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This paper presents the design, modeling, and control of an isolated dc-dc three-port converter (TPC) based on an interleaved-boost full-bridge converter with pulsewidth modulation (PWM) and phase-shift control for hybrid renewable energy systems. In the proposed topology, the switches are driven by phase-shifted PWM signals, where both phase angle and duty cycle are the controlled variables. The power flow between the two inputs is controlled through the duty cycle, whereas the output voltage can be regulated effectively through the phase shift. The primary-side MOSFETs can achieve zero-voltage-switching (ZVS) operation without additional circuitry. Additionally, due to the ac output inductor, the secondary-side diodes can operate under zero-current-switching (ZCS) conditions. In this study, the operation principles of the converter are analyzed and the critical design considerations are discussed. The dynamic behavior of the proposed ac-inductor-based TPC is investigated by performing state-space modeling. Moreover, the derived mathematical models are validated by simulation and measurements. In order to verify the validity of the theoretical analysis, design, and power decoupling control scheme, a prototype is constructed and tested under the various modes, depending on the availability of the renewable energy source and the load consumption. The experimental results show that the two decoupled control variables achieve effective regulation of the power flow among the three ports. [ABSTRACT FROM PUBLISHER]

Modular multilevel converter (MMC) is very popular in medium-voltage applications, such as high-voltage direct current transmission, static Var generator, and motor drives. The arm capacitor voltage of MMC is usually constant and the output voltage is adjusted by regulating the pulse width modulation (PWM) index for switches in previous studies. In this paper, a novel flexible capacitor voltage control strategy for MMC as motor drives was proposed, with which the arm capacitor voltage was controlled flexibly according to the motor speed, by regulating the dc component and ac component of the PWM reference signal, and unsymmetrical control was used for the control of the upper arm and the lower arm in MMC. With the proposed control strategy, the circuit efficiency and the precision of the output voltage of the converter could be improved when the motor speed was low, and di/dt and d v/dt of the motor windings could be decreased. These proposals were implemented on a laboratory prototype, and experiments were carried out. The validity of the control strategy under both steady and dynamic states was verified. [ABSTRACT FROM AUTHOR]

This paper proposes a dual-bridge (DB) LLC resonant converter for wide input applications. The topology is an integration of a half-bridge (HB) LLC circuit and a full-bridge (FB) LLC circuit. The fixed-frequency pulsewidth-modulated (PWM) control is employed and a range of twice the minimum input voltage can be covered. Compared with the traditional pulse frequency modulation (PFM) controlled HB/FB LLC resonant converter, the voltage gain range is independent of the quality factor, and the magnetizing inductor has little influence on the voltage gain, which can simplify the parameter selection process and benefit the design of magnetic components as well. Over the full load range, zero-voltage switching (ZVS) and zero-current switching (ZCS) can be achieved for primary switches and secondary rectifier diodes, respectively. Detailed analysis on the modulation schedule and operating principle of the proposed converter is presented along with the converter performance. Finally, all theoretical analysis and characteristics are verified by experimental results from a 120-V to 240-V input 24 V/20 A output converter prototype. [ABSTRACT FROM AUTHOR]

This paper proposes a high-performance transformerless single-stage high step-up ac–dc matrix converter based on Cockcroft–Walton (CW) voltage multiplier. Deploying a four-bidirectional-switch matrix converter between the ac source and CW circuit, the proposed converter provides high quality of line conditions, adjustable output voltage, and low output ripple. The matrix converter is operated with two independent frequencies. One of which is associated with power factor correction (PFC) control, and the other is used to set the output frequency of the matrix converter. Moreover, the relationship among the latter frequency, line frequency, and output ripple will be discussed. This paper adopts one-cycle control method to achieve PFC, and a commercial control IC associating with a preprogrammed complex programmable logic device is built as the system controller. The operation principle, control strategy, and design considerations of the proposed converter are all detailed in this paper. A 1.2-kV/500-W laboratory prototype of the proposed converter is built for test, measurement, and evaluation. At full-load condition, the measured power factor, the system efficiency, and the output ripple factor are 99.9%, 90.3%, and 0.3%, respectively. The experimental results demonstrate the high performance of the proposed converter and the validity for high step-up ac–dc applications. [ABSTRACT FROM PUBLISHER]

In this paper, a built-in voltage gain extension cell is proposed to give a universal topology derivation on next-generation high step-up converters for large voltage gain conversion systems. Several improved single-switch high step-up converters with built-in transformer voltage multiplier cell are derived with some advantageous performance, which includes extremely large voltage conversion ratio, minimized power device voltage stress, effective diode reverse-recovery alleviation, and soft-switching operation. The turns ratio of the built-in transformer can be employed as another design freedom to extend the voltage gain, which shows great design flexibility. Compared with their active clamp counterpart, only one MOSFET is required to simplify the circuit configuration and improve the system reliability. The over resonance frequency and the below resonance frequency operation modes are studied to explore the circuit performance, and the key parameter design criterion is provided to show a valuable guidance for future industrial applications. Finally, the experimental results from a 500 W 36-380 V prototype are provided to validate the effectiveness of the main contributions in this paper. [ABSTRACT FROM AUTHOR]

