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In this paper, a new class of bidirectional partial-resonance power converters is presented. The proposed family can be configured to interface single- or multi-port dc, single- or multi-phase ac systems at input-side and/or output-side. The proposed family offers a very modular structure, which can lead to cost reduction from a common designed module. In this converter, which accomplishes power conversion in a single stage, a small inductor placed in series with the input and output switch-bridges forms the link. This small link inductor is responsible for transferring power between different ports of the system. The proposed topologies can operate in buck, boost, and buck–boost modes of operation to step up and/or step down the voltage. In buck–boost mode of operation, the converter is controlled such that the power is entirely transferred through the link inductor; whereas, in buck or boost modes of operation only a fraction of the power is transferred through the link inductor, and the remaining power is directly transferred from input phases to the output phases. Galvanic isolation, which is typically a prominent factor contributing to power density of a converter, can be provided by means of a compact and lightweight single-phase high-frequency transformer added to the link. In comparison with earlier generations of partial-resonance inductive-link power converters, in the proposed converter, the level of link peak current and consequently power-loss, as well as voltage and current stress of switches are dramatically decreased. A very small film capacitor can be placed in parallel with the link inductor to facilitate zero-voltage-switching (ZVS) operation for all the switches/diodes. Apart from increasing the overall efficiency, minimized dv/dt stress and improvement in power density are achieved by adding the link capacitor. The proposed converter employs four-quadrant switches, i.e., bidirectional-conducting bidirectional-blocking switches, and charges the link inductor in both positive and negative directions in each cycle. In view of this, better utilization of the link inductor and lower total harmonic distortion (THD) are offered. Furthermore, two distinct switching algorithms are developed for the proposed family of converters. In this paper, the detailed behavior of the proposed family is investigated analytically, and simulation and experimental results are presented to evaluate the performance and effectiveness of the proposed converter. A low-power proof-of-concept prototype with input voltage of 59 V/161 V, load voltage of 178 V/73.5 V, maximum switching frequency of 4.9 kHz/3.65 kHz at 215 W/450 W in a step-up/step-down operation is considered for the experimental verification. [ABSTRACT FROM AUTHOR]

In this paper, a new structure for a nonisolated boost dc–dc converter is proposed. The proposed converter generates higher voltage gain than some conventional nonisolated boost dc–dc converters. In this paper, the voltage and current equations of the elements and voltage gain in continuous conduction mode and discontinuous conduction mode are extracted. Then, the critical inductance converter is extracted and the current stresses in the switches are calculated. To achieve high voltage gain, a generalized structure based on the proposed structure generates for dc–dc converters. Meanwhile, the root mean square current relations of devices are obtained for an extended structure. Finally, the results of PSCAD/EMTDC software and laboratory prototype are used to reconfirm theoretical concept. [ABSTRACT FROM AUTHOR]

In this paper, a high step-up quasi-Z Source (QZS) dc–dc converter is proposed. This converter uses a hybrid switched-capacitors switched-inductor method in order to achieve high voltage gains. The proposed converter have resolved the voltage gain limitation of the basic QZS dc–dc converter while keeping its main advantages, such as continuous input current and low voltage stress on capacitors. Compared to the basic converter, the duty cycle is not limited, and the voltage stress on the diodes and switch is not increased. In addition to these features, the proposed converter has a flexible structure, and extra stages could be added to it in order to achieve even higher voltage gains without increasing the voltage stress on devices or limiting the duty cycle. The operation principle of the converter and related relationships and waveforms are presented in the paper. Also, a comprehensive comparison between the proposed and other QZS based dc–dc converters is provided which confirms the superiority of the proposed converter. Simulations are done in power systems computer aided design (PSCAD) in order to investigate the maximum power point tracking (MPPT) capability of the converter. In addition, the valid performance and practicality of the converter are studied through the results obtained from the laboratory built prototype. [ABSTRACT FROM AUTHOR]

An extended-duty-ratio (EDR) boost converter is studied extensively in this paper for high voltage gain applications with a wide input (and/or output) voltage range. The EDR is a unique combination of an interleaved, multiphase boost converter and switched capacitor configuration that achieves high voltage gain with significantly lower switch voltage stress and switching losses compared to conventional high-gain solutions. Most of the switches in the multiphase EDR experience only a fixed fraction of the output voltage ($1/M, 2/M$ , etc., where $M$ is the number of phases). Through extensive analysis over a wide operating range, it is shown here that the EDR boost converter has inherent current sharing among the phases only in a limited range of duty ratio— $(M-1)/M \leq D \leq 1$. As the duty ratio reduces beyond this range as required in wide input voltage applications, inherent current sharing property is lost. In this paper, techniques to ensure current sharing under all operating zones without requiring current sensors are presented. Instead of having equal duty ratio for each phase, it is adjusted for each phase according to the operating region of the converter. Extensive analysis is presented to derive the required duty ratio changes for the different phases. The proposed concept is validated with experimental results from a 250 W, 3-phase EDR boost, and GaN-based hardware prototype. [ABSTRACT FROM AUTHOR]

