Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input AC mains and precisely regulated DC output in buck, boost, buck-boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode AC-DC converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference.

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A review of single-phase improved power quality AC-DC converters

A system and method for variable power transfer in an inductive charging or power system. In accordance with an embodiment the system comprises a pad or similar base unit that contains a primary, which creates an alternating magnetic field. A receiver comprises a means for receiving the energy from the alternating magnetic field from the pad and transferring it to a mobile device, battery, or other device. In accordance with various embodiments, additional features can be incorporated into the system to provide greater power transfer efficiency, and to allow the system to be easily modified for applications that have different power requirements. These include variations in the material used to manufacture the primary and/or the receiver coils; modified circuit designs to be used on the primary and/or receiver side; and additional circuits and components that perform specialized tasks, such as mobile device or battery identification, and automatic voltage or power-setting for different devices or batteries.

System and method for inductive charging of portable devices

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.

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Step-Up DC–DC Converters: A Comprehensive Review of Voltage-Boosting Techniques, Topologies, and Applications

In this paper, the principle of modularity is used to derive the different multilevel voltage and current source converter topologies. The paper is primarily focused on high-power applications and specifically on high-voltage dc systems. The derived converter cells are treated as building blocks and are contributing to the modularity of the system. By combining the different building blocks, i.e., the converter cells, a variety of voltage and current source modular multilevel converter topologies are derived and thoroughly discussed. Furthermore, by applying the modularity principle at the system level, various types of high-power converters are introduced. The modularity of the multilevel converters is studied in depth, and the challenges as well as the opportunities for high-power applications are illustrated.

Modular Multilevel Converters for HVDC Applications: Review on Converter Cells and Functionalities

This paper reviews the state of the art of field- programmable gate array (FPGA) design methodologies with a focus on industrial control system applications. This paper starts with an overview of FPGA technology development, followed by a presentation of design methodologies, development tools and relevant CAD environments, including the use of portable hardware description languages and system level programming/design tools. They enable a holistic functional approach with the major advantage of setting up a unique modeling and evaluation environment for complete industrial electronics systems. Three main design rules are then presented. These are algorithm refinement, modularity, and systematic search for the best compromise between the control performance and the architectural constraints. An overview of contributions and limits of FPGAs is also given, followed by a short survey of FPGA-based intelligent controllers for modern industrial systems. Finally, two complete and timely case studies are presented to illustrate the benefits of an FPGA implementation when using the proposed system modeling and design methodology. These consist of the direct torque control for induction motor drives and the control of a diesel-driven synchronous stand-alone generator with the help of fuzzy logic.

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FPGA Design Methodology for Industrial Control Systems—A Review

Piezoelectric transformers (PTs) present an attractive solution compared with magnetic transformers because they have alternative characteristics that are appropriate for particular applications, namely high power density and high isolation levels with low EMI content. The behavior of PTs is very dependent on the material type, geometry and number of layers. Since PTs should be used in a power topology, it is necessary to establish design rules in order to select the proper specifications of the PT for each particular application. This work presents some design guidelines as well as the description of the influence of several constructive parameters on the behavior of the multi-layer PTs.

Design considerations of multi-layer piezoelectric transformers

1D magnetic component models are very useful to study particular cases in which 1D approximations can be assumed. The field distribution can be considered as 1D when the magnetic field (H) shows negligible values in two of the three dimensions, and the magnitude of the nonzero coordinate keeps constant along this 1D direction. Therefore, 1D models should be modified in order to be used with planar transformers, because their magnetic field vector has a constant direction, but its magnitude is not constant along that direction. This work presents a 1D model for planar magnetic transformers. Since those components are widely applied this procedure can become a useful analysis tool. Some comparisons between 2D approaches and the proposed 1D model have been carried out in order to show the accuracy of the proposed method.

http://ieeexplore.ieee.org/iel5/6364/17081/00789076.pdf

1D magnetic component model for planar structures

This work presents a study of the influence of the winding strategy on the parasitic effects of toroidal transformers Finite element analysis solvers have been used in order to obtain the energies and losses of these magnetic components The study has been carried out generating a frequency and geometry dependent model that can be used in an electrical simulator in order to obtain the leakage inductance and AC resistance A novel procedure based in 2D FEA solvers is used in order to study the 3D field distribution of the toroidal transformers It is shown that the parasitic effects can be drastically reduced if the proper winding strategy is chosen The qualification of this reduction allows the designer to avoid bad designs in terms of winding strategy

Influence of the winding strategy in toroidal transformers

This paper presents a micro-inverter to be integrated into a photovoltaic panel. The proposed single-stage solution combines a forward converter with a constant off-time boundary mode control, providing MPPT capability and unity power factor. The transformer structure of the power stage remains as in the classical DC-DC forward converter. Transformer primary windings are utilized for power transfer or demagnetization depending on the grid semi-cycle. Furthermore, bidirectional switches are used on the secondary side allowing direct connection of the inverter to the grid. Design considerations regarding the inductance value, transformer turns ratio and frequency variation during a line semi-cycle are provided. The decoupling of the twice the line frequency power pulsation is also discussed, as well as the maximum power point tracking (MPPT) capability. Simulation and experimental results for a 50W@110V prototype are enclosed.

Single-stage grid-connected forward microinverter with constant off-time boundary mode control

The control proposed and analyzed in this paper is based on the peak current mode control of the output capacitor current of a Buck converter. The output capacitor current loop provides fast dynamic response to the control since it behaves as a feed-forward of the load current while the voltage loop provides accurate steady state regulation. A simulation oriented averaged model of the proposed control has been developed to design the external voltage loop. As shown in simulations, with the converter switching at 5 MHz, the proposed control with a voltage loop of 50 kHz bandwidth has the same voltage drop and a similar dynamic response as a 1 MHz bandwidth voltage mode control. The reduction of the bandwidth makes easier the control implementation and integration. Finally, experimental results have been achieved verifying the fast dynamic response of the proposed control under load steps.

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J.A. Cobos

Papers

Design considerations of multi-layer piezoelectric transformers

1D magnetic component model for planar structures

Influence of the winding strategy in toroidal transformers

Single-stage grid-connected forward microinverter with constant off-time boundary mode control

Fast control technique based on peak current mode control of the output capacitor current