Single-stage Converter Research Articles

A fuzzy-logic-controlled single-stage converter for PV-powered lighting system applications

This paper presents a fuzzy-logic-controlled single-stage power converter (SSC) for photovoltaic (PV)-powered lighting system applications. The SSC is the integration of a bidirectional buck-boost charger/discharger and a class-D series resonant parallel loaded inverter. The designed fuzzy logic controller (FLC) can control both the charging and discharging current, and can improve its dynamic and steady-state performance. Furthermore, a maximum power point tracker (MPPT) based on a perturb-and-observe method is also realized to effectively draw power from PV arrays. Both the FLC and the MPPT are implemented on a single-chip microprocessor. Simulated and experimental results obtained from the proposed circuit with an FLC have verified the adaptivity, robustness and feasibility.

A new single-phase high-power-factor converter with buck and buck–boost hybrid operation

In recent years, a wide variety of high-power-factor converter schemes have been proposed to solve the harmonic problem. The schemes are based on conventional boost, buck, or buck–boost topology, and their performance, such as output voltage control range in the boost and buck topology or efficiency in the buck–boost topology, is limited. To solve this, the authors propose a single-phase high-power-factor converter with a new topology obtained from a combination of buck and buck–boost topology. The power stage performs the buck and buck–boost operations by a compact single-stage converter circuit while the simple controller/modulator appropriately controls the alternation of the buck and buck–boost operation and maintains a high-quality input current during both the buck and buck–boost operations. The proposed scheme results in a high-performance rectifier with no limitation of output voltage control range and a high efficiency. In this paper, the principle and operation of the proposed converter scheme are described in detail and the theory is confirmed through experimental results obtained from 2-kW prototype converter. © 2000 Scripta Technica, Electr Eng Jpn, 131(3): 91–100, 2000

Soft-switching single-stage AC-to-DC converter with low harmonic distortion

A 1 /spl phi/ high-frequency (HF) transformer isolated, soft-switching single-stage ac-dc converter with low line-current harmonic distortion is presented. Its operation is explained with equivalent circuits for the various intervals. The converter is analyzed and design curves are obtained. An optimization parameter is introduced and a systematic design procedure is illustrated with a design example. Detailed SPICE simulation and experimental results of a 500 W converter with load as well as line voltage variation are given to verify theory. The proposed converter employs a zero-voltage transition (ZVT) network to ensure zero-voltage switching (ZVS) at all loads, and natural power factor correction is ensured using a simple control circuit.

High-power-factor single-stage converter with robust controller for universal off-line applications

This paper presents a robust-controlled single-stage converter (SSC) operating either in discontinuous conduction mode (DCM) or in continuous conduction mode (CCM) to achieve high power factor for universal line voltage range from 90 to 264 V/sub rms/. At light load, the proposed system is operated in the DCM, while at heavy load the system is operated in the CCM, thus, the DC-link voltage can be properly controlled within a certain voltage range and the efficiency can be improved as well. The overall system is with a robust controller and is operated in a fixed frequency. In the design, the load variation and line voltage variation are treated as plant uncertainty and control disturbance, respectively. The H/sup /spl infin// robust control method is adopted to design a proper robust controller to achieve robust stability and robust performance. The measured results from a prototype have confirmed the effectiveness and feasibility of the proposed system.

Modeling of single-stage converters with high power factor and fast regulation

This paper presents an approach to systematically model single-stage DC/DC converters operated in discontinuous conduction mode (DCM) based on the graft scheme. With the graft scheme, the active switches which are with a common node and operating in unison can be integrated to form a single stage converter (SSC). The small-signal models of the SSC can, therefore, be derived by combining those of its originally separate converters. Using the proposed approach can help yield highly related dynamic models of the converters in a family and, in addition, physical insights between the converters can be readily identified. Moreover, the expressions of the small-signal models for the SSCs operated in DCM can be extended to those in continuous-conduction-mode operation. These have made the proposed modeling method valuable and viable. Experimental measurements have demonstrated that the small-signal model of an SSC derived with the proposed approach is relatively accurate.

