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.

/pdf/a-review-of-single-phase-improved-power-quality-ac-dc-2pm6h4zjxq.pdf

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

A review on electrochemical double-layer capacitors

This paper proposes a novel dual-phase-shift (DPS) control strategy for a dual-active-bridge isolated bidirectional DC-DC converter. The proposed DPS control consists of a phase shift between the primary and secondary voltages of the isolation transformer, and a phase shift between the gate signals of the diagonal switches of each H-bridge. Simulation on a 600-V/5-kW prototype shows that the DPS control has excellent dynamic and static performance compared to the traditional phase-shift control (single phase shift). In this paper, the concept of ldquoreactive powerrdquo is defined, and the corresponding equations are derived for isolated bidirectional DC-DC converters. It is shown that the reactive power in traditional phase-shift control is inherent, and is the main factor contributing to large peak current and large system loss. The DPS control can eliminate reactive power in isolated bidirectional DC-DC converters. In addition, the DPS control can decrease the peak inrush current and steady-state current, improve system efficiency, increase system power capability (by 33%), and minimize the output capacitance as compared to the traditional phase-shift control. The soft-switching range and the influence of short-time-scale factors, such as deadband and system-level safe operation area, are also discussed in detail. Under certain operation conditions, deadband compensation can be implemented easily in the DPS control without a current sensor.

/pdf/eliminate-reactive-power-and-increase-system-efficiency-of-3j7gowjzlm.pdf

Eliminate Reactive Power and Increase System Efficiency of Isolated Bidirectional Dual-Active-Bridge DC–DC Converters Using Novel Dual-Phase-Shift Control

Supercapacitors (SCs) have high power density and exceptional durability. Progress has been made in their materials and chemistries, while extensive research has been carried out to address challenges of SC management. The potential engineering applications of SCs are being continually explored. This paper presents a review of SC modeling, state estimation, and industrial applications reported in the literature, with the overarching goal to summarize recent research progress and stimulate innovative thoughts for SC control/management. For SC modeling, the state-of-the-art models for electrical, self-discharge, and thermal behaviors are systematically reviewed, where electrochemical, equivalent circuit, intelligent, and fractional-order models for electrical behavior simulation are highlighted. For SC state estimation, methods for State-of-Charge (SOC) estimation and State-of-Health (SOH) monitoring are covered, together with an underlying analysis of aging mechanism and its influencing factors. Finally, a wide range of potential SC applications is summarized. Particularly, co-working with high energy-density devices constitutes hybrid energy storage for renewable energy systems and electric vehicles (EVs), sufficiently reaping synergistic benefits of multiple energy-storage units.

A review of supercapacitor modeling, estimation, and applications: A control/management perspective

This paper presents a comprehensive review of step-up single-phase non-isolated inverters suitable for ac-module applications. In order to compare the most feasible solutions of the reviewed topologies, a benchmark is set. This benchmark is based on a typical ac-module application considering the requirements for the solar panels and the grid. The selected solutions are designed and simulated complying with the benchmark obtaining passive and semiconductor components ratings in order to perform a comparison in terms of size and cost. A discussion of the analyzed topologies regarding the obtained ratings as well as ground currents is presented. Recommendations for topological solutions complying with the application benchmark are provided.

/pdf/review-and-comparison-of-step-up-transformerless-topologies-ubtxng7ots.pdf

Review and Comparison of Step-Up Transformerless Topologies for Photovoltaic AC-Module Application

In this paper, a critical evaluation of the effect of voltage sags on adjustable-speed drives (ASDs) is presented. In particular, the DC-link voltage variation under voltage sag and its dependence on source impedance, DC-link inductance and output load is computed. It is shown that, for larger source impedance, the DC-link voltage variation under a voltage sag is also large and increases the susceptibility of an ASD and may result in a nuisance trip. The results from the analysis are plotted in per-unit quantities and serve as a design guide to assess ASD performance for a variety of sags. In order to improve the performance of ASDs, this paper proposes an integrated boost converter approach. This approach provides ride-through to critical ASD load during voltage sags without any additional energy storage device. Upon detection of a voltage sag, the boost converter operates with suitable duty ratio and maintains the DC-link voltage within acceptable limits. This prevents nuisance tripping and facilitates continuous operation of critical ASD load at rated torque. The proposed integrated boost converter does not introduce any additional semiconductors in the series path of the power flow and is low in cost. A commercially available 480 V 22 kVA ASD is modified with the integrated boost converter approach, and details are discussed. Analysis, simulation, and experimental performance of the ride-through approach are presented.

