Search

This article proposes a new single switch trans-inverse high step-up converter applicable in sustainable sources of energies such as photovoltaic (PV) and fuel cell (FC). Through developing a single-ended primary-inductor converter by a three-winding built-in transformer (BIT) mixed with a switched-capacitor voltage multiplier cell, high voltage gains as well as low voltage stress across the mosfet can be achieved to reduce the required duty cycle and the conduction losses. The third winding of the BIT acts in a trans-inverse manner whose turns ratio should be lower than unity. Hence, with a lower number of windings the voltage gain can also be improved. Furthermore, the quasi-resonance operation of the proposed converter, reduces the associated switching losses of the mosfet and also guarantees zero current switching of diodes through the whole switching cycle. Meanwhile, low input current of the proposed converter serves as an interesting feature to maintain PV and FC lifetime. The detailed steady-state analysis of the proposed high-efficiency converter is presented with an extensive performance comparison to explore its advantages. Finally, a 200-W prototype with 20–250-V voltage conversion is developed in the laboratory to examine the carried steady-state analysis. [ABSTRACT FROM AUTHOR]

In this article, a new high step-up transformerless dc–dc converter based on a voltage multiplier and a coupled inductor topology is presented. The proposed converter has two stages. In the first stage, a modified boost converter is designed by the coupled inductor, and in the second stage, a new voltage multiplier by using a coupled inductor is illustrated. In this converter, high voltage gain can be achieved by adjusting the turn ratio of two coupled inductors and the duty cycle, which result in three degrees of design freedom. Using a single power switch with low on-resistance in the converter structure leads to simple control and low conduction loss. In addition, total voltage stresses of active elements are decreased, which increases efficiency. Steady-state performance and theoretical achievements are confirmed by experimental test results on a test setup with one 200-W dc–dc prototype. [ABSTRACT FROM AUTHOR]

In this article, a new triple-switch triple-mode (TS-TM) high step-up dc–dc converter is proposed. The proposed converter consists of three switches, four diodes, two magnetically coupled inductors, and three capacitors. This converter can provide a high voltage conversion ratio with high power efficiency and low voltage stress across the power semiconductor components. Due to the low voltage stresses of the power semiconductors and implementing the coupled inductors technique, the proposed converter is a low-cost and high-efficient structure in comparison to the other similar TS-TM structures. In order to clarify the advantages of the proposed converter, the required mathematical calculations and comparison results with similar converters are presented. Also, a novel TS-TM with transformer is proposed to overcome the electromagnetic interface problems. Furthermore, a 500 W experimental prototype is built and its performance with different values of duty cycles is tested to prove the claimed features of the proposed converter. A total of 94.5% maximum power efficiency of the assembled prototype has been obtained at 260 W output power. [ABSTRACT FROM AUTHOR]

This article proposes a novel single-source high step-up asymmetrical multilevel inverter (MLI) topology based on Marx generator configuration with voltage multiplying capability. The operating principles of the proposed converter (which is named Marxiplier) are completely different from the MLIs presented in the literature. Proposed converter uses a low-voltage dc source with high-frequency inverter (low-voltage ac input) and charges a series of capacitors multiple times of input voltage. These capacitors which work as asymmetrical sources can generate a high-amplitude ac output voltage with high number of levels. Another important aspect of this converter is producing negative levels in the output voltage without using a high-voltage full-bridge inverter and reducing the number of the components. MATLAB simulations and a laboratory test results of a 21-level prototype are employed in order to verify the proposed converter operation. [ABSTRACT FROM AUTHOR]