In this paper, a family of bidirectional dual-input dc/dc converters is proposed to combine a photovoltaic system and battery energy storage system. This family of converters utilizes a full-bridge, or half-bridge current-source circuit, as the primary side, and a quasi-switched-capacitor circuit as the secondary side. Depending on the power level of the primary side and voltage level of the battery, different topologies can be selected. Compared to other bidirectional multiple-input dc/dc converters with galvanic isolation, this family of converters requires less switches and passive components, reduces voltage stress on switches, and realizes soft switching for all switches. The operation principle of the converter is presented, and a power sharing strategy between two input sources is proposed. A 2-kW full-bridge circuit prototype is built in the lab, based on Gallium Nitride (GaN) switching devices. Simulation and experimental results are also presented to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper proposes a combined inductive and capacitive wireless power transfer (WPT) system with LC -compensated topology for electric vehicle charging application. The circuit topology is a combination of the LCC-compensated inductive power transfer (IPT) system and the LCLC-compensated capacitive power transfer (CPT) system. The working principle of the combined circuit topology is analyzed in detail, providing the relationship between the circuit parameters and the system power. The design of the inductive and capacitive coupling is implemented by the finite-element analysis. The equivalent circuit model of the coupling plates is derived. A 3.0-kW WPT system is designed and implemented as an example of combined inductive and capacitive coupling. The inductive coupler size is 300 mm × 300 mm and the capacitive coupler is 610 mm × 610 mm. The air-gap distance is 150 mm for both couplers. The output power of the combined system is the sum of the IPT and CPT system. The prototype has achieved 2.84-kW output power with 94.5% efficiency at 1-MHz switching frequency, and performs better under misalignment than the IPT System. This demonstrates that the inductive–capacitive combined WPT system is a potential solution to the electric vehicle charging application. [ABSTRACT FROM AUTHOR]

Electronic ballasts are implemented for obtaining a high power factor and a good operation of the lamp; these goals are reached traditionally by implementing multiple stages. On the first stage, a unity power factor is obtained and the second stage is designed in order to feed properly the lamp. Different topologies have been studied not only for decreasing the number of employed controllers and stages, but also reducing the number of components and active switches. Electronic ballasts, which are based on the “Z” and “qZ” source inverters, are considered in this paper, where the proposed systems have a single stage. Two topologies are illustrated: the first one for the fluorescent lamps and the second one for the high intensity discharge lamps, where electronic ballasts with a high power factor are obtained. The operation, analysis, and experimental results are shown. [ABSTRACT FROM PUBLISHER]

This paper presents a distributed control strategy for state-of-charge balancing between the battery modules of a reconfigurable battery energy storage system. The autonomous modules share state-of-charge information with their neighbors over a sparse communication network and cooperate to reach a balanced state of charge. The proposed control strategy provides advantages in terms of reduced communication requirements and increased modularity, over a centralized battery management system. Steady-state analysis provides bounds on the mean error and mean-squared error of the distributed average state-of-charge estimates used for autonomous balancing control. The proposed control strategy enforces module topology constraints specific to the particular reconfigurable battery implementation. The state-of-charge balancing mode current controller prevents current spikes during module topology transitions. Experimental results demonstrate the performance of the proposed control strategy for a reconfigurable energy storage system made up of four 6-V, 7-Ah lead-acid battery modules. [ABSTRACT FROM PUBLISHER]

Conventional matrix converters (MCs) have limited voltage gain that is less than 0.866, whether for direct MC (DMC) or indirect MC (IMC). The Z-source MCs (ZSMCs) overcome the voltage gain limitation of the traditional MC and achieve buck and boost operation with reduced switches count, thereby achieving low cost, high efficiency, and reliability, compared to the back-to-back converter. Furthermore, it will leads to more MC industrial applications. This paper presents an up-to-date comprehensive overview of the different ZSMC topologies and their configurations, circuit analyses, modulation schemes, and applications. This study offers a comprehensive and systematic reference for the future development of the ZSMCs. [ABSTRACT FROM PUBLISHER]

In this paper, a novel high step-up dc–dc converter with a multicoupled inductor (MCI) and voltage multiplier is proposed for a sustainable energy system. The combinatorial employment of these components significantly extends the voltage boostability and reduces the voltage stress of the main switches. The special structure of branch cross coupling makes the two branches of current autobalance. Meanwhile, the utilization of MCIs makes the most of the magnetic core to further improve the power density. The diode reverse-recovery problem is alleviated because its current falling rate is controlled by the leakage inductance of the MCI. Moreover, the voltage spike of the main switches at their turn-off is clamped by a clamp capacitor. The interleaved operation results in the cancelation of the input current and output voltage. Next, the operating principle and performance of the converter are discussed in detail. Finally, a prototype circuit with 1-kW output power is implemented to verify the performance of the proposed converter. [ABSTRACT FROM AUTHOR]

By inserting a small inductor between the transformer center tap and the midpoint of two split output capacitors in the dual active bridge (DAB) topology, this paper proposes a modified DAB converter for wide-input applications. A hybrid phase-shift (HPS) control scheme is proposed to allow all power switches to achieve practical ZVS over the full operating range; thereby, significantly minimizing the switching losses and alleviating electromagnetic interference. Moreover, the proposed control scheme does not significantly increase the conduction losses in comparison with the extended phase-shift (EPS) control. Therefore, the modified DAB can operate efficiently. The topology derivation and description are first presented. Then, the EPS and triple phase-shift (TPS) modulations are applied, and the corresponding operating principles and characteristics, including the soft-switching, power transfer, and root-mean-square current, are investigated in detail. To achieve practical ZVS operation of all switches over full operating range, while minimizing the conduction losses, the EPS and TPS are combined, and an HPS control scheme is proposed. Finally, experimental results from a 1.4-kW converter prototype with 200–400-V input and 400-V output are presented to verify the feasibility and advantages of the converter and control. [ABSTRACT FROM AUTHOR]

This paper presents an analytical and experimental comparison of a two-phase buck converter and a two-phase, series capacitor buck converter. The limitations of a conventional buck converter in high-current (10 A or more), and high-frequency (HF, 3–30 MHz) point-of-load voltage regulators with large voltage conversion ratios (10-to-1) are highlighted. The series capacitor buck converter exhibits desirable characteristics at HF, including lower switching loss, less inductor current ripple, automatic phase current balancing, duty ratio extension, and soft charging of the energy transfer capacitor. Analysis of the topologies indicates that switching loss and inductor core loss can dominate at HF. Results from side-by-side 12 V input, 1.2 V output hardware prototypes demonstrate that the series capacitor buck converter has up to 12 percentage points higher efficiency at 3 MHz and reduces power loss by up to 33% at full load (10 A). Some guidelines for inductor selection are provided, and a switch stress comparison reveals that the maximum converter switch stress is reduced by 30%. [ABSTRACT FROM AUTHOR]

