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Three-port converters with high voltage gain are desirable solutions for integrating renewable energy and energy storage devices into high voltage dc bus. A high gain three-port converter with soft switching is proposed in this paper, which can realize zero voltage switching for all switches and zero current switching for all diodes in various operating modes. Single coupled inductor is used to achieve high voltage gain and to reduce the voltage stress of switches so that switches with low on-resistance can be selected to reduce the conduction loss. In addition, the advantages of fewer components, higher voltage gain, and very low switch voltage stresses make the proposed converter more suitable for application in renewable energy systems than similar solutions. Various operating modes, performance analysis, design considerations, efficiency analysis, and control method of the proposed converter are discussed. A laboratory prototype with 30 V renewable energy source, 48 V energy storage device and 400 V output is designed to verify the performance of the proposed three-port converter. [ABSTRACT FROM AUTHOR]

In applications that demand single-input dual-output (SIDO) or dual-input single-output (DISO) dc–dc converters, employing two separate single-input single-output (SISO) converters is a solution. However, the number of components is doubled, resulting in high overall cost. In order to reduce costs, this paper proposes a novel topology synthesis methodology, with which a variety of SIDO and DISO dc–dc converters with reduced components can be derived. The principle of topology synthesis states that integrated SIDO and DISO dc–dc converters can be easily developed from conventional SISO converters by replacing a diode with a basic cell inclusive of additional input/output port. The principle is effective for many SISO dc–dc converters, and as an example, topology synthesis based on buck, boost, buck–boost, Cuk, sepic, and zeta SISO converters is performed in this paper. In order to achieve better understanding of the proposed converters, the integrated SIDO Cuk converter is specifically analyzed and experimentally verified. In comparison with the conventional scheme of two separate SISO Cuk converters, good cross regulation is retained while the number of diodes, inductors, and capacitors is reduced in the proposed SIDO Cuk converter. In addition, zero-voltage-switching operation of one switch is achieved, contributing to lower switching losses. Finally, a prototype circuit with 48-V input and 156 V/1 A, 24 V/4 A outputs is built to validate the theoretical analysis. [ABSTRACT FROM PUBLISHER]

The development of a high static gain dc–dc converter with the integration of the voltage multiplier cell and the coupled inductors operating with soft switching is presented in this paper. The use of coupled inductors and voltage multiplier techniques allow the operation with low switch voltage and low conduction losses. The switch turn-on commutation occurs with zero current switching due to the presence of the coupled-inductor leakage inductance. The leakage inductance also reduces the reverse recovery current of all diodes. The zero voltage switching at the power switch turn-off is obtained with the inclusion of only a diode and a snubber capacitor per phase, without the use of auxiliary switches. The soft-switching range is independent of the load and is maintained even with a light load. The theoretical analysis, design procedure, and experimental results are presented in this paper. A two-phase boost converter with one voltage multiplier and coupling inductors was built with an input voltage $V_{{\text{in}}}= { \text{24 V}}, output voltage Vo= { \text{432 V}}, and output power Po= { \text{400 W}}. The efficiency obtained is equal to 94.55% at the nominal power. [ABSTRACT FROM PUBLISHER]

In this paper, a nonisolated dc–dc converter with high voltage gain is presented. Three diodes, three capacitors, an inductor, and a coupled inductor are employed in the presented converter. Since the inductor is connected to the input, the low input current ripple is achieved, which is important for tracking maximum power point of photovoltaic panels. The voltage stress across switch S is clamped by diode D 1 and capacitor C1. Therefore, a main switch with low on-resistance RDS (on) can be employed to reduce the conduction loss. Besides, the main switch is turned on under zero current. This reduces the switching loss. The steady-state analysis of the proposed converter is discussed in this paper. Finally, the proposed converter prototype circuit is implemented to justify the validity of the analysis. [ABSTRACT FROM PUBLISHER]

Resonant modular multilevel converters (RMMCs) have been proposed for high-voltage dc–dc applications. Using different modulation strategies, RMMC operates in different modes and achieves flexible step ratio. To provide a comprehensive study of RMMCs, this paper presents the modulation method achieving a wide range of step ratio with the ability of inherent-balancing. The conditions for guaranteeing the inherent-balancing ability are provided. The operation principle and performance of the RMMC are presented in this paper, which have been explored in a case study. The experimental results are obtained from a bench-scale setup, which have verified the theoretical analysis. [ABSTRACT FROM PUBLISHER]

This paper introduces the bridgeless triple-mode resonant ac–dc converter and presents its dynamic model and control technique. The proposed converter operates in triple mode: discontinuous-conduction mode (DCM), continuous-conduction mode (CCM), and missing resonance mode (MRM). It has the advantages of small number of required components, medium power capacity, and high efficiency, but it is difficult to control because DCM, CCM, and MRM have their own dynamic characteristics. To solve this control problem, the mode boundaries are first identified and, corresponding to each mode, the dynamic model is developed to design the controller. In each mode, we propose to add a repetitive controller (RC) with a phase-lead compensator to the conventional duty ratio plus feedback controller. The RC is used to suppress the deterministic periodic disturbances and the phase-lead compensator is used to compensate for the incurred phase lag. A 1-kW digitally controlled converter prototype is built and used to demonstrate the validity of the proposed modeling and control approach. [ABSTRACT FROM AUTHOR]

In this paper, eight ultrahigh-voltage gain dc–dc converters are proposed. These sets of converters are derived by the association of boost cells, coupled inductor, voltage multiplier, switched capacitors, and LC filter cells. The nonpulsating input and output converters are evaluated in terms of: principle of operation, voltage gain, voltage and current stress, estimated power losses, and efficiency. Following full analysis prototypes built in the laboratory show experimental results verifying the theoretical analysis. [ABSTRACT FROM AUTHOR]

