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

AC distributed power systems (DPS) can be found in several new and emerging applications. Similar to dc distributed power systems, an ac DPS relies on power electronics and control to realize its functions and achieve the required performance. System stability and power quality are important issues in both types of systems due to the complex system behavior resulted from active control at both the source and the load side. Traditional small-signal analysis methods cannot be directly applied to an ac DPS because of the periodically time-varying system operation trajectory. Possible solutions to this problem include transformation into a rotating (dq) reference frame, modeling using dynamic phasors, reduced-order modeling, and harmonic linearization. This paper reviews these small-signal methods and discusses their utilities as well as limitations. Compatibility of each type of models with state-space and impedance-based system analysis approaches will also be discussed. Problems related to the linearization of phasor-based models and their use in impedance-based system analysis are highlighted in particular.

Small-Signal Methods for AC Distributed Power Systems–A Review

A DC to DC Converter includes an electrical circuit that allows batteries and other electrical energy storage devices to be charged from or to discharge to a variable voltage DC bus. This electrical circuit also enables seamless integration with other energy storage devices and/or DC power sources, such as fuel cells, to provide DC power for a Power Management System. A Power Management System preferably provides both full power source management and power conditioning. The Power Management System is able to manage power flow to and from multiple, isolated power sources and energy storage devices to deliver high quality alternating current (“AC”) power to a load.

Dc to dc converter and power management system

State-space average-value modeling of pulsewidth modulation converters in continuous and discontinuous modes has received significant attention in the literature, and various models have been developed. This paper presents a new approach for generating the state-space average-value model. In the proposed methodology, the so-called duty-ratio constraint and the correction term are extracted numerically using the detailed simulation and are expressed as nonlinear functions of the duty cycle and average-value of the fast state variable. The parasitic effects of circuit elements are readily included. The resulting average-value model is compared to a hardware prototype, a detailed simulation, and several previously published models. The proposed model is shown to be very accurate in predicting the large-signal time-domain transients as well as the small-signal frequency-domain characteristics.

Numerical state-space average-value modeling of PWM DC-DC converters operating in DCM and CCM

A power system having a power converter with an adaptive controller. The power system is coupled to a load and includes a power system controller that receives a signal indicating a system operational state of the load and selects a power converter operational state as a function thereof. The power system also includes a power converter with a power switch that conducts for a duty cycle to provide a regulated output characteristic at an output thereof. The power converter also includes a controller that receives a command from the power system controller to enter the power converter operational state and provides a signal to control the duty cycle of the power switch as a function of the output characteristic and in accordance with the command, thereby regulating an internal operating characteristic of the power converter to improve an operating efficiency thereof as a function of the system operational state.

Power system with power converters having an adaptive controller

This paper addresses modeling and practical design issues for PWM converters with average current control. A straight-forward averaged modeling method is proposed, and the resulting models are shown to be accurate enough for practical design purpose. Limitations of previously published models that incorporate sampling effect are discussed. The proposed averaged model is then applied for stability analysis and control design. In particular, conditions under which switching instability may occur are identified, and design method that avoids the instability problem is presented. The proposed modeling and design methods are demonstrated and further validated by a prototype synchronous-switch buck converter with 5 V input and 2 V output.

Modeling and practical design issues for average current control

A composite magnetic core formed of a high permeability material and a lower permeability, high saturation flux density material prevents core saturation without an air gap and reduces eddy current losses and loss of inductance. The composite core is configured such that the low permeability, high saturation material is located where the flux accumulates from the high permeability sections. The presence of magnetic material having a relatively high permeability keeps the flux confined within the core thereby preventing fringing flux from spilling out into the winding arrangement. This composite core configuration balances the requirements of preventing core saturation and minimizing eddy current losses without increasing either the height or width of the core or the number of windings.

Composite magnetic core for switch-mode power converters

This paper presents a unified analysis of half-bridge converters with current-doubler rectifier using an averaged circuit model. The model is applicable for both symmetrical and asymmetrical control. Different approaches to integrating the transformer with the inductors are discussed and their equivalent circuit models for use with the averaged converter model are developed. In addition, an inductor loop formed by the transformer and the two filter inductors is identified, and its effects on converter operation and control design are discussed. Numerical simulation and experimental results from a prototype converter are also reported.

Unified analysis of half-bridge converters with current-doubler rectifier

This paper presents an improved current-doubler rectifier (CDR) circuit and its implementation with integrated magnetics for high efficiency, high power-density DC/DC converter applications. Compared to previously published integrated magnetics for CDR circuits, the proposed design significantly increases the equivalent filtering inductance resulting in lower voltage and current ripple and higher efficiency, especially under fight load. Operation of the integrated magnetics is explained, along with an equivalent circuit model suitable for steady state and dynamic response analysis. Experimental results from two 100 W, 3.3 V output half-bridge prototype converters are presented to validate the concept and the analysis.

https://ieeexplore.ieee.org/iel5/7757/21322/00989340.pdf

An improved current-doubler rectifier with integrated magnetics

Unified averaged switch models for PWM converters are presented. The models are applicable for both continuous and discontinuous conduction modes. They have been implemented in SABER and are intended for stability analysis of large distributed power systems. In addition to their simplicity and improved accuracy over existing models, the new models are also capable of providing inductor ripple information. This makes it possible to implement peak current limiting and other protection functions, which is important for large-signal stability analysis of distributed power systems, but has not been possible with existing averaged models. Simulation results from both a DC/DC and a power factor corrected AC/DC converters are presented to validate the accuracy of the models and to demonstrate the robustness of the implementation, especially under abnormal operation conditions.

Jian Sun

Papers

Modeling and practical design issues for average current control

Composite magnetic core for switch-mode power converters

Unified analysis of half-bridge converters with current-doubler rectifier

An improved current-doubler rectifier with integrated magnetics

Unified averaged switch models for stability analysis of large distributed power systems