Effect of voltage sags on adjustable-speed drives: a critical evaluation and an approach to improve performance

Adjustable speed drives (ASDs) under short-term power interruptions (STPIs) can interrupt a critical process. In this paper an approach to provide ride-through with flyback converter modules (FBCMs) powered by super capacitors is explored. The proposed approach is modular and facilitates additional modules to be added to suit higher voltage/power ratings. Both unidirectional and bidirectional flyback DC/DC converter topologies are examined. Simulation and experimental results are presented.

An approach to achieve ride-through of an adjustable speed drive with flyback converter modules powered by super capacitors

In one embodiment of the present invention, a system for ride-through of an adjustable speed drive for voltage sags is provided. The system comprises an adjustable speed drive including a three phase electric utility, a diode rectifier, a dc-link, an inverter, and a motor. Coupled to the adjustable speed drive is a ride-through circuit which includes a controller having a first input and a second input, the first input operable to receive the voltage from each phase of the three phase electric utility and determine the magnitude and phase of the voltage sag, and the second input operable to receive the dc-link voltage to ensure that the rated dc-link voltage is not exceeded. Also included is an IGBT coupled to an output of the controller and operable to switch on and off rapidly based on the amount of voltage sag. An inductor associated with the IGBT and operable to store energy when the IGBT is switched on and to transfer energy to the dc-link when the IGBT is off is also included. This maintains the dc-link voltage to provide ride-through operation of the adjustable speed drive.

Method and system for ride-through of an adjustable speed drive for voltage sags and short-term power interruption

In this paper it is presented an approach for power conditioning of a PV (photo-voltaic) cell array. In particular, an array of solar cells is employed as an alternative renewable resource (ARR) to provide clean electric energy to remote rural residential or industrial nonlinear loads. The approach employs a series-combined connected boost and buck-boost dc-dc converter for power conditioning of the dc voltage provided by a photo-voltaic array. The input voltage to the combined converters is 100 V provided from two series-connected PV cells, which is converted and increased to 400 V at the dc output voltage. Series-combined connected boost and buck-boost dc-dc converters operate in alternate fashion each other. This helps to reduce the input ripple current and provide the required 400 Vdc on a sinusoidal PWM three-phase inverter. Analysis of the two series-combined dc-dc converters is presented along with simulation results. Evaluation of the combined and series connected topologies is carried out to compare their performance against individual and separate power conditioning structures. Simulations of the series-combined dc-dc converters are presented with an output dc voltage of 400 V and a maximum output load of P/sub o/ = 600 W.

Analysis and evaluation of a series-combined connected boost and buck-boost dc-dc converter for photovoltaic application

In this paper, a critical evaluation of the effect of voltage sags on adjustable speed drives (ASDs) is presented. In particular the DC-link voltage variation under voltage sag and its dependence on source impedance, DC-link inductance and output load is computed. It is shown that for larger source impedance, the DC-link voltage variation under a voltage sag is also large and increases the susceptibility of an ASD and may result in a nuisance trip. The results from the analysis are plotted in per unit quantities and serve as a design guide to assess ASD performance for a variety of sags. In order to improve the performance of ASDs, this paper proposes an integrated boost converter approach. This approach provides ridethrough to critical ASD load during voltage sags without any additional energy storage device. Upon detection of a voltage sag the boost converter operates with suitable duty ratio and maintains the DC-link voltage within acceptable limits. This prevents nuisance tripping and facilitates continuous operation of critical ASD load at rated torque. The proposed integrated boost converter does not introduce any additional semiconductors in the series path of the power flow and is low in cost. A commercially available 480 V, 22 kVA ASD is modified with the integrated boost converter approach and details are discussed. Analysis, simulation and experimental performance of the ridethrough approach are presented.

J.L. Duran-Gomez

Papers

Effect of voltage sags on adjustable-speed drives: a critical evaluation and an approach to improve performance

An approach to achieve ride-through of an adjustable speed drive with flyback converter modules powered by super capacitors

Method and system for ride-through of an adjustable speed drive for voltage sags and short-term power interruption

Analysis and evaluation of a series-combined connected boost and buck-boost dc-dc converter for photovoltaic application

Effect of voltage sags on adjustable speed drives-a critical evaluation and an approach to improve its performance