In this article, an interleaved high-voltage gain dc–dc converter is proposed for use with photovoltaic (PV) systems. By integrating two three-winding coupled inductors (CIs) with switched capacitor cells, the voltage gain is further extended. Through passive diode-capacitor clamp circuits, the energy stored in the leakage inductances is absorbed; additionally, the voltage stress of the power switches is clamped to a value far lower than the output voltage, which enables designers to select switches with low-voltage ratings. Due to the interleaved structure of the proposed converter, the input current has a small ripple, which leads to the increased lifespan of the PV panels. In addition, the current stress on the components is reduced. Thanks to the leakage inductances of the CIs, the zero-current switching condition is intrinsically provided for the diodes; accordingly, the adverse impact of the diodes’ reverse-recovery is alleviated. The operating principles, steady-state analyses, and design considerations of the proposed converter are presented in this article. A comparison with other similar converters is carried out to verify the merits of the proposed converter. Finally, the theoretical analyses are confirmed through the experimental results of a 400-W prototype with an output voltage of 400 V. [ABSTRACT FROM AUTHOR]

A high step-up dc–dc converter with multiple magnetic devices and switched-capacitor voltage multiplier cell (SC VMC) is proposed in this article. By simultaneous implementation of a coupled inductor (CI) and a built-in transformer (BIT), the voltage gain is flexibly increased with an additional degree of freedom in comparison with the converters with only BIT or CI. To further increase the voltage gain, the secondary winding of the CI is inserted in series with the primary winding of the BIT. This new architecture leads to multiplication of the turns ratios of the CI and BIT in the voltage gain expression, as well. The SC VMC not only extends the voltage gain but also reduces the voltage stress across the MOSFETs. To have a better device utilization, the blocking capacitor is participated in voltage gain improvement. Moreover, through active clamp circuit, the leakage energy of the magnetic devices is recycled and zero voltage switching (ZVS) performance is obtained for the main and auxiliary MOSFETs. In such a case, the switching frequency can be increased to reduce the volume of the converter. Finally, a 400-W laboratory prototype with 25– 400 V voltage conversion is fabricated to demonstrate the effectiveness of the proposed converter. [ABSTRACT FROM AUTHOR]

In this article, a nonisolated high step-up three-port converter is proposed based on the single-ended primary-inductor converter. The proposed converter includes two switches, which are turned on under zero voltage switching or low-voltage condition intrinsically. The overall number of elements used in the converter is small. Furthermore, the conduction losses are reduced by reducing the number of the semiconductor elements in both battery and photovoltaic (PV) current flow paths. The input inductor is not coupled to any inductors to reduce the PV current ripple and enhance the realization of maximum power point tracking (MPPT). Since low-voltage switches with low on-resistance are selectable, conduction losses are reduced. All modes of operation in the steady-state condition are discussed and design considerations in each mode are presented. Finally, the experimental prototype of the proposed converter with a 24 V PV source, 36 V battery pack, and a 380 V-200 W load is presented. [ABSTRACT FROM AUTHOR]

This article proposes an isolated high step-up resonant converter which is suitable for low power application. The proposed converter is simple in structure since it employs only one switch while not necessitating a clamp circuit. Also, the proposed converter is able to achieve ZCS turn-on and turn-off of the switch and ZCS turn-off of diodes using a parallel resonant circuit, resulting in high efficiency. Furthermore, the proposed converter has reduced transformer volume due to zero dc-offset current in transformer. Experimental results on 450-W prototype are provided to validate the proposed concept. [ABSTRACT FROM AUTHOR]

Recently, an extended-duty-ratio (EDR) boost converter has attracted great attention of many scholars. However, the EDR boost converter with fix phase shifts is difficult to achieve phase-to-phase current sharing over a wide range of duty ratio. In this article, a variable phase-shift control strategy is proposed to further expand its current sharing range for the EDR boost converter. Under the proposed control strategy, the EDR boost converter can operate in wide range of duty ratio varying from 0.5 to 1 with automatic current sharing between phases since two adjacent phase shifts can be adjusted to guarantee that the energy stored in certain inductor is only transferred to the next phase capacitor step by step for generating high step-up output voltage. Next, the steady-state analysis of the EDR boost converter under the proposed control strategy is discussed thoroughly, and the switch voltage stresses and current stresses are also analyzed. Finally, a 300 W, 3.3 V to 38.9 V, four-phase EDR boost hardware prototype has been built. The effectiveness of the proposed control strategy is verified by the experimental results of the built prototype. [ABSTRACT FROM AUTHOR]