In recent years, a number of bidirectional inductive power transfer systems (BD-IPT) suitable for wireless grid integration of electric vehicles have been developed. These developments have been fueled by the enhanced efficiency and spatial tolerance offered by BD-IPT systems. A typical BD-IPT system utilizes two synchronized full-bridge converters operating at fixed duty cycles to drive the primary and secondary magnetic couplers. However, in order to cater for a wide range of loading conditions, additional circuitry is employed at the expense of cost and power density. As an alternative solution, this paper proposes a novel power converter, named a boost active bridge (BAB), to replace the full-bridge converters. The BAB topology caters to a wide range of loading conditions without the need for any extra switching devices. A comprehensive mathematical model that predicts steady-state currents, voltages, and power transfer is presented to highlight the operating principles of the BAB technology. Experimental results obtained from a 3.5-kW prototype show a nearly constant efficiency under all loading conditions, validating the viability of the proposed BAB topology. [ABSTRACT FROM AUTHOR]

In this paper, a new high-frequency resonant boost converter is presented. Zero-voltage switching (ZVS) for the switches and zero-current switching (ZCS) for the rectifying diode are attained. The provided ZVS conditions reduce switching losses considerably, and ZCS conditions for the diode decrease voltage oscillations. Both switches are grounded which simplifies the gate-drive circuit and enhances the converter potential for high-frequency operation. All passive elements are high-frequency resonant type and thereby the converter power density is enhanced. The resonant inductor placed in front of the converter can operate in continuous conduction mode and smoothens the converter input current. Experimental results from a 160 W/500 kHz laboratory discrete prototype with an almost high-voltage conversion ratio of 100 to 300 V confirm the integrity of the proposed converter operation. [ABSTRACT FROM AUTHOR]

This paper presents a new highly integrable hybrid step-down converter that merges switched-inductor and switched-capacitor operations and significantly reduces onboard loss by using the input cable's parasitic inductance as its main inductor. This converter has the inductor placed at the input with a smaller voltage swing, leading to possible use of a smaller inductor and low-voltage rating switches that generally translate to reduced conduction losses. Analyses of converter operation and losses to reveal its original characteristics and design guidelines are presented to facilitate the components optimization. The converter architecture is verified by a proof-of-concept 15-W inductor-less lithium-ion battery charger prototype that uses a 1-m USB 3.0 cable as inductor. The converter, switched at 2 MHz from a 5-V input, experimentally achieves 89.7% peak efficiency and 6% higher efficiency at full load than a Buck converter counterpart. This high efficiency and zero onboard inductor yield a relative 45.7% onboard loss reduction at full load, promising excellent integration feasibility and superior system thermal management. [ABSTRACT FROM AUTHOR]

Condition monitoring of aluminum electrolytic capacitors (AECs) is essential for predictive maintenance of power electronic converters. The AEC is considered at the end of its life when its capacitance or equivalent series resistance (ESR) reaches corresponding critical values. In the literature, it is found that either of these parameters may reach its critical limit depending on the operating conditions and applications. However, most of the existing health monitoring techniques of the AEC in dc–dc converters are based on the estimation of ESR. To address the aforementioned issue, this paper proposes to estimate the low-frequency impedance of the AEC, which is dominated by its capacitance value, thereby allowing health monitoring based on the capacitance value. The technique is based on injection of a low-frequency current ripple into the AEC using duty ratio control of the dc–dc converter. The parameters of new and aged capacitors are experimentally obtained at various temperatures and are used to establish the failure criteria. Furthermore, the proposed method is applicable for both the continuous conduction mode and the discontinuous conduction mode (DCM) of operation. For DCM operation, a sampling instant to recover a low-frequency waveform is suggested based on mathematical analysis. Detailed simulation studies are performed and results are included in this paper. Experimentation is carried out on a dc–dc boost converter integrating solar photovoltaic with the dc system. Experimental results are found to be in agreement with simulation results. [ABSTRACT FROM PUBLISHER]

In this paper, a new soft switching flyback dc–dc converter with a simple zero-voltage and zero-current switching (ZVZCS) cell is proposed. The auxiliary resonant cell consists of one switch, one diode, one inductor, and two capacitors. It provides ZVZCS not only for the main switch but also for the auxiliary switch at both turn-on and turn-off times. In addition, all the auxiliary diodes and body diodes of the switches operate under full ZVZCS except the output diode which turns off only with zero current switching. This soft switching technique makes the proposed converter have less switching losses which leads the converter to operate in higher frequencies and efficiency. Another outstanding feature of the proposed converter is using the auxiliary resonant cell out of the main power path to have lower voltage stress on the switches. In this paper, pulse width modulation (PWM) is employed to control the main switch. A detailed mode analysis of the proposed converter operation is presented along with design procedure. Finally, the accuracy performance of the converter is verified through a 60 W experimental prototype results. [ABSTRACT FROM AUTHOR]

This paper presents predictive current-mode control for a single-phase high-frequency transformer-isolated dual-active bridge dc-to-dc converter. The predictive control algorithm increases the bandwidth of the current loop of the converter which enables tracking of the current reference within one switching cycle. The paper further demonstrates that the application of the predictive control algorithm can remove transient dc offset from the current in high-frequency isolation transformer within one switching cycle. Direct control of the converter current protects the transformer from saturation even at transient conditions. The control algorithm has been implemented on an experimental setup and transient tests have been performed to validate controller performance. Since the predictive control algorithm is dependent on the measured value of the leakage inductance of the transformer, a compensator has been implemented to improve the parameter insensitivity of the proposed controller. [ABSTRACT FROM PUBLISHER]

