Cascade Cockcroft–Walton Voltage Multiplier Applied to Transformerless High Step-Up DC–DC Converter
TL;DR: In this paper, the proposed control strategy employs two independent frequencies, one of which operates at high frequency to minimize the size of the inductor while the other one operates at relatively low frequency according to the desired output voltage ripple.
Abstract: This paper proposes a high step-up dc-dc converter based on the Cockcroft-Walton (CW) voltage multiplier without a step-up transformer. Providing continuous input current with low ripple, high voltage ratio, and low voltage stress on the switches, diodes, and capacitors, the proposed converter is quite suitable for applying to low-input-level dc generation systems. Moreover, based on the n-stage CW voltage multiplier, the proposed converter can provide a suitable dc source for an n + 1-level multilevel inverter. In this paper, the proposed control strategy employs two independent frequencies, one of which operates at high frequency to minimize the size of the inductor while the other one operates at relatively low frequency according to the desired output voltage ripple. A 200-W laboratory prototype is built for test, and both simulation and experimental results demonstrate the validity of the proposed converter.
Citations
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TL;DR: In this paper, the authors comprehensively review and classify various step-up dc-dc converters based on their characteristics and voltage-boosting techniques, and discuss the advantages and disadvantages of these voltage boosting techniques and associated converters.
Abstract: DC–DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts to megawatts. The literature has reported on various voltage-boosting techniques, in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit. These techniques include switched capacitor (charge pump), voltage multiplier, switched inductor/voltage lift, magnetic coupling, and multistage/-level, and each has its own merits and demerits depending on application, in terms of cost, complexity, power density, reliability, and efficiency. To meet the growing demand for such applications, new power converter topologies that use the above voltage-boosting techniques, as well as some active and passive components, are continuously being proposed. The permutations and combinations of the various voltage-boosting techniques with additional components in a circuit allow for numerous new topologies and configurations, which are often confusing and difficult to follow. Therefore, to present a clear picture on the general law and framework of the development of next-generation step-up dc–dc converters, this paper aims to comprehensively review and classify various step-up dc–dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc–dc converters are presented and summarized with comparative study of different voltage-boosting techniques.
1,230 citations
Cites background from "Cascade Cockcroft–Walton Voltage Mu..."
...itary), high-voltage/power dc–dc converters, and high-voltage dc (HVDC) systems in utility grid applications [24], [38], [41], [42], [53], [114]–[122], [139], [178]–[188], [221]–[223], [228],...
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...dc–dc converters in network server and data center applications [121], [139]....
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...in high-voltage applications [139], [218], [227], [247]–[249], [290], [297]....
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...LLC, CLLC, and LCL resonant networks that can be used in dc–dc converters [139], [218], [227], [247]–[249], [290], [297]....
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TL;DR: To integrate the advantages of the high voltage gain of a switched-capacitor (SC) converter and excellent output regulation of a switching-mode dc-dc converter, a method of combining the two types of converters is proposed in this paper.
Abstract: In a photovoltaic (PV)- or fuel-cell-based grid-connected power system, a high step-up dc-dc converter is required to boost the low voltage of a PV or fuel cell to a relatively high bus voltage for the downstream dc-ac grid-connected inverter. To integrate the advantages of the high voltage gain of a switched-capacitor (SC) converter and excellent output regulation of a switching-mode dc-dc converter, a method of combining the two types of converters is proposed in this paper. The basic idea is that when the switch is turned on, the inductor is charged, and the capacitors are connected in series to supply the load, and when the switch is turned off, the inductor releases energy to charge multiple capacitors in parallel, whose voltages are controlled by a pulsewidth modulation technique. Thus, a high voltage gain of the dc-dc converter can be obtained with good regulation. Based on this principle, a series of new topologies are derived, and the operating principles and voltage gains of the proposed converters are analyzed. Finally, the design of the proposed converter is given, and the experiment results are provided to verify the theoretical analysis.
331 citations
TL;DR: In this article, a family of nonisolated high-voltage-gain dc-dc power electronic converters is proposed, which can be used as multiport converters and draw continuous current from two input sources.
Abstract: A family of nonisolated high-voltage-gain dc–dc power electronic converters is proposed. The suggested topologies can be used as multiport converters and draw continuous current from two input sources. They can also draw continuous current from a single source in an interleaved manner. This versatility makes them appealing in renewable applications such as solar farms. The proposed converters can easily achieve a gain of 20 while benefiting from a continuous input current. Such a converter can individually link a PV panel to a 400-V dc bus. The design and component selection procedures are presented. A 400-W prototype of the proposed converter with $V_{\text{in}} = 20$ and $V_{\text{out}} = 400$ V has been developed to validate the analytical results.
281 citations
Cites background or methods from "Cascade Cockcroft–Walton Voltage Mu..."
