modular multilevel cascade converters based on double-star chopper cells (MMCCs-DSCCs). Each of the twoDSCCs connected back-to-back consists of multiple cascaded chopper cells and a center-tapped inductor per leg. Lowvoltage steps bring significant reductions in harmonic voltage and current to the BTB system. Neither dc-link capacitornor voltage sensor is required for regulating the dc-link voltage and controlling the dc-link current. A three-phase200-V, 10-kW, 50-Hz downscaled BTB system with phase-shifted PWM is designed, constructed, and tested to verify itsoperating principles and performance. Analytical, simulated, and experimental results agree well with each other insteady and transient states. Experimental waveforms confirm the effectiveness of a self-starting/restartingprocedure. [ABSTRACT FROM AUTHOR]

This paper proposes a single-stage three-phase-to-single-phase current-fed high step-up ac–dc matrix converter. The proposed converter inserts a boost-type matrix converter, which is formed by three boost inductors and six bidirectional switches, between a three-phase ac source and a Cockcroft–Walton voltage multiplier (CWVM). By using this topology associated with power factor correction technique, the proposed converter not only achieves almost unity power factor and sinusoidal input currents with low distortion but also obtains high voltage gain at the output end. Moreover, the matrix converter generates an adjustable-frequency and adjustable-amplitude current, which injects into the CWVM to regulate the dc output voltage and smooth its ripple. With this flexible injection current, the performance of the proposed converter is superior to the conventional CWVM, which is usually energized by a single-phase ac source. The operation principle, control strategy, and design considerations of the proposed converter are detailed in this paper. Finally, simulation and experimental results demonstrate the claims and validity of the proposed converter. [ABSTRACT FROM PUBLISHER]

This paper presents a modular push–pull PWM converter (MPC) for a battery energy storage system, which is intended for grid connections to medium- or high-voltage power systems. The converter per phase consists of a center-tapped transformer and two arms based on a cascade connection of multiple bidirectional PWM chopper-cells with floating dc capacitors. This paper discusses the operating performance and control method of the MPC, focusing on voltage balancing of all the floating dc capacitors. Moreover, a comparison is made between the MPC and a modular multilevel converter (MMC), under an assumption that both are used as the same battery energy storage system. The validity of the operating performance and control method is confirmed by both computer simulation using the “PSCAD/EMTDC” software package and experiment using a three-phase, 200-V, 5-kW downscaled model. [ABSTRACT FROM PUBLISHER]

This paper deals with the setting-parameter optimization procedure for a multiphase induction heating system considering transverse flux heating. This system is able to achieve uniform static heating of different thin/size metal pieces without movable inductor parts, yokes, or magnetic screens. The goal is reached by the predetermination of the induced power-density distribution using an optimization procedure that leads to the required inductor supplying currents. The purpose of the paper is to describe the optimization program with the different solution obtained and to show that some compromise must be done between the accuracy of the temperature profile and the energy consumption, with the calculation of the losses. [ABSTRACT FROM PUBLISHER]

This paper presents a multiphase induction system modeling for a metal disc heating and further industrial applications such as hot strip mill. An original architecture, with three concentric inductors supplied by three resonant current inverters, leads to a reduced element system, without any coupling transformers, phase loop, mobile screens, or mobile magnetic cores as it could be found in classical solutions. A simulation model is built, based on simplified equivalent models of electric and thermal phenomena. It takes into account the data extracted from Flux2D finite-element software, concerning the energy transfer between the inductor currents and the piece to be heated. It is implemented in a versatile software PSIM, initially dedicated to power electronics. An optimization procedure calculates the optimal supply currents in the inverters in order to obtain a desired power density profile in the work piece. This paper deals with the simulated and experimental results which are compared in open loop and closed loop. This paper ends with a current control method which sets rms inductor currents in continuous and digital conditions. [ABSTRACT FROM PUBLISHER]