In this paper, a nonisolated bidirectional dc–dc converter is presented. The proposed converter consists of two boost converters to enhance the voltage gain. Four power switches with their body diodes are employed in the proposed converter. Also, two inductors and a capacitor are used as passive components. The input current is divided to the inductors which causes the efficiency to be high. The voltage gain of the proposed converter is higher than the conventional cascaded bidirectional buck/boost converter (CCBC) in step-up mode. Besides, the voltage gain in step-down mode is lower than CCBC. Besides, the efficiency of the proposed converter more than CCBC while the total stress on active switches are same. The simple structure of the proposed converter causes its control to be easy. The steady-state analysis of the proposed converter is discussed in this paper thoroughly. The stress on converters’ devices and the efficiency of the proposed converter and CCBC are compared in this paper. Finally, the proposed converter prototype circuit is implemented to justify the validity of the analysis. [ABSTRACT FROM PUBLISHER]

Series–parallel forward dc–dc converter system is a good option in high-voltage high-power applications. A switch fault, in this converter, should be detected as soon as possible, to avoid further damage and save maintenance cost. In this paper, a new switch fault diagnosis method, which treats output inductor voltages as diagnostic criteria, is proposed for this system. With the proposed method, expensive sensors are needless, since diagnostic signal can be easily acquired by adding a small auxiliary winding into inductor magnetic core. Based on the feature of diagnostic signals in such a system, a low-cost diagnostic circuit is designed. The failed module caused by open-circuit fault or short-circuit fault could be detected within one switching period, allowing for an immediate fault-tolerant action. This method also shows generality for different connections and buck-type isolated topologies. Besides, it works reliably under input-voltage variation and load step, and no misdiagnosis will occur during normal dynamic process. Finally, experimental result verifies the effectiveness of this method. The proposed scheme has a good potential to be applied in real applications for its simplicity and robustness. [ABSTRACT FROM AUTHOR]

A nonisolated bidirectional dc–dc converter with high voltage gain, low voltage stress, low component count, and soft-switching features is presented in this paper. In this topology, coupled inductors and voltage multiplier cells are merged to achieve high step-up/down voltage gain. Also, due to using active clamp circuits, the voltage stress of power switches is relatively low. Thus, the low voltage switches with low on-resistance can be employed to reduce the conduction losses. Furthermore, zero-voltage switching is accomplished in both high step-up and high step-down modes for all power switches, and due to zero-current switching operation of all antiparallel diodes, the reverse recovery losses are reduced. In order to verify the theoretical analysis and the converter performance, a 200 W prototype circuit of the proposed converter is implemented in the laboratory. [ABSTRACT FROM AUTHOR]

The development of a photovoltaic ac module composed of a high static gain nonisolated dc–dc converter with current source output characteristic followed by an unfolding low-frequency inverter is presented in this paper. The operation of the dc–dc converter with high static gain and with reduced switch voltage is obtained using the Cuk converter integrated with the switched-inductor technique. The nonisolated structure allows the elimination of the volume and losses of the power transformer and leakage inductance, and an output filter configuration is proposed to reduce the high-frequency ground leakage current. The grid-tied inverter operating in a discontinuous conduction mode (DCM) allows a sinusoidal output current with low harmonic distortion (THD = 3.72%) to be obtained without current control loop and without the use of a current sensor at the output. The maximum power point tracking operation is obtained without the use of the current sensor. The DCM operation increases the current stress, but the proposed converter presents two switches and two input inductors sharing the input current in these components. The theoretical analysis, design procedure, and experimental results are presented for a prototype with a dc input voltage Vi = 30 V, an ac output voltage Vo = 127 V, and output power Po = 180 W. [ABSTRACT FROM AUTHOR]

In this paper, the averaged small-signal model of the dual-interleaved buck converter is extended to include the phase interaction effects that arise from the interleaved sampling of the phase currents. Sampler decomposition techniques are used to extend the averaged model, revealing a slow-scale instability that can place significant restrictions on the choice of controller parameters. The model is confirmed by simulations and measurements using a 60-kW dual-interleaved prototype with an interphase transformer; however, the analysis is equally applicable to interleaved converters without magnetic coupling. [ABSTRACT FROM AUTHOR]

In this paper, a new modified single-switch single-ended primary inductor converter (MS2-SEPIC)-based high step-up dc–dc converter is presented. The proposed topology uses the coupled-inductor (CL) technique and a voltage tripler rectifier, which results in a high voltage gain for the converter. Here, the switching loss has been reduced significantly owing to the quasi-resonance operation of the circuit created by the leakage inductance of the CL along with circuit capacitors. The operational principles and steady-state analysis are discussed. Experimental results based on a 100 W laboratory prototype verify the validity of theoretical analysis. [ABSTRACT FROM AUTHOR]

MR16 lighting system with a high-frequency step-down electronic transformer is widely used in commercial lighting. In this paper, a single-switch quadratic boost light emitting diode (LED) driver compatible with electronic transformers for the MR16 lighting system is proposed and analyzed. It combines a prestage boost power factor correction (PFC) converter and a second-stage boost dc–dc converter with a single switch. The effect of the dc link voltage ripple of the prestage boost PFC converter on the output of the second-stage boost dc–dc converter is eliminated by a fast voltage mode control loop of a second-stage circuit. Therefore, flicker-free low ripple LED current is achieved. With a small dc link voltage ripple of prestage, the turn-on time of the active switch is almost constant in a half-line cycle. Therefore, PFC can be achieved with inductor current of prestage operating in a discontinuous conduction mode. With small input capacitance, the proposed LED driver presents a good compatibility performance with different kinds of electronic transformers. Furthermore, the proposed LED driver needs only one active switch and one control loop, which makes circuit volume small and low cost. Finally, a 4 W LED driver for a small-size MR16 lighting system is provided to verify the studied results. [ABSTRACT FROM AUTHOR]