This paper proposes a family of soft-switching bidirectional converters. In many applications, the bidirectional converters operate over a wide range of duty cycle and load variations. In the proposed converters, in order to extend the zero-voltage switching operation range, two supplemental voltage sources utilizing passive components are implemented in the auxiliary circuit. By using this method, the soft-switching features are ensured for an extensive range of the converter duty cycles. This is achieved independent of the output power value or the converter operation mode, and so, soft switching is ensured within the entire converter operating region. In these converters, all semiconductors components are soft switched, and the auxiliary circuit does not contribute to the complexity of the control circuit. Also, no extra voltage stress exists on the main switches and the voltage stress on the auxiliary switches is lower than the main switches voltage stress. In this paper, the proposed bidirectional buck/boost converter is analyzed and to confirm the feasibility of the proposed method, experimental results of a 150-W prototype converter are presented. [ABSTRACT FROM PUBLISHER]

This paper introduces a novel five-level nested neutral point piloted (NNPP) converter and analyzes the operating principle of five-level NNPP converter. This paper presents a novel space vector pulse width modulation (SVPWM) algorithm based on gh coordinate for five-level NNPP converter. First, the common-mode voltage is reduced by choosing the appropriate redundant switching states. After that, the floating-capacitor voltage balance control strategy is presented. The appropriate switch combinations of each phase are determined by the control requirements of floating-capacitor voltages respectively and the hardware mapping method of the switching states is presented. Furthermore, the neutral-point voltage balance control strategy is presented. In order to balance the dc-link capacitor voltages, the seven-segment switching sequence is selected according to the control requirements of dc-link capacitor voltages and the neutral-point voltage regulatory factor is introduced to regulate the durations of the redundant switching states in a switching cycle. Finally, the validity of the novel SVPWM algorithm with decoupling control strategies of floating-capacitor voltages and dc-link capacitor voltages is verified by the experimental results of five-level NNPP converter under steady-state and dynamic conditions. [ABSTRACT FROM AUTHOR]

A novel high step-down dc–dc converter with voltage demultiplier cell is proposed in this paper, which is widely used in the high step-down applications such as electric vehicle and digital circuits. The combination of switched-capacitor and coupled-inductor is employed to build extended voltage demultiplier in the proposed converter, which makes a quite higher voltage conversion ratio than that of the existing counterparts. Thus, the proposed converter can achieve extremely low output voltage with an appropriate duty ratio, and the extreme duty cycle is avoided. Accordingly, voltage stress on power switches is greatly reduced. Then, mosfets with low conduction resistance could be utilized to reduce conduction loss. Importantly, zero-voltage switching could be achieved for the main switch, which promotes the conversion efficiency further. In addition, the coupled inductor operates not only as a filter inductor, but also as a transformer when the main switch is in the off state, which reduces the volume of the magnetic core and improves the power density of the converter. The operation principle, performance analysis, design considerations of the proposed converter and performance comparison with recent counterparts are discussed in detail, and finally, an experimental prototype is built to verify the theoretical analysis and performance of the proposed converter. [ABSTRACT FROM AUTHOR]

A family of bidirectional switched-capacitor (SC) converters with high-gain ratio of any positive integer is proposed in this paper for distributed energy resources applications. As compared with other existing SC converters achieving a same conversion gain, the main advantages of the proposed converters are that they require a relatively lower number of switches and capacitors, have a relatively lower switch's and capacitor's stress, and that their associated driver circuits are simpler to realize. Importantly, with the achievable conversion ratio being flexible and that the input and output of the proposed converters are of common ground, the proposed converters are widely suitable for many applications. Moreover, as the proposed converters do not possess magnetic component or any component that can severely degrade the converters’ performance at high temperature, they are especially useful for high-temperature applications. Besides, the proposed converters are capable of delivering bidirectional power, which is a key requirement for emerging applications with battery storages. Different aspects of the proposed converters, including a simple auxiliary power supply circuit for the MOSFETs’ drivers, will be discussed in this paper. A nine-time SC converter prototype that operates with 20-V input voltage, 100-W output, and at 75 kHz, is constructed and tested. Experiment results show that the maximum efficiency achievable with this prototype is over 98% (without driver's loss) and the efficiency over the entire load range between 25 and 100 W is over 95.5% including the driver's loss. The output voltage ripple of the SC converter is less than 1%. When the SC converter is open-loop controlled, the load voltage regulation is relatively well kept at less than 5% between full load and no load conditions. [ABSTRACT FROM PUBLISHER]

This paper proposes a high-frequency isolated dc/dc converter, whose switching frequency is 20 MHz. Meanwhile, the switch voltage stress is reduced based on optimal switch impedance. In the proposed converter, the switch can operate in ZVS condition, which can help to reduce the switching loss. A mathematical model of the proposed high frequency converter is built, which provides an effective design method for the system parameters. Meanwhile, the design method for PCB air-core transformer has been proposed and depicted. To verify the feasibility of the proposed converter and mathematic model, a 10 W prototype is built. [ABSTRACT FROM AUTHOR]

