Showing papers on "Inductor published in 2018"

High-Efficiency High Step-Up DC–DC Converter With Dual Coupled Inductors for Grid-Connected Photovoltaic Systems

Abstract: This paper introduces a non-isolated high step-up dc–dc converter with dual coupled inductors suitable for distributed generation applications. By implementing an input parallel connection, the proposed dc–dc structure inherits shared input current with low ripple, which also requires small capacitive filter at its input. Moreover, this topology can reach high voltage gain by using dual coupled inductors in series connection at the output stage. The proposed converter uses active clamp circuits with a shared clamp capacitor for the main switches. In addition to the active clamp circuit, the leakage energy is recycled to the output by using an integrated regenerative snubber. Indeed, these circuits allow soft-switching conditions, i.e., zero voltage switching and zero current switching for active and passive switching devices, respectively. The mentioned features along with a common ground connection of the input and output make the proposed topology a proper candidate for transformer-less grid-connected photovoltaic systems. The operating performance, analysis and mathematical derivations of the proposed dc–dc converter have been demonstrated in the paper. Moreover, the main features of the proposed converter have been verified through experimental results of a 1-kW laboratory prototype.

High Step-Up DC–DC Converter With Active Switched-Inductor and Passive Switched-Capacitor Networks

Abstract: High-gain voltage conversion is a feature required for several applications, especially for power processing of low-voltage renewable sources in grid-connected systems. In this scope, the presented paper proposes a novel transformerless high gain step-up dc–dc converter based on an active switched-inductor and a passive switched-capacitor networks. The main advantages of the proposed converter are the high voltage gain (>10), the reduced voltage stresses across the switches and the reduced number of components when compared to topologies that provide the same voltage gain using similar principles. The detailed analysis of the proposed converter and a comparison considering other topologies previously published in the literature are also presented in this manuscript. In order to verify the proposed converter performance, a prototype has been built for a power of 200 W, input and output voltages of 20 and 260 V, respectively, and switching frequency of 50 kHz. Experimental results validate the effectiveness of the theoretical analysis proving the satisfactory converter performance, which peak efficiency is around 95.5%.

An Active-Rectifier-Based Maximum Efficiency Tracking Method Using an Additional Measurement Coil for Wireless Power Transfer

Abstract: The efficiency of wireless power transfer (WPT) systems is highly dependent on the load, which may change in a wide range in field applications. Besides, the detuning of WPT systems caused by the component tolerance and aging of inductors and capacitors can also decrease the system efficiency. In order to track the maximum system efficiency under varied loads and detuning conditions in real time, an active single-phase rectifier (ASPR) with an auxiliary measurement coil (AMC) and its corresponding control method are proposed in this paper. Both the equivalent load impedance and the output voltage can be regulated by the ASPR and the inverter, separately. First, the fundamental harmonic analysis model is established to analyze the influence of the load and the detuning on the system efficiency. Second, the soft-switching conditions and the equivalent input impedance of ASPR with different phase shifts and pulse widths are investigated in detail. Then, the analysis of the AMC and the maximum efficiency control strategy are provided in detail. Finally, an 800-W prototype is set up to validate the performance of the proposed method. The experimental results show that with 10% tolerance of the resonant capacitor in the receiver side, the system efficiency with the proposed approach reaches 91.7% at rated 800-W load and 91.1% at 300-W light load, which has an improvement by 2% and 10% separately compared with the traditional diode rectifier.

Analysis and Implementation of a New SEPIC-Based Single-Switch Buck–Boost DC–DC Converter With Continuous Input Current

Abstract: In this paper, a novel buck–boost dc–dc converter with continuous input current is proposed The voltage gain of the presented converter is higher than conventional converters, such as buck–boost, single-ended primary-inductance converter, Cuk, and Zeta converters This converter works only by one switch and voltage stress across the switch is low Input current of the proposed converter is continuous so a large filter at the input is not needed Furthermore, continuous input current has made this converter suitable for renewable energy and fuel cell applications In this converter, noninverting output voltage is obtained and high gain of voltage is achieved as well So it can operate at wide output voltage range only by changing the duty cycle of the power switch pulse The presented converter can easily controlled in continuous conduction mode operation, because of using only one power switch In the following, the principle of operation and the mathematical analyses of the proposed converter are explained, finally, validity of the proposed dc–dc converter is verified by the experimental results