In this article, a new high step-up soft-switched double-input micro-inverter is introduced, which is proper for low-power applications. This inverter is composed of a forward resonant inverter and two series boost converters that are coupled electrically and apply five switches. The input powers are controlled separately using the duty-cycle of input switches, and if one of the inputs is omitted, the operation of the inverter is not interrupted. The energy is transmitted to the output and provides soft-switching conditions without any auxiliary switch. Secondary side switches are controlled at low frequency to control the direction of current in each half-cycle of the output voltage. The proposed inverter is analyzed, and design considerations and soft-switching range are discussed. Also, the schematic of the control circuit is presented. The proposed inverter is implemented to supply a 100-W load, and experimental results are presented to justify the theoretical analysis. [ABSTRACT FROM AUTHOR]

In this article, we propose a novel interleaved high step-up converter. The proposed converter integrates the built-in transformer voltage multiplier cell (VMC) to the interleaved boost converter with voltage lift capacitor. The voltage gain is increased by both of the turns ratio of the built-in transformer and the voltage lift capacitor. Hence, there is no need to operate the converter around unity duty cycles to obtain high voltage gains. Meanwhile, the voltage stress across semiconductors is reduced considerably, facilitating the utilizing of mosfets with low on-state resistance and diodes with low forward voltage drop decreasing the conduction losses. The leakage inductance of the built-in transformer not only provides zero current switching (ZCS) for mosfets but also controls the falling current rate of the diodes alleviating the reverse current recovery problem. In addition, the energy of the leakage inductance is recycled by the clamp capacitor avoiding high spikes across switches. In comparison with the recently published converters, the proposed converter introduces all of the abovementioned advantages with a low number of components that make it an interesting solution for high efficiency and high step-up applications. Finally, a 40-V to 580-V prototype with 930 W power is fabricated to explore the merits of the proposed converter. [ABSTRACT FROM AUTHOR]

In this article, a novel dual active clamp converter with high voltage gain is proposed for dc–dc applications. The active clamps’ switches turn on and off under zero-current switching (ZCS). In addition, the main switch turns on under ZCS condition, as well. Therefore, switching losses are significantly reduced. The converter is also capable of operating under quasi-resonance (QR) mode. In this mode, switching losses are reduced further by lowering the voltage and current, at which the main switch turns off. In comparison with the conventional interleaved converter, the voltage gain of the proposed converter is almost the same, but the number of semiconductors and switching loss are significantly reduced. The switching frequency of the active clamps’ switches is half of the main switching frequency. The operation principles of the proposed converter are studied in both pulsewidth modulation and QR modes, and the advantages are investigated. A 200-W prototype is implemented to validate the desired functionality of the converter, and experimental results are compared in both modes. [ABSTRACT FROM AUTHOR]

Conventional boost converters, while having a high level of simplicity and robustness, are known to have a poor efficiency at high step-up regimes. More complicated topologies have been extensively explored to increase the step-up ratio while keeping a high efficiency; however, an efficient regulated dc–dc power conversion at high step-up regimes still remains a challenge. In this letter, we demonstrate fully soft-switched operation of boost converters based on impulse rectification, which results in an efficient power conversion at very high step-up regimes. Contrary to the conventional analysis of boost converters which seeks to minimize conduction and switching losses, our approach considers reactive power as the key parameter limiting the efficiency. A theoretical basis enabled an appropriate design resulting in power conversion efficiencies above 90% for voltage gain values of 5, 10, 25, and 50, with a peak efficiency of 97%. The guidelines to design boost converters based on the proposed approach are discussed. The simplicity and high performance of this approach opens new avenues in designing regulated dc–dc converters with a high step-up. [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]

