Converter In Continuous Conduction Mode Research Articles

Conversor Cc-cc de Alto Ganho e com Compartilhamento da Corrente de Entrada Empregado em Células A Combustível

Este artigo propõe uma configuração de conversores cc-cc aplicada ao processamento de energia proveniente de células a combustível. Tal configuração é baseada no uso de conversores Forward com entradas interligadas em paralelo e saídas interligadas em série e traz, como vantagens, elevado ganho estático, compartilhamento da corrente de entrada e emprego de um único sinal de comando para o acionamento de todos os interruptores. No decorrer deste artigo são apresentadas as etapas de operação, as principais formas de onda, uma metodologia para redução da configuração proposta a um conversor Buck equivalente e a modelagem orientada ao controle. Para validar a análise teórica, um protótipo com tensão de entrada de 26 V, tensão de saída de 210 V, potência nominal de 900 W e rendimento de 89,7% em potência nominal foi construído e testado. A configuração de conversores também foi avaliada como parte integrante de uma microrrede híbrida composta por outras fontes renováveis. Resultados experimentais são apresentados e discutidos.

Unified model of boost converter in continuous and discontinuous conduction modes

Much effort has been made to build appropriate models for a boost converter. However, these models were described as inexact or complicated expressions in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM). This study proposes a new modelling method based on propositional calculus and linear constraint. First, the equivalent operating conditions (OCs) of the boost converter in CCM and DCM are formulated. Second, according to the equivalent translation principle, the OCs of the boost converter in three different modes can be transformed into two linear inequalities. Moreover then, a unified model of the boost converter in CCM and DCM is obtained. Compared with mixed logical dynamical model, the proposed model (PM) of the boost converter is more concise. In addition, the PM is a large-signal model in the theoretical analysis. Finally, the model is simulated in MATLAB under different load conditions and its effectiveness is well verified by simulation results. Moreover, the experimental results are consistent with the simulation results.

Implementation of Rapid Prototyping Tools for Power Loss and Cost Minimization of DC-DC Converters

In this paper, power loss and cost models of power electronic converters based on converter ratings and datasheet information are presented. These models aid in creating rapid prototypes which facilitate the component selection process. Through rapid prototyping, users can estimate power loss and cost which are essential in design decisions. The proposed approach treats main power electronic components of a converter as building blocks that can be arranged to obtain multiple topologies to facilitate rapid prototyping. In order to get system-level power loss and cost models, two processes are implemented. The first process automatically provides minimum power loss or cost estimates and identifies components for specific applications and ratings; the second process estimates power losses and costs of each component of interest as well as the whole system. Two examples are used to illustrate the proposed approaches—boost and buck converters in continuous conduction mode. Achieved cost and loss estimates are over 93% accurate when compared to measured losses and real cost data. This research presents derivations of the proposed models, experimental validation of the models and demonstration of a user friendly interface that integrates all the models. Tools presented in this paper are expected to be very useful for practicing engineers, designers, and researchers, and are flexible and adaptable with changing or new technologies and varying component prices.

Model Predictive Voltage Control for Single-Inductor Multiple-Output DC–DC Converter With Reduced Cross Regulation

This paper presents a model predictive voltage control (MPVC) method for the single-inductor multiple-output (SIMO) dc-dc converter. The proposed MPVC method is able to solve the cross-regulation problem, which is a critical issue in SIMO dc-dc converters. The design of the proposed method including augmented state-space model, cost function, enumerated algorithm, and constraints for the SIMO dc-dc converter is discussed. Simulation for the influences of predict horizon N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</sub> , control horizon N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> , and Lagrange multiplier λ on the voltage ripple is conducted to guide the control parameters' setting for hardware implementation. Steady-state operation and dynamic performance of the proposed MPVC method are conducted in simulation and experiment based on the single-inductor dual-output (SIDO) buck converter to verify the proposed MPVC method. In addition, the comparison between the proposed method and state-of-art methods for the SIMO dc-dc converters is presented. Simulation and experimental results demonstrate that the MPVC method guarantees low cross regulation for the SIMO dc-dc converter in continuous-conduction mode (CCM) and has a fast response speed to variations in load and reference.