A Switched-Capacitor Bidirectional DC–DC Converter With Wide Voltage Gain Range for Electric Vehicles With Hybrid Energy Sources

Abstract: A switched-capacitor bidirectional dc–dc converter with a high step-up/step-down voltage gain is proposed for electric vehicles with a hybrid energy source system. The converter presented has the advantages of being a simple circuit, a reduced number of components, a wide voltage-gain range, a low voltage stress, and a common ground. In addition, the synchronous rectifiers allow zero voltage switching turn-on and turn-off without requiring any extra hardware, and the efficiency of the converter is improved. A 300 W prototype has been developed, which validates the wide voltage-gain range of this converter using a variable low-voltage side (40–100 V) and to give a constant high-voltage side (300 V). The maximum efficiency of the converter is 94.45% in step-down mode and 94.39% in step-up mode. The experimental results also validate the feasibility and the effectiveness of the proposed topology.

A High-Efficiency High-Density Wide-Bandgap Device-Based Bidirectional On-Board Charger

Abstract: This paper proposes a novel two-stage topology for a 6.6-kW on-board charger. The first stage, employing an interleaved bridgeless totem-pole ac/dc in critical conduction mode to realize zero-voltage switching, is operated at over 300 kHz. A bidirectional CLLC resonant converter operating at 500 kHz is chosen for the second stage. A variable dc-link voltage is adopted to track the wide battery voltage range, so that the CLLC resonant converter can always operate at its most efficient point. The 1.2-kV SiC devices are adopted for the ac/dc stage and the primary side of dc/dc stage, while 650-V GaN devices are used for the secondary side of dc/dc stage. In addition, PCB winding coupled inductors and integrated transformer are implemented in ac/dc stage and dc/dc stage, respectively, for the purpose of high density and manufacture automation. The proposed structure is demonstrated to have 37-W/in3 power density and above 96% efficiency over the entire battery voltage range, which far exceeds the current practice.

Load-Independent Class E/EF Inverters and Rectifiers for MHz-Switching Applications

Abstract: This paper presents a unified framework for the modeling, analysis, and design of load-independent Class E and Class EF inverters and rectifiers. These circuits are able to maintain zero-voltage switching and, hence, high efficiency for a wide load range without requiring tuning or use of a feedback loop, and to simultaneously achieve a constant amplitude ac voltage or current in inversion and a constant dc output voltage or current in rectification. As switching frequencies are gradually stepping into the megahertz (MHz) region with the use of wide-bandgap (WBG) devices such as GaN and SiC, switching loss, implementing fast control loops, and current sensing become a challenge, which load-independent operation is able to address, thus allowing exploitation of the high-frequency capability of WBG devices. The traditional Class E and EF topologies are first presented, and the conditions for load-independent operation are derived mathematically; then, a thorough analytical characterization of the circuit performance is carried out in terms of voltage and current stresses and the power-output capability. From this, design contours and tables are presented to enable the rapid implementation of these converters given particular power and load requirements. Three different design examples are used to showcase the capability of these converters in typical MHz power conversion applications using the design equations and methods presented in this paper. The design examples are chosen toward enabling efficient and high-power-density MHz converters for wireless power transfer (WPT) applications and dc/dc conversion. Specifically, a 150-W 13.56-MHz Class EF inverter for WPT, a 150-W 10-MHz miniature Class E boost converter, and a lightweight wirelessly powered drone using a 20-W 13.56-MHz Class E synchronous rectifier have been designed and are presented here.