In this paper, a new multi-input multi-output (MIMO) dc–dc converter with high step-up capability is proposed for wide power ranges. Also, in order to increase each output voltage, diode–capacitor voltage multiplier (VM) stages are utilized in the proposed converter. The number of input stages, output stages, and VM stages are arbitrary and dependent on design conditions. At first, the general structure of proposed MIMO converter is presented. Then, in order to explain the converter operation, we walk through the design of a 1-kW four-input two-output example, including loss and efficiency calculations. We validate the design with a prototype that matches efficiency calculations. [ABSTRACT FROM AUTHOR]

This paper presents a new reconfiguration module for asymmetrical multilevel inverters in which the capacitors are used as the dc links to create the levels for staircase waveforms. This configuration of the multilevel converter makes a reduction in dc sources. On the other hand, it is possible to generate 13 levels with lower dc sources. The proposed module of the multilevel inverter generates 13 levels with two unequal dc sources (2VDC and 1VDC). It also involves two chargeable capacitors and 14 semiconductor switches. The capacitors are self-charging without any extra circuit. The lower number of components makes it desirable to be used in wide range of applications. The module is schematized as two back-to-back T-type inverters and some other switches around it. Also, it can be connected as a cascade modular which leads to a modular topology with more voltage levels at higher voltages. The proposed module makes the inherent creation of the negative voltage levels without any additional circuit (such as H-bridge circuit). Nearest level control switching modulation scheme is applied to achieve high-quality sinusoidal output voltage. Simulations are executed in MATLAB/Simulink and a prototype is implemented in the power electronics laboratory in which the simulation and experimental results show a good performance. [ABSTRACT FROM AUTHOR]

The interleaved bidirectional buck–boost converter dual active half-bridge (IBBC-DAHB) dc–dc converter consists of two converters IBBC and DAHB and a coupled inductor. The IBBC-DAHB converter has significant features such as low ripple current at the low-voltage side, low current stress on the input inductors, voltage stress across the switches less than the high-voltage side, high voltage gain, and zero-voltage soft switching. The converter offers high efficiency using phase-shift modulation when it operates at a nominal design operating point. However, the efficiency decreases due to high circulating current, high current stress, and limited soft-switching range when the source and load voltages deviate from their nominal values. This paper employs both duty cycle and phase-shift modulation methods to improve the above mentioned shortcomings using voltage matching for the DAHB converter. The proposed converter is analyzed and a 500-W experimental prototype with 40–60 V input voltage and 400 V output voltage under 100 kHz switching frequency is implemented to verify the theoretical results. The maximum efficiency of 97.15% is achieved at 60 V and 400 W. A flat efficiency characteristic for the converter is derived by the proposed control method, where the efficiency at 20% of nominal load is 91% and much higher than the phase-shift control, which is 70.8%. [ABSTRACT FROM AUTHOR]

A high-performance impedance-source converter utilizing switched inductor is proposed in this paper, which can be adopted in the applications demanding high-voltage conversion. The proposed converter not only retains the advantage of quasi-Z-source of sharing common ground between the input and output but also possesses the superiorities of enhanced boost ability and lower stresses as well as higher efficiency. Mathematical analysis of the converter and its performance comparison with other converters are presented in detail. Finally, a 100 W prototype is built and the experimental results are provided to verify the feasibility of the proposed converter. [ABSTRACT FROM AUTHOR]

A high step-up DC–DC converter with active switched LC-network is proposed in this paper, which can be used in the photovoltaic system as the front-end stage to generate the required DC bus voltage. Based on the transformerless DC–DC converter with an active switched inductor (ASL) network, this proposed converter introduces an active switched capacitor (ASC) network, where only one capacitor and one diode are added, while the voltage gain is efficiently increased by a compound of ASL and ASC networks. The structure of the proposed converter is simple and voltage stresses on the additional diode and capacitor are low. In addition, unlike other voltage-boosting structures that utilized switched capacitor, the proposed converter avoids the extreme instantaneous currents of capacitor. The detailed analysis of the proposed converter and performance comparison with recently published ASL network-based converters are presented. Finally, a 100 W, 20/200 V prototype circuit is operated to verify its performance. [ABSTRACT FROM AUTHOR]

A dual-input high step-up DC/DC converter with zero voltage turn-off (ZVT) auxiliary circuit is presented in this paper. The cost of whole photovoltaic (PV) power could be decreased significantly by the proposed converter because it allows two PV panels to be connected at the same time. ZVT auxiliary circuit provides soft switching in a wide range of load variations with six passive components. Turn-off switching losses could be decreased and the efficiency of the whole converter could be improved. In , the operation principle and performance characteristics of the proposed converter have been analyzed and an 800 W experimental prototype has been built to validate the analytical results in. In , a dual-input maximum power point tracking (DMPPT) control algorithm has been designed for the proposed converter. Experimental results show that two PV panels can achieve the maximum power output state separately by the proposed DMPPT control algorithm. [ABSTRACT FROM AUTHOR]

