A step‐up PWM DC–DC converter for renewable energy applications

A step‐up pulse width modulation (PWM) direct current (DC)–DC converter is presented in this paper, which has its origin in quasi Z‐source inverter. Analysis of this converter in steady state is presented, and relevant expressions are derived for the proposed converter operating in continuous conduction mode. The power loss expressions for each component of the converter are derived, and thereby, obtained expressions for overall converter efficiency are presented. Further, a dynamic model is derived to design an appropriate controller for this converter. The simulation and experimental results are presented to support the theoretical analysis. The advantages such as continuous input current, high step‐up gain at lower duty ratio, and common ground for source, load, and switch makes the converter suitable for renewable energy applications. Copyright © 2015 John Wiley & Sons, Ltd.     

A high step‐up half‐bridge DC/DC converter with a special coupled inductor for input current ripple cancelation and extended voltage doubler circuit for power conditioning of fuel cell systems

This paper presents a high step‐up soft switched dc–dc converter having the feature of current ripple cancelation in the input stage that is specialized for power conditioning of fuel cell systems. The converter comprises a special half‐bridge converter and a rectifier stage based upon the voltage‐doubler circuit, in which the coupled‐inductor technology is amalgamated with switched‐capacitor circuit. The input current with no ripple is the principal characteristics of this topology that is achieved by utilizing a small coupled inductor. In addition, the low clamped voltage stress across both power switches and output diodes is another advantage of the proposed converter, which allows employing the metal–oxide–semiconductor field‐effect transistors with minuscule on‐state resistance and diodes with lower forward voltage‐drop, and thereby, the semiconductors' conduction losses diminish considerably. The inherent nature of this topology handles the switching scheme based on the asymmetrical pulse width modulation in order for switches to establish the zero voltage switching, leading to lower switching losses. Besides, because of the absence of the reverse‐recovery phenomenon, all diodes turn off with zero current switching. At last, a 250‐W laboratory prototype with the input voltage 24 V and output voltage 380 V is implemented to verify the especial features of the proposed converter. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.     

A new integrated high step‐up quasi‐resonant flyback‐forward converter

This study presents a new high step‐up, high efficiency, flyback‐forward converter. The proposed converter employs 2 transformers, operating in flyback and forward modes at different intervals, to achieve the high voltage gain. In favor of high power density, transformers have been installed on 1 core. Furthermore, all switches are turned on under zero voltage switching condition, and all diodes are turned off under zero current switching condition. Also, the proposed converter utilizes resonant operation that leads to a reduction in switching loss, turning the converter to a highly efficient one. A 150‐W prototype has been implemented to verify the theoretical analysis, and a complete analysis has been done to investigate the effect of transformers integration.     

A non‐isolated high step‐up DC‐DC converter with integrated 3 winding coupled inductor and reduced switch voltage stress

In this paper, a non‐isolated high step‐up dc‐dc converter based on coupled inductor is proposed. The proposed converter can be used in renewable energy applications. In suggested converter, the high voltage is achieved using 3‐winding coupled inductor, which leads to low voltage rate of the switch. A clamp circuit is used to recycle the leakage inductance energy. Also, the clamp circuit prevents the creation of voltage spikes on semiconductor devices and causes the voltage stress of elements are limited to less than the output voltage. The presented theoretical analyses show that the operation of suggested converter in continuous conduction mode needs to small magnetic inductor. Therefore, the size of coupled inductor's core is reduced, and so the size and cost of presented converter will be decreased. Analysis of the proposed converter is provided with laboratory results to verify its performance.     

An interleaved high step‐up DC‐DC converter with double boost paths

This paper proposed a novel high step‐up converter with double boost paths. The circuit uses two switches and one double‐path voltage multiplier cell to own the double boost and interleaved effects simultaneously. The voltage gain ratio of the proposed DC‐DC converter can be three times the ratio of the conventional boost converter such that the voltage stress of the switch can be lower. The high step‐up performance is in accordance with only one double‐path voltage multiplier cell. Therefore, the number of diodes and capacitors in the proposed converter can be reduced. Furthermore, the interleaved property of the proposed circuit can reduce the losses in the rectifier diode and capacitor. The prototype circuit with 24‐V input voltage, 250‐V output voltage, and 150‐W output power is experimentally realized to verify the validity and effectiveness of the proposed converter. Copyright © 2014 John Wiley & Sons, Ltd.     