In order to reduce short-circuit level in a power augmentation generation project in an oil refinery, it installed a duplex reactor as an alternative solution when comparing to usual techniques. Duplex reactor concept was born in the beginning of XX century, and its application is similar to conventional series reactors: limiting system maximum short-circuit current to match rated equipment short-circuit duty, protecting personal and electrical installations. However, in some electrical networks, duplex reactors have best performances than conventional ones. Selection of duplex reactor instead of other classical options is discussed in this paper. Technical and economic characteristics about the duplex reactor are also presented along this paper. [ABSTRACT FROM PUBLISHER]

This paper proposes a single-stage single-switch light-emitting diode (LED) driver that integrates a buck–boost circuit with a Class-E resonant converter by sharing single-switch device. The buck–boost circuit, working as a power-factor correction (PFC) stage, operates in the discontinuous conduction mode (DCM) to shape the input current. The Class-E converter steps down the voltage to drive the LED. For specific component parameters, the Class-E converter can achieve soft-switching on the power switch and two rectifier diodes, and reduce switch losses at high frequencies. Electrolytic capacitors are used in the proposed converter to achieve a lower cost, but the system reliability decreases. To overcome this disadvantage, film capacitors can be used, but the current ripple increases. Neglecting the cost, multilayered film capacitors are the best option, if higher reliability and lower current ripple are required. The proposed driver features high efficiency (90.8%), and a high power factor (PF) (0.995). In this paper, analytical results and design considerations at 100 kHz are presented, and a 100-W prototype with 110 \textV\text{AC} input was built to validate the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper presents a Scott-transformer-based power factor correction (PFC) rectifier for a three-level neutral-point-clamped (NPC) inverter-fed induction motor drive (IMD) for enhanced power quality at ac mains. Here, the Scott-transformer-based PFC rectifier is digitally controlled by a current feedforward control. The torque component of the stator current is added to the output of the dc-bus voltage proportional plus integral (PI) controller as a feedforward term, which enhances the dynamic performance of the dc-bus voltage regulation. The three-level NPC inverter is controlled by a space vector-modulated (SVM) indirect vector control scheme. The performance of the proposed dc-bus voltage loop with feedforward control is compared with the conventional one and found to offer faster response with less overshoot and undershoot. The proposed IMD system is simulated using MATLAB/Simulink and the same is validated experimentally. The proposed drive system is analyzed for a wide variation in reference speed and load torques demonstrating significant improvement in the performance indices. [ABSTRACT FROM AUTHOR]

In this paper, a new technique to equalize light-emitting diode (LED) currents in multiarray LED lamps is proposed. The current through the LEDs is controlled by changing the inductance of a variable inductor. The proposed technique can be employed to control the current through each LED branch independently. The operation principle of this technique and a design example of the proposed system are presented in detail in this paper. As an example, a forward converter has been selected to supply the LED branches, which can be designed to operate with one or several outputs. The component values of the converter as well as the LED current control circuit are also calculated as a design example. A prototype of the circuit has been implemented. The experimental results obtained at the laboratory are satisfactory and in accordance to the proposed design methodology. The proposed technique can prove to be very cost-effective for LED drivers in the range of 100 W and beyond with multiple independent LED arrays. [ABSTRACT FROM AUTHOR]

This paper provides experimental verification of a modular multilevel cascade converter based on triple-star bridge cells (MMCC-TSBC) for a low-speed, high-torque motor drive. The TSBC is one of direct ac-to-ac power converters capable of achieving bidirectional power flow and drawing/feeding three-phase sinusoidal input (supply-side) and output (motor-side) currents with any power factor at both sides. This paper designs, constructs, and tests a downscaled drive system combining a 400-V, 15-kW, phase-shifted-carrier PWM TSBC equipped with four bridge cells per cluster and a 320-V, 38-Hz, 6-pole, 15-kW induction motor loaded at the rated torque. Experimental waveforms obtained from the downscaled drive system verify stable operation across a broad range from a standstill to the rated speed, showing satisfactory start-up performance. [ABSTRACT FROM PUBLISHER]