This paper proposes a circuit structure that can improve the power-conversion efficiency \eta e of an AC–DC boost converter. The circuit uses a 1:1 transformer and a voltage boost circuit composed of an inductor, a capacitor, and a diode. The transformer forces the converter to operate in continuous conduction mode for input current, and thereby reduces input ripple. The voltage boost circuit enables the switch to operate in critical conduction mode, so the power loss due to turn-on of switch and reverse recovery of diode is minimized. The proposed converter has high \eta e over a wide range of AC input voltage $V_{{\rm{ac}}}:\,\eta _{e}= 92.9\% $ at $V_{{\rm{ac}}}= {\text{85}}\,{\text{V}} and \eta e= 97.4\% at V{\rm{ac}}= {\text{265}}\,{\text{V}}, when the converter was operated at DC output voltage of 400 V and output power of 500 W. The temperature of the switch stabilized at ∼84 °C for $V_{{\rm{ac}}}= {\text{85}}\,{\text{V}}$ , at ∼70 °C for $V_{{\rm{ac}}}= {\text{110}}\,{\text{V}}$, and at ∼42 °C for $V_{{\rm{ac}}}= {\text{220}}\,{\text{V}}$, whereas that in other AC–DC converters either failed or stabilized at much higher levels. The proposed converter is well suited to systems that require an input voltage range of 85–265 V in root-mean-square value. [ABSTRACT FROM AUTHOR]

A novel high step-up converter, which is suitable for a renewable energy system, is proposed in this paper. The proposed converter is composed of the dual switches structure, three-winding coupled inductor, and two voltage multiplier cells in order to achieve the high step-up voltage gain. The dual switches structure is beneficial to reduce the voltage stress and current stress of the switch. In addition, two multiplier capacitors are, respectively, charged during the switch-on period and switch-off period, which increases the voltage conversion gain. Meanwhile, the energy stored in the leakage inductor is recycled with the use of clamped capacitors. Thus, two main power switches with low on-resistance and low current stress are available. As the leakage inductor, diode reverse-recovery problem is also alleviated. Therefore, the efficiency is improved. This paper illustrates the operation principle of the proposed converter; discusses the effect of the leakage inductor; analyzes the influence of parasitic parameters on the voltage gain and efficiency, the voltage stresses and current stresses of power devices are shown; and a comparison between the performance of the proposed converter and the previous high step-up converters is performed. Finally, the prototype circuit with input voltage 20 V, output voltage 200 V, and rated power 200 W is operated to verify its performance. [ABSTRACT FROM AUTHOR]

In this paper, we introduced an improved transformer-based parallel-resonant converter, suitable for high voltage, high power dc loads. The resonant capacitors are connected in parallel with diodes of the high voltage rectifier, thus restraining dv/dt stress in high voltage circuits. The LC tank resonant frequency is well beyond the switching frequency, reducing in this way the VA rating of LC components. With rated load, the output current of the IGBT bridge is equal to zero at switching instants, and the switching losses are very low. Proposed subresonant circuit requires lower primary current for the given output power and it has reduced IGBT losses. Experimental setup delivers 79 kW with an efficiency of 96.78%. The paper explains the switching states of the devised topology, and provides the guidelines for designing the power transformer, the LC tank and controls. Analytical prediction of the performance curves is verified both in laboratory and by the field tests with an electrostatic precipitator plant. [ABSTRACT FROM AUTHOR]

This paper proposes an interleaved buck converter (IBC) with continuous input current, extremely low output current ripple, low switching losses, and improved step-down conversion ratio. Unlike the conventional IBC, the proposed converter has a continuous input current, and its output current ripple is extremely low. The proposed converter has a lower voltage stress in comparison to the conventional IBC and can also provide a high step-down ratio, which makes it a proper choice for high-power applications where a nonisolated step-down converter with low output current ripple and continuous input current is required. Also, the proposed converter can provide current sharing between two interleaved modules without using additional current-sharing control method. All of these benefits are obtained without any additional stress on the circuit components. A prototype converter with 200-V input and 24-V–10-A output is implemented to verify the theoretical analysis. Operational principles and experimental results are presented in this paper. [ABSTRACT FROM PUBLISHER]

A single-phase bridgeless Cuk ac/dc power factor correction (PFC) rectifier with positive output voltage is proposed in this paper. For low output voltage product applications, the rectifier is designed to convert high input voltage to low output voltage. Due to no bridge diodes required and thus decreased input conduction losses, the proposed rectifier efficiency can be improved. The proposed rectifier operates in discontinuous conduction mode, and the current-loop circuit is hence not needed. In addition, only a single switch is used in the rectifier to simplify the control circuit design. A simple translation method to have the positive output voltage in the Cuk converter is presented in the rectifier to reduce the component counts and the cost. The operational principles, steady-state analysis, and design procedure of the proposed rectifier are addressed in detail in this paper. Simulation and experimental results obtained from a 150-W rated prototype circuit with input of 90–130 Vrms, 60 Hz, and output of 48 Vdc have verified the validity of the proposed rectifier. [ABSTRACT FROM PUBLISHER]