Comment on “A Unified State-Space Model of Constant-Frequency Current-Mode Controlled Power Converters in Continuous Conduction Mode”

In their recent paper [ IEEE Trans. Ind. Electron ., vol. 62, no. 7, pp. 4514–4524, Jul. 2015], Smithson and Williamson propose a unified state-space model for power converters in peak current-mode control. As a part of their experimental section, the control-to-output frequency response is compared against the models of Ridley and Kondrath. The comparison reveals a significant difference between Ridley’s model and the proposed model as well as the measured frequency response. If this were true, controller designs relying on Ridley’s model would possibly have to be called into question, presumably affecting many practical designs. For this reason, the model comparison will be repeated here, showing that the results of Ridley’s model are in fact very close to the proposed model of Smithson and Williamson if the correct model formulation is being used.

A new DC-DC converter based on voltage-lift technique

Summary In this paper, a new boost dc–dc converter based on voltage lift (VL) technique is proposed. There is any need for transformer, coupled inductances and sequential connections in the proposed boost converter topology. In this paper, the operating of proposed boost dc–dc converter in continuous conduction mode (CCM) and discontinuous conduction mode (DCM) was discussed, and the current and voltage equations of the inductors and capacitors were obtained with details. So, the value of critical inductance and the operating of the proposed dc–dc converter between CCM and DCM were presented. The switching currents of each switch were analyzed. The switches, diodes, inductors and capacitors root-mean-square (RMS) current stresses were discussed. Finally, the correct performance of the proposed converter based on presented theoretical issues is verified by using simulation results on EMTDC/PSCAD software program and experimental results by using laboratory prototype. Copyright © 2015 John Wiley & Sons, Ltd.

A Unified State-Space Model of Constant-Frequency Current-Mode-Controlled Power Converters in Continuous Conduction Mode

While current-mode control of dc–dc converters provides numerous benefits over voltage-mode control, previous models of the control strategy have been limited to the form of classical control models. Through the use of a state-space averaged (SSA) model of current-mode control, both the open-loop and closed-loop circuit parameters of open-loop control-to-output frequency response, conducted susceptibility, input admittance, output impedance, and any other desired response can be easily obtained. In this paper, SSA models of current-mode-controlled converters are derived and presented for buck, boost, and flyback topologies operating in continuous conduction mode. The new model allows for simpler and more accurate modeling than possible with previous methods, facilitates the modeling of cascaded converters, and allows for the use of state-variable feedback and other modern control methods in applications that use current-mode control.

Improved small signal model for voltage‐boosting converter with hybrid energy pumping

Voltage-boosting converter with hybrid energy pumping, which possesses high voltage conversion, small voltage stress on the low-side switch and diode and easy to drive, is a good topology of DC–DC converters for obtaining high output voltage to satisfy the requirements in practical applications. In this study, after indicating the drawbacks of the existing small signal model of the voltage-boosting converter with hybrid energy pumping from the comparisons between the theoretical calculations and the power electronics simulator (PSIM) simulations, an improved small signal model and corresponding transfer functions of this new converter in continuous conduction mode and discontinuous conduction mode operations are derived and analysed. The results from the theoretical analysis, PSIM simulations and circuit experiments show that the improved small signal model of the voltage-boosting converter with hybrid energy pumping here is more effective, accurate and general than the existing model.

English

Dc power supplies are extensively used inside most of electrical and electronic appliances such as in computers, televisions, audio sets and others.And the electrical energy available in the utility grid is not suitable for direct use .So in particular, applications requiring DC source must involve an interface device between the AC power line and the load requiring the DC voltage. Conventional AC/DC conversion involves diode rectifiers with large capacitor to reduce DC voltage ripple. The filter capacitor reduces the ripple present in the output voltage but draws non sinusoidal line current which reduces the power factor. So power factor correction (PFC) techniques are gaining increasing attention. The most popular topology for active PFC is boost converter as it draws continuous input current. This input current can be manipulated by average current mode control technique. But there are ripple in the input current due to inductor of boost converter which can be minimized by using two phase interleaved boost converter. So here average current mode controlled interleaved boost converter in continuous conduction mode using PI controller, is represented which provides high power factor and low THD

Digital control of isolated Cuk power factor correction converter under wide range of load variation

This study presents a novel digital double-loop control method, that is, inner current loop and outer voltage loop, for a single-stage isolated Cuk power factor correction (PFC) converter in continuous conduction mode (CCM). First, control law of current loop, consisting of a current term and a voltage term, is derived. Considering that inductance value of inductors varies with load change, an adaptive gain scheduling method is applied to change the current term. Second, control law of voltage loop is derived based on proportional-integral control with introducing linearisation and feedforward compensation. Meanwhile, a moving average filter is utilised to decrease ripple effect of output voltage, and thus smoother input signal for current loop and fast dynamic response for voltage loop are guaranteed. A 1600 W one-phase isolated Cuk PFC converter controlled by a digital signal processor is developed and achieves power factor higher than 0.99, total harmonic distortion of input current lower than 8.5% with load varying from 25 to 100% and fast dynamic response performance. Finally, a 4800 W three-phase AC–DC converter based on the above PFC converter is implemented and its performance additionally indicate that current sharing issue can be easy to deal with by using the proposed control method.