We propose a high step-up resonant dc–dc converter that can achieve voltage balance of the resonant capacitors in distributed generation systems. By incorporating a switching mechanism on the secondary side, we achieve high step-up voltage gain with a minimum number of devices and without reverse-recovery problem. An active-clamp circuit installed on the primary side suppresses the surge voltage that occurs at switch components, recycles the energy stored in the leakage inductance, and provides an alternate resonant-current path formed by the leakage inductance and the output resonant capacitors. A dual resonance that occurs at the secondary side of the converter is exploited to reduce the turn-off current and switching loss significantly, and to achieve high power conversion efficiency. The resonant capacitor voltages remain in balance because the duty cycle of the primary-side switches is always set to 0.5, regardless of the input voltages and load variations. Design and analysis of the proposed converter are presented, and tests using a 400-W experimental prototype verify its superior performance. [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]

A previously proposed high step-up dc–dc converter based on Z-source circuit is improved such that conduction losses of the converter and current stress of its power switch are reduced. The improved converter contains only one magnetic core and all of the inductors are coupled. It is shown that using one core allows us to use windings with lower copper resistance that results in reducing resistive losses of the coupled inductors. Also, by rearranging two diodes of the converter, the switch current and its conduction loss are reduced. In addition, a previously proposed auxiliary circuit for zero-voltage-transition operation is employed with a minor modification that makes it possible to use a relatively large snubber capacitor that significantly decreases current–voltage overlap of the main switch at turn-off instant. Improvement in the overall efficiency of the presented structure over the existing high step-up Z-source converter is demonstrated by implementing a 100-W prototype of each converter for 30- to 300-V voltage conversion. [ABSTRACT FROM AUTHOR]

The traditional switched-inductor technique for high-step-up conversion is widely utilized in industrial applications, especially multicell technique is combined to realize ultra-high voltage. However, the component currents are accordingly increasing with the increasing number of cells, which results in high cost, low efficiency, and low stability. In order to solve these problems, an improved multicell structure of switched inductor is devised, which can be utilized to replace traditional switched-inductor cells for higher actual boost ratio and lower diode currents. An example of the proposed structure-based boost converter is demonstrated for a detailed analysis, and it is followed with a comparison to verify its features. Finally, simulations and experiments are conducted to validate the effectiveness. [ABSTRACT FROM AUTHOR]

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]

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]

In this paper, a new cascaded high step-up multilevel converter topology is designed, which is based on the series connection of several switched-capacitor submultilevel units. The voltage gain of proposed multilevel converter is related to the number of used switches-capacitor units. The main advantage of proposed topology is inherent voltage balancing of used capacitors. The proposed cascade topology is optimized to minimize the number of capacitors, power switches, and the value of voltage on switches for given levels. The proposed topology is compared with other high step-up multilevel converter topologies and conventional structures. The comparison results show that the presented structure requires the least number of switches and dc sources. Moreover, the voltage on the switches of proposed topology is low. In order to confirm the operation of proposed high step-up multilevel converter, both experimental and simulation works are provided. [ABSTRACT FROM PUBLISHER]

For the high-voltage direct-current (HVDC) power transmission system of offshore wind power, dc/dc converters are the potential solution to collect the power generated by off-shore wind farms to HVDC terminals. The converters operate with high-voltage gain, high efficiency, and fault tolerance over a wide range of operating conditions. In this paper, an isolated ultrahigh step-up dc/dc converter with a scalable modular structure is proposed for HVDC offshore wind power collection. A flyback-forward converter is employed as the power cell to form the expandable electrically isolated modular dc/dc converter. The duty ratio and phase-shift angle control are also developed for the proposed converter. Fault-tolerant characteristics of the converter are illustrated through the redundancy operation and fault-ride-through tests. Redundancy operation is designed to maintain high operation efficiency of the converters and fault-ride-through operation improves the converter reliability under harsh operating conditions. Analytical studies are carried out, and a 750-W prototype with three modular cells is built and experimentally tested to verify the performance of the proposed modular dc/dc converter. [ABSTRACT FROM AUTHOR]