In this paper, a new negative output (N/O) buck–boost converter, which can be applied for applications that need wide range of inverse voltage, is proposed. The steady-state, small-signal model and power losses of the proposed converter operating in a continuous conduction mode are analyzed. Comparisons among the traditional buck–boost converter, N/O hybrid buck–boost converter and N/O self-lift Luo converter are presented, and it is found that the proposed converter possesses a widest voltage conversion ratio in these four converters. Finally, a prototype is built, and the simulated waveforms from the PSIM software and the experimental results are presented for validation. [ABSTRACT FROM AUTHOR]

This paper proposes a novel high step-up nonisolated single switch dc–dc converter suitable for regulating dc bus in various microsources especially for photovoltaic (PV) sources. Quadratic boost and switched-capacitor technique are used as primary and secondary circuits, respectively. A coupled inductor is applied to make a connection between them, so a high dc voltage gain is achieved. High efficiency is yield where voltage stress on active switch is alleviated by clamped capacitor; consequently, smaller \rmR\rm{DS(ON)} for power switch is required. On the other hand, input current of the proposed converter is continued, hence stress on the input source is reduced. The operating principles and steady-state analyses are discussed in detail for both continuous and discontinuous conduction modes. Also, the boundary condition is computed. To verify the performance of the proposed converter and theoretical calculations, a 250-W prototype converter is implemented with an input voltage of 24 V and an output voltage of 400 V designed especially for PV sources in continuous conduction mode operation. Finally, simulation results are confirmed by experimental results; maximum efficiency is occurred at 150 W and full-load efficiency is 92.96%. [ABSTRACT FROM AUTHOR]

In this paper, a novel four-phase interleaved high step-down converter is presented. The proposed converter can provide an extremely high step-down voltage conversion ratio within a moderate duty cycle. There are four main advantages of the proposed converter. First, the blocking capacitors can store energy as usual. Therefore, they are used as voltage sources to reduce the input voltage as well as to reduce the switch voltage stresses. Second, due to the charge balance of the dc blocking capacitors, the converter possesses an automatic uniform current sharing characteristic of the interleaved phases without adopting any extra circuitry. Third, due to the phase shift between the interleaved phases, the architecture provides a low output current ripple. Fourth, the number of phases can be expanded or reduced to any even phases; therefore, the converter has a wide range of applications. Finally, the operating principles and analysis of this architecture are given, and an experimental prototype is also provided to verify the effectiveness of the proposed converter. [ABSTRACT FROM PUBLISHER]

A new resonant converter having low voltage stress and nearly constant efficiency against line variation for high- and wide-input-voltage applications is presented in this paper. It is similar to a three-level zero-voltage-switching pulsewidth modulation converter (TL ZVS PWMC) with two flying capacitors. In the proposed converter, however, two flying capacitors are used as the resonant capacitors, and the output voltage regulation is achieved by frequency modulation. The main advantages of the proposed converter are that, since the sum of the voltages of two resonant capacitors is constant and is equal to half of the input voltage, the voltage across each switch clamps to half of the input voltage and keeps the balance. Moreover, all main switches and rectifier diodes are softly switched under full-line and full-load conditions, and high efficiency can be constantly achieved over a wide input voltage range. These advantages solve the drawbacks on TL ZVS PWMCs. The features, operation principles, and relevant analysis results over a wide input voltage range of the proposed converter are presented in this paper. The validity of this study is confirmed by the experimental results of a prototype converter with 400–600-V input, 48-V/10-A output, and 200-kHz resonant frequency. The experimental results show that the maximum efficiency of the proposed converter is 95.08% under a full-load and a 600-V input and slightly varies across the 400–600-V input voltage range. [ABSTRACT FROM AUTHOR]

First, the limitations of the conventional interleaved boost converters in high-step-up and high-output-voltage applications are addressed in this paper. Then, a general derivation law of the nonisolated converters from their isolated counterparts is proposed and studied to give a universal solution for high-performance topology deduction. By employing the direct energy transfer concept, a family of nonisolated high-step-up interleaved boost converters is originated to make the turns ratio of a built-in transformer as another design freedom for the voltage gain extension. The derived converters have the advantages of large voltage conversion ratio, low power switch voltage stress, small input current ripple, and zero-voltage-switching soft-switching performance. The steady-state operation of the derived converter is analyzed, and the circuit performance is summarized to explore its advantages in the high-step-up, high-output-voltage, and large-current conversion systems. Finally, a 1-kW prototype with 40-V input and 380-V output voltages is implemented and tested to show the effectiveness of the derived converters. One of the main contributions of this paper is that a clear picture is made on the universal derivation law to generate high-step-up and high-performance dc/dc converters. [ABSTRACT FROM PUBLISHER]