Variable Off-Time Control Loop for Current-Mode Floating Buck Converters in LED Driving Applications

A versatile controller architecture, used in current-mode floating buck converters for LED driving, is developed. State-of-the-art controllers rely on a fixed switching period and variable duty cycle, focusing on current averaging circuits. Instead, the proposed controller architecture is based on fixed peak current and adaptable off time as the average current control method. The control loop is comprised of an averaging block, transconductance amplifier, and an innovative time modulator. This modulator is intended to provide constant control loop response regardless of input voltage, current storage inductor, and number of LEDs in order to improve converter applicability for LED drivers. Fabricated in a 5 V standard 0.5 $\mu\hbox{m}$ CMOS technology, the prototype controller is implemented and tested in a current-mode floating buck converter. The converter exhibits sound continuous conduction mode (CCM) operation for input voltages between 11 and 20 V, and a wide inductor range of 100–1000 $\mu \hbox{H}$ . In all instances, the measured average LED current variation was lower than 10% of the desired value. A maximum conversion efficiency of 91% is obtained when driving 50 mA through four LEDs (with 14 V input voltage and an inductor of 470 $\mu \hbox{H}$ ). A stable CCM converter operation is also proven by simulation for nine LEDs and 45 V input voltage.

Analysis and Design of Single Phase AC-DC Modified SEPIC Converter

Power electronic devices with front-end rectifier are widely used in industry, commerce and transportation, which result in low power factor. Though there are several proposed solutions to this, Single Ended Primary Inductance Converter (SEPIC) converter was the most successful one. But the conventional SEPIC converters suffer from high switching losses. Hence in this paper, a modified SEPIC converter is used to improve the power factor at the mains side. This paper presents the simulation and analysis of single phase single-switch, converter topologies of AC-DC SEPIC converter and modified SEPIC converter for Continuous Conduction Mode (CCM) of operation with 48V, 100W output power. The results of SEPIC converter and modified SEPIC converter are compared for closed loop analysis in simulation which is done in PSIM. It is found that modified SEPIC converter has high regulated output voltage and high power factor.

Critical output‐capacitor ESR for stability of V 2 controlled buck converter in CCM and DCM

It has been reported that subharmonic instability exists in the V2 controlled buck converter in continuous conduction mode (CCM) when the duty ratio is above 0.5 (D > 0.5) and no stability issue exists in discontinuous conduction mode (DCM) when 0 < D < 1. However, the CCM and DCM instabilities will appear in the safe duty ratio range when the equivalent series resistance (ESR) of the output capacitor is below a critical value. The critical output-capacitor ESR for the stabiiity of a V2 controlled buck converter in CCM and DCM is investigated by using the discrete-time model and verified by circuit simulations.

Multivariable Control of Single-Inductor Dual-Output Buck Converters

Cross regulation is the main technical challenge of a single-inductor multiple-output (SIMO) dc-dc converter. This paper proposes a multivariable digital controller to suppress the cross regulation of a single-inductor dual-output (SIDO) buck converter in continuous conduction mode (CCM) operation. The controller design methodology originates from the open-loop shaping of the multi-input multi-output (MIMO) systems. The control design procedure includes: 1) determination of a family of nonparametric models of the SIDO converter at operating points of interest, 2) determination of the class of the controller, and 3) system open-loop shaping by the convex minimization of the summation of the square second norm of the errors between the system open-loop transfer function matrices and a desired open-loop transfer function matrix. The proposed controller minimizes the coupling between the outputs of the SIDO converter and provides satisfactory dynamic performance in CCM operation. This paper describes the theoretical aspects involved in the design procedure of the controller and evaluates the performance of the controller based on simulation studies and experiments.