In photovoltaic systems, dc–dc converters have been identified as one of the most critical and challenging subsystem in terms of failure rate. Thus, this paper proposes fault-tolerant operation of a two-stage buck/buck–boost converter under open-circuit switch failure. Remedial actions are efficient in any failure of one of the two switches of the converter. Here, a new unified approach is considered, for the overall fault-tolerant operation of the two stages of the converter. The fault-tolerant circuit we propose lies on performing redundancy by implementing the equivalent synchronous switch for the two main switches of the two stages, in offline mode. The fault-tolerant circuit results from the basic two-stage buck/buck-boost converter and its equivalent circuit with a synchronous switch, merged together to form the new dc–dc fault-tolerant circuit. Therefore, postfault operation at full power can also be performed. By using a switch fault management unit with reduced complexity, inserted between the control block and the switches, we have designed an unified, efficient, and optimized fault-tolerant control, suitable in both healthy and postfault operations. Some selected experimental tests, which all confirm the good performances of the proposed fault-tolerant approach, are presented and discussed. [ABSTRACT FROM AUTHOR]

High step-up converters are required for distributed photovoltaic generation systems, due to the low voltage of the photovoltaic source. In this paper, a new hybrid high voltage gain dc–dc converter is created by merging the standard boost converter with a coupled inductor and different switched-capacitor techniques. With a single switch and no requirement of higher duty cycle values, the proposed converter achieves a high voltage gain and high efficiency, in addition to lowered voltage and current stresses of the components. A 200-W prototype was implemented experimentally to evaluate the converter, which reached a maximum efficiency of 97.6%. [ABSTRACT FROM AUTHOR]

In this paper, a hybrid switched-capacitor/switched-quasi-Z-source bidirectional dc–dc converter is proposed for electric vehicles (EVs) with hybrid energy sources, which has a wide voltage gain range in the bidirectional energy flows. Compared with the traditional quasi-Z-source bidirectional dc–dc converter, the proposed converter only changes the position of the main power switch and employs a switched-capacitor cell at the output of the high-voltage side. Therefore, the advantages of the wide voltage gain range and the lower voltage stresses across the power switches can be achieved. The operating principle, the voltage and current stresses across the power switches, and the comparisons with other converters are analyzed in detail. Furthermore, the parameter design of the main components, the dynamic modeling analysis, and the voltage control scheme are also presented. Finally, the experimental results obtained from a 400 W prototype validate the characteristics and the theoretical analysis of the proposed converter. [ABSTRACT FROM AUTHOR]

A new light emitting diode (LED) driver circuit is presented in this paper based on the buck converter with coupled inductors for automotive applications. Soft-switching condition is provided for the switch via a passive resonant circuit incorporating the leakage inductance of the coupled inductors. Also, the leakage inductance energy is recycled to the output. The proposed converter has a very simple structure as well as high efficiency, which makes it a good candidate for battery-operated applications. The proposed converter only applies one magnetic element and the leakage and magnetizing inductances are used as resonant elements. Also, during the resonance, a resonance capacitor is approximately charged to the input voltage, and therefore, the capacitor voltage stress and semiconductor devices voltage stress are low. These are the main advantages of the proposed converter over other similar converters. The theoretical analysis is provided and the operating principles and design considerations are explained. An 8 W laboratory prototype is implemented in order to prove the validity of the theoretical analysis. [ABSTRACT FROM AUTHOR]

Linear ramp slope compensation (LRC) and quadratic slope compensation (QSC) are commonly implemented in peak-current-mode-controlled dc–dc converters in order to minimize subharmonic and chaotic oscillations. Both compensating schemes rely on the linearized state-space averaged model (LSSA) of the converter. The LSSA ignores the impact that switching actions have on the stability of converters. In order to include switching events, the nonlinear analysis method based on the Monodromy matrix was introduced to describe a complete-cycle stability. Analyses on analog-controlled dc–dc converters applying this method show that system stability is strongly dependent on the change of the derivative of the slope at the time of switching instant. However, in a mixed-signal-controlled system, the digitalization effect contributes differently to system stability. This paper shows a full complete-cycle stability analysis using this nonlinear analysis method, which is applied to a mixed-signal-controlled converter. Through this analysis, a generalized equation is derived that reveals for the first time the real boundary stability limits for LRC and QSC. Furthermore, this generalized equation allows the design of a new compensating scheme, which is able to increase system stability. The proposed scheme is called polynomial curve slope compensation (PCSC) and it is demonstrated that PCSC increases the stable margin by 30% compared to LRC and 20% to QSC. This outcome is proved experimentally by using an interleaved dc–dc converter that is built for this work. [ABSTRACT FROM AUTHOR]