This paper proposes a three-phase, reduced-switch, buck-type converter that can operate with input-power-factor correction. The key feature of the proposed converter is that a switch in the converter has a lower peak voltage stress than a switch in a conventional three-phase, single-switch buck converter. The voltage stress in the proposed converter is limited to the peak value of the phase voltage of the input capacitors rather than the peak value of the line-to-line voltage, as is the case in the conventional converter. The reduction in the voltage stresses is therefore almost half as compared to that of conventional converter. This allows lower rated, standard devices to be used in the converters and reduces switching losses. In this paper, the steady-state operation of the converter is presented and general properties and design considerations are discussed. The feasibility of the proposed converter is confirmed with results obtained from an experimental prototype. [ABSTRACT FROM PUBLISHER]

Switched-capacitor (SC) converters were initially introduced for low-power applications and monolithic integration. In recent years, SC converter has found high-power applications. However, voltage regulation remains an issue. This paper addresses regulation challenges for high-power SC converters, based on charge-balance transient-calculation (CT) modeling method and peak current stress estimation. With the help of CT model, due to its accuracy and comprehensive relationship, circuit and control parameters’ impacts on regulation become straightforward and concerns on components stresses can be addressed quantitatively. The suitability of CT method for regulation analysis is confirmed by comparison with traditional modeling methods. The CT method is used in a 1-kW 3X two-switch boosting switched-capacitor converter (TBSC) circuit for steady-state analysis and current stress estimation. The soft rising input current and nature interleaving properties of 3X TBSC make it well suited for high-power application. Finally, the small-signal model of the 3X TBSC is developed and a closed-loop operation is achieved under 1 kW power rating. [ABSTRACT FROM AUTHOR]

An advanced hybrid LLC series resonant converter with integrated flying-capacitor cell is proposed in this paper to enable the high step-down conversion in the high input voltage applications. The inherent flying-capacitor branch in the primary side can effectively halve the primary switch voltage stress compared with the half-bridge LLC converters. And the input voltage can be shared equally and automatically between the two series half-bridge modules without additional balance circuit or control strategies due to the built-in flying-capacitor cell. Moreover, the inherent soft switching performance during wide load range that exists in the LLC converters is still kept to reduce the switching losses, which ensures the high efficiency. Besides, the proposed converter can be extended to further decrease the switch voltage stress by employing stacked connection. Finally, a 500 ∼ 640 V-input 48 V-output 1 kW prototype is built and tested to verify the effectiveness of the proposed converter. The results prove that the proposed converter is an excellent candidate for the high input voltage and high step-down dc/dc conversion systems. [ABSTRACT FROM PUBLISHER]

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]

In this paper, we propose a novel transformer-less direct current (dc) converter that features low switch voltage stress and automatic uniform current sharing. An interleaved four-phase voltage divider operating from a 400 V dc bus is used to achieve a high step-down conversion ratio with a moderate duty ratio. Based on the capacitive voltage division, the proposed converter achieves two major objectives, i.e., increased voltage conversion ratio, due to energy storage in the blocking capacitors, and reduced voltage stress of active switches and diodes. As a result, the proposed converter permits the use of lower voltage rating MOSFETs to reduce both switching and conduction losses, thereby improving the overall efficiency. In addition, due to the charge balance of the capacitors, the proposed converter enables automatic uniform current sharing of the interleaved phases without adding extra circuitry or complex control methods. The operation principles and performance analyses of the proposed converter are presented, and its effectiveness is verified by a 500 W output power prototype circuit that converts 400 V input voltage into 24 V output voltage. [ABSTRACT FROM AUTHOR]

A family of “Two-Switch Boosting Switched-Capacitor Converters (TBSC)” is introduced, which distinguishes itself from the prior arts by symmetrically interleaved operation, reduced output ripple, low yet even voltage stress on components, and systematic expandability. Along with the topologies, a modeling method is formulated, which provokes the converter regulation method through duty cycle and frequency adjustment. In addition, the paper also provides guidance for circuit components and parameter selection. A 1-kW 3X TBSC was built to demonstrate the converter feasibility, regulation capability via duty cycle and frequency, which achieved a peak efficiency of 97.5% at the rated power. [ABSTRACT FROM AUTHOR]

Conventional dual-active bridge topologies provide galvanic isolation and soft-switching over a reasonable operating range without dedicated resonant circuits. However, scaling the two-level dual-active bridge to higher dc voltage levels is impeded by several challenges among which the high dv/dt stress on the coupling transformer insulation. Gating and thermal characteristics of series switch arrays add to the limitations. To avoid the use of standard bulky modular multilevel bridges, this paper analyzes an alternative modulation technique, where staircase approximated trapezoidal voltage waveforms are produced; thus, alleviating developed dv/dt stresses. Modular design is realized by the utilization of half-bridge chopper cells. This way the analyzed dc-dc transformer employs modular multilevel converters operated in a new mode with minimal common-mode arm currents, as well as reduced capacitor size, hence reduced cell footprint. Suitable switching patterns are developed and various design and operation aspects are studied. Soft-switching characteristics will be shown to be comparable to those of the two-level dual-active bridge. Experimental results from a scaled test rig validate the presented concept. [ABSTRACT FROM AUTHOR]

