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A multi-level boost topology based on a flying capacitor is compared in this work with the hybrid, multi-level, partial power processing topology already presented in the literature for use as a highly efficient and compact dc/dc stage in 1500-V, two-stage, grid-connected PV systems. Different variations of the resonant stage of the hybrid topology are analyzed and compared in terms of losses, volume and complexity. Full multivariable optimization is conducted for the multi-level boost topology with different number of levels and for all the analyzed variations of the resonant stage of the hybrid topology. Appropriately rated new classes of 650-V and 900-V WBG devices are included in the optimization algorithm. It is concluded that due to the dominant conduction losses and gap in the voltage rating of the commercially available WBG devices between 650V and 200V, increase of the number of levels over 4 leads to the deteriorated loss and volume performances. All the analysis related to the resonant stage of the hybrid topology is confirmed by detailed and comprehensive measurements of two prototypes of 4kW of nominal and 7kW of maximal power. Additionally, all the loss models applied in the optimization algorithms presented in this paper are confirmed by detailed measurements, thermal calibration and finite element thermal simulations of the wide bandgap devices and inductor designs employed in this work. [ABSTRACT FROM AUTHOR]

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 proposes a soft-switched modulation technique with synchronous rectification for an isolated single-stage single-phase matrix-type dc–ac converter. The dc side consists of a full bridge inverter, and the ac side is a 2×2 matrix converter-based cycloconverter. The proposed unipolar modulation strategy provides zero current switching/zero voltage switching (ZVS) for the ac side devices and ZVS-on for the dc side devices. It also allows natural commutation of the current flowing through the secondary side leakage inductor of the isolation transformer and the grid inductor during unity power factor (UPF) condition, thus eliminates the requirement of snubber circuit. An improved soft-switched flyback-based regenerative snubber circuit is also presented for non-UPF operation. Proposed snubber circuit recycles the energy stored in the snubber capacitors in every switching cycle. A guideline to design snubber circuit along with a comparative study is discussed in this paper. Performance of the proposed hybrid modulation technique is evaluated in an SiC mosfet based 1.2-kW dc–ac converter prototype. A detailed analysis of the converter performance has been presented in this paper considering the circuit non-idealities. [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]

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]

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]

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]

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 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]

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]

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]

In this paper, an electric vehicle (EV) battery charger with interleaved Landsman converter (ILC) followed by a flyback converter, is designed and evaluated for improved power quality (PQ) charging of battery. A built-in wave-shaping is obtained at the charger front-end due to improved PQ characteristics of ILC. This PFC converter consists of two Landsman converter cells, which are designed in discontinuous conduction mode (DCM) to share the input and output currents. The current sharing at input results into lower input current ripple as well as peak current stress through the switch, is reduced. This, further improves the input current harmonics profile. Moreover, the reduced output voltage ripple gives reduced rms current in the output capacitor. A phase shift PWM scheme (PSPWM) is used for ILC and the duty cycle for the switches is selected below 50%. This allows the ripple cancellation at line and load sides. The interleaving at PFC stage as well as DCM based design ensures a low cost charging solution as compared to the conventional Landsman converter (CLC) based chargers in this power range. However, the flyback converter provides the current control during the charging of the battery in constant current (CC) and constant voltage (CV) regions. The harmonics spectrum of mains current follows the recommended PQ regulations over a range of varying line voltages and loadings. [ABSTRACT FROM AUTHOR]

High penetration of renewable energy sources, such as photovoltaic (PV), promotes the clean and sustainable energy spread. Subject to the environmental conditions, intermittency in irradiation change poses the challenge in terms of variable power input to the electrical system. Conventional interfacing power converters such as a boost converter integrating photovoltaic source to the dc utility microgrid in order to push the requisite power to the microgrid suffer from increased stress, resulting in a drop of the system efficiency and possible shutdown of the system. This paper proposes a continuous input current, modular T-impedance boost converter for photovoltaic applications. The boosting capabilities of the converter during both normal boost and shoot-through conditions ensure efficient operation over wide input voltages with reduced stress on the switches. The proposed half-bridge floating ground structure restricts the flow of the common-mode current through the converter. The converter response under intermittent irradiation changes and partial shading conditions are simulated under MATLAB Simulink environment and also are experimentally validated to affirm the capability of the converter. [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]