The extended commutation cell is a four-port four-switch cell that allows for bidirectional energy transport in two orthogonal directions throughout the cell. By cascading multiple cells, a multilevel converter can be constructed with a high number of levels. The voltage across each cell capacitor can be adjusted independently of the load, resulting in high flexibility in output levels. This paper presents an improved method for capacitor voltage control, based on a system model and the measured output current. The proposed method is analyzed and verified on a 4.4\text-\mathrmk\mathrmW eight-level dc–ac converter. The obtained reduction in capacitor voltage ripple is more than $75\%$. [ABSTRACT FROM AUTHOR]

This paper proposes a linear state-space model for a phase-controlled resonant dual active bridge with a tuned capacitor–inductor–inductor–capacitor network. The proposed model is useful for fast simulation and for the estimation of state variables under large signal variation. The model is also useful for control design because the slow changing dynamics of the dq variables are relatively easy to control. Using the proposed model, a decoupled control scheme was designed which allows for the control of the high frequency link currents while also improving the soft switching range of the converter. Using steady-state relationships between state variables and the system inputs, the controller was simplified from three proportional integral (PI) controllers to a single PI controller. The controller was implemented on a low cost digital signal processor and verified experimentally. The experimental and simulation results showed the proposed model's usefulness for control design and fast simulation. [ABSTRACT FROM AUTHOR]

Hardware-in-the-Loop tests of components for high-voltage dc transmission grids, for example circuit breakers, require converter systems capable of generating a high output current with fast transients of the output signal at different output voltages. In this paper, a three-level buck converter (N3L) employing three different supply voltages to enable a wide voltage operation range is presented. The modulation of the converter is investigated in detail with special focus on ripple cancellation, the startup of the interleaved converter and the level shifting between different converter output voltages. A prototype system is designed and constructed, optimized for pulsed power operation and compared to a two level and to a neutral point clamped converter design. The system has been simulated numerically and the design boundaries are validated by measurements on the prototype system. [ABSTRACT FROM AUTHOR]

A single-stage, bidirectional, current-source converter (CSC) topology to interface a dc microgrid with an ac grid is reported in the literature. In this topology, under a balanced grid voltage condition, the dc-link inductor current can be regulated over a wide range—from zero to rated value—while the ac-side current has low harmonic distortion. However, unbalanced grid voltages result in second-harmonic pulsation in the current and power on the dc side of the converter. In addition, the ac-side currents will be unbalanced due to the presence of a negative-sequence component. This would result in undesired tripping of the converter if one of the phase currents exceeded its rated value. Various control loop structures for the operation of voltage-source converter under unbalanced grid voltage conditions are reported in the literature. However, use of similar control loop structures for CSC may lead to unstable operation. Therefore, a control scheme to inject balanced three-phase currents into the ac grid under an unbalanced grid voltage condition is proposed in this paper. The stability of the proposed control scheme is studied using a small-signal model of the converter. Performance of the proposed control scheme is studied using MATLAB/Simulink and is experimentally validated. [ABSTRACT FROM AUTHOR]

Various ac/dc LED driver topologies have been proposed to meet the challenges of achieving a compact, efficient, low-cost, and robust multistring LED lighting system. These LED drivers typically employ a two-stage topology to realize the functions of ac/dc rectification and independent current control of each LED string. The choice of having two stage conversions involves additional hardware components and a more complicated controller design process. Such two-stage topologies suffer from a higher system cost, increased power loss, and large form factor. In this paper, a single-stage ac/dc single-inductor multiple-output LED driver is proposed. It uses only one single inductor and N + 1 active power switches (N being the number of LED strings) with reduced component count and smaller form factor. The proposed driver can achieve both functions of ac/dc rectification with a high power factor and precise independent current control of each individual LED string simultaneously. A prototype of an ac/dc single-inductor triple-output LED driver is constructed for verification. Experimental results corroborate that precise and independent current regulation of each individual LED string is achievable with the proposed driver. A power factor of above 0.99 and a peak efficiency of 89% at 30-W rated output power are attainable. [ABSTRACT FROM AUTHOR]

High-performance buck converters are often required in modern power electronic applications. An augmented buck converter (a main buck converter with augmentation circuits) can achieve fast transient recovery and small output voltage deviation. Compared with other augmentation circuits, a resonant augmentation circuit offers potential electromagnetic interference reduction due to the relatively low $di/dt$ value and compacts the circuit through a reduced inductance for resonance. In this paper, the performance analysis of an augmented buck converter constructed with the resonant circuit are described in detail in terms of voltage-deviation band and power loss. A circuit design and control principle is also proposed for achieving the required voltage deviation for a given transient-detection delay. A 12-to-5-V converter prototype is built to verify the analysis and effectiveness of the proposed methodology. It is demonstrated that the voltage deviation is reduced from 360 to 200 mV using the proposed resonant augmentation circuits and control scheme. The efficiency study shows that the power loss varies from 0.02 to 0.72 W, when the repetition frequency of 5-to-10-A transients changes from 100 to 5 kHz. [ABSTRACT FROM AUTHOR]