Analysis and implementation of a high step‐up converter for fuel cell power‐generation systems

This paper presents a high step‐up converter, which utilizes a three‐winding coupled inductor and a rectified voltage‐doubler circuit to obtain high step‐up gain for fuel cells. The proposed converter functions as an active‐clamp circuit, which relieves large voltage spikes across the power switches. Thus, power switches with low‐voltage‐rated can be utilized to reduce conduction losses and circuit cost. Energy stored in leakage inductances of the coupled inductor is recycled to the output terminal, resulting in efficiency improvements. In addition, the coupled inductor in the presented converter can also have extra windings in order to achieve higher voltage gain. Finally, a prototype circuit with an input voltage of 60 V and an output voltage of 380 V is developed for a 1000 W‐rated fuel cell power‐generation system to validate its performance, and experimental waveforms and measured efficiency under different input voltages and output power level are demonstrated. Copyright © 2016 John Wiley & Sons, Ltd.     

Single‐stage single‐switch PFC converter for wide‐input extreme step‐down voltage applications

This paper presents a new single‐stage single‐switch high power factor correction AC/DC converter suitable for low‐power applications (< 150 W) with a universal input voltage range (90–265 V_rms). The proposed topology integrates a buck–boost input current shaper followed by a buck and a buck–boost converter, respectively. As a result, the proposed converter can operate with larger duty cycles compared with the existing single‐stage single‐switch topologies, hence, making them suitable for extreme step‐down voltage conversion applications. Several desirable features are gained when the three integrated converter cells operate in discontinuous conduction mode. These features include low semiconductor voltage stress, zero‐current switch at turn‐on, and simple control with a fast well‐regulated output voltage. A detailed circuit analysis is performed to derive the design equations. The theoretical analysis and effectiveness of the proposed approach are confirmed by experimental results obtained from a 100‐W/24‐V_dc laboratory prototype. Copyright © 2011 John Wiley & Sons, Ltd.     

Non‐isolated large step‐down voltage conversion ratio converter with non‐pulsating output current

A non‐isolated dual half‐bridge large step‐down voltage conversion ratio converter with non‐pulsating output current, utilizing one coupled inductor, one energy‐transferring capacitor, and one output inductor, is presented herein. The coupled inductor is connected between the input voltage and the output inductor and plays a role to step down the input voltage. Furthermore, the output inductor is used not only to further step down the voltage but also to provide a non‐pulsating output current. Moreover, the proposed converter can achieve zero‐voltage switching. In this study, detailed theoretical deductions and some experimental results of a prototype with 48 V input voltage, 3.3 V output voltage, and 10 A output current are provided to demonstrate the feasibility and effectiveness of the proposed converter. Copyright © 2015 John Wiley & Sons, Ltd.     

A soft‐switching high step‐up DC‐DC converter with a single magnetic component

A soft‐switching high step‐up DC‐DC converter with a single magnetic component is presented in this paper. The proposed converter can provide high voltage gain with a relatively low turn ratio of a transformer. Voltage doubler structure is selected for the output stage. Due to this structure, the voltage gain can be increased, and the voltage stresses of output diodes are clamped as the output voltage. Moreover, the output diode currents are controlled by a leakage inductance of a transformer, and the reverse‐recovery loss of the output diodes is significantly reduced. Two power switches in the proposed converter can operate with soft‐switching due to the reflected secondary current. The voltages across the power switches are confined to the clamping capacitor voltage. Steady‐state analysis, simulation, and experimental results for the proposed converter are presented to validate the feasibility and the performance of the proposed converter. Copyright © 2012 John Wiley & Sons, Ltd.     

Non‐isolated single‐switch DC–DC converters with extended duty cycle for high step‐down voltage applications

Several new topologies of single‐switch non‐isolated DC–DC converters with wide conversion gain and reduced semiconductor voltage stress are proposed in this paper. Most of the proposed topologies are derived from the conventional inverse of SEPIC (Zeta) converter. The proposed topologies can operate with larger switch duty cycles compared with the existing single switch topologies, hence, making them well suitable for high step‐down voltage conversion applications. With extended duty cycle, the current stress in the active power switch is reduced, leading to a significant improvement of the system losses. Moreover, the active power switch in some of the proposed topologies is utilized much better compared to the conventional Zeta and quadratic‐buck converters. The principle of operation, theoretical analysis, and comparison of circuit performances with other step‐down converters are discussed regarding voltage and current stress and switch silicon utilization. Finally, simulation and experimental results for a design example of a 50 W/5 V at 42‐V input voltage operating at 50 kHz will be provided to evaluate the performance of the proposed converters. Copyright © 2014 John Wiley & Sons, Ltd.     