An LC/S Compensation Topology and Coil Design Technique for Wireless Power Transfer

Abstract: Wireless power transfer (WPT) has attracted a lot of attention these years due to its convenience, safety, reliability, and weather proof features. First and foremost, the consistency of mutual model and T model of loosely coupled transformer (LCT) was deduced. The application scenarios of these two models were then concluded so as to choose suitable model in circuit analysis. Then, a new WPT compensation topology, which is referred to as LC /S compensation topology and consists of one inductor and two capacitors, is proposed. The constant-current-output (CCOut) characteristic of the newly proposed topology is analyzed in detail on the basis of the discussion about LC and CL resonant tank. The equivalent resistance of the rectifier, filter, and resistor circuit is also analyzed to simplify circuit analysis. Then, the current and voltage stress on each component and the system performance under imperfect resonant condition are studied with the help of MATLAB. The LCT is deliberately designed by the finite element analysis software ANSYS Maxwell as well because the coupling coefficient, primary, and secondary self-inductance have a significant impact on system efficiency, power level, and density. The LCT design approach employed in this paper can be extended to magnetic design of almost all WPT systems. Theoretical analyses are verified by both Pspice simulation and practical experiments. Practical output currents with transient loads show an excellent CCOut characteristic of LC /S compensation topology.

On Stability of Voltage Source Inverters in Weak Grids

Abstract: As the number of inverters increases in the power grid, the stability of grid-tied inverters becomes an important concern for the power industry. In particular, a weak grid can lead to voltage fluctuations at the inverter terminals and consequently cause inverter instability. In this paper, impacts of circuit and control parameters on the stability of voltage source inverters are studied using a small-signal state-space model in the synchronously rotating $dq$ -frame of reference. The full-order state-space model developed in this paper is directly extracted from the pulsewidth modulation switching pattern and enables the stability analysis of concurrent variations in the three-phase circuit and control parameters. This paper demonstrates that the full-order model of a grid-tied active (P) and reactive (Q) power (PQ)-controlled voltage source inverter (VSI) can be significantly reduced to a second-order model, preserving the overall system stability in the case of grid impedance variations. This paper also shows that a decrease in the grid inductance does not necessarily improve the stability of grid-tied VSIs. The system stability is a function of both the grid R/X ratio and grid inductance. Despite the grid-side inductor of the LCL filter is in series with the grid impedance, they have different impacts on the stability of a grid-tied PQ-controlled VSI, i.e., an increase in the filter inductance may improve the system stability in a weak grid. These findings are verified through simulated and experimentally obtained data.

High Step-Up Coupled-Inductor Cascade Boost DC–DC Converter With Lossless Passive Snubber

Abstract: In this paper, a high step-up coupled-inductor cascade boost dc–dc converter with lossless passive snubber is proposed. Although a conventional cascade boost converter has larger voltage gain compared to a boost converter, it is still not suitable for high step-up voltage conversion. In the proposed converter, a coupled inductor is adopted for the cascaded boost converter to further increase the voltage gain. However, a leakage inductance of the coupled inductor causes a high voltage spike at a main switch. A resistor–capacitor–diode snubber is commonly used to simply solve this problem, but it is also the cause of additional power loss. Therefore, the lossless passive snubber is suggested in this paper in order to prevent efficiency drop by a snubber circuit. In conclusion, the proposed converter has high voltage gain and improved power efficiency. Experimental results from an output 400-V 200-W prototype at a constant switching frequency of 50 kHz are presented to verify the performance of the proposed converter.

Analysis of Faults in Multiterminal HVDC Grid for Definition of Test Requirements of HVDC Circuit Breakers

Abstract: This paper provides a detailed analysis of the temporal development of fault currents in a multiterminal high-voltage direct-current (MT-HVDC) grid composed of a bipolar converter configuration. The sequence of events following the occurrence of a pole-to-ground fault is identified, divided into three distinct periods; namely, submodule capacitor discharge, arm current decay, and ac in-feed periods. The critical parameters that have a significant impact on the fault current in each period are discussed. The impacts of various parameters of the HVDC grid such as the size of the current limiting reactor, ac grid strength, as well as the location of the fault within the grid are studied through PSCAD/EMTDC simulation. Then, a fault current interruption process using models of various HVDC circuit breaker technologies and the resulting stresses are studied. Both serve as important inputs to define test procedures. It is found that the HVDC circuit breakers are subjected to not only dc current and voltage stresses but also energy stress. These stresses are translated into test requirements.