Paralleled inverters are not only a suitable approach to increase the power capacity, but also have the capability of common mode voltage (CMV) reduction, or even elimination. The original zero CMV modulation scheme for paralleled inverters suffers from the current jump problem in phase-leg currents. This current jump phenomenon amplifies the peak values of differential-mode circulating current (DMCC) and zero-sequence circulating current (ZSCC), which is adverse for the design of coupled inductor and common-mode inductor. This paper introduces the modified modulation scheme, which can keep volt-seconds balance in whole fundamental period and mitigate the current jump in phase-leg currents. In addition, the reduction effect of the DMCC and ZSCC can be achieved. To verify the analysis, both the simulation and experimental results are presented, which validates the proposed methods and show that they are beneficial for DMCC and ZSCC reduction. [ABSTRACT FROM AUTHOR]

This paper presents a single-stage nonisolated switched capacitor ac–dc converter for power-factor correction (PFC). This converter features reduced passive components, single switch, transformerless high voltage gain, and improves the power factor, reduces total harmonic distortion, and voltage stress across the switch. The peak current mode with a dynamic resonant perturbation scheme compensates the subharmonics that exist at zero crossing of the source current is implemented for PFC. In this paper, the principle of operation, large signal modeling of the circuit, and control method for the proposed PFC converter are provided. [ABSTRACT FROM PUBLISHER]

With offline single-phase power supplies moving toward the megahertz switching frequency range, the converter's bus capacitor becomes the bottleneck of further improvement of power density. Partial constant power operation is effective in reducing the bus capacitance and capacitor current stress for low-power applications. However, its impact on circuit design and operation design has not been studied thoroughly. With the developed circuit operation and loss model, this paper presents design considerations and power loss analysis of megahertz ac/dc converters in partial constant power operation. An adaptive constant power control is also proposed, based on the developed models, to improve the light-load efficiency and power factor. A 65 W, megahertz critical conduction mode GaN-based ac/dc converter prototype has been developed to validate the analysis and circuit operation method. Compared with power factor correction (PFC) operation, partial constant power control exhibits an efficiency drop of less than 1%. However, a 50% reduction of bus capacitance can be realized. With the proposed adaptive constant power control, the light-load efficiency and power factor can be improved to be a level similar to the PFC operation. This paper ends with a discussion of the possibility of extending the proposed operation method to higher power applications. [ABSTRACT FROM PUBLISHER]

This paper presents a systematic and comprehensive approach for differential mode (DM) electromagnetic interference (EMI) filter design in a three-phase boost-type power factor correction (PFC) rectifier. Since the DM EMI filter forms a significant portion of the overall filter as well as converter volume, the reduction of DM filter component size is kept as a major objective in the filter design process in order to improve the power density. In addition to the objectives of volume optimization and conducted emission attenuation requirement to comply with the EMI standard, the filter design process also ensures a near-unity power factor operation with the optimal set of EMI filter parameters. To accomplish this, the paper analyzes the effect of EMI filter component selection on the overall lower order (1–100 kHz) frequency response, which is important for evaluating the dynamic response and stability. The results from the proposed design approach are validated through simulation, the DM Bode plot, and frequency response of the input current with and without EMI filter. As a proof-of-concept verification, the proposed EMI filter is implemented in a 4-kW three-phase boost-PFC prototype, which demonstrates minimal phase displacement (<5°) of the input current. [ABSTRACT FROM PUBLISHER]

Replacing the batteries of wearable medical devices is an inconvenience to the user. Wireless power transfer (WPT) could be a solution for this problem. However, the structure should be compact to satisfy the wearable device requirements and the power efficiency should be as high as possible for prolonging the user experience. Besides, as algorithms embedded in these devices become more complex, the device power consumption also increases. Fulfilling these specifications in a compact structure with better efficiency is the aim of this research paper. This paper proposes a power processing module for WPT applications. This module is embedded within the WPT path to convert receiving end ac power to dc power, and to simultaneously provide multiple dc–dc power conversion for wearable medical devices. The ac–dc circuit is specifically designed using a compact topology to convert wireless ac power to stable dc power. The dc power is further regulated by different mode controls either to perform battery charging or to provide independent voltage supplies to dc loads. The integrated circuit occupies an area of 1.9 × 2.3 mm when implemented on a 0.25 μm high voltage CMOS process. [ABSTRACT FROM AUTHOR]