The two-switch cascade converter is the most appropriate solution for efficient high-power applications among the existing converter topologies. However, the cascade structure and the nonlinear dc gain of boost circuit are more likely to cause severe oscillations if the criterion for the selection of the operation mode is chosen improperly during step-up/step-down transition. A novel high-power input-parallel output-series buck-half-bridge (IPOSBHB) converter is proposed in this paper. The circuit structure, operating principles, and basic relations are analyzed. Comparisons between IPOSBHB and two-switch cascade converter are also elaborated on with respect to voltage and current stress, total volume of magnetic components, and efficiency. In addition, the inconformity of the transfer functions, the discontinuity caused by the switching time delay, and the disturbance of input voltage are analyzed. Methods for compensation are also proposed. The proposed converter can achieve satisfactory comprehensive performance when the step-up ratio is low. The combinational control strategy and the compensation methods proposed in this paper are easy to carry out in order to achieve effective control at steady state, smooth transition at mode change, and reduction of the adverse effect caused by the disturbance of input voltage. A 15-kW prototype is used to validate the proposed theory. [ABSTRACT FROM AUTHOR]

This paper presents a novel ZVZCS full-bridge DC/DC converter, which is able to process and deliver power efficiently over very wide load variations. The proposed DC/DC converter is part of a plug-in AC/DC converter used to charge the traction battery (high voltage battery) in an electric vehicle. The key challenge in this application is operation of the full-bridge converter from absolutely no-load to full-load conditions. In order to confirm reliable operation of the full-bridge converter under such wide load variations, the converter should not only operate with soft-switching from full load to no-load condition with satisfactory efficiency for the full range of operation, but also the voltage across the output diode bridge needs to be clamped to avoid any adverse voltage overshoots arising during turn-OFF of the output diodes as commonly found in regular full bridge converters. In order to achieve such stringent requirements and high reliability, the converter employs a symmetric passive near lossless auxiliary circuit to provide the reactive current for the full-bridge semiconductor switches, which guarantees zero voltage switching at turn-ON times for all load conditions. Moreover the proposed topology is based on a current driven rectifier in order to clamp the voltage of the output diode bridge and also satisfy ZVZCS operation of the converter resulting in superior efficiency for all load conditions. In this paper operation of the converter is presented in detail followed by analytical design procedure. Experimental results provided from a 3KW prototype validate the feasibility and superior performance of the proposed converter. [ABSTRACT FROM AUTHOR]

This paper deepens in the study of the recently described coupled-inductor buck-boost converter. The output voltage of this dc-dc converter can be regulated above and/or below its input voltage with high efficiency and wide bandwidth. The control of the input and/or output nonpulsating converter currents is addressed in this paper. The small-signal control-to-input/output-current transfer functions in open-loop permits the design of the respective average current-mode controllers. The combination of the input- and output-current controllers with an additional output voltage limiter loop is proposed as a method to regulate one of the currents while limiting the maximum values of the other two variables. The theoretical analyses have been validated by means of simulations and also experimentally on a 48-V 800-W purpose built-prototype. In particular, the frequency response measurements that have been carried out for a representative set of the converter operating points are in good agreement with the simulations. [ABSTRACT FROM AUTHOR]

In this paper, a three-phase current-fed dual-active-bridge (DAB) bidirectional DC-DC converter is presented. Compared to the voltage source DAB converter, the proposed converter allows low RMS current and maintains zero voltage switching (ZVS) in the whole operating range by keeping the ratio between primary side and secondary side DC-link voltage constant, leading to high efficient energy conversion over a wide input voltage range. In addition, the ZVS conditions can be maintained using small DC inductors and the input current ripple still remains small because of high DC inductor current ripples being alleviated by three-phase interleaving structure. Furthermore, the proposed topology with Y-Y connected transformers is proven to have better current sharing capability compared with other three-phase topologies with different transformer connections. The operation mode analysis, soft switching conditions, and hardware design guidelines are derived in this paper. A 6-kW hardware prototype with input voltage range of 24~48 V and rated 288 V output voltage is developed and tested in the laboratory. The experimental results verified that the proposed converter could maintain high efficiency over a wide input voltage and power range. [ABSTRACT FROM AUTHOR]

This paper deals with a new family of high boost voltage inverters called switched-inductor quasi-Z-source inverters (SL-qZSIs). The proposed SL-qZSI is based on the well-known qZSI topology and adds only one inductor and three diodes. In comparison to the SL-ZSI, for the same input and output voltages, the proposed SL-qZSI provides continuous input current, a common ground with the dc source, reduced the passive component count, reduced voltage stress on capacitors, lower shoot-through current, and lower current stress on inductors and diodes. In addition, the proposed SL-qZSI can suppress inrush current at startup, which might destroy the devices. This paper presents the operating principles, analysis, and simulation results, and compares them with those of the SL-ZSI. To verify the performance of the proposed converter, a laboratory prototype was constructed with 48 Vdc input and an ac output line-to-line voltage of 120 Vrms. The simulation and experimental results verified that the converter has high step-up inversion ability. [ABSTRACT FROM AUTHOR]

In many modern energy conversion systems, a dc voltage, which is provided from a sustainable energy source or energy storage device, must be boosted and converted to an ac voltage with a fixed amplitude and frequency. In this paper, a switching pattern based on the concept of the conventional space-vector pulsewidth-modulated (SVPWM) technique is developed for single-stage, three-phase boost-inverters using the topology of current-source inverters. The six main switching states, and two zeros, with three switches conducting at any given instant in conventional SVPWM techniques are modified herein into three-charging states and six discharging states with only two switches conducting at any given instant. The charging states are necessary in order to boost the dc input voltage. The developed switching pattern was experimentally verified through a laboratory-scaled three-phase 500-W boost inverter and the results are presented in this paper. [ABSTRACT FROM AUTHOR]

This paper proposes a novel dc–dc converter topology to achieve an ultrahigh step-up ratio while maintaining a high conversion efficiency. It adopts a three degree of freedom approach in the circuit design. It also demonstrates the flexibility of the proposed converter to combine with the features of modularity, electrical isolation, soft-switching, low voltage stress on switching devices, and is thus considered to be an improved topology over traditional dc–dc converters. New control strategies including the two-section output voltage control and cell idle control are also developed to improve the converter performance. With the cell idle control, the secondary winding inductance of the idle module is bypassed to decrease its power loss. A 400-W dc–dc converter is prototyped and tested to verify the proposed techniques, in addition to a simulation study. The step-up conversion ratio can reach 1:14 with a peak efficiency of 94% and the proposed techniques can be applied to a wide range of high voltage and high power distributed generation and dc power transmission. [ABSTRACT FROM AUTHOR]