This paper proposes novel multilevel ac/dc/ac converters with reduced number of semiconductor devices to achieve light weight, efficiency, and better input current quality. The proposed three-phase front-end bidirectional five-level (5L) rectifier and rear-end 5L inverter are constructed based on multiple-pole multilevel diode-clamped (M2DCC) approach, which consist a total number of 24 diode components clamped. Based on the M2DCC concept, the number of switching devices can be further reduced to construct a new unidirectional front-end rectifier (M2SCR). Comparative studies are conducted to analyze the performances of the two proposed front-end rectifiers with supportive mathematical derivations. Experimental prototypes have proven the feasibility of the proposed ac/dc/ac configurations. Results obtained show that low current harmonic distortions of 5% and high power factor of 0.99 are achieved with small input inductors despite low-switching-frequency operation at 1 kHz. [ABSTRACT FROM PUBLISHER]

High voltage gain dc-dc converters are required in many industrial applications such as photovoltaic and fuel cell energy systems, high-intensity discharge lamp (HID), dc back-up energy systems, and electric vehicles. This paper presents a novel input-parallel output-series boost converter with dual coupled inductors and a voltage multiplier module. On the one hand, the primary windings of two coupled inductors are connected in parallel to share the input current and reduce the current ripple at the input. On the other hand, the proposed converter inherits the merits of interleaved series-connected output capacitors for high voltage gain, low output voltage ripple, and low switch voltage stress. Moreover, the secondary sides of two coupled inductors are connected in series to a regenerative capacitor by a diode for extending the voltage gain and balancing the primary-parallel currents. In addition, the active switches are turned on at zero current and the reverse recovery problem of diodes is alleviated by reasonable leakage inductances of the coupled inductors. Besides, the energy of leakage inductances can be recycled. A prototype circuit rated 500-W output power is implemented in the laboratory, and the experimental results shows satisfactory agreement with the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper presents a high step-up converter for fuel cell energy source applications. The proposed high step-up dc-dc converter is devised for boosting the voltage generated from fuel cell to be a 400-V dc-bus voltage. Through the three-winding coupled inductor and voltage doubler circuit, the proposed converter achieve high step-up voltage gain without large duty cycle. The passive lossless clamped technology not only recycles leakage energy to improve efficiency but also alleviates large voltage spike to limit the voltage stress. Finally, the fuel cell as input voltage source 60-90 V integrated into a 2-kW prototype converter was implemented for performance verification. Under output voltage 400-V operation, the highest efficiency is up to 96.81%, and the full-load efficiency is 91.32%. [ABSTRACT FROM AUTHOR]

This paper proposes a novel wide-range soft-switching pulse-width modulation three-level (TL) combined dc-dc converter characterized with no added primary clamping devices and reduced output inductance value. It is well suited for high input voltage dc-dc industrial applications due to following desirable features: all the switches sustain half of the input voltage; off state voltage of the switches is directly clamped by the bulky input capacitors, and no added primary clamping devices such as clamping diodes, flying capacitors, are required; TL waveform before output filter can be achieved, which significantly reduces the value of the output inductance; the modified phase-shift control method can be utilized to achieve wide output range. The converter can obtain zero-voltage switching (ZVS) for all power switches in wide load range; furthermore, less conduction loss is added to achieve ZVS. The operation and theoretical analysis of the proposed converter are presented. Experiments are carried out to validate the proposed converter, and efficiency curves are tested and given. [ABSTRACT FROM AUTHOR]

In this paper, a novel transformer-less adjustable voltage quadrupler dc-dc converter with high-voltage transfer gain and reduced semiconductor voltage stress is proposed. The proposed topology utilizes input-parallel output-series configuration for providing a much higher voltage gain without adopting an extreme large duty cycle. The proposed converter cannot only achieve high step-up voltage gain with reduced component count but also reduce the voltage stress of both active switches and diodes. This will allow one to choose lower voltage rating MOSFETs and diodes to reduce both switching and conduction losses. In addition, due to the charge balance of the blocking capacitor, the converter features automatic uniform current sharing characteristic of the two interleaved phases for voltage boosting mode without adding extra circuitry or complex control methods. The operation principle and steady analysis as well as a comparison with other recent existing high step-up topologies are presented. Finally, some simulation and experimental results are also presented to demonstrate the effectiveness of the proposed converter. [ABSTRACT FROM AUTHOR]