Adjustable speed drive (ASD) and motors, if selected as a prime mover for compressors, pumps, extruders, etc., can provide various electromechanical benefits to its operators and stakeholders. Their benefits and application considerations have been well documented in past papers and tutorials. However, a successful installation of a multimegawatt motor and ASD system requires detailed application, engineering, manufacturing, testing, and installation considerations. Many times testing is requested by the operator and/or consultant, but navigating the types of tests available, test procedures, plans, and how they comply with appropriate standards is often not fully understood. This can lead to surprises, shipment delays, price adders, and ultimately the equipment itself not being in compliance with the stated project objectives. This paper attempts to address the factory acceptance testing phase of a medium voltage motor and ASD system whether procured separately or as a package. Issues such as type of test selection, specifications, standards, preparation, acceptance criteria, and finally string testing will be covered. This paper serves as a guideline of how one can select, prepare, witness, and sign off on a medium voltage motor and ASD test. [ABSTRACT FROM AUTHOR]

In this paper, it is described how the circulating current flows between inverters that have isolated dc link such as cascaded H-bridge (CHB) topology when they are operating in parallel. In this case, zero sequence circulating current, which normally flows through shared dc link, cannot flow between inverters in parallel. However, circulating current is provoked by asynchronous switching instant of devices, difference of dc-link voltages of parallel inverters, and unbalanced impedance. The circulating current should be suppressed by a sharing inductor that is inserted between inverters. Generally, all of the inverters should synthesize the same output voltage reference for load current control to minimize the size of this sharing reactor. However, this conventional method cannot guarantee diminishing circulating current in the transient state and even in the steady state. In this paper, in order to reduce sharing reactance, after deriving circulating current model from general case of n-parallel operation, circulating current control method is devised based on the model. This proposed algorithm is applied to active front end five-level-CHB inverter system for medium voltage drive. Simulation and experimental results are provided to verify the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

This paper presents the performance analysis and comparison of two types of bidirectional dc–dc converters—cascaded buck–boost capacitor in the middle and cascaded buck–boost inductor in the middle for use in plug-in electric and hybrid electric vehicles. The comparison of the two converters is based on device requirements, rating of switches and components, control strategy, and performance. Each of the converter topologies has some advantages over the other in certain aspects. Efficiency analysis has been carried out for specific scenarios in vehicle applications. The simulation and experimental results are provided for both converter types. [ABSTRACT FROM PUBLISHER]

An induction heating appliance designed to uniformly heat up metallic plates is studied in this paper. It consists of one planar inductor with two concentric coils attached to a mechanism, which allows moving the inductor under the plate while heating. This system is a possible solution for the growing concept of flexible induction cooking hobs, improving their performance in flexibility and in thermal distribution in the pans. With different combinations of motion and the selective activation of the inductor coils, any pan can be uniformly heated regardless its size or position on the hob. In this paper, we develop a thermal model to analyze the temperature distribution obtained in the pans for each diameter and strategy used. The model is solved using finite differences, and it is validated with experimental measurements. From the calculations, the best strategy for each pan diameter is obtained. [ABSTRACT FROM AUTHOR]

With ever more stringent \NOX emissions, it is necessary to examine removal of nitrogen oxide from diesel engine exhaust. This paper describes the study of \NOX reduction from 5.9-kW stationary diesel engine exhaust under nanosecond pulse energization. Two plasma reactors characterized by dielectric barrier discharge has been designed, built, and evaluated. One of the reactor designs include nine numbers of electrodes kept in parallel, and the exhaust was allowed to pass axially, whereas the second reactor consists of nine parallel electrodes and the exhaust was allowed to pass radially. The reactors were individually tested for the treatment of nitrogen oxides for gas flow rate of 2, 5, and 10 L/min. Both the reactors have been individually tested, and results show an appreciable removal of \NOX with equal discharge volume. From the results, it was found that both the reactors were an efficient \NOX removal. With consumption of only 36 J/L, the reactors had shown a considerable 45% \DeNOX efficiency. [ABSTRACT FROM AUTHOR]