Conventional power supply systems for xenon lamps have only limited applicability in sintering, because sintering needs to drive the lamp itself as well as enable instantaneous and strong discharge of voltage and current for generating intense light. This implies that, for sintering applications, a method should be developed that would enable instantaneous and strong discharge of energy. In this paper, we propose a new xenon lamp sintering system with an additional capacitor charger and bank. The proposed system features three power supplies. Two power supplies, called the trigger and the simmer, ionize gaseous xenon using a 23-kV trigger pulse output and sustain the ionized xenon gas using a 2.5-kW simmer power supply. The used trigger is also specially designed to conduct high current through its transformer, and it makes the proposed system an outstanding high voltage blocking capability. Another 36-kW power supply charges a 130-mF capacitor bank with a high-efficiency resonant converter. In addition, some components such as the simmer blocking diode and the trigger output capacitor are introduced, because combining different power supplies causes operational problems. These components are analyzed with some circuits that show its features, and finally, the validity of the suggested system was confirmed in two steps. First, the simmer power supply and the capacitor charger were tested for the rated operating performance by using a resistive load condition. As a result, the rated operation of the simmer power supply was confirmed under the 2.5-kW output condition, and the efficiency of the capacitor charger was found to be greater than 96% at the rated 36-kW rated load condition. In addition, a pulse discharge current of 900 A was also observed with the equivalent resistor load through a pulsed discharge experiment of the capacitor bank, which was charged at 1500 V. The trigger power supply, whose equivalent resistive load was difficult to realize, was experimented directly using the real xenon lamp to check the stable trigger operation of the xenon lamp at its 23-kV output pulse voltage. After the verification using the resistive load condition, the real operation and performance of the combined xenon lamp power supply system that includes three kinds of power supplies were finally tested and verified by using the actual xenon lamp as a total system. [ABSTRACT FROM AUTHOR]

A new class of impedance networks is proposed in this paper. The proposed coupled-inductors-based impedance cells, called the series and the tapped switched-coupled-inductors, are employed within the (quasi) switched boost networks. The achieved impedance networks based on the proposed cells offer very high conversion gains with less-than-unity turn ratios (n < 1), which simplifies the realization of the magnetic element and at the same time reduces the number and size of passive components. The high boosting capability is achieved with small shoot-through durations that bring some additional advantages, such as low ratings of switching devices. The circuit analysis and operation concepts as well as a design procedure for the components of the proposed impedance networks are presented. Theoretical achievements are confirmed through experiments on a 220 W dc–dc converter laboratory setup. [ABSTRACT FROM AUTHOR]

A major advantage of the dual active bridge (DAB) dc–dc converter is its ability to operate under zero voltage switching (ZVS) conditions to reduce switching losses. However, when the ac link coupling transformer is conventionally designed to minimize its magnetizing current, nonideal switching conditions almost invariably lead to hard switching operation at particular power transfer levels and dc–dc voltage ratios. This paper presents a mathematically based design approach for a coupling transformer with a reduced magnetizing inductance that creates just sufficient ac link circulating current to maintain continuous ZVS operation over the converter's entire specified operating range without incurring significant additional losses. The required magnetizing inductance reduction is found to be a function of the inherent transformer leakage inductances, switching dead-time, and device parasitic capacitances. The analysis approach is validated by matching experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive analysis of the current-stress optimization and soft-switching operation of the isolated bidirectional dual active bridge (DAB) dc–dc converter with the unified triple-phase-shift (UTPS) control. On this basis, the current-stress-optimized modulation scheme is proposed for DAB, which leads to the minimum current stress with the required transmission power and voltage conversion ratio in the whole load range. Moreover, the full soft-switching operation is achieved for the converter simultaneously. Distinct from the previous modulation schemes, the proposed optimized modulation scheme is deduced from a unified analysis of TPS where all effective switching modes are investigated. A novel algorithm based on the Karush–Kuhn–Tucker (KKT) conditions is originally proposed to derive closed-form solutions for the global optimal control parameters. This paper also presents a typical closed-loop control strategy for DAB with TPS control and detailed descriptions about the closed-loop operation. A laboratory prototype is applied, and the experimental results validate that the current-stress optimization and efficiency improvement are realized by applying the optimized modulation scheme. The experimental results also verify the effectiveness of the closed-loop control strategy for DAB with TPS control. [ABSTRACT FROM PUBLISHER]

A conventional asymmetrical half-bridge (AHB) converter is widely used for dc–dc stage in low-to-medium power system. However, since the asymmetric operation of AHB converter causes the low efficiency over entire load condition, the conventional AHB converter is not usually considered for the candidate of server power system. In order to overcome the problems of the conventional AHB converter, a wide zero-voltage-switching (ZVS) range AHB converter with a clamp switch and a clamp diode is proposed in this paper. The proposed AHB converter (PAHBC) replaces a low-side clamp diode with a MOSFET switch and adds an auxiliary winding, which changes the transformer turns-ratio. From these modifications and the pulsewidth-modulation (PWM) control of clamp switch, the PAHBC can be designed optimally at nominal input condition and obtains additional dc gain at hold-up time condition. These advantages achieve the high conversion efficiency over the entire load condition. The operational principle and analysis of the PAHBC are presented in this paper and verified by a 340–400 V input and 50 V/500 W output laboratory prototype. [ABSTRACT FROM PUBLISHER]

Single-stage power-factor-corrected (S2PFC) power supplies usually suffer from high voltage stress, due to lack of control on the intermediate bus capacitor voltage. In the past, analysis of such voltage stress was mostly based on steady-state condition without providing sufficient explanation during the transient circuit operation. This paper revisits the problem at circuit level and reports that the root cause is due to the inherent negative current feedback property of the output inductor or the transformer operating in continuous conduction mode (CCM). Based on the finding, this paper further proposes a new approach to reducing the voltage stress by adding an auxiliary circuit branch to existing S2PFC converters. The additional circuit branch limits the effect of negative current feedback by suppressing the change of output current slope due to change of load. This assists the pulsewidth modulation controller to track the change of load better such that the bus capacitor voltage range is reduced through duty cycle control. The auxiliary circuit branch also reduces reverse-recovery-related losses of the converter under CCM operation. A laboratory prototype using the popular boost PFC converter combined flyback dc/dc converter was built and tested to confirm the analysis and effectiveness of the approach. [ABSTRACT FROM AUTHOR]