Buck converter‐based power supply design for low power light emitting diode lamp lighting

This study deals with the analysis and implementation of an HPF (high power factor) single-stage, single switch buck converter-based power supply design for an LED (light emitting diode) lamp load of 13 W operated at the universal ac mains. In general purpose lighting applications, a buck converter is a good candidate for power factor correction with low component count and reduced cost. In low-power lighting, it is a tough task to control the THD i (total harmonic distortion) of ac mains current under the limits of strict international standards such as IEC-61000-3-2 with universal ac mains for class D equipments. In the proposed optocouplerless topology, HPF operation at input ac mains is achieved by operating the buck ac-dc converter in continuous conduction mode. The design, modelling and simulation of the proposed topology are executed using MATLAB-Simulink and sim-power system toolboxes. A prototype of the power supply for LED lamp is developed for multiple LEDs connected in series configuration. The efficiency of the proposed LED lamp driver is observed as 83.76% at rated voltage of 220 V and the THD of ac mains current less than 17.27% for a wide range of voltages of 90-270 V.

Constant-Frequency Peak-Ripple-Based Control of Buck Converter in CCM: Review, Unification, and Duality

The operation principles of peak current control, V2 control, and enhanced- V2 control of buck converter in continuous conduction mode are reviewed and compared. By the use of weight factors of inductor current and output voltage, they are unified as constant-frequency peak-ripple-based (CF-PR) analog control. It is revealed that conventional peak current control and V2 control are two boundaries of the unified CF-PR control. The duality items between CF-PR control and constant-frequency valley-ripple-based (CF-VR) control are proposed. As the duality of CF-PR analog control, CF-VR analog control is investigated. Unified CF-PR and CF-VR digital control laws with different modulations and their stabilities are investigated in terms of the duality. Experimental results verify the theory analysis.

Fractional order Buck–Boost converter in CCM: modelling, analysis and simulations

In this paper, the modelling, analysis and the power electronics simulator (PSIM) simulations of the fractional order Buck–Boost converter operating in continuous conduction mode (CCM) operation are investigated. Based on the three-terminal switch device method, the average circuit model of the fractional order Buck–Boost converter is established, and the corresponding DC equivalent circuit model and AC small signal equivalent circuit model are presented. And then, the equilibrium point and the transfer functions are derived. It is found that the equilibrium point is not influenced by the inductor’s or the capacitor’s order, but both these orders are included in the derived transfer functions. Finally, the comparisons between the theoretical analysis and the PSIM simulations are given for confirmation.

Analytical Solution for Steady and Transient States of Buck DC–DC Converter in CCM

In this paper, a new method is proposed for mathematical modeling of buck dc–dc converter in continuous conduction mode. In this method, the differential equations of inductor current and capacitor voltage are firstly obtained. Then, using Laplace and Z transforms, the differential equations of inductor current and output voltage of converter are solved to obtain the relations of them. In the proposed method, the Laplace transform is used to determine the general equations of inductor current and output voltage and the Z-transform is used to determine their initial conditions. The transient and steady states responses of converter are analyzed using the obtained mathematical model. In addition, the effect of converter components on output voltage and inductor current ripples is investigated. The validity of proposed method is reconfirmed by experimental and simulation results using PSCAD/EMTDC software.

Power loss analysis of active clamp forward converter in continuous conduction mode and discontinuous conduction mode operating modes

In order to improve the light-load efficiency of active clamp forward converter with synchronous rectifier (SR), power loss analysis of the converter operating in continuous conduction mode (CCM) and discontinuous conduction mode (DCM) are presented in this study. The light-load efficiency of normal ACF converter with SR is low because the output inductor current can go negative when operating in CCM. Considering the fixed frequency control only, to shift the converter's operating mode from CCM to DCM at a critical point of output current at light-load is a solution for efficiency improvement. Based on the CCM and DCM power dissipation models proposed in this study, the power loss characteristics of the converter are analysed, and the critical shift point of output current can be derived, which has also been verified by an experimental prototype.

Small-Signal Modeling of Open-Loop PWM Z-Source Converter by Circuit-Averaging Technique

This paper presents the ac small-signal modeling of the power stage of pulsewidth-modulated Z-source converter in continuous conduction mode by the circuit-averaging technique. The small-signal models used to derive the open-loop power-stage input voltage-to-capacitor voltage, input voltage-to-inductor current, control-to-capacitor voltage, and control-to-inductor current transfer functions are derived. Open-loop power-stage transfer functions corresponding to the capacitor voltage loop and inductor current loop are derived. The transfer functions derived take into account the equivalent series resistances of the inductors and capacitors. Experimental validation of the derived small-signal models is presented for a laboratory prototype. The theoretical predictions are in good agreement with the experimental results.