Design and analysis of power‐CMOS‐gate‐based switched‐capacitor DC–DC converter with step‐down and step‐up modes

A unified multi‐stage power‐CMOS‐transmission‐gate‐based quasi‐switched‐capacitor (QSC) DC–DC converter is proposed to integrate both step‐down and step‐up modes all in one circuit configuration for low‐power applications. In this paper, by using power‐CMOS‐transmission‐gate as a bi‐directional switch, the various topologies for step‐down and step‐up modes can be integrated in the same circuit configuration, and the configuration does not require any inductive elements, so the IC fabrication is promising for realization. In addition, both large‐signal state‐space equation and small‐signal transfer function are derived by state‐space averaging technique, and expressed all in one unified formulation for both modes. Based on the unified model, it is all presented for control design and theoretical analysis, including steady‐state output and power, power efficiency, maximum voltage conversion ratio, maximum power efficiency, maximum output power, output voltage ripple percentage, capacitance selection, closed‐loop control and stability, etc. Finally, a multi‐stage QSC DC–DC converter with step‐down and step‐up modes is made in circuit layout by PSPICE tool, and some topics are discussed, including (1) voltage conversion, output ripple percentage, and power efficiency, (2) output robustness against source noises and (3) regulation capability of converter with loading variation. The simulated results are illustrated to show the efficacy of the unified configuration proposed. Copyright © 2003 John Wiley & Sons, Ltd.     

Design of a ZVS PWM DC–DC converter for high gain applications

In this paper, a pulse width modulation DC‐DC converter with high step‐up voltage gain is proposed. The proposed converter achieves high step‐up voltage gain with appropriate duty ratio, coupled inductor, and voltage multiplier technique. The energy stored in the leakage inductor of the coupled inductor can be recycled in the proposed converter. Moreover, because both main and auxiliary switches can be turned on with zero‐voltage switching, switching loss can be reduced by soft‐switching technique. So the overall conversion efficiency is improved significantly. The theoretical steady‐state analyses and the operating principles of the proposed converter are discussed in detail for both continuous conduction mode and discontinuous conduction mode. Finally, a laboratory prototype circuit of the proposed converter is implemented to verify the performance of the proposed converter. Copyright © 2015 John Wiley & Sons, Ltd.     

A DC/DC converter topology for renewable energy systems

This paper presents a DC/DC converter topology for renewable energy systems. The proposed DC/DC converter can be used to obtain a well‐regulated output voltage from low‐voltage power source, such as wind turbine, photovoltaic array, fuel cell, etc. It has the merits of high efficiency, low device stresses, and low current ripple. The operating principle, theoretical analysis, and design criteria are provided in this paper. A laboratory prototype was successfully implemented. The simulation and experimental results are given to verify the feasibility of the proposed scheme. Copyright © 2008 John Wiley & Sons, Ltd.     

A switch‐utilization‐improved switched‐inductor switched‐capacitor converter with adapting stage number

A novel closed‐loop switched‐inductor switched‐capacitor converter (SISCC) is proposed by using the pulse‐width‐modulation (PWM) compensation for the step‐up DC–DC conversion/regulation, and together by combining the adaptive‐stage‐number (ASN), control for the higher switch utilization and wider supply voltage range. The power part of SISCC is composed of two cascaded sub‐circuits, including (i) a serial‐parallel switched‐capacitor circuit with n_c pumping capacitors and (ii) a switched‐inductor booster with m_c resonant capacitors, so as to obtain the high step‐up gain of (n_c + 1) × m_c /(1 ? D) at most, where D is the duty cycle of PWM adopted to enhance output regulation as well as robustness to source/loading variation. Besides, the ASN control is presented with adapting the stage number n (n = 0, 1, 2, …, n_c) of pumping capacitors to obtain a flexible gain of (n + 1) × m_c /(1 ? D), and further in order to make the SISCC operating at a properly small duty cycle for improving switch utilization and/or supply voltage range. Some theoretical analysis and control design include formulation, steady‐state analysis, ASN‐based conversion ratio, efficiency, output ripple, stability, inductance and capacitance selection, and control design. Finally, the performance of this scheme is verified experimentally on an ASN‐based SISCC prototype, and all results are illustrated to show the efficacy of this scheme. Copyright © 2015 John Wiley & Sons, Ltd.     

Efficiency of magnetic coupled boost DC‐DC converters mainly dedicated to renewable energy systems: influence of the coupling factor

This paper presents a specific analysis of an individual basic magnetically coupled direct current‐to‐direct current (DC–DC) converter specially designed for integration in a distributed architecture of renewable energy generators for smart grid applications. In such distributed architecture dedicated for renewable energy, parallel high‐voltage DC presents many advantages over the classical centralized one. We show that in such setup, high voltage can be advantageously produced using a specific magnetically coupled boost converter, and we point out the influence of the coupling factor, generally considered equal to one, on the overall performance of the converter and on the global energy efficiency of the installation. In this study, the generalized concepts of system energy parameters of DC–DC converters are introduced and applied to the transient analysis. Consequently, the operation of a magnetic coupled DC–DC converter with a recovery stage is modeled. The simulation results are compared with those of the behavioral study, deduced from the model pointing out the large influence of the coupling factor value on the global behavior and mainly on the value of the recovery voltage, in all the various parts of the switching cycle. The renewable energy generator operating parameters, such as current and voltage values, can then be predicted in a more useful way to compute new similar DC–DC converter systems. Copyright © 2014 John Wiley & Sons, Ltd.     