A modular quasi-resonant bidirectional dc–dc converter composed of half-bridge gallium nitride modules (HBGM) with reduced switch voltage stress is proposed in this paper. By using an auxiliary capacitor, a resonant circuit is formed to shape the current and voltage so that zero-voltage switching at turn-on instant is achieved. Since the switching loss dominates the power losses in a high-frequency dc–dc converter, the soft-switching performance leads to a noticeable reduction in the total loss; so, the operating temperature will decrease, and consequently, size of the heatsink will be reduced. The proposed circuit takes advantage of enhancement-mode gallium nitride (eGaN) switches regarding their small on-resistance RDS(on), low gate charge, and fast switching speed to improve both efficiency and power density. The main performance issue of adopting GaN switches in a bidirectional dc–dc converter is the high voltage stress of GaN devices, which is handled by connecting the HBGM in the active-clamped stacked configuration, as well as optimizing printed circuit board layout design. Finally, a 1 kW, 600 V laboratory prototype operating at 100 kHz is implemented to validate the proposed concept. [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]

DC microgrid is gaining attraction and a recent trend in distribution power generation system due to penetration of renewables (especially photovoltaic or fuel cell). In this paper, a new triple-switch-triple-mode high step-up converter (TSTM-HS converter) is presented for dc microgrid applications. In the proposed converter, voltage lift technique is employed and range of duty cycle is extended by incorporating an additional switch in converter circuitry. By doing this, high voltage conversion ratio is achieved without using a transformer, coupled inductor, and multiple stages of switched capacitors. Moreover, the TSTM-HS converter operated in three modes with two types of the duty cycles to achieve low to high voltage conversion without using high duty cycle for each switch. The effects of difference in the inductance values on the regulation and operating behavior of the TSTM-HS converter are discussed. The continuous conduction mode and discontinuous conduction mode characteristics of the TSTM-HS converter are discussed in detail with steady-state analysis and boundary condition. The comparison is provided to highlight the benefits of the TSTM-HS converter. The selection of semiconductor devices and the design of reactive components are discussed for the TSTM-HS converter. The experimental results of the proposed converter are provided which validate the theoretical approach, performance, and feasibility of converter. [ABSTRACT FROM AUTHOR]

The increasing transistor power loss brought by the high switching frequency places a limit to the future high power density converter design. A review of resonant gate drivers is given in this paper to provide a vision for its future application. Various resonant gate driver topologies from the prior-art research is categorized and thoroughly compared in terms of the implementation frequency and the percentage gate driver loss reduction. Moreover, a case study of two representative resonant gate driver topologies is given. The conventional gate drive and two resonant gate drivers are implemented to driver Silicon MOSFETs and Gallium Nitride transistors, respectively. The feasibility and effectiveness of implementing resonant gate drivers in wide-bandgap semiconductor transistors is discussed according to a detailed comparison of loss decomposition. [ABSTRACT FROM AUTHOR]

Parallel interleaved two-level (2L) three-phase voltage source inverters (VSIs) are widely used due to their distinct advantages of high power delivery, modularity, low current rating devices, etc. Along with these advantages, the parallel interleaved 2L VSIs could also be analyzed as a single three-level (3L) VSI. Conventionally parallel interleaved 2L VSIs are modulated using the 2L pulsewidth modulation (PWM) techniques. However, implementation of parallel interleaved 2L VSIs using the 2L PWM techniques may generate a higher ac side current ripple as compared to implementing the parallel interleaved 2L VSIs using 3L PWM techniques. This paper proposes a carrier-based method for implementing different 3L discontinuous PWM (DPWM) techniques for parallel interleaved 2L three-phase VSIs. Comparison of different 2L switching sequences for implementing a 3L DPWM switching sequence based on circulating current, line current ripple, and switching loss is also carried out. Simulation and experimental results are also displayed to validate the proposal. [ABSTRACT FROM AUTHOR]

High slew rate of the line voltage $(\boldsymbol {dv}/\boldsymbol {dt})$ has been a concern for power inverters based on the emerging wide bandgap switching devices, such as silicon carbide (SiC) mosfets. Particularly, for SiC-based power inverters feeding electric machines interconnected with long cables, there could be more severe insulation stress on the stator windings in electric machines, due to the higher dv/dt output from the SiC inverters. Compared to the conventional lower voltage electric transportation applications (e.g., 270 V dc), higher dc bus voltage of 500–600 V can dramatically reduce cable weight and systematic copper losses, hence improve the power density and efficiency of power converters. However, high dc bus voltage further increases the $\boldsymbol {dv}/\boldsymbol {dt}$ level in the converter ac line voltages. Driven by the necessity of developing SiC inverters with 500 V dc bus in electric transportation applications while attenuating the $\boldsymbol {dv}/\boldsymbol {dt}$ stress to a low level, this paper presents a multi-domain design approach for dv/dt filters that comprehensively considers the constraints in electrical, magnetic, and thermal domains. Experimental results based on a 75 kW SiC inverter are provided to verify the efficacy of this design approach. [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]