Single-stage converters for PV lighting systems with MPPT and energy backup

Single-stage converters (SSCs) are proposed for applications of photovoltaic powered lighting system (PPLS). The synchronous switch technique is employed to develop the SSCs which can fulfill maximum power point tracking (MPPT), battery charging, discharging, and lamp ballasting features. Several typical SSCs are discussed. One of the proposed SSCs, which is the integration of a buck-boost charger/discharger and a class-D series resonant parallel loaded inverter, is analyzed and designed into a PPLS. Both pulsewidth modulation (PWM) and variable-frequency controls are used to govern the system operation. The controller is implemented on a single-chip microprocessor. Simulated and experimental results of the proposed system for driving up to sixteen GE TBX 26 W fluorescent lamps are used to verify the theoretical prediction and feasibility. The proposed system has a simple configuration, as well as a zero voltage switching (ZVS) feature, and can achieve the same functions as those in conventional systems when abrupt insolation changes do not occur frequently. These result in the inherent merits of lower cost, more compact size and possibly achieving higher reliability over conventional systems.

Modular single-stage, three-phase full-bridge converter with inherent power factor correction and isolated output

The modular development of a three-phase, single-stage AC-DC power converter based on single-phase AC-DC full-bridge converters is described. Three-wired and four-wired modular converter systems are examined and compared. The three-wired system is found to have inherent power factor correction and is better than the four-wired system in terms of harmonic content. The fluctuation of the converter neutral voltage in the three-wired system and the voltage stress on the power switches are analysed. A simulation based on a PSPICE model is included. The modular converter does not have a minimum component count when compared with non-modular converters. But the modular converter offers attractive features such as simple DC-DC switching control, electrically isolated output, inherent power factor correction and single-stage power conversion without using power devices with excessively high voltages and current ratings. It also has flexible power expandability and the potential to simplify the design and production of high-power AC-DC power converter products. The operation of the modular full-bridge converter has been confirmed with a 1.5 kW prototype. Both predictions and measurements show that the power quality of three-wired modular converter system is good and well above IEC-1000 standards.

Novel single-switch converter with power factor correction

A new single-stage single-switch power factor correction converter with output electrical isolation is presented. The configuration of this converter is achieved by combining a flyback circuit and a forward circuit in one power stage. The principle of operation and steady-state analysis of the proposed topology is given. Based on its steady-state operation constraints, a design procedure along with a specific design example is reported. To verify the theoretical analysis of the proposed converter, a design example is given with its PSPICE simulation and experimental results.

Paralleling power converters for AC–DC step-down power conversion with inherent power factor correction

The authors describe the modular development of a single-stage AC-DC step-down power converter. The converter offers advantages such as simple DC-DC type switching control, electrically isolated output and inherent power factor correction. It also provides single-stage power conversion without using power devices with excessively high voltage and current rating, the flexibility for expansion of power capability, and a simplification of design and production procedure for the manufacturing of power converter products. The operating modes of the converter are described and analysed. Experiments have confirmed the validity of the modular converter operation.

Analysis and design of an isolated single-stage converter achieving power-factor correction and fast regulation

This paper presents the analysis and design of an isolated single-stage converter achieving high-power-factor correction and fast regulation. By using the technique suggested by Wu et al., a buck-boost converter and a flyback converter can be integrated to form the discussed converter. The buck-boost semistage working in the discontinuous conduction mode (DCM) functions as a power-factor corrector, and the flyback semistage operating in the DCM is a voltage regulator which is controlled, theoretically, to be independent of load variation. An approximated small-signal model of the converter operating in the DCM is developed. Design of a peak-current feedback loop with an optimal proportional integral controller is also presented. A prototype is implemented to verify that the analysis and design are effective and feasible.

An alternative approach to synthesizing single-stage converters with power-factor-correction feature

An alternative approach to synthesizing single-stage converters (SSCs) with power-factor-correction (PFC) feature is presented in this paper. The proposed approach is primarily based on the concept of dither effect, from which PFC cells composed of energy buffers and high-frequency dither signals are introduced. Properly selecting an eligible PFC cell and inserting it in between input rectifier and DC-link capacitor can yield an SSC which can improve the input power factor significantly. In this paper, principle and configuration of PFC cells are addressed; thus, quite a few families of SSCs can be synthesized from the derived PFC cells. With this approach, not only can the SSCs discussed in the literature be developed alternatively, but novel SSCs can be synthesized. Most of the SSCs have been proved in the literature to be feasible in applications with moderate power levels.