This paper investigates time-domain analysis of sampling effect in digital pulsewidth modulation (DPWM) of dc–dc converters. The relation between the sampling delay, duty ratio, and multisampling factor (sampling to carrier frequency ratio) has been characterized. The sampling delay of the digital controller used for DPWM of the dc–dc converter has close relation with the actual pulsewidth-modulation output. An increase in the multisampling factor can reduce the delay effect of the DPWM. The output voltage varies as a stepped function of the duty ratio instead of the linear function as observed in ideal modulation. It is shown in this paper that this delay is a periodic function of the duty ratio. The effect of variations in the sampling frequency, switching frequency, and modulation index has been analyzed. The proposed sampling effect has been verified analytically for the buck, boost, and buck–boost dc–dc converters. The experimental results for the buck and boost converters have been obtained with the control circuit realized through a field-programmable gate array-based digital controller. [ABSTRACT FROM PUBLISHER]

The current-fed dual active bridge (CF-DAB) dc–dc converter gains growing applications in photovoltaic (PV) and energy storage systems due to its advantages, e.g., a wide input voltage range, a high step-up ratio, a low input current ripple, and a multiport interface capability. In addition, the direct input current controllability and extra control freedom of the CF-DAB converter make it possible to buffer the double-line-frequency energy in grid-interactive PV systems without using electrolytic capacitors in the dc link. Therefore, a PV system achieves high reliability and highly efficient maximum power point tracking. This paper studies the optimized operation of a CF-DAB converter for a PV application in order to improve the system efficiency. The operating principle and soft-switching conditions over the wide operating range are thoroughly analyzed with phase-shift control and duty-cycle control, and an optimized operating mode is proposed to achieve the minimum root-mean-square transformer current. The proposed operating mode can extend the soft-switching region and reduce the power loss, particularly under a heavy load and a high input voltage. Moreover, the efficiency can be further improved with a higher dc-link voltage. A 5-kW hardware prototype was built in the laboratory, and experimental results are provided for verification. This paper provides a design guideline for the CF-DAB converter applied to PV systems, as well as other applications with a wide input voltage variation. [ABSTRACT FROM PUBLISHER]

This paper describes a systematic procedure using power flow graphs for generating all possible double-input single-output (DISO) dc/dc converters. To maximize the generality of applications, the input ports can possibly be connected with voltage source(s) or current source(s), and the output port can be connected with a voltage load or current load. The control methods are described in this paper. A DISO converter with two voltage sources and one voltage load is taken as an example to analyze a few key properties of practical relevance, including input voltage range, efficiency, power distribution, and switching stress. A popular application of DISO converters involves the use of a battery as storage element, and for this specific case, possible choices for the converters, the control method, and the attainable efficiency are discussed. Finally, experimental results are presented to verify the analytical results. [ABSTRACT FROM PUBLISHER]

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%. [ABSTRACT FROM PUBLISHER]

Quasi single-stage single-phase ac–dc power converters based on a three-port bridgeless power factor corrector (TPB-PFC) are proposed in this paper. The TPB-PFC, which is able to provide an ac input port, a dc load port, and a dc bus port simultaneously, is derived by introducing a new dc load port into a conventional bridgeless PFC. The load, whose voltage can be either lower or higher than the peak amplitude of the ac line voltage, is connected to the dc load port of the TPB-PFC directly. Therefore, the ac input power can be fed to the dc load with the single-stage power conversion when the instantaneous ac voltage is lower than the voltage of the dc load. Although another dc–dc converter is required to accomplish the power transmission between the dc bus port and the dc load port of the TPB-PFC, the power rating and losses of the dc–dc converter are reduced significantly, in comparison with a two-stage ac–dc converter. Furthermore, the switching losses of the TPB-PFC are reduced thanks to the three-level characteristic of the proposed converter. The topology derivation, operation principles, modulation strategies, and characteristics of the proposed ac–dc converter are analyzed and verified experimentally with a 2-kW prototype. [ABSTRACT FROM PUBLISHER]

Peak current mode (PCM) control has been widely used for the control of switching dc–dc converters due to its excellent transient performance. With the development of single-inductor dual-output (SIDO) dc–dc converters, PCM control technique is introduced to the control of SIDO dc–dc converters. Conventional PCM buck converter has only one reference current, with two inductor current borderlines are used to divide the operation modes of inductor current. However, PCM SIDO buck converter has more inductor current borderlines as it has one more reference current than that of PCM buck converter. In this paper, inductor current borderlines of PCM SIDO buck converter are investigated, and unified discrete iterative model of PCM SIDO buck converter is established. The effect of the difference of reference currents, initial inductor current and input voltage on the stability of PCM SIDO buck converter has been discussed by using bifurcation diagrams. The study results show that the stability of PCM SIDO buck converter is sensitive to the difference of reference currents, initial inductor current and input voltage. The stability boundary of the difference of reference currents, stability region of initial inductor current, and stability boundary of input voltage are derived. Lyapunov exponent and experimental results are carried out to verify the theoretical analysis results. [ABSTRACT FROM PUBLISHER]