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

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

A systematic method for developing isolated buck-boost (IBB) converters is proposed in this paper, and single-stage power conversion, soft-switching operation, and high-efficiency performance can be achieved with the proposed family of converters. On the basis of a nonisolated two-switch buck-boost converter, the proposed IBB converters are generated by replacing the dc buck-cell and boost-cell in the non-IBB converter with the ac buck-cell and boost-cell, respectively. Furthermore, a family of semiactive rectifiers (SARs) is proposed to serve as the secondary rectification circuit for the IBB converters, which helps to extend the converter voltage gain and reduce the voltage stresses on the devices in the rectification circuit. Hence, the efficiency is improved by employing a transformer with a smaller turns ratio and reduced parasitic parameters, by using low-voltage rating MOSFETs and diodes with better switching and conduction performances. A full-bridge IBB converter is proposed and analyzed in detail as an example. The phase-shift modulation strategy is applied to the full-bridge IBB converter to achieve IBB conversion. Moreover, soft-switching performance of all active switches and diodes can be achieved over a wide load and voltage range by the proposed converter and control strategy. A 380-V-output prototype is fabricated to verify the effectiveness of the proposed family of IBB converters, the SARs, and the control strategies. [ABSTRACT FROM AUTHOR]

High-power and high-voltage gain dc–dc converters are key to high-voltage direct current (HVDC) power transmission for offshore wind power. This paper presents an isolated ultra-high step-up dc–dc converter in matrix transformer configuration. A flyback-forward converter is adopted as the power cell and the secondary side matrix connection is introduced to increase the power level and to improve fault tolerance. Because of the modular structure of the converter, the stress on the switching devices is decreased and so is the transformer size. The proposed topology can be operated in column interleaved modes, row interleaved modes, and hybrid working modes in order to deal with the varying energy from the wind farm. Furthermore, fault-tolerant operation is also realized in several fault scenarios. A 400-W dc–dc converter with four cells is developed and experimentally tested to validate the proposed technique, which can be applied to high-power high-voltage dc power transmission. [ABSTRACT FROM AUTHOR]

High step-up voltage gain dc–dc converters are widely applied in fuel cell stacks, photovoltaic arrays, battery sources, and high intensity discharge lamps power systems. Active-network converters with coupled inductors (CL-ANC) are derived from switched inductor active-network converters (SL-ANC). The proposed converter contains two coupled inductors which can be integrated into one magnetic core and two power switches. The converter can provide a relatively high voltage conversion ratio with a small duty cycle; the voltage and current stress of power switches are low which is helpful to reduce the losses. This paper shows the key waveforms of the CL-ANC and detailed derivation of the steady-state operation principle. The voltage conversion ratio and the effect of the leakage inductance on voltage gain are discussed. The voltage stress and current stress on the power devices are illustrated and the comparison between the proposed converter and SL-ANC are given. Finally, the prototype has been established in the lab with 200 V and 400 V output under different turn ratios. Experimental results are given to verify the correctness of the analysis. [ABSTRACT FROM AUTHOR]

In applications where the high voltage gain is required, such as photovoltaic grid-connected system, fuel-cell and high-intensity discharge lamps for automobile, high step-up dc-dc converters have been introduced to boost the low voltage to a high bus voltage. The voltage gain of traditional boost converter is limited, considering the issues such as the system efficiency and current ripple. This paper proposes a class of hybrid switched-inductor converters (H-SLCs) for high step-up voltage gain conversion. First, the topological derivation of H-SLCs is deduced by combining the passive and active switched-inductor unit; second, this paper illustrates the operation modes of the proposed asymmetrical and symmetrical converters; third, the performance of the proposed converters is analyzed in detail and compared with existing converters; finally, a prototype is established in the laboratory, and the experimental results are given to verify the correctness of the analysis. [ABSTRACT FROM PUBLISHER]

In this paper, a single-phase high step-up converter is proposed, designed not only to boost the relatively low photovoltaic (PV) voltage to a high bus voltage with high efficiency, but also to offer a neutral point terminal for the half-bridge-based inverters. First and foremost, two symmetrical high step-up converters are combined and integrated to derive an improved converter with neutral point terminal, which is strongly expected for the half-bridge-based inverters. Secondly, the voltage gain of the converter is extended and the narrow turn-off period is avoided by using the coupled inductor multiplier. Furthermore, the coupled inductor multiplier reduces the voltage stress of all the power devices. As a result, the low voltage-rated power devices can be employed to minimize the conduction losses. More importantly, all the active switches work in the zero-voltage-switching condition, which reduces the switching losses effectively. All these factors improve the circuit performance in the high step-up applications, especially for the half-bridge based PV inverter systems. Finally, the experimental results from a 500 W, 48 -760 V prototype at 100 kHz switching frequency are provided to verify the effectiveness of the proposed converter. The highest efficiency of the prototype is 96.5% and the efficiency is over 94% in a wide load range. [ABSTRACT FROM AUTHOR]