...Current fed converters are superior in comparison to the voltage fed counterparts as they have lower input current ripple [19]....
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...Similar converters with interleaved boost input have been proposed earlier using the Cockcroft–Walton (CW) voltage multiplier (VM) [18], [19]....
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TL;DR: A novel high voltage gain, high-efficiency dc-dc converter based on coupled inductor, intermediate capacitor, and leakage energy recovery scheme, which enables the use of low voltage rating switch (with low “on-state” resistance), improving the overall efficiency of the system.
Abstract: Renewable sources like solar photovoltaic (PV) and fuel cell stack are preferred to be operated at low voltages. For applications such as grid-tied systems, this necessitates high voltage boosting resulting in efficiency reduction. To handle this issue, this paper proposes a novel high voltage gain, high-efficiency dc–dc converter based on coupled inductor, intermediate capacitor, and leakage energy recovery scheme. The input energy acquired from the source is first stored in the magnetic field of coupled inductor and intermediate capacitor in a lossless manner. In subsequent stages, it is passed on to the output section for load consumption. A passive clamp network around the primary inductor ensures the recovery of energy trapped in the leakage inductance, leading to drastic improvement in the voltage gain and efficiency of the system. Exorbitant duty cycle values are not required for high voltage gain, which prevents problems such as diode reverse recovery. Presence of a passive clamp network causes reduced voltage stress on the switch. This enables the use of low voltage rating switch (with low “ on -state” resistance), improving the overall efficiency of the system. Analytical details of the proposed converter and its hardware results are included.
154 citations
Cites background from "Cascade Cockcroft–Walton Voltage Mu..."
...Converter configurations with coupled inductor in association with a voltage multiplier circuit [21] and/or intermediate capacitor [22], [23] have also been reported to achieve high voltage gain....
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TL;DR: In this article, a switched-coupled-inductor quasi-Z-source inverter (SCL-qZSI) is proposed, which integrates a switch-capacitor and a three-winding switched-Coupled Inductive inductor into a conventional qZSI.
Abstract: Z-source inverters have become a research hotspot because of their single-stage buck–boost inversion ability, and better immunity to EMI noises. However, their boost gains are limited, because of higher component-voltage stresses and poor output power quality, which results from the tradeoff between the shoot-through interval and the modulation index. To overcome these drawbacks, a new high-voltage boost impedance-source inverter called a switched-coupled-inductor quasi-Z-source inverter (SCL-qZSI) is proposed, which integrates a switched-capacitor and a three-winding switched-coupled inductor (SCL) into a conventional qZSI. The proposed SCL-qZSI adds only one capacitor and two diodes to a classical qZSI, and even with a turns ratio of 1, it has a stronger voltage boost-inversion ability than existing high-voltage boost (q)ZSI topologies. Therefore, compared with other (q)ZSIs for the same input and output voltages, the proposed SCL-qZSI utilizes higher modulation index with lower component-voltage stresses, has better spectral performance, and has a lower input inductor current ripple and flux density swing or, alternately, it can reduce the number of turns or size of the input inductor. The size of the coupled inductor and the total number of turns required for three windings are comparable to those of a single inductor in (q)ZSIs. To validate its advantages, analytical, simulation, and experimental results are also presented.
129 citations
References
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TL;DR: In this article, power electronics, the technology of efficiently processing electric power, play an essential part in the integration of the dispersed generation units for good efficiency and high performance of the power systems.
Abstract: The global electrical energy consumption is rising and there is a steady increase of the demand on the power capacity, efficient production, distribution and utilization of energy. The traditional power systems are changing globally, a large number of dispersed generation (DG) units, including both renewable and nonrenewable energy sources such as wind turbines, photovoltaic (PV) generators, fuel cells, small hydro, wave generators, and gas/steam powered combined heat and power stations, are being integrated into power systems at the distribution level. Power electronics, the technology of efficiently processing electric power, play an essential part in the integration of the dispersed generation units for good efficiency and high performance of the power systems. This paper reviews the applications of power electronics in the integration of DG units, in particular, wind power, fuel cells and PV generators.
2,296 citations
"Cascade Cockcroft–Walton Voltage Mu..." refers background in this paper
...Consequently, researchers and governments worldwide have made efforts on renewable energy applications for mitigating natural energy consumption and environmental concerns [1], [2]....
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Journal Article•
TL;DR: In this article, power electronics, the technology of efficiently processing electric power, play an essential part in the integration of the dispersed generation units for good efficiency and high performance of the power systems.
Abstract: The global electrical energy consumption is rising and there is a steady increase of the demand on the power capacity, efficient production, distribution and utilization of energy. The traditional power systems are changing globally, a large number of dispersed generation (DG) units, including both renewable and nonrenewable energy sources such as wind turbines, photovoltaic (PV) generators, fuel cells, small hydro, wave generators, and gas/steam powered combined heat and power stations, are being integrated into power systems at the distribution level. Power electronics, the technology of efficiently processing electric power, play an essential part in the integration of the dispersed generation units for good efficiency and high performance of the power systems. This paper reviews the applications of power electronics in the integration of DG units, in particular, wind power, fuel cells and PV generators.