A common ground switched-quasi-Z-source bidirectional dc–dc converter is proposed for electric vehicles with hybrid energy sources. The proposed converter is based on the traditional two-level quasi- Z-source bidirectional dc–dc converter, changing the position of the main power switch. It has the advantages of a wide-voltage-gain range, a lower voltage stress across the power switches, and an absolute common ground. The operating principle, the voltage and current stresses on the power switches, the comparisons with the other converters, the small signal analysis, and the controller design are presented in this paper. Finally, a 300 W prototype with $U_{{\rm{high}}}= {240 \ \rm{V}}$ and $U_{{\rm{low}}}= {40\sim 120\ \rm{V}}$ is developed, and the experimental results validate the performance and the feasibility of the proposed converter. [ABSTRACT FROM PUBLISHER]

As for ripple-current mode control, it cannot achieve average current tracking, resulting in poor current accuracy and even current waveform distortion. Meanwhile, fast-scale instability may occur in some operating conditions. To solve these problems effectively, a current-ripple compensation (CRC) control technique is proposed in this paper. The error between the average of the controlled current and the reference current is compensated by certain compensation signal, achieving average current tracking while suppressing fast-scale instability. On this basis, the compensator in the outer-voltage loop is further simplified to a proportional part by introducing a rebuilt average reference current. The idea and design procedure of the proposed CRC control technique are discussed in detail. Accordingly, two available implementation schemes for the proposed CRC are presented, including slope compensated and parabolic compensated schemes. Finally, two application cases, respectively, to dc–dc Buck converter and Boost PFC converter, are presented to verify the proposed CRC control technique. [ABSTRACT FROM PUBLISHER]

This paper presents a comparative evaluation of eight high-voltage step-up converters based on different associations of boost and zeta standard dc–dc pulse width modulation (PWM) cells. These eight converters present different characteristics such as cascaded and stacked PWM cell associations, as well as isolated winding coupled inductors, tapped winding coupled inductors, and noncoupled inductors. In order to explore the advantages and address the limitations of each topology, several comparative evaluations concerning static voltage gain, power losses, current and voltage stresses, component stress factors, power density, relative cost, and efficiency were carried out. From the theoretical analysis and experimental results, the association named stacked boost–zeta with autotransformer yielded the highest efficiency and power density and resulted in the most attractive converter for the case study. [ABSTRACT FROM PUBLISHER]

In high-voltage output applications, the rectifier diodes in the conventional full-bridge converter have to bear the whole secondary voltage of a transformer. In this paper, a three-level rectifier structure with flying capacitors is proposed for the dc–dc converter. Compared with the conventional dc–dc converter, the converter with the proposed rectifier structure has the following advantages: low-voltage diodes could be used for high-voltage output applications; due to the secondary flying capacitors, there are no voltage spikes on the rectifier diodes even if no snubber circuits are attached; not only can the leading switches realize zero voltage switching (ZVS) as the same as the conventional converters, but also the lagging switches can realize zero current switching in discontinuous-conduction mode and ZVS in continuous-conduction mode; and the rectified voltage has no zero-state voltage, it has been raised to half of the input voltage, so the voltage fluctuation is lower than the conventional converter under the same modulation strategy, and the current ripple of the filter inductor can be reduced by half. The operation principle of the proposed rectifier structure is analyzed in details, and a prototype is fabricated to verify the features of the proposed converter. [ABSTRACT FROM PUBLISHER]

This paper presents an isolated bidirectional interleaved converter with minimum active switches to achieve high conversion ratio. The proposed converter has symmetric structure for easy control, and incorporates two coupled inductors for galvanic isolation and high voltage ratio achievement. A dual-inductor-capacitor-diode (LCD) snubber with common resonant inductor at low-voltage side is in charge of leakage energy recycling for efficiency improvement. In addition, the converter can obtain interleaved terminal current at low-voltage side for lowering current ripples, no matter in boost mode or buck mode. Finally, a 400-W prototype is built for validation, where the experimental results indicate that the highest efficiencies in boost and buck modes are 95.5% and 95.4%, respectively. [ABSTRACT FROM PUBLISHER]

Reliable operation of dc–dc converters is vital for many applications. An appropriate converter monitoring scheme is required for fault detection and adoption of effective remedial strategies. Switch faults and degradation of electrolytic capacitor account for a considerable portion of the converter failures. Although rate of diode failures is not remarkable, power switch may be damaged in case of diode fault occurrence. Furthermore, for applications in which a redundant switch is employed as a remedy, it will be also endangered by diode failures if diode fault detection has not been considered in the monitoring scheme. Therefore, diode condition monitoring improves reliability of the converter monitoring approaches. This paper presents a simple diagnosis technique for open-circuit and short-circuit faults of the switch and diode in nonisolated dc–dc converters. The technique only employs diode voltage as the detection signature. The diode voltage and gate driver signal are processed in a simple logic circuit to generate some indicators for switch and diode fault diagnosis. Basis of the technique is discussed in detail. Several experiments have been carried out on buck, boost, and buck–boost converters. The results confirm the technique capability for switch and diode fault diagnosis in less than one switching cycle. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel structure for a boost dc/dc converter. The presented structure is based on the SEPIC converter. Therefore, the converter benefits from various advantages that the SEPIC converter has such as continuous input current. Also, high voltage conversion gain and higher efficiency are the other advantages of the proposed converter. Input current continuity makes the presented converter suitable for renewable energy sources. Employing a coupled inductor with a voltage multiplier cell in this structure increases its high voltage gain. In addition, lower voltage stress on the main power switch leads to higher conversion efficiency. Also, the energy stored in the leakage inductance of the coupled inductor is recycled, which improves the efficiency more. The steady state analysis and the design of the converter are discussed thoroughly. Experimental results are provided by a 220 W prototype. The results verify the proper operation and feasibility of the presented converter. [ABSTRACT FROM PUBLISHER]