In this paper, the built-in transformer voltage multiplier cell is inserted into each phase of the conventional interleaved boost converter to provide additional control freedom for the voltage gain extension without extreme duty cycle. The voltage multiplier cell is only composed of the built-in transformer windings, diodes and small capacitors. And additional active switches are not required to simplify the circuit configuration. Furthermore, the switch voltage stress and the diode peak current are also minimized due to the built-in transformer voltage multiplier cells to improve the conversion efficiency. Moreover, there is no reverse-recovery problem for the clamp diodes and the reverse-recovery current for the regenerative and output diodes are controlled by the leakage inductance of the built-in transformer to reduce the relative losses. In addition, the switch turn-off voltage spikes are suppressed effectively by the ingenious and inherent passive clamp scheme and zero current switch (ZCS) turn-on is realized for the switches, which can enhance the power device reliability. Finally, a 40 V-input 380 V-output 1 kW prototype is built to demonstrate the clear advantages of the proposed converter. [ABSTRACT FROM AUTHOR]

In this paper, a soft-switched dc–dc converter using voltage multiplier cells is proposed for high-step up application. The proposed converter has the following advantages: 1) doubled voltage conversion ratio of the basic configuration (N = 1) compared to the conventional boost converter; 2) zero voltage switching turn ON of switches and zero current switching turn OFF of diodes; 3) low input current ripple, reduced size of the passive component and current stresses of switches due to interleaved structure, and 4) increased flexibility in device selection by adjusting the number of voltage multiplier cells. The proposed converter is compared to some high step-up converters. Experimental results from a 1-kW prototype are provided to validate the proposed concept. [ABSTRACT FROM PUBLISHER]

A novel high step-up converter is proposed for a front-end photovoltaic system. Through a voltage multiplier module, an asymmetrical interleaved high step-up converter obtains high step-up gain without operating at an extreme duty ratio. The voltage multiplier module is composed of a conventional boost converter and coupled inductors. An extra conventional boost converter is integrated into the first phase to achieve a considerably higher voltage conversion ratio. The two-phase configuration not only reduces the current stress through each power switch, but also constrains the input current ripple, which decreases the conduction losses of metal–oxide–semiconductor field-effect transistors (MOSFETs). In addition, the proposed converter functions as an active clamp circuit, which alleviates large voltage spikes across the power switches. Thus, the low-voltage-rated MOSFETs can be adopted for reductions of conduction losses and cost. Efficiency improves because the energy stored in leakage inductances is recycled to the output terminal. Finally, the prototype circuit with a 40-V input voltage, 380-V output, and 1000- W output power is operated to verify its performance. The highest efficiency is 96.8%. [ABSTRACT FROM AUTHOR]

An advanced symmetrical voltage quadrupler rectifier (SVQR) is derived in this paper to serve as the secondary rectification topology, which helps to extend the converter voltage gain and reduce the output diode voltage stresses. The output voltage is four times of the conventional full-bridge voltage rectifier with the same transformer ratio, which benefits to reduce the turns ratio of the transformer and decrease the parasitic parameters. Also, low voltage-rated diodes with high switching performance can be applied to improve the efficiency. Meanwhile, all the diodes in SVQR have the same voltage and current stresses, which simplifies the thermal design. Furthermore, two output electrolytic capacitors are connected in series to share the high output voltage, and the voltage balance can be realized naturally without any additional voltage-sharing scheme. A clear picture is made in this paper to give a general framework and universal applications for the derived SVQRs for high step-up and high output voltage conversion systems. A dual boost converter is used as an example to demonstrate the clear advantages of the derived SVQRs. [ABSTRACT FROM AUTHOR]