An improved bridgeless (BL) Cuk converter-based electric vehicle (EV) battery charger with high power factor and increased efficiency is designed and developed in this paper. It provides low cost and high-power-density-based charging solution for the EV. This charger incorporates less number of devices operating over one switching cycle, which reduces the additional conduction loss incurred by a diode bridge rectifier of the conventional charger. Hence, it improves the charger's efficiency. The added advantage of the proposed topology is that the unwanted capacitive coupling loop is removed, as well as the unwanted conduction through the body diode of the inactive switch in the previously developed BL Cuk converter is avoided. This significantly improves the charger's efficiency. For the constant current and constant voltage charging, the commands are synchronized by a flyback converter. The proposed charger draws a sinusoidal current from ac mains and the total harmonic distortion in the supply current is reduced to the limits specified by the IEC 61000-3-2 guidelines. The improved efficiency and power quality indices of the proposed charger are investigated to demonstrate its satisfactory charging operation at all operating conditions. [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]

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]

Usually, the high-gain high-efficiency dc–dc converters consist of many passive components, which increases the order of the system. As the order increases, system modeling and control become more complex. Thus, there is a need for the simplification of the small signal modeling process of such converters. This paper presents a generalized small signal model and equivalent circuit for an $n$ th-order coupled-inductor-based high-voltage gain converters (CIHVGC) that can be conveniently used for the control design. The state variable representation of a generalized coupled inductor with p windings is included. A simplified step by step procedure to obtain small signal model using visual inspection is presented. Analysis is included and verified using simulations and experiments for the output voltage regulation of high-voltage gain converters. The usefulness and versatility of the proposed model is verified with three examples of high gain converters belonging to the CIHVGC family. All the analytical, simulation, and experimental details of this paper are presented. [ABSTRACT FROM AUTHOR]

This paper proposes a novel single-switch dc/dc converter for the future renewable electric energy delivery and management system to implement the distributed renewable energy resources (DRER). The DRER is responsible for the maximum power point tracking of the photovoltaic panel (PV) module and also for the control of central energy storage device. Due to the characteristics of the PV module and the dc-bus, the single power stage must provide low current ripple in the input and output terminals, must operate with output current and voltage regulation, and present a high-voltage conversion ratio. To achieve such features, this paper proposes a novel integrated Boost–Zeta converter. To avoid a complex modeling and control, we propose a disaggregation concept for this. Experimental results are presented for the purpose of operating the converter and also for the operation of the system. [ABSTRACT FROM PUBLISHER]

Power density and size are important features in compact ac–dc power adapters today. The push for power density, however, requires high conversion efficiency to reduce thermal stresses and smaller magnetics to fit into the required volume. Flyback converters have traditionally been adopted in compact power adapters due to their simplicity, acceptable performance, and low cost. In this paper, we present the design and fabrication of a high-density laptop adapter with a single-stage clamped series-resonant converter as a possible alternative for power adapters in portable electronics. The target is to achieve power densities and scalability in power from 45 to 100\,\mathrm{W}. The converter is frequency controlled and all switches exhibit zero-current switching. In this paper, we show that by utilizing the magnetizing inductance, the converter can be tuned for zero-voltage switching, and by adding a switched capacitor circuit to extend the input voltage range, we can realize a very compact design that is suitable for power adapters with or without power factor correction. Low transformer stresses compared with Flyback-type designs enable high densities, even with a resonant magnetic. Prototype test results with a 45-W laptop adapter are presented. Results are presented from a prototype design demonstrating high efficiency with a power converter density of 8.5$  W/{\mathrm{in}}^3 and means to further increasing the conversion efficiency with synchronous rectification are discussed. [ABSTRACT FROM PUBLISHER]

Compared with the conventional hard switching battery equalizers, hierarchical battery equalizer based on the bipolar continuous-conduction mode buck–boost units could effectively reduce the switching loss and improve the conversion efficiency. This paper mainly addresses the key technical challenges associated with the optimal design of this battery equalizer. The inductor current is controlled to enter into the negative region. Thus, the mosfet body diode provides a freewheeling path for the inductor current during the dead band. This ensures zero-voltage switching turn-on of both power mosfets in each buck–boost unit without auxiliary snubbers. Therefore, the switching losses are significantly reduced. Meanwhile, the integral of the inductor negative current is precisely controlled to minimize the circulating current. This guarantees both minimized conduction losses and suitable equalization speed. Furthermore, an equalization algorithm, which compensates the battery internal resistance induced state-of-charge error, is proposed to improve the equalization accuracy. The operating principles and design considerations are analyzed in detail. An experimental prototype to balance four series-connected lithium-ion battery cells is implemented. The experimental results validate the design of the equalizer and demonstrate obvious efficiency enhancement over the conventional method. [ABSTRACT FROM AUTHOR]