Three-level buck dc–dc converters have advantages over the traditional buck converters: half switch voltage stress, doubling effective switching frequency, smaller inductor size, and the higher power density. To benefit from those advantages, the flying capacitor voltage must be balanced at half of the input voltage. Most existing methods of balancing the flying capacitor voltage require current sensing, which increases the cost and noise sensitivity. This paper proposes a novel state-machine structure of second-order sliding-mode (SOSM) control for three-level buck dc–dc converters without sensing currents. With insensitivity to parameter variations of SOSM control, the proposed control approach tackles the strongly coupled problem of output voltage and flying capacitor voltage in three-level buck dc–dc converters. Compared to existing approaches, the controller achieves fast start-up without overshoots, fast load disturbances rejection, and robustness against parameter uncertainties for the output voltage, and balance of the flying capacitor voltage without sensing the current of flying capacitor. The proposed approach is verified with experimental results of a 1.25 V, 2.5 A prototype. [ABSTRACT FROM PUBLISHER]

This paper proposes a soft switching nonisolated dc/dc interleaved converter incorporating coupled inductors and switched capacitors for high step-up applications. The converter integrates the interleaved structure and winding-cross-coupled inductors technique to reduce current stress of semiconductor devices and diminish the input current ripple considerably. In addition, the interleaved converter has the automatic current sharing characteristic. The applied zero voltage transition cell provides soft switching in a wide range of load variations with a minimum number of elements. In this topology, all semiconductor devices are soft switched, having eliminated switching losses and alleviating the reverse recovery problem of the output diodes. In addition, the voltage stress across the switches is very low. The theoretical analysis and design procedure of the introduced topology are presented. Also, the proposed converter is compared to the latest similar soft switched high step-up converters. The accuracy of the theoretical analysis is validated by a 200-W prototype operating at 100 kHz. [ABSTRACT FROM PUBLISHER]

The asymmetrical modulation strategy is widely used in various types of three-level (TL) dc/dc converters, while the current imbalance among the power switches is one of the important issues. In this paper, a novel periodically swapping modulation (PSM) strategy is proposed for balancing the power switches’ currents in various types of TL dc/dc converters. In the proposed PSM strategy, the driving signals of the switch pairs are swapped periodically, which guarantees that the currents through the power switches are kept balanced in every two switching periods. Therefore, the proposed PSM strategy can effectively improve the reliability of the converter by balancing the power losses and thermal stresses among the power switches. The operation principle and performances of the proposed PSM strategy are analyzed in detail. Finally, the simulation and experimental results are presented to verify the proposed modulation strategy. [ABSTRACT FROM PUBLISHER]

This paper presents a low-power batteryless energy harvesting system for Internet of Things (IoT) applications. A dual-mode dc–dc converter is used to harvest the energy of a microscale photovoltaic (PV) transducer and provides energy, in the boost mode, to a super capacitor for storage. In the buck mode, the dc–dc converter provides energy to the load on demand. A piezoelectric transducer is used as a secondary input source to guarantee system self startup. The proposed system includes a smart control to adaptively adjust the number of sensors at the load, leading to better usage of the available energy at any given time. The implementation also includes a programmable switch sizing to optimize the overall system's efficiency for different load conditions. A maximum power point tracking is used to extract the maximum power of the PV transducer under various illumination conditions. The system has been implemented in a CMOS 130-nm technology and tested in various modes of operation. Self startup has been verified, and a peak efficiency of 90.5% has been measured. [ABSTRACT FROM PUBLISHER]

A resonant zero-voltage and zero-current-switching (ZVZCS) dc–dc converter is proposed in this paper for a medium-voltage dc collection system of offshore wind farms. The resonant converter is composed of two full-bridge cells sharing a bridge leg, two transformers with uneven power ratings and different functions, whose secondary windings are connected in series and a voltage-doubler rectifier. The converter operates in discontinuous current mode and can achieve zero-current switching for four main power switches and rectifier diodes over the whole load range. The two auxiliary switches with small forward current can be turned on with ZVZCS, and turned off with zero-voltage switching. Hence, the switching loss can be reduced and efficiency is improved. The operation principle of the converter is analyzed and design rules of main parameters are presented. The influences of the turn ratios of auxiliary transformer and resonant capacitance on the peak and switching-off currents are discussed in detail. Furthermore, a model is built in PLECS and simulation results are given. A 150–1500 V/2 kW prototype is established and tested to verify the operation principle and design rules. [ABSTRACT FROM PUBLISHER]

Current-fed converters offer enormous potential as power conditioning units for fuel cell applications, owing to precise fuel cell stack current control, short-circuit protection, voltage gain, and stiff fuel cell dc current. Aspects such as low current ripple and smaller input current slope ensure energy efficient operation and better fuel utilization, and enhance the lifetime of the fuel cell stack. However, the demerits of turn-off voltage spike across semiconductor devices limits the operating frequency. This paper proposes, analyzes, and implements a simple and cost-effective impulse commutated modular three-phase circuit to eliminate and solve the associated turn-off spike problem. Impulse commutation permits soft turn-off of devices and clamps the device voltage. The converter efficiently handles the variations in the fuel cell stack voltage and current with variable frequency modulation. Detailed steady-state operation, analysis, and performance of the proposed modular converter with impulse commutation are reported. The proposed impulse commutated three-phase circuit is a potential candidate for high-current applications. The validation of the converter operation on a 1-kW proof-of-concept hardware prototype is performed to substantiate the claims. [ABSTRACT FROM AUTHOR]