Extendable Nonisolated High Gain DC–DC Converter Based on Active–Passive Inductor Cells

Abstract: In this paper, a new nonisolated high step-up dc–dc converter is proposed. Active–passive inductor cells (APICs) are used to extend the topology. The ability to achieve high gains is the main merit of the proposed topology. The proposed converter operates based on parallel charging and series discharging of the inductors. The converter also achieves high step-up voltage gain with appropriate duty cycle and low voltage and current stress on the power switches and diodes. The proposed converter is analyzed in operation modes. The main parameters of the converter such as voltage gain, voltage stress of semiconductor devices are calculated to compare with other structures. Considering the output voltage ripple and filter size, the proposed converter is designed. Moreover, the losses and efficiency of the converter are calculated. The performance of the proposed converter is validated by experimental results.

A Dual-Coupled LCC-Compensated IPT System With a Compact Magnetic Coupler

Abstract: This paper proposes a dual-coupled LCC -compen-sated inductive power transfer system with a compact magnetic coupler to improve misalignment performance. In the magnetic coupler, the main coils form the first coupling, and compensation inductors are integrated with the main coils to form a second coupling. In the design presented in this paper, the main coils are unipolar and the compensation inductors are in a Double D structure. The fundamental harmonics approximation method is used to analyze the circuit, and the couplings between the main coils and compensation inductors are considered to determine the net power flow. In misalignment cases, it is shown that the coupling between the compensation inductors, and the cross couplings between the compensation inductors and main coils, contribute to increasing the system power. A 3.5 kW prototype is designed and implemented to validate the proposed dual-coupled system. The primary coil size is ${\text{450 mm}\times \text{450 mm}}$ , and the secondary coil size is ${\text{300 mm}\times \text{300 mm}}$ . Experimental results show that the proposed dual-coupled system can significantly improve the misalignment performance, and retains at least 56.8% and 82.6% of the well-aligned power at 150 mm misalignment in the x - and y -directions, respectively.

Soft-Switched Nonisolated High Step-Up Three-Port DC–DC Converter for Hybrid Energy Systems

Abstract: In this paper, a nonisolated high step-up three-port converter is proposed which provides two separate power flow paths from each input source to the output load. In order to reduce the number of converter components, some components play multiple roles. Accordingly, the energy storage device is charged with the same components which are used in transferring power to the load. In this converter, the coupled inductors technique is used to increase the voltage gain, and to mitigate the leakage inductance effect and to provide soft-switching condition, two active clamp circuits are employed. Since the voltages across the switches are clamped, switches with low voltage stress and consequently low conduction loss can be used. Various converter operating modes are discussed and design considerations are presented. A converter prototype to supply a 150 W–400 V load is implemented and the theoretical analysis is validated by the experimental results.

Study on a High Voltage Gain SEPIC-Based DC–DC Converter With Continuous Input Current for Sustainable Energy Applications

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

High Step-Up DC–DC Converter Based on Switched Capacitor and Coupled Inductor

Abstract: Due to the relatively low output voltage of photovoltaic (PV) source, a high step-up converter with high efficiency is needed when the PV source is connected to the power grid. A novel high step-up converter based on two switched capacitors and a coupled inductor is proposed in this paper. The operating principle is analyzed and the voltage gain is derived. A 100-W prototype is fabricated in the laboratory to verify the theoretical analysis, and the highest efficiency is 96.4%.

A Single-Switch Quadratic Buck–Boost Converter With Continuous Input Port Current and Continuous Output Port Current

Abstract: A single-switch quadratic buck–boost converter with continuous input port current and continuous output port current is proposed in this paper. Compared with the traditional buck-boost converter, the proposed converter can obtain a wider range of the voltage conversion ratio with the same duty cycle. Moreover, the proposed converter can operate with continuous input port current and continuous output port current compared to the existing counterparts with inherently discontinuous input port current and discontinuous output port current. The operating principle and steady-state performance of the proposed converter under continuous inductor current mode is analyzed in detail. Then, the comparison between the proposed converter and the existing quadratic buck–boost converters has been conducted to demonstrate the unique features of the proposed one. Finally, experimental results from a prototype built in the lab are recorded to verify the effectiveness and validity of the proposed quadratic buck–boost converter.