A simple and cost-effective precharge method for modular multilevel converter (MMC) by using a low-voltage direct current (dc) source is proposed in this paper. The submodule (SM) capacitors in MMC are required to be precharged to their nominal voltage values at start-up to ensure MMC work normally. Conventional methods perform the precharging either through grid side or dc side by using costly high-voltage bypass breakers, charging resistors or a high-voltage dc source. Voltage of the high-voltage dc source must be equal to SM capacitor voltage and could be as high as thousands of volts. By contrast, the proposed method employs a very low voltage dc source on dc bus through a series-connected blocking diode, and requires no charging resistor and bypass breakers. It takes advantages of the existing power devices, arm inductors, and SM capacitors in MMC, and configures them into boost circuit for the precharging. The proposed method is simple and cost-effective. Moreover, the characteristics of the boost circuit render the proposed method flexible. For instance, the voltage selection of the dc source is flexible and not restricted to a fixed value. The SM capacitors can be charged in different groups. In addition, the method is applicable to different MMC SMs, including SM with different capacitor voltages. The effectiveness of the proposed method is verified through simulation and experiment. [ABSTRACT FROM AUTHOR]

One important test for the formation and grading of a lithium-ion battery is to confirm the performance of the battery while discharging it down to zero volts. In this paper, a novel soft-switching charge/discharge converter with the zero voltage discharge function is proposed. The proposed converter is able to discharge a battery until its voltage reaches zero volts. The phase-shift full-bridge method is used to charge the battery and the current-fed push–pull method with bidirectional switches is used for the discharge. Zero voltage switching (ZVS) of the switches is achieved at turn-on during the charge operation. ZVS turn-on and zero current switching turn-off of the switches are achieved during the discharge operation. The charge/discharge controllers are designed taking into account the internal impedance of the battery. The performance of the system is verified by the experiments using lithium-ion batteries. [ABSTRACT FROM AUTHOR]

A systematic method for deriving soft-switching three-port converters (TPCs), which can interface multiple energy, is proposed in this paper. Novel full-bridge (FB) TPCs featuring single-stage power conversion, reduced conduction loss, and low-voltage stress are derived. Two nonisolated bidirectional power ports and one isolated unidirectional load port are provided by integrating an interleaved bidirectional Buck/Boost converter and a bridgeless Boost rectifier via a high-frequency transformer. The switching bridges on the primary side are shared; hence, the number of active switches is reduced. Primary-side pulse width modulation and secondary-side phase shift control strategy are employed to provide two control freedoms. Voltage and power regulations over two of the three power ports are achieved. Furthermore, the current/voltage ripples on the primary-side power ports are reduced due to the interleaving operation. Zero-voltage switching and zero-current switching are realized for the active switches and diodes, respectively. A typical FB-TPC with voltage-doubler rectifier developed by the proposed method is analyzed in detail. Operation principles, control strategy, and characteristics of the FB-TPC are presented. Experiments have been carried out to demonstrate the feasibility and effectiveness of the proposed topology derivation method. [ABSTRACT FROM AUTHOR]

Existing methods of incorporating an active filter into an AC/DC converter for eliminating electrolytic capacitors usually require extra power switches. This inevitably leads to an increased system cost and degraded energy efficiency. In this paper, a concept of active-filter integration for single-phase AC/DC converters is reported. The resultant converters can provide simultaneous functions of power factor correction, DC voltage regulation, and active power decoupling for mitigating the low-frequency DC voltage ripple, without an electrolytic capacitor and extra power switch. To complement the operation, two closed-loop voltage-ripple-based reference generation methods are developed for controlling the energy storage components to achieve active power decoupling. Both simulation and experiment have confirmed the eligibility of the proposed concept and control methods in a 210-W rectification system comprising an H-bridge converter with a half-bridge active filter. Interestingly, the end converters (Type I and Type II) can be readily available using a conventional H-bridge converter with minor hardware modification. A stable DC output with merely 1.1% ripple is realized with two 50-μF film capacitors. For the same ripple performance, a 900-μF capacitor is required in conventional converters without an active filter. Moreover, it is found out that the active-filter integration concept might even improve the efficiency performance of the end converters as compared with the original AC/DC converter without integration. [ABSTRACT FROM AUTHOR]

Magnetic resonance coupling working at megahertz (MHz) is widely considered as a promising technology for the mid-range transfer of a medium amount of power. It is known that the soft-switching-based Class E rectifiers are suitable for high-frequency rectification, and thus potentially improve the overall efficiency of MHz wireless power transfer (WPT) systems. This paper reports new results on optimized parameter design of a MHz WPT system based on the analytical derivation of a Class E current-driven rectifier. The input impedance of the Class E rectifier is accurately derived, for the first time, considering the on-resistance of the diode and the equivalent series resistance of the filter inductor. This derived input impedance is then used to develop and guide design procedures that determine the optimal parameters of the rectifier, coupling coils, and a Class E PA in an example 6.78-MHz WPT system. Furthermore, the efficiencies of these three components and the overall WPT system are also analytically derived for design and evaluation purposes. In the final experiments, the analytical results are found to well match the experimental results. With loosely coupled coils (mutual inductance coefficient $k$ =0.1327), the experimental 6.78-MHz WPT system can achieve 84% efficiency at a power level of 20 Watts. [ABSTRACT FROM AUTHOR]