カルシウム還元法によるネオジム‐鉄‐ホウ素系合金粉末中の酸素およびカルシウムの低減と磁石適応性

The reduction-diffusion process using Ca as reducing agent has been practiced industrially in the production of the SmCo5 type, the Nd-Fe-B type and the Td-Fe-Co type magnetic materials. The advantages of the R-D process are the generally high yield of rare earth metals and the single-stage conversion of mixture of oxides and metal powders into a product of rare earth alloy powders. On the other hand, its disadvantages are the slightly high contents of O and Ca. These disadvantages are remarkable in the Nd-Fe-B type. An experimental study was carried out on oxygen and calcium reduction technique for Nd-Fe-B alloy powders produced by reduction-diffusion method using metallic Ca as reductant. One technique is to dope Co or Ni into the raw powders, and another is to reduce Nd content from the atomic ratio of Nd15Fe77B8. These alloy powders are suitable for the production of Nd-Fe-B sintered magnets and are expected higher magnetic properties.

Production of high octane gasoline components by hydroprocessing of coal-derived aromatic hydrocarbons

The catalytic conversion of coal liquids to desirable gasoline components was modeled by the hydroprocessing of 1-methylnaphthalene. The conversion aims at a maximum yield of non-aromatic high octane gasoline components, i.e. isoparaffins and substituted cyclohexanes and cyclopentanes. Experiments were performed in one or two stages using various catalysts. The highest single-stage conversion was achieved in 10 h with a sulfided NiW/SiO 2Al 2O 3 catalyst at 325°C and 6.7 MPa with a feed/catalyst ratio of 10:1. In the two-stage operation, 1-methylnaphthalene was first hydrogenated to methyldecalins at 325°C and 6.7 MPa with 100% conversion in 10 h using a sulfided NiMo/TiO 2Al 2O 3 catalyst. In the second stage, the methyldecalins underwent hydrocracking at 325°C and 4.7 MPa using a Pd/REX catalyst (where REX is a rare earth exchange X-type zeolite). The results showed promise for reducing the aromatic content in coal liquids to less than 2% while achieving a potential conversion to high octane gasoline components of 62.2 wt%.

Unified approach to developing single-stage power converters

A unified approach to developing single-stage power converters which can fulfil multiple functions is presented. Four synchronous switches corresponding to the four common node types of two active switches are introduced. The approach is then to replace the active switches in multistage converters (in cascade or cascode connection) with one or several of the synchronous switches and their degenerated versions to form a single-stage converter. Illustrations of using these switches to develop single-stage converters are presented. These are started with the development of the well-known single-stage switch-mode converters (SMCs), buck-boost, Cuk, sepic, and Zeta (also named dual sepic), from the basic converters, buck and boost. Then, synthesis and applications of other single-stage converters are addressed. Due to increased component stresses, the developed single-stage converters are primarily suitable for applications with moderate power levels.

Protonolysis of Dialkyl- and Alkylarylplatinum(II) Complexes and Geometrical Isomerization of the Derived Monoorgano-Solvento Complexes: Clear-Cut Examples of Associative and Dissociative Pathways in Platinum(II) Chemistry.

Protonolysis of the complexes cis-[PtR(2)(PEt(3))(2)] (R = Me, Et, Pr(n)(), Bu(n)(), CH(2)C(Me)(3), CH(2)Si(Me)(3)) and cis-[Pt(R)(R')(PEt(3))(2)] (R = Ph, 2-MeC(6)H(4), 2,4,6-Me(3)C(6)H(2); R' = Me) in methanol selectively cleaves one alkyl group, yielding cis-[Pt(R)(PEt(3))(2)(MeOH)](+) and alkanes. The reactions occur as single-stage conversions from the substrate to the product. There is no evidence by UV and by low-temperature (1)H and (31)P NMR spectroscopy for the presence of significant amounts of Pt(II) or Pt(IV) intermediate species. Reactions are first order with respect to complex and proton concentrations and are strongly retarded by steric congestion at the Pt-C bond, varying from k(2) = (2.65 +/- 0.08) x 10(5) M(-)(1) s(-)(1) for R = R' = Et to k(2) = 9.80 +/- 0.44 M(-)(1)s(-)(1) for R = R'= CH(2)Si(Me)(3). Low enthalpies of activation and largely negative volumes of activation are associated with the process. The mechanism involves a rate-determining proton transfer either to the metal-carbon sigma bond (S(E)2 mechanism) or to the metal center (S(E)(oxidative) mechanism), followed by fast extrusion of the alkane and simultaneous blocking of the vacant coordination site by the solvent to generate cis-[Pt(R)(PEt(3))(2)(MeOH)](+) species. The subsequent slower process, cis to trans isomerization of cis-[Pt(R)(PEt(3))(2)(MeOH)](+), is characterized by high values of enthalpies of activation, positive entropies of activation, and largely positive volumes of activation. The reaction is shown to proceed through the dissociative loss of the weakly bonded molecule of solvent and the interconversion of two geometrically distinct T-shaped 14-electron 3-coordinate intermediates. The presence of beta-hydrogens on the residual alkyl chain produces a great acceleration of the rate (R = Me, k(i) = 0.0026 s(-)(1); R = Et, k(i) = 44.9 s(-)(1)) as a consequence of the stabilization of the 3-coordinate [Pt(R)(PEt(3))(2)](+) transition state through an incipient agostic interaction. The results of this work, together with those of a previous paper, give a rationale of the "elusive" nature of these compounds. The following factors concur: (i) electron release by the phosphine ligands, (ii) steric repulsion and distortion of the square-planar configuration, and (iii) interaction of the metal with beta-hydrogens.