A Novel Single-Input Dual-Output Three-Level DC–DC Converter

Abstract: This paper proposes a novel nonisolated single-input dual-output three-level dc–dc converter (SIDO-TLC) appropriate for medium- and high-voltage applications. The SIDO-TLC is an integration of the three-level buck and boost converters, whose output voltages are regulated simultaneously. Reducing voltage stress across semiconductor devices, improving efficiency, and reducing inductors size are among the main merits of the new topology. Moreover, due to the considerably reduced volume of the step-down filter capacitor, a small film capacitor can be used instead, whose advantages are lower equivalent series resistance and a longer lifespan. A closed-loop control system has been designed based on a small-signal model derivation in order to regulate the output voltages along with the capacitors’ voltage balancing. In order to verify the theoretical and simulation results, a 300-W prototype was built and experimented. The results prove the aforementioned advantages of the SIDO-TLC, and the high effectiveness of the balancing control strategy. Furthermore, the converter shows very good stability, even under simultaneous step changes of the loads and input voltage.

Integrated Coil Design for EV Wireless Charging Systems Using LCC Compensation Topology

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

SOC Estimation-Based Quasi-Sliding Mode Control for Cell Balancing in Lithium-Ion Battery Packs

Abstract: The successful and safe operation of a serially connected battery pack necessitates dynamic energy equalizing to adjust each cell's state of charge (SOC) to the same level, since there exists energy imbalance among its cells. Bidirectional Modified Cuk converters are utilized as the cell equalizers due to their advantages of integrated infrastructure and modular design. Distinguished from the literature, the maximum allowed cell equalizing current is designed to vary with the change of the battery pack's external current rather than a constant to avoid the cell's current exceeding its limitation. With adaptive quasi-sliding mode observers designed for the cells’ SOC estimation, a discrete-time quasi-sliding-mode-based strategy with saturated equalizing current constraints is proposed to have the converters work together efficiently to achieve the cells’ SOC equalization. As analyzed in mathematical proofs and shown in experimental results, the cells’ actual SOC differences can converge to a tolerant range around the origin in a relatively short time under the designed SOC estimation-based cell balancing method.

A New Interleaved Coupled-Inductor Nonisolated Soft-Switching Bidirectional DC–DC Converter With High Voltage Gain Ratio

Abstract: This paper presents a new interleaved coupled-inductor nonisolated bidirectional dc–dc converter that provides high voltage gain ratio (VGR), low ripple current at the low-voltage side (LVS), and soft switching. The high VGR is obtained by connecting in series the outputs of an interleaved bidirectional buck–boost converter and a dual-active half-bridge converter, using the turns ratio of a coupled inductor. Since the voltage of the high-voltage side is shared between the converters outputs, the voltage stress across the active switches decrease. The active switches turn ON under zero-voltage switching condition in both directions. Moreover, the low current ripple at the LVS is achieved due to the applied interleaved technique. By employing the phase-shift angle modulation, the output voltage is regulated. The proposed converter is analyzed in details and a 900-W experimental prototype with 48-V input voltage and 400-V output voltage under 100-kHz switching frequency is implemented to verify the theoretical results.

A Three-Winding Coupled-Inductor DC–DC Converter Topology With High Voltage Gain and Reduced Switch Stress

Abstract: This paper presents a dc–dc boost converter topology for low input and high output voltage applications, such as photovoltaic systems, fuel cell systems, high-intensity discharge lamp, and electric vehicles. The suggested configuration consists of a three-winding coupled-inductor, a single switch and two hybrid voltage multiplier cells. Furthermore, two independent hybrid voltage multiplier cells are in parallel when the single switch S is turned on , and they are in series when the switch S is turned off . So, the advantages of the proposed converter structure are summarized as follows: 1) A coupled inductor with three windings is introduced in the presented converter structure. The two secondary windings of the coupled inductor are, respectively, used to form a hybrid multiplier cell on the one hand, on the other hand, it increases the control freedom of the voltage gain, enhances the utility rate of magnetic core and power density, and reduces the stress of power components to provide a stable constant dc output voltage. 2) The two hybrid multiplier cells can absorb synchronously the energy of stray inductance, which not only reduces the current stress of corresponding diodes, but also greatly alleviates the spike voltage of the main switch, which improves the efficiency. 3) The two hybrid multiplier cells are connected in series to supply power energy for the load, so the voltage gain is extended greatly due to this particular structure. Thus, low-voltage low-conduction-loss devices can be selected and the reverse-recovery currents within the diodes are inhibited. The operating principles and the steady state analyses of the proposed converter are discussed in detail. Finally, a test prototype has been implemented in the laboratory, and the simulated and experimental results show satisfactory agreement with the theoretical analysis.