Fuel cell stacks and photovoltaic panels generate rather low dc voltages and these voltages need to be boosted before converted to ac voltage. Therefore, high step-up ratio dc-dc converters are preferred in renewable energy systems. A new Z-source-based topology that can boost the input voltage to desired levels with low duty ratios is proposed in this paper. The topology utilizes coupled inductor. The leakage inductance energy can efficiently be discharged. Since the device stresses are low in this topology, low-voltage MOSFETs with small RDS(on) values can be selected to reduce the conduction loss. These features improve the converter efficiency. Also, the converter has a galvanic isolation between source and load. The operating principles and steady-state analysis of continuous and discontinuous conduction modes are discussed in detail. Finally, experimental results are given for a prototype converter that converts 25 V dc to 400 V dc at various power levels with over 90% efficiency to verify the effectiveness of the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper presents a new three-level zero-voltage switching (ZVS) dc/dc converter for high input voltage applications. There are two ZVS circuits in the proposed converter to share load current. Thus, the size of the output chokes is reduced. These two circuits use the same power switches. Thus, the proposed converter has less switch counts compared with the conventional parallel three-level ZVS dc/dc converter. In the proposed converter, each circuit combines one half-bridge converter and one three-level converter. The transformer secondary windings of two converters are connected in series to reduce the size of output inductor. The voltage stress of each power switch is limited at one-half of input voltage due to three-level circuit topology. Based on the resonant behavior by the output capacitance of active switches and the leakage inductance (or external inductance) at the transition interval, power switches are turned on at ZVS within the desired load range. Experiments based on a 1.5 kW prototype are provided to demonstrate the performance of the proposed converter. [ABSTRACT FROM AUTHOR]

In this paper, a number of alternate-cascaded switched-inductor and tapped-inductor networks have been proposed for Z-source inverters. The resulting topologies have enhanced voltage-boost capability while retaining the usual voltage-buck flexibility of a conventional voltage-source inverter. The enhanced capability is achieved by using lower rated components that can more readily be found. These components are assembled without direct series connection and hence avoid unbalanced voltage sharing problems and losses linked to balancing resistive circuits. The component count is, however, high, meaning that the proposed inverters should only be considered when a design requires multiple lower rated components rather than a few higher rated ones. Analysis, simulation, and experimental results have already validated the concepts discussed. [ABSTRACT FROM PUBLISHER]

In this paper, an isolated series asymmetrical half-bridge converter (SA-HBC) is proposed to satisfy the high power and high input-voltage requirements. In the proposed converter, two half-bridge modules with series configuration are adopted in the primary side to reduce the switch voltage stress to half of the input voltage. Moreover, the series half-bridge cells share the same transformer and leakage inductance, which simplifies the circuit structure. Zero-voltage-switching transition is achieved for all the active switches by employing the asymmetrical control scheme to reduce the switching losses. Furthermore, the voltages of the input capacitors are automatically balanced without any additional components or complex control methods. In addition, a family of dc–dc converters with series half-bridge structure is explored to give a universal discussion and extensive applications of the proposed contributions for the high input-voltage systems. Finally, a 500–600-V input 48-V output 1-kW prototype operating with 100 kHz switching frequency is built and tested to demonstrate the effectiveness of the proposed SA-HBC converter. The efficiency of 95% at full load is realized. [ABSTRACT FROM AUTHOR]

This paper discusses the major issues that exist in the single-stage ac/dc converters with power factor correction (PFC) and presents a novel converter based on a quasi-active PFC scheme. Two additional windings wound in the transformer of a conventional dc/dc flyback converter are used to drive and achieve continuous current mode operation of an input inductor. In addition, direct energy transfer paths are provided through the additional windings to improve the conversion efficiency and to reduce the dc bus capacitor voltage below 450 V for universal line applications. The proposed converter can be easily designed to comply with IEC 61000-3-2 Class D requirement and to achieve fast output voltage regulation. By properly tuning the converter parameters, a good tradeoff between efficiency, dc bus capacitor voltage stress, and harmonic content can be achieved. Operating principles, analysis, and experimental results of the proposed method are presented. [ABSTRACT FROM PUBLISHER]

A novel high step-up dc-dc converter with coupled-inductor and switched-capacitor techniques is proposed in this paper. The capacitors are charged in parallel and are discharged in series by the coupled inductor, stacking on the output capacitor. Thus, the proposed converter can achieve high step-up voltage gain with appropriate duty ratio. Besides, the voltage spike on the main switch can be clamped. Therefore, low on-state resistance RDS(ON) of the main switch can be adopted to reduce the conduction loss. The efficiency can be improved. The operating principle and steady-state analyses are discussed in detail. Finally, a prototype circuit with 24-V input voltage, 400-V output voltage, and 200-W output power is implemented in the laboratory. Experiment results confirm the analysis and advantages of the proposed converter. [ABSTRACT FROM PUBLISHER]

This paper proposes a new high step-up dc–dc converter designed especially for regulating the dc interface between various microsources and a dc–ac inverter to electricity grid. The figuration of the proposed converter is a quadratic boost converter with the coupled inductor in the second boost converter. The converter achieves high step-up voltage gain with appropriate duty ratio and low voltage stress on the power switch. Additionally, the energy stored in the leakage inductor of the coupled inductor can be recycled to the output capacitor. The operating principles and steady-state analyses of continuous-conduction mode and boundary-conduction mode are discussed in detail. To verify the performance of the proposed converter, a 280-W prototype sample is implemented with an input voltage range of 20–40 V and an output voltage of up to 400 V. The upmost efficiency of 93.3% is reached with high-line input; on the other hand, the full-load efficiency remains at 89.3% during low-line input. [ABSTRACT FROM AUTHOR]