A novel two-switch high-step-up isolated converter with voltage lift is proposed in this paper. The proposed isolated converter utilizes a transformer with low turn ratio to achieve high step-up gain. The secondary winding charges two boosting capacitors in parallel as switches during the switch-on period, and two boosting capacitors are discharged in series during the switch-off period. Thus, the converter has high voltage gain with appropriate duty ratio. In addition, by using two clamping diodes and a capacitor on the primary side, leakage energy is recycled, and the voltage spikes of the two active switches are clamped, thereby improving conversion efficiency. Finally, experimental results based on a prototype implemented in the laboratory with an input voltage of 24 V, an output voltage of 200 V, and an output power of 200 W verify the performance of the proposed isolated converter; full-load efficiency is nearly 93%. [ABSTRACT FROM PUBLISHER]

In this paper, a novel high step-up dc–dc converter for distributed generation systems is proposed. The concept is to utilize two capacitors and one coupled inductor. The two capacitors are charged in parallel during the switch-off period and are discharged in series during the switch-on period by the energy stored in the coupled inductor to achieve a high step-up voltage gain. In addition, the leakage-inductor energy of the coupled inductor is recycled with a passive clamp circuit. Thus, the voltage stress on the main switch is reduced. The switch with low resistance RDS(ON) can be adopted to reduce the conduction loss. In addition, the reverse-recovery problem of the diodes is alleviated, and thus, the efficiency can be further 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 to verify the performance of the proposed converter. [ABSTRACT FROM PUBLISHER]

In this paper, the concept of built-in transformer voltage doubler cell is derived to generate an improved interleaved high step-up converter for distributed photovoltaic generation applications. The proposed built-in transformer voltage doubler cell is composed of three transformer windings, two voltage doubler diodes, and two voltage doubler capacitors. The voltage doubler capacitors are charged and discharged alternatively to double the voltage gain. The switch duty cycle and the transformer turns ratio can be employed as two controllable freedoms to lift the voltage ratio flexibly. The power device voltage stress can also be reduced to improve the circuit performance. Furthermore, the active clamp scheme is adopted to recycle the leakage energy, absorb the switch turn-off voltage spikes, and achieve zero-voltage switching (ZVS) operation for all active switches. Meanwhile, the diode reverse-recovery problem is alleviated by the leakage inductance of the built-in transformer. All these factors benefit the circuit performance improvements in the high step-up and large current applications. Finally, a 1-kW prototype with 40-380 V conversion is built and tested to demonstrate the effectiveness of the proposed converter. [ABSTRACT FROM AUTHOR]

The demand for nonisolated high step-up dc-dc converters in applications such as dc backup energy systems for UPS, photovoltaic and fuel cell systems, and hybrid electric vehicles has been gradually increasing. This paper proposes nonisolated step-up dc-dc converters with an improved switching method. The proposed converter shows zero-voltage switching turn-on of the switches in continuous conduction mode as well as reduced turn- off switching losses owing to the switching method that utilizes Lr-Cr resonance in the auxiliary circuit. Also, as a result of the proposed switching method, the switching losses associated with diode reverse recovery become negligible even in the small duty cycle. The capacitance in the auxiliary circuit is significantly reduced compared to the pulsewidth modulation method. The duty cycle loss is further reduced resulting in increased step-up ratio. Experimental results from a 2-kW prototype of a two-phase interleaved version are also provided to validate the proposed concept. [ABSTRACT FROM AUTHOR]