This paper presents the analysis and design of a 30 MHz resonant SEPIC converter. With the conventional design method, tuning the amplitude and phase of the fundamental input voltage and current of the rectifier stage affect each other so that the design procedure is coupled seriously. Based on the circuit duality theory, an improved design method is proposed by redividing the resonant SEPIC topology to realize the independent tuning of the amplitude and phase. The implementation and loss analysis of the SEPIC with the new design are provided in details. Moreover, a novel structure of the PCB embedded inductors is introduced and the comparison among the discrete inductor, the planar spiral inductor and the four-layered solenoid PCB inductor is given in terms of the loss. A 15 V input, 25 W/28 V output/30 MHz SEPIC converter was built to verify the proposed design method and the benefit of the new structure of the PCB embedded inductors. The power density of the power stage is realized over 200 W/in3 and the efficiency is 82.5% at the rated output. The temperature of the proposed PCB embedded inductor is reduced from 102.6 °C (the discrete inductor) to 64.8 °C (a reduction of 37%) and the efficiency is improved 2% over the discrete solution at the full load. [ABSTRACT FROM AUTHOR]

This paper proposes a new type of ac–ac converter which can operate as traditional noninverting buck and boost converters, and inverting buck–boost converter as well. The proposed converter uses six unidirectional current flowing and bidirectional voltage blocking switches, implemented by six reverse blocking insulated-gate bipolar transistors (IGBTs) or series mosfet–diode pairs, two input and output filter capacitors, and one inductor. It has no shoot-through problem of voltage source (or capacitor) even when all switches are turned-on, and therefore, pulsewidth modulation dead-times are not needed resulting in high-quality waveforms, and solves the commutation problem without using bulky and lossy RC snubbers or dedicated soft-commutation strategies. It has smaller switching losses because only two switches out of six are switched at high frequency during each half-cycle of input voltage, and it can use power MOSFETs as body diode never conducts, making it immune from mosfet failure risk which otherwise may occur due to poor reverse recovery problem of body diode. The noninverting buck–boost mode of the proposed converter can be used in applications with both step-up and step-down demand, while the inverting buck–boost mode can also be used in its application as dynamic voltage restorer. Detailed analysis of the proposed converter is given, and experimental results are also provided. [ABSTRACT FROM AUTHOR]

Constant current sources are required to drive multiple color LED strings and the LED drivers that drive these LED lighting systems should provide multiple constant currents from a single dc source. In this paper, a single inductor multiple current output (SIMCO) converter that can provide N- independently controllable constant current outputs is reported. The average current in each color LED string is controlled independently by using hybrid average current mode control (HACMC). The HACMC combines the advantage of both average current mode control and charge control method. Traditional dimming approaches such as pulse width modulation and analog dimming can be incorporated in the proposed topology for color tunability and correlated color temperature control. The proposed approach uses a simple control logic, which is modular and can be scalable to N color LED lighting systems. The operation of the SIMCO converter with the HACMC is explained in detail. Simulation and experimental results with 48 V input and 12 W for $N = 3$ (RGB) color systems are presented. [ABSTRACT FROM AUTHOR]

This paper introduces a multiple-input multiple-output modular multilevel dc–dc converter (MIMO-MMC) and its associated control scheme. The proposed topology has a bidirectional structure and may be utilized in both low- and high-power applications ranging from approximately 100 W–10 MW. The modular structure of the MIMO-MMC enables efficient component utilization through module voltage and current sharing capabilities. The topology can supply or extract regulated power from an arbitrary number of controllable voltage nodes without requiring source or load multiplexing, resulting in minimized filtering requirements. The MIMO-MMC's structure is described, and the steady-state operation of the converter is theoretically analyzed. The dynamic models of the converter for both step-down and step-up configuration are derived and employed to devise an effective control algorithm for closed-loop operation. A general method is provided for stability analysis of the proposed closed-loop system followed by a case study verifying stability of the system at different operating points. The steady-state operation and dynamic response of the converter under both configurations is investigated through simulation and experiment. [ABSTRACT FROM PUBLISHER]

In series-connected battery systems, typically, separate converters for intramodule balancing bidirectional connection to a load and charging from an external power source are employed. In this paper, an integrated reconfigurable converter for high-voltage series-connected battery storage systems is proposed. The main advantage of the proposed converter is that it can be reconfigured to operate in different operating modes: feeding the load from the battery system, feeding the load from a backup power source, regenerative mode, intramodule balancing mode, and charging mode. Unlike conventional systems, the proposed topology shares the semiconductor devices and an inductor among the different operating modes which makes it compact. The proposed converter exhibits redundant modes which together with a backup mode increase its reliability. Additionally, the proposed topology minimizes stress on the batteries during the charging/discharging cycles. A scaled down experimental prototype of the proposed converter is implemented for a five-module battery system to verify its viability and demonstrate all operating modes. [ABSTRACT FROM PUBLISHER]

Although a large number of typical resonant converter topologies have been developed for use in contactless power transfer applications, these topologies need to be precisely optimized to obtain maximum efficiency and maximum power transferring capacity. High-order resonant power converters with flexible designs are invariably required to develop energy-efficient and cost-effective converter systems. An ideal converter topology can contribute toward realizing efficient converter systems if it is capable of providing an optimized output that is insensitive to load variations, coupling coefficient, type of the wireless transformer used, and other operating conditions. This paper presents a new contactless power converter topology for a low-coupling (0.14) ferrite-core transformer that has low cost, small size, high efficiency, and a wide gap (20 mm). In addition, the merits and demerits of conventional converter topologies are studied herein, and results for these topologies are compared with those for the proposed converter topology. [ABSTRACT FROM PUBLISHER]