The implementation of a non-isolated dual input bridge-type dc–dc converter for hybrid energy source integration is discussed in this paper. The proposed converter accommodates two sources using an inductor, a capacitor, two insulated-gate bipolar transistors (IGBTs) without the anti-parallel diode and two IGBTs with the anti-parallel diode. The different modes of operation of the converter are explained with detailed analytical waveforms and equivalent circuits. From the analysis, the steady-state output equation of the converter is derived. The boundary condition between the continuous conduction mode and discontinuous conduction mode operations is also derived. The dynamics of the converter is analyzed in detail with the help of a small signal model. The step response of different transfer functions is discussed. The computer simulations of the proposed converter topology have been carried out using MATLAB/Simulink. An experimental prototype of the proposed converter is also built and tested successfully in the laboratory environment. Performance comparison of the proposed converter is carried out with the conventional converter topologies in terms of component counts, efficiency, loss breakdown, and power density. [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 proposes a control method for the initial charge of the dc-capacitor in voltage-source power converters. The proposed method is suitable for the power converter equipped with a small dc capacitor and is capable of removing the initial charge circuit. The proposed method makes a leg short circuit by using power devices employed in the power converter, discharges the dc capacitor, and suppresses its overvoltage due to the initial charge. The short-circuit operation only occurs for a short time and is used once in each leg to distribute the loss to each power device. The experimental verification using a 200-V, 5-kVA three-phase converter shows that the proposed method can reduce the peak voltage of the dc capacitor from 520 to 420 V. The experimental results exhibit a good capability of the proposed method to suppress the overvoltage due to initial charge without fatal damage to the power devices. As a result, the proposed method enables removal of the initial charge circuit, resulting in a reduction in the size and cost of power converters. [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]

A three-port converter (TPC) as a compact dc/dc energy conversion unit can effectively integrate renewable energy sources (RESs) and energy storage units (ESUs) into dc microgrids (MGs). In this paper, a series-resonance-based isolated TPC is developed to integrate photovoltaic (PV) and ESUs into dc MGs. A hardware decoupling approach using a series-connected capacitor in the half-bridge of the isolated TPC is proposed and studied. The decoupled power flow model among different ports is derived based on the equivalent circuit model of the converter, and the power transmission principle of the resonant circuit is analyzed. On this basis, considering the characteristics and operation modes of PV and ESU, which are connected at the two input ports of the TPC, a unified autonomous control method based on minimum value competition logic is proposed to coordinate the operation of PV and ESU, and achieve voltage regulation of the common bus in dc MGs. Simulation and experimental results are obtained in different test scenarios to demonstrate the effectiveness of the power decoupling effect and the proposed control method. [ABSTRACT FROM AUTHOR]

This paper proposes a switching strategy for the Z-source inverter (ZSI), which has unequal short-through intervals to reduce the current ripple in the inductor of its impedance source. A size reduction of the inductor of the ZSI is one of the important issues in improving the power density of the ZSI, and the inductor current ripple reduction is required to achieve it. The proposed method can reduce the inductor current ripple by 27.8% compared with the conventional method that has equal short-through intervals without increasing the number of inverter switching. The proposed operation and ripple reduction were confirmed in experiments with a 3-kW-class laboratory prototype. Its result agreed to the calculated results, and it was confirmed that there is no increase in circuit losses caused by the application of the proposed method. [ABSTRACT FROM AUTHOR]

The utilization of wide band gap devices has enabled high frequency operation of totem pole bridgeless PFC rectifier. However, most of the designs reported in the literature with frequency higher than 100 kHz operate under discontinuous conduction mode or critical mode to reduce the switching loss. This paper proposes a zero-voltage-transition (ZVT) technique for totem-pole PFC rectifier under continuous conduction mode operation which enables efficient operation at switching frequencies well above 100 kHz. A simple auxiliary circuit consisting of a small auxiliary inductor and two active switches is placed in parallel with the main input filter inductor to achieve zero-voltage-switching of the main switches. The auxiliary switches operate with zero-current-switching (ZCS) and conduct current as short resonant pulses only during the critical turn-on transition which results in very low losses in the auxiliary circuit. The timing of the auxiliary switches is adaptively controlled with respect to the grid voltage angle for optimized overall efficiency. The effectiveness of the proposed ZVT scheme has been validated through experiments based on a 2.4 kW 400 kHz hardware prototype with 98.35% peak efficiency. [ABSTRACT FROM AUTHOR]