2,076 citations
TL;DR: The superiority of the new, hybrid converters is mainly based on less energy in the magnetic field, leading to saving in the size and cost of the inductors, and less current stresses in the switching elements, lead to smaller conduction losses.
Abstract: A few simple switching structures, formed by either two capacitors and two-three diodes (C-switching), or two inductors and two-three diodes (L-switching) are proposed. These structures can be of two types: ldquostep-downrdquo and ldquostep-up.rdquo These blocks are inserted in classical converters: buck, boost, buck-boost, Cuk, Zeta, Sepic. The ldquostep-downrdquo C- or L-switching structures can be combined with the buck, buck-boost, Cuk, Zeta, Sepic converters in order to get a step-down function. When the active switch of the converter is on, the inductors in the L-switching blocks are charged in series or the capacitors in the C-switching blocks are discharged in parallel. When the active switch is off, the inductors in the L-switching blocks are discharged in parallel or the capacitors in the C-switching blocks are charged in series. The ldquostep-uprdquo C- or L-switching structures are combined with the boost, buck-boost, Cuk, Zeta, Sepic converters, to get a step-up function. The steady-state analysis of the new hybrid converters allows for determing their DC line-to-output voltage ratio. The gain formula shows that the hybrid converters are able to reduce/increase the line voltage more times than the original, classical converters. The proposed hybrid converters contain the same number of elements as the quadratic converters. Their performances (DC gain, voltage and current stresses on the active switch and diodes, currents through the inductors) are compared to those of the available quadratic converters. The superiority of the new, hybrid converters is mainly based on less energy in the magnetic field, leading to saving in the size and cost of the inductors, and less current stresses in the switching elements, leading to smaller conduction losses. Experimental results confirm the theoretical analysis.
1,186 citations
"Cascade Cockcroft–Walton Voltage Mu..." refers background in this paper
...[22], which consists of a conventional boost converter and an n-stage diode–capacitor multiplier detailed in [23]....
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...Some other structures with switched-capacitor or switched-inductor circuits combined with basic transformerless topologies were proposed in [22]....
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TL;DR: A general conceptual circuit for high-step-up, low-cost, and high-efficiency dc/dc conversion is proposed to derive the next-generation topologies for the PV grid-connected power system.
Abstract: The photovoltaic (PV) grid-connected power system in the residential applications is becoming a fast growing segment in the PV market due to the shortage of the fossil fuel energy and the great environmental pollution. A new research trend in the residential generation system is to employ the PV parallel-connected configuration rather than the series-connected configuration to satisfy the safety requirements and to make full use of the PV generated power. How to achieve high-step-up, low-cost, and high-efficiency dc/dc conversion is the major consideration due to the low PV output voltage with the parallel-connected structure. The limitations of the conventional boost converters in these applications are analyzed. Then, most of the topologies with high-step-up, low-cost, and high-efficiency performance are covered and classified into several categories. The advantages and disadvantages of these converters are discussed. Furthermore, a general conceptual circuit for high-step-up, low-cost, and high-efficiency dc/dc conversion is proposed to derive the next-generation topologies for the PV grid-connected power system. Finally, the major challenges of high-step-up, low-cost, and high-efficiency dc/dc converters are summarized. This paper would like to make a clear picture on the general law and framework for the next-generation nonisolated high-step-up dc/dc converters.
1,162 citations
TL;DR: In this paper, a topology study of the PV MICs in the power range below 500 W and covers most topologies recently proposed for MIC applications is presented, where the MIC topologies are classified into three different arrangements based on the dc link configurations.
Abstract: The annual world photovoltaic (PV) cell/module production is growing at almost an exponential rate and has reached 1727 MW in 2005. Building integrated PV (BIPV) projects are emerging as the strongest part of the PV market and grid interactive inverters are a key component in determining the total system cost. Module integrated converter (MIC) technology has become a global trend in grid interactive PV applications and may assist in driving down the balance of system costs to secure an improved total system cost. This paper concentrates on the topology study of the PV MICs in the power range below 500 W and covers most topologies recently proposed for MIC applications. The MIC topologies are classified into three different arrangements based on the dc link configurations. A systematic discussion is also provided at the end of the paper that focuses on the major advantages and disadvantages of each MIC arrangement. These are considered in detail and will provide a useful framework and point of reference for the next generation MIC designs and applications.
1,158 citations
"Cascade Cockcroft–Walton Voltage Mu..." refers background in this paper
...Among various renewable energy sources, the photovoltaic (PV) cell and fuel cell have been considered attractive choices [3]–[5]....
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