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

In this paper, A single-phase improved active clamp coupled-inductor-based converter with extended voltage doubler cell is proposed for large-voltage conversion ratio applications. The secondary winding of the coupled inductor is inserted into the half-wave voltage doubler cell to extend the voltage gain dramatically and decrease the switch voltage stress effectively. By combining the coupled inductor and voltage doubler cell structure, the disadvantage of the potential resonance between the leakage inductance and the diode stray capacitor is cancelled, and the unexpected high pulsed current in the voltage doubler cell is decreased due to the inherent leakage inductance of the coupled inductor. Meanwhile, the active clamp scheme is employed to recycle the leakage energy, suppress the switch turn-off voltage spikes, and implement zero-voltage-switching turn-on operation. In addition, there is only one magnetic component in the proposed converter and the coupled inductor operates not only as a filter inductor, but also as a transformer when the main switch is in the ON state, which reduces the volume of the magnetic core and improves the power density of the converter. A 500 W prototype operating at 100 kHz with 48 V input and 380 V output is built to verify the analysis. The maximum efficiency of the prototype is nearly 97% and the efficiency is higher than 96% over a wide load range. [ABSTRACT FROM AUTHOR]

The concept of winding-cross-coupled inductors (WCCIs) and voltage multiplier cells is integrated to derive a novel interleaved high step-up converter in this paper. The voltage gain is extended and the switch voltage stress is reduced by the WCCIs and the voltage multiplier cells in the presented circuit, which minimizes the peak current ripple of the power devices and makes low-voltage MOSFETs with high performance available in high step-up and high output voltage applications. Moreover, the output diode reverse-recovery problem is alleviated by the leakage inductance of the WCCIs, which reduces the reverse-recovery losses. Zero current switching (ZCS) turn-on is realized for the power switches to reduce the switching losses. Furthermore, the voltage spikes on the MOSFETs are clamped and the leakage energy is recycled by the voltage multiplier cells, when the switch turns off. A 1 kW prototype with 35-45 V input and 380 V output operating at 50 kHz switching frequency is built and tested to verify the significant improvements of the proposed converter. [ABSTRACT FROM AUTHOR]

This paper proposes a generalized scheme of new soft-switching interleaved boost converters that is suitable for high step-up and high-power applications. The proposed converter is configured with proper numbers of series and parallel connected basic cells in order to fulfill the required output voltage and power levels, respectively. This leads to flexibility in device selection resulting in high component availability and easy thermal distribution. Design examples of determining the optimum circuit configuration for given output voltage and power level are presented. Experimental results from a 1.5-kW prototype are provided to validate the proposed concept. [ABSTRACT FROM AUTHOR]

A novel high step-up dc–dc converter for a distributed generation system is proposed in this paper. The concept is composed of two capacitors, two diodes, and one coupled inductor. Two capacitors are charged in parallel, and are discharged in series by the coupled inductor. Thus, high step-up voltage gain can be achieved with an appropriate duty ratio. The voltage stresses on the main switch and output diode are reduced by a passive clamp circuit. Therefore, low resistance R DS(ON) for the main switch can be adopted to reduce conduction loss. In addition, the reverse-recovery problem of the diode is alleviated, and thus, the efficiency can be further improved. The operating principle and steady-state analyses of the voltage gain are also discussed in detail. Finally, a 24-V input voltage, 400-V output voltage, and 400-W output power prototype circuit of the proposed converter are implemented in the laboratory to verify the performance. [ABSTRACT FROM AUTHOR]

In this paper, a voltage multiplier cell is inserted in the conventional boost converter operated in continuous conduction mode (CCM) to provide another design freedom for the voltage-gain extension. Thus, the voltage conversion ratio is enlarged and the narrow turn-OFF period is avoided in the high step-up applications. Furthermore, the voltage multiplier cell makes the voltage stress of all the power devices lower than the high output voltage. As a result, the low-voltage-rated power devices can be employed to reduce the conduction losses and to improve the power device reliability. Moreover, zero-voltage switching soft-switching operation is achieved for the power MOSFETs in the whole-switching transition. Zero-current switching turn-OFF condition is provided for the diodes. Therefore, the power device switching losses and the diode reverse-recovery losses are minimized greatly. In addition, the input current ripple is reduced due to the CCM operation compared with most of the published single-stage single-phase high step-up converters, which makes it more advantageous in the hybrid electric vehicles and the fuel-cell power conversion systems. Finally, the experimental results from a 500-W, 36–380-V prototype are provided to validate the effectiveness of the proposed converter. [ABSTRACT FROM PUBLISHER]