Unlimited Accumulation of Electromagnetic Energy Using Time-Varying Reactive Elements

Abstract: Accumulation of energy by reactive elements is limited by the amplitude of time-harmonic external sources. In the steady-state regime, all incident power is fully reflected back to the source, and the stored energy does not increase in time, although the external source continuously supplies energy. Here, we show that this claim is not true if the reactive element is time-varying, and time-varying lossless loads of a transmission line or lossless metasurfaces can accumulate electromagnetic energy supplied by a time-harmonic source continuously in time without any theoretical limit. We analytically derive the required time dependence of the load reactance and show that it can be in principle realized as a series connection of mixers and filters. Furthermore, we prove that properly designing time-varying LC circuits one can arbitrarily engineer the time dependence of the current in the circuit fed by a given time-harmonic source. As an example, we theoretically demonstrate a circuit with a linearly increasing current through the inductor. Such LC circuits can accumulate huge energy from both the time-harmonic external source and the pump which works on varying the circuit elements in time. Finally, we discuss how this stored energy can be released in form of a time-compressed pulse.

On-chip intercalated-graphene inductors for next-generation radio frequency electronics

Abstract: On-chip metal inductors that revolutionized radio frequency electronics in the 1990s suffer from an inherent limitation in their scalability in state-of-the-art radio frequency integrated circuits. This is because the inductance density values for conventional metal inductors, which result from magnetic inductance alone, are limited by the laws of electromagnetic induction. Here, we report inductors made of intercalated graphene that uniquely exploit the relatively large kinetic inductance and high conductivity of the material to achieve both small form-factors and high inductance values, a combination that has proved difficult to attain so far. Our two-turn spiral inductors based on bromine-intercalated multilayer graphene exhibit a 1.5-fold higher inductance density, leading to a one-third area reduction, compared to conventional inductors, while providing undiminished Q-factors of up to 12. This purely material-enabled technique provides an attractive solution to the longstanding scaling problem of on-chip inductors and opens an unconventional path for the development of ultra-compact wireless communication systems.

Modified Single-Phase Single-Stage Grid-Tied Flying Inductor Inverter With MPPT and Suppressed Leakage Current

Abstract: In this paper, an improved transformerless single-phase single-stage grid-tied flying inductor inverter is presented. The negative terminal of the photovoltaic (PV) array is grounded in the improved topology, which increases reliability and suppresses the leakage current. The proposed topology has buck–boost capability without increasing the number of required components and has a high efficiency. An improved control algorithm for proper operation of the proposed topology which decreases switching losses has been investigated. Moreover, a perturbation and observation maximum power point tracking (MPPT) algorithm has been adapted to the proposed inverter, which does not utilize proportional–integral (PI) controllers, for the purpose of the MPPT. Furthermore, a design procedure of the passive elements of the converter based on the corresponding operating has been demonstrated. Simulation in MATLAB Simulink plus an experimental prototype is developed to reconfirm the designed results. Finally, a comparison study has been investigated for better clarification of the advantages and disadvantages of the proposed inverter.

LVRT Performance Enhancement of DFIG-Based Wind Farms by Capacitive Bridge-Type Fault Current Limiter

Abstract: Low voltage ride-through (LVRT) is one of the main requirements of the new grid codes for integration of wind farms (WFs) to power system. In this paper, to enhance the LVRT capability of doubly-fed induction generator (DFIG)-based WFs, a capacitive bridge-type fault current limiter (CBFCL) is proposed. The CBFCL is based on the conventional inductive bridge-type fault current limiter (IBFCL), in which the limiting impedance (LI) of the IBFCL is adapted according to WFs requirement to provide the reactive power needed of WFs after fault clearance. The WF has been modeled based on an equivalent aggregated DFIG. To check the effectiveness of the CBFCL, its performance is compared with the IBFCL. The PSCAD/EMTDC simulation results show that the CBFCL is an effective and novel solution for LVRT augmentation and short circuit current limitation of WFs. Also, it was found that the CBFCL is more competent to satisfy the LVRT requirements than the IBFCL.