High‐efficiency current‐doubler rectifier with low output current ripple and high step‐down voltage ratio

This paper presents a current‐doubler rectifier with low output current ripple and high step‐down voltage ratio. In the proposed rectifier, two extra inductors are introduced to extend the duty ratio of the switches, which in turn reduces the peak current through the isolation transformer as well as the output current ripple; two extra diodes are used to provide discharge paths for the two extra inductors. To highlight the merits of the proposed rectifier, its performance indexes, such as voltage gain function, secondary winding peak current of the isolation transformer, and output current ripple, are analyzed and compared with the conventional current‐doubler rectifier. In this paper, a zero‐voltage‐switching phase‐shift full‐bridge converter with the proposed rectifier with an input voltage of 400 V, output voltage of 12 V, and full load power of 500 W has been implemented and verified, and experimental results have shown that 90% conversion efficiency could be achieved at full load. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

An extensible two‐phase high voltage‐boosting converter with automatic current balance

In this study, an extensible 2‐phase interleaved high step‐up converter with automatic current balance is presented. This converter uses coupled inductors and energy‐transferring capacitors to improve the voltage gain of the traditional 2‐phase interleaved boost converter as well as employs these energy transferring capacitors to do automatic current balance. Furthermore, the voltage gain can be enhanced not only by adjusting the turns ratio but also by increasing the numbers of phases, diodes, and energy‐transferring capacitors. Therefore, it can be used in high input current and high step‐up voltage applications. In this paper, the basic operating principles of the proposed converter are described and analyzed, and finally, its effectiveness is demonstrated by experiment. In addition, the field‐programmable gate array, named EP13T100C8N and manufactured by Altera Co, is used as a control kernel, and an experimental prototype, with input voltage of 12 V, output voltage of 200 V, and rated output power of 200 W, is given to provide the effectiveness of the proposed converter.     

A current sensorless MPPT control method for a stand‐alone‐type PV generation system

In this paper, a current sensorless MPPT control method for a stand‐alone‐type PV generation system is proposed. This control method offers advantages of the simplified hardware configuration and low cost by using only one sensor to measure the PV output voltage. When used as a stand‐alone‐type with a battery load, the experimental results show that the estimated values of PV output current are accurate, and the use of the proposed MPPT control increases the PV generated energy by 16.3% compared to the conventional system. Furthermore, the authors clarified that the proposed method has an extremely high UUF (useful utilization factor) of 98.7%. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(2): 65– 71, 2006; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20424     

High‐power‐factor single‐switch AC to DC converter for LED lighting

In this paper, we report a novel single‐switch AC to DC step‐down converter suitable for light emitting diodes. The proposed topology has a buck and a buck–boost converter. The circuit is designed to operate in the discontinuous conduction mode in order to improve the power factor. In this topology, a part of the input power is connected to the load directly. This feature of the proposed topology increases the efficiency of power conversion, improves the input power factor, produces less voltage stress on intermediate stages, and reduces the output voltage in the absence of a step‐down transformer. The theoretical analysis, design procedure, and performance of the proposed converter are verified by simulation and experiment. A 36 V, 60 W prototype has been built to demonstrate the merits of this circuit. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Output‐voltage feedback control topology for inverters dedicated to renewable energy systems

We present a new control topology for inverters, mainly dedicated to renewable energy applications. The originality is due to the integration in the inverter of an adaptive regulation of its output voltage controlled by a closed feedback loop allowing compensating the voltage drops induced by load variations. The feedback control is based on an adaptive pulse wave modulation (APWM) technique, that controls the power switches of the inverter to obtain the purest possible sine‐wave voltage. The APWM technique straightforwardly compares the inverter output voltage with a reference signal at the grid frequency. In this contribution, this technique is applied to a single‐phase push‐pull inverter but could have been integrated for the control of all kinds of inverter topologies in renewable energy systems. We have shown that the APWM technique allows generating pure sine‐wave voltage, with low total harmonic distortion compared with the generally obtained by classical systems and that load variations do not affect the quality of the output. An experimental prototype of a single‐phase inverter with an adaptive regulation based on APWM technique was developed. The experimental characterizations of the prototype confirm the simulations. Copyright © 2017 John Wiley & Sons, Ltd.