Off-line applications with single-stage converters

Offline applications with single-stage power converters (SSCs) are presented in this paper. The approach used in synthesizing the SSCs is first described, and their applications are then introduced. In addition, viable control strategies for the SSCs are addressed. The developed SSCs can fulfill multifunctions, such as input power factor correction, fast output regulation and lamp ballasting, and possess the merits of compact size, simple driver design and high reliability. Prototypes of SSCs, applied to an electronic dimming ballast and a DC regulator, are built which show high feasibility in such moderate power applications.

Extra-Wide Tuning Range Mid-Ir Optical Parametric Generator Pumped by Er-Laser Pulses

AbstractInfrared pulses, continuously tunable in the 3–19 μm range, and with up to 1MW peak power, have been achieved using single-stage frequency conversion in a travelling-wave optical parametric generator (OPG) based on ZnGeP2, CdSe and GaSe crystals. The OPG was pumped by 100ps pulses from an actively mode-locked, Q-switched and cavity dumped 2.8 μm Cr,Er:YSGG laser. The quantum conversion efficiency reached 17%.

Analysis of steady‐state characteristics in a push‐pull current‐fed high‐power factor converter using a two‐input‐winding transformer technique

AbstractA two‐input winding transformer technique for high‐power factor converters has been developed. This technique results in reduced size and enhanced conversion efficiency. Input‐current wave‐shaping and fast output‐voltage regulation are achieved by controlling charge and discharge of an energy‐storage capacitor on the primary side of the transformer to compensate for the difference between the ac input and the dc output power. Thus, most of the input power is supplied to the output through only a single conversion stage and the low‐frequency ripple in the output voltage can be reduced with a small output capacitor. In addition, operation in the continuous conduction mode makes it possible to reduce the size of the input filter, concomitantly decreasing conduction loss.This paper discusses a push‐pull current‐fed converter that uses this technique. In this circuit, it is necessary to restrict the pulsewidth for the input current control because the pulsewidth for the output voltage control should be expanded to decrease the rms value of the current flowing in the switches. The characteristics of input current distortion caused by this restriction are analyzed and optimization, which takes into account harmonic current characteristics and reduction of conduction loss, is clarified. High‐power factor and an efficiency of 88 percent were achieved experimentally.

Switching converters with wide DC conversion range

Compared to basic converter topologies (buck, boost, buck-boost, Cuk, etc.), pulse-width modulation (PWM) converters with quadratic DC conversion ratios, M(D)=D/sup 2/, M(D)=D/sup 2//(1-D) or M(D)=D/sup 2//(1-D)/sup 2/, offer a significantly wider conversion range. For a given minimum ON-time and, consequently, for a given minimum duty ratio D/sub min/, D/sup 2/ in the numerator of M(D) yields a much lower limit on the minimum attainable conversion ratio. By applying a systematic synthesis procedure, six novel single-transistor converter configurations with quadratic DC conversion ratios are found. The simpler, single-transistor realization is the most important advantage over the straightforward cascade of two basic converters. As far as conversion efficiency is concerned, it is clear that a single-stage converter is usually a better choice than a two-stage converter. The quadratic converters proposed are intended for applications where conventional single-stage converters are inadequate-for high-frequency applications where the specified range of input voltages and the specified range of output voltages call for an extremely large range of conversion ratios.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Determination of double-bond position in linear alkenes by oxyselenation and gas chromatography-mass spectrometry

A series of alkenes having different positions of the double bond has been subjected to single-stage conversion into mixed ethers containing oxygen and selenium. The products show characteristic mass-spectral fragmentation, which allows immediate recognition of the original position of the double bond, and are suitable derivatives for gas chromatography-mass spectrometry.