A New ZVS Full-Bridge DC–DC Converter for Battery Charging With Reduced Losses Over Full-Load Range

Abstract: A new zero-voltage switching full-bridge dc–dc converter for battery charging is proposed in this paper. The proposed isolated dc–dc converter is used for the dc–dc conversion stage of the electric vehicle charger. The primary switches in dc–dc converter turn- on at zero voltage over the battery-charging range with the help of passive auxiliary circuit. The diode clamping circuit on the primary side minimizes the severity of voltage spikes across the secondary rectifier diodes, which are commonly present in conventional full-bridge dc–dc converters. The main switches are controlled with an asymmetrical pulse-width modulation (APWM) technique resulting in higher efficiency. APWM reduces the current stress of the main switches and the circulating losses compared with the conventional phase-shift modulation method by controlling the auxiliary inductor current over the entire operating range of the proposed converter. The steady-state analysis of auxiliary circuit and its design considerations are discussed in detail. A 100-kHz 1.2-kW full-bridge dc–dc converter prototype is developed. The experimental results are presented to validate the analysis and efficiency of the proposed converter.

Analytical Design of Passive LCL Filter for Three-Phase Two-Level Power Factor Correction Rectifiers

Abstract: This paper proposes a comprehensive analytical LCL filter design method for three-phase two-level power factor correction rectifiers (PFCs) The high-frequency converter current ripple generates the high-frequency current harmonics that need to be attenuated with respect to the grid standards Studying the high-frequency current of each element proposes a noniterative solution for designing an LCL filter In this paper, the converter current ripple is thoroughly analyzed to generalize the current ripple behavior and find the maximum current ripple for sinusoidal pulse width modulation (PWM) and third-harmonic injection PWM Consequently, the current ripple is used to accurately determine the required filter capacitance based on the maximum charge of the filter capacitor To choose the grid-side inductance, two methods are investigated First method uses the structure of the damping to express the grid-side filter inductance as a function of the converter current ripple Reducing the power loss in the filter and optimizing the grid-side filter inductance is the main focus of the second method which is achieved by employing line impedance stabilization network (LISN) Accordingly, two LCL filters are designed for a 5 kW silicon-carbide-based three-phase PFC Various experimental scenarios are performed to verify the filters attenuation and performance

Multimode Operation of Resonant and Hybrid Switched-Capacitor Topologies

Abstract: This paper presents an overview of resonant and hybrid switched-capacitor converters with a particular focus on multimode operation. The multimode approach is discussed as a tool to affect high efficiency and power density across a wide load range, provide variable regulation, and, as a general framework, to conceptualize the advantages and opportunities of the approach compared to more traditional dc–dc converters. A general analysis is provided to quantify the advantage of hybrid and resonant converters that factors in the tradeoffs between size and loss in the magnetic component and voltage stress on the active devices. A broader set of operating modes is presented that spans continuous and discontinuous conduction and includes resonant, quasi-resonant, and more traditional buck- or boost-like operation. A prototype flying-capacitor multilevel converter is presented to demonstrate the variety of operating modes and motivate important considerations such as voltage balance on the flying capacitors.

A Family of Resonant Two-Switch Boosting Switched-Capacitor Converter With ZVS Operation and a Wide Line Regulation Range

Abstract: In this paper, a family of resonant two-switch boosting switched-capacitor converters (RTBSCs) with ZVS operation and a wide line regulation range is proposed. Based on our previously proposed two-switch boosting switched-capacitor converters (TBSCs), only a small resonant inductor is added, while two bulky capacitor banks are replaced by two much smaller resonant capacitors. Furthermore, by operating RTBSC above the resonant frequency, the transistors are ZVS turned on and diodes are Zero-current-switching (ZCS) turned on / off . This eliminates the hard-switched phenomenon of TBSC, leading to reduced component size by increasing the operating frequency without sacrificing the overall efficiency. In addition, the voltage-gain range of the RTBSCs is largely expanded and hence the input-voltage range is increased remarkably for regulated output voltage applications. Meantime, the voltage stress on transistors and diodes remains low, equal to the input voltage. A 3X RTBSC prototype with maximum output voltage 150 V, maximum output power 140 W, and a peak efficiency of 98.3% was built. The analysis is verified by simulation and experimental results.