This paper presents a novel integrated magnetic three-port converter (IMTPC) with high power density and all three ports’ current ripple cancellation. The proposed IMTPC can interface one PV port, one bidirectional battery port, and one load port of the PV-battery dc power system. Only two high power magnetic devices are needed in an IMTPC for realizing power conversion, ripple cancellation, and switch driver simultaneously. Three extra capacitors were added to achieve three ports’ current ripple cancellation. Therefore, the port of the IMTPC will always in continuous-conduction mode with “zero current ripple,” thus, size of passive filter can be reduced and accuracy of maximum power point tracking can be improved. Meanwhile, simple driving of the high-side switch can be realized by integrated magnetic winding, which is responsible for MOSFET driver's voltage level shift. The using of the integrated magnetic technique not only performs aforementioned advantages but also shows great potential for reducing the weight and volume of the dc–dc converter. Finally, experimental verifications are given to illustrate the feasibility and effectiveness of the proposed topology and control method. [ABSTRACT FROM PUBLISHER]

Recently, novel direct pulse width modulated (PWM) ac–ac converters using coupled inductors with switching cell structure have been introduced as an alternative to the conventional ac–ac converter topology. The converters can effectively solve the commutation problem associated with the conventional direct PWM ac–ac converters. However, the two coupled inductors used in the topology make the converters less attractive for use in practical applications. This paper proposes magnetic integration of the discrete-coupled inductors in single-phase ac–ac converters. The dc offset fluxes generated by the common-mode currents are cancelled out perfectly when the windings on the common core are appropriately arranged, resulting in ac flux only. The proposed inductor shows significant improvements over discrete-coupled inductors, in that the proposed inductor does not have an air gap, it exhibits symmetrical winding currents, and it has smaller volume with large current handling capability. The proposed inductor can handle an unlimited amount of current due to the absence of core saturation caused by the current and is well suitable for high power ac–ac conversion applications. The performance evaluation and comparison of the experimental results show that the net volume of the coupled magnetic components can be reduced by more than 50% with the proposed integration scheme. [ABSTRACT FROM PUBLISHER]

This paper revisits the switched flow graph (SFG) technique. A general and unified equivalent SFG model of a three-terminal switcher encountered in regular and tapped inductor converters operating in the continuous conduction mode is proposed. The model can be applied to most PWM topologies and facilitates construction of a complete flow graph of a given converter. The approach can be helpful in theoretical analysis and derivation of analytical expressions of converter's small-signal transfer functions. The suggested methodology extends the previously proposed SFG analysis technique and alleviates the principal difficulties involved. Furthermore, the approach is straightforward and expeditious. Application guidelines and examples are presented and compared to simulation and earlier theoretical results. [ABSTRACT FROM PUBLISHER]

Due to exponential (Moores law) scaling of advanced CMOS technologies, the challenges associated with delivering power to performance and mobile computing systems are outpacing the capabilities of conventional voltage regulator (VR) topologies. To continue to scale throughput at constant power density, the level of parallelism in microprocessor architectures is expected to increase substantially. In this paper, we present a power conversion topology to provide independent multicore regulation in the 0.8–1.4 V range from a 12-V dc bus. The topology uses a multistage ladder converter to manage power delivery to digital circuits stacked in vertical voltage domains. This approach has several advantages with regard to systems efficiency as it allows a more moderate conversion ratio of the main dc–dc converter. Moreover, the parallel converter only needs to process a fraction of the power of each core as the current can be “recycled” by adjacent cores in the stack. We develop a dynamical model for a multiple-input, multiple-output control scheme that uses a simple integral-control law, augmented with fast voltage- and current-mode feedforward. Measurement results of a discrete prototype verify the control scheme and demonstrate the potential advantages in system efficiency but also emphasize the remaining challenges in meeting stringent VR dynamic response requirements. [ABSTRACT FROM PUBLISHER]

A new method for deriving isolated buck-boost (IBB) converter with single-stage power conversion is proposed in this paper and novel IBB converters based on high-frequency bridgeless-interleaved boost rectifiers are presented. The semiconductors, conduction losses, and switching losses are reduced significantly by integrating the interleaved boost converters into the full-bridge diode-rectifier. Various high-frequency bridgeless boost rectifiers are harvested based on different types of interleaved boost converters, including the conventional boost converter and high step-up boost converters with voltage multiplier and coupled inductor. The full-bridge IBB converter with voltage multiplier is analyzed in detail. The voltage multiplier helps to enhance the voltage gain and reduce the voltage stresses of the semiconductors in the rectification circuit. Hence, a transformer with reduced turns ratio and parasitic parameters, and low-voltage rated MOSFETs and diodes with better switching and conduction performances can be applied to improve the efficiency. Moreover, optimized phase-shift modulation strategy is applied to the full-bridge IBB converter to achieve isolated buck and boost conversion. What's more, soft-switching performance of all of the active switches and diodes within the whole operating range is achieved. A 380-V output prototype is fabricated to verify the effectiveness of the proposed IBB converters and its control strategies. [ABSTRACT FROM PUBLISHER]

A novel interleaved dual buck full-bridge three-level inverter (IDBFTI) is proposed for the grid-connected system in this paper. It retains the advantages of interleaved parallel technology for inverter as follows: reducing the output ripple current and the total harmonic distortion of the output current, increasing the power density of system, and reducing the current stress and thermal stress of power devices. Besides, it can solve the problem of zero sequence circulation current (ZSCC) in interleaved inverter system by the circuit structure, and it also has the advantages of no shoot-through problem, no reverse recovery of the body diode, and three-level output. The interleaved inverter circuits share two power-frequency switches, which are resized for each specific application, and it is easier to extend the system by improving current capability of the two switches. The working principle of this system is introduced in detail, and a 2-kW experimental prototype has been established and tested. Test results verify the principle and the excellent performance of IDBFTI. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel single-phase ac–ac Z-source converter based on the Γ-structure. The proposed converter uses a coupled transformer to produce the required gain. The obtained gain can be tuned by varying the turn ratio $\gamma _\Gamma$ of the transformer within the narrow range of $1 < \gamma _\Gamma < 2$. Also, the gain factor increases with decrease of the transformer turns ratio, $\gamma _\Gamma$ . Small transformer turn ratio results in more practical topology in some voltage gains. It makes the transformer design easier and reduces construction cost. Also, in the proposed topology, the input and output voltages share the same ground. In order to avoid voltage and current spikes on the switches, a commutation strategy is proposed and safe commutation is achieved without using a snubber circuit. The operating principles and steady-state analyses are presented to verify the operational concept of the proposed topology. Also, experimental results are given to verify the validation of the proposed converter. [ABSTRACT FROM AUTHOR]