An electric machine supported by an active magnetic bearing (AMB) can realize ultrahigh speed and high power density, and it is developing toward the trends of higher rotation speed and higher power density. The displacement sensor used for an AMB is one of the most important components in a magnetic suspension electric machine, so improving the dynamic response and the resolution of the displacement sensor become a critical technology. In this paper, a novel self-differential eddy-current displacement sensor (ECDS) based on the Hartley principle for a high-speed magnetic suspension electric machine is proposed and verified. First, the integral structure of the ECDS probe and the novel design scheme are presented. Second, the phase advance network method is described in detail to improve the dynamic characteristic of the sensor. Third, the detailed suppression procedure of the sensor-to-sensor crosstalk noise is given to improve the sensor's resolution. Finally, a series of experiments is carried out on two typical prototypes of a high-speed magnetic suspension electric machine. The experimental results indicate that the proposed ECDS with high dynamic response and resolution is valid in the application of the high-speed magnetic suspension rotating machinery in industrial applications. [ABSTRACT FROM AUTHOR]

A switching-capacitor-based buck–boost converter (with common ground) for point of load applications is proposed in this paper. It is capable of operating in stand-alone buck or boost mode in addition to its primary operation of performing the buck–boost conversion. The striking feature of the proposed converter is low source current ripple content irrespective of its mode of operation (buck–boost, buck, or boost). First, feasible pulsewidth modulation schemes for the proposed converter are identified and thereafter the corresponding circuit performance analysis, steady-state analysis, and state-space modelling is established. Through steady-state analysis, voltage gain expressions are formulated and equations defining L-C components are derived in terms of their ripple quantities. The state-space models are used to formulate small-signal analysis and to obtain the relevant transfer functions required in the controller design. A voltage-mode/current-mode controller is designed, with a tradeoff in bandwidth, to control the proposed converter and transit it from buck to boost mode or vice versa seamlessly. A 30–55 W, 100 kHz, prototype point of load converter with 36-V input dc source is built to supply power at constant load voltage of either 48 or 28 V. The proposed converters’ effectiveness is demonstrated experimentally in terms of reduced source current ripple along with seamless transition from buck to boost mode and vice versa. [ABSTRACT FROM AUTHOR]

The proposed paper presents the development of a highly efficient and highly immune misalignment tolerant loosely coupled inductive power transfer system using dynamic wireless power transfer concept to charge a 48-V battery bank at 500 W through a 16-cm airgap. The purpose of this work is to investigate the influence of a third coil functioning as a transmitter coil. The resonant circuit as well as the electronic power converters used to implement a prototype are deeply explained. [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]

In this paper, a fifth-order boost point-of-load converter is developed by cascading a modified fourth-order boost converter with a combination of L–C and diode. This topology has the following salient features: Single-switch topology, common ground between source and load, low-voltage stress across intermediate capacitors, and voltage gain same as other reported fifth-order boost converters with no common ground. Steady-state and dynamic analyses demonstrate the proposed converter's boosting feature and dynamic performance, respectively. A contoured robust Bode plot methodology is employed to design the robust voltage-mode controller to ensure load voltage regulation in the presence of uncertainties. The necessary and sufficient conditions under which the designed controller guarantees the load voltage regulation and robust stability are obtained. A step-by-step robust controller design procedure is outlined. The salient features of the proposed converter and its robust performance are studied analytically, using the MATLAB platform, and validated experimentally on a 60-W prototype module. [ABSTRACT FROM AUTHOR]

This paper presents a dual output power factor correction (PFC) converter for switched reluctance motor (SRM) drives. Here, a modified single-ended primary inductance converter (SEPIC) is proposed for a wide range of speed control and to achieve PFC at ac mains. The switching frequency of the converter is considered to be 20 kHz. The converter is designed to operate in the discontinuous conduction mode (DCM) of operation, which reduces the size of the output inductor. The DCM mode to obtain PFC also reduces the sensor requirement as compared to the continuous conduction mode (CCM), where two voltage sensors and one current sensor add to the drive cost. The drive is proposed for universal ac mains (90–270 V ac). Simulated and experimental results are demonstrated to validate the performance of the drive during different operating conditions. The input current total harmonic distortion is reduced to comply with an IEC 61000-3-2 standard. [ABSTRACT FROM AUTHOR]