A novel converter topology for high-power battery charger applications is proposed in this paper. The topology adopts the integration structure of two full-bridge converters, which shares one leg of switching device called center-leg. The two full-bridge converters are placed in parallel on the primary side, and are driven in a phase-shift manner. The integrated form of two current-doubler rectifier is adopted on the secondary side, and it has full-bridge structure. With this structure, the proposed converter can overcome drawbacks of the conventional phase-shift full-bridge converter; narrow zero-voltage-switching range, large duty-cycle loss, and high component counts. The validation of the proposed converter is confirmed by the experiment with a prototype battery charger of 5.7 kW and 13.5 A. [ABSTRACT FROM PUBLISHER]

Due to the merits of sinusoidal input currents and excellent conversion efficiency, buck-type active third-harmonic injection converters have received increasing attention in recent years. However, three major problems of these converters still exist in theory and practice. First, the existence of the dc-link capacitor, utilized by early researchers, causes inrush transient and distorts the input currents. Second, in some specific situations, such as wind energy conversion system and flexible ac transmission system, these converters' capabilities of generating input reactive power need sufficient improvements. Third, proper selection of the third-harmonic injection inductor is the key challenge to implement these converters, since the inductor affects not only the current ripple but also the tracking performance of the third-harmonic current. To solve these problems, this paper studies the two-stage matrix converter with third harmonics injection and demonstrates that the dc-link capacitor can be removed by bidirectional implementation and proper control of the rectifier. Then, an algorithm enhancing the input reactive power capability is developed. Thus, sinusoidal input currents are achieved and the reactive power control range is extended significantly. Moreover, the design criteria of the third-harmonic injection inductor are discussed. Finally, the proposed method is verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

With ever-growing energy crisis in wireless communication, effective envelope tracking solutions are in high demand for efficient operation of power amplifiers. Conventionally, a linear regulator is utilized to assist a switching converter to achieve fast tracking performance, but is highly inefficient. To overcome such an efficiency limitation, a dual-phase switching-converter-only topology is proposed in this paper. Synchronized adaptive voltage tracking control is introduced, which enables both clock synchronization and fast response for high-speed envelope tracking. To mitigate the inductor current slew rate limit of the switching converter, a push–pull slew rate enhancer (SRE) is designed. The SRE only operates when the switching converter reaches its inductor current slew rate limit, thereby maximizing the efficiency. The proposed envelope modulator is fabricated with a 0.18-μm CMOS process, achieving 85.8% peak efficiency at 1.5 W, tracking a 10-MHz LTE envelope. [ABSTRACT FROM AUTHOR]

This paper introduces the application of a switched-diode-capacitor voltage accumulator (SDCVA) on conventional boost converter. This study aims to obtain two different kinds of multi-input step-up converters with high voltage gains, low component stresses, low ripples, simple control, and high conversion efficiencies: one is based on the parallel SDCVA and the other based on the serial SDCVA. The double-input step-up converter based on the parallel SDCVA and the double-input step-up converter based on the serial SDCVA are, respectively, taken as an example to do theoretical analysis, including operating principles and performance analyses when they work individually and simultaneously. The two proposed converters are implemented with a voltage closed-loop control at the switching frequency of 30 kHz. Experimental results obtained from the implemented prototypes are provided to validate the feasibility and effectiveness of the proposed converters. [ABSTRACT FROM AUTHOR]

Electroactive polymer (EAP) actuators have been investigated to convert electrical energy into mechanical deformation in autonomous microrobots. The use of dielectric EAP actuators comes with several challenges to address requirements such as high excitation voltages, explicit driving signals, and low conversion efficiency. External bulky and heavy power sources are used to generate and provide required excitation voltages. The development of a miniature, high voltage gain, and highly efficient power electronic interface is required to overcome such challenges and enable autonomous operation of miniature robots. In this paper, a bidirectional single-stage resonant dc–dc step-up converter is introduced and developed to efficiently drive high-voltage EAP actuators in mobile microrobots. The converter utilizes resonant capacitors and a coupled inductor as a soft-switched LC network to step up low input voltage. High-frequency soft-switching operation owing to LC resonance allows small footprint of the circuit without suffering from switching losses, which in turn increases the efficiency. The circuit is capable of generating explicit high-voltage actuation signals, with capability of recovering unused energy from EAP actuators. A 4-mm × 8-mm, 100-mg, and 600-mW prototype has been designed and fabricated to drive an in-plane gap-closing electrostatic inchworm motor. Experimental validations have been carried out to verify the circuit's ability to step up voltage from 2 to 100 V and generate two 1-kHz, 100-V driving voltages at 2-nF capacitive loads. [ABSTRACT FROM PUBLISHER]

Coupled-inductor interleaved boost converters are under development for high-current, high-power applications ranging from automotive to distributed generation. The operating modes of these coupled-inductor converters can be complex. This paper presents an investigation of the various continuous-current (CCM) and discontinuous-current (DCM) modes of operation of the coupled-inductor interleaved two-phase boost converter. The various CCM and DCM of the converter are identified together with their submodes of operation. The standard discrete-inductor interleaved two-phase boost can be seen as a subset of the coupled-inductor converter family with zero mutual coupling between the phases. The steady-state operating characteristics, equations and waveforms for the many CCM and DCM will be presented for the converter family. Mode maps will be developed to map the converter operation across the modes over the operating range. Experimental validation is presented from a 3.6 kW laboratory prototype. Design considerations and experimental results are presented for a 72 kW prototype. [ABSTRACT FROM AUTHOR]