Extreme Duty Cycle Research Articles

Design and analysis of an improved voltage‐lift‐based extended quadratic gain boost converter with reduced voltage stress across components

SummaryIncreasing the voltage gain of traditional boost converter topologies necessitates an unsustainable increase in the operating duty ratio. Because of their inherent architecture, these topologies are incapable of shielding their individual components from the detrimental effects of extreme duty cycle operation, resulting in increased power loss and inefficient performance. With the objective of attaining a higher voltage gain at a lower duty cycle, this research presents a new quadratic type boost converter derived from an improved voltage‐lift (IVL) cell and the conventional boost converter (CBC). By including an IVL cell in CBC, the voltage conversion ratio is quadratic in nature, and the steady‐state performances are improved over those of CBC. This proposed architecture includes a few new parts, such as capacitors, diodes, and an inductor but no controllable switches, thus the close loop control stays the same. During the entire range of the duty cycle, the proposed boost topology outperforms the conventional quadratic boost converter (CQBC) in terms of dc voltage gain. In addition, the voltage stresses on devices (such as switch and diodes) and intermediate capacitors are reduced compared with CQBC. In steady‐state conditions, the voltage gain and design expressions of the storage elements are determined using time‐domain analysis. The suggested extended quadratic gain boost converter (EQGBC) stands out because of its multiple benefits over existing step‐up converter topologies. The suggested EQGBC has been tested by simulation and hardware implementation to ensure its key performance features. A laboratory‐scaled prototype is developed, which has the capability of boosting the low input voltage of 12 V to a higher value of 48 V at a switching frequency of 100 kHz. The experimental outputs are in close accord with the simulation findings and mathematical analysis.

Enhanced quadratic DC–DC boost converters with super‐wide voltage gain ranges and ultra‐low voltage stress for renewable energy systems

AbstractAs the promising and ideal clean energies, wind and solar energy systems are in desperate need of high‐performance DC–DC converters to realize efficient and reliable energy transformation. Conventional DC–DC converters for renewable energy systems will work at extreme duty cycles and affect the system efficiency and reliability owing to their limited voltage gains and high‐voltage stress. In this paper, by adopting the hybrid voltage multiplier cells, two enhanced quadratic boost converters (EQBCs) which are highly desirable for renewable energy applications are proposed and analyzed. The EQBCs possess super‐wide voltage gain ranges and ultra‐low voltage stress; therefore, small duty cycle conditions can be achieved and components with low‐rated voltages can be chosen to decrease system volumes and increase system efficiencies. Besides, the EQBCs possess continuous input currents, which can realize small input current ripples and avoid the serious effect of pulsating current on the input sources. What's more, stable output voltages and simple controller circuits are realized by the EQBCs because of the common grounded structures of the input terminal, the single active switch and the output terminal. Detailed principle analyses, parameter designs, performance comparisons and experimental prototypes are conducted to verify the characteristics and feasibilities of the EQBCs.

An Extendable Interleaved Quasi Z-Source High Step-Up DC–DC Converter

A quasi z-source high step-up dc–dc converter is proposed here by integrating a coupled-inductor and a quadruple voltage rectifier technique. This converter can be used for high-voltage gain applications, without using extreme duty cycle and transformer high turns ratio values. Furthermore, low-voltage rating <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s, which have small <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -resistances, can be used to reduce conduction losses and improve the converter efficiency. Also, single-core coupled inductors with multiwindings are used to reduce the magnetic components count. Using the interleaved technique at the converter input stage reduces the current stresses of the power <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s as well as the current stresses of the primary side windings of the coupled inductor. For high power applications, number of the input stage interleaved legs can be properly chosen to reduce the input current and output voltage ripples values, which reduce the input and output filters volumes. Leakage inductances energy recovery is another benefit of the given converter. To confirm performance of the proposed converter and its operating principles, as well as the given simulation results and mathematical analyses, a two-leg topology of the introduced converter has been implemented and tested by applying both interleaved and noninterleaved gate-drive signals at different conditions.

A new extended single-switch high gain DC–DC boost converter for renewable energy applications

High-gain DC/DC converters are considered one of the most important components of green energy systems. Large numbers of these converters are used for increasing the voltage gain by using an extreme duty cycle. However, it increases losses and the cost, degrades the system performance, and hence obtains a low efficiency. In this article, a new design of a high-gain DC/DC boost converter is proposed. This converter has the potential to be used in low input voltage applications that need a high voltage gain such as systems powered by solar photovoltaic panels and fuel cells. The new topology is characterized by its simplicity of operation, high voltage gain, better efficiency, continuity of the input current, reduced number of inductors and capacitors, and can be extended to get higher gains. The converter structure, principle of operation, and design consideration of inductors and capacitors are presented in detail. Derivation of power losses and efficiency is presented. A laboratory prototype is implemented, and various experimental tests are given. The achievement of the suggested design is confirmed and compared with other recent high-gain converters.

Adaptive Sliding Mode Control for Interleaved Nx Multilevel Boost Converter

Interleaved <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Nx</i> multilevel boost converter ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Nx</i> MBC) has the advantages of low current stress, high efficiency, and high voltage gain without extreme duty cycle. However, it is difficult to design a controller for interleaved <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Nx</i> MBC due to the high order of state-space equations. A reduced order state-space averaged model of the interleaved <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Nx</i> MBC is proposed to reduce the complexity of the model. For the case of constant power load (CPL), an adaptive sliding mode controller based on nonlinear disturbance observer is designed on the basis of its reduced order state-space averaged model. The nonlinear observer is used to estimate the output power and avoid sampling error caused by interference. In order to ensure the large signal stability of the system, an adaptive law is introduced into the sliding mode controller to suppress the chattering phenomenon. Simulation and experimental results show that the proposed control algorithm has good dynamic regulation characteristics when the CPL and input power supply are disturbed.

A novel ultra-high step-up interleaved DC–DC converter based on the three-winding coupled inductor for distributed generation power system

Abstract In this paper, a non-isolated DC–DC converter with three-winding coupled inductors and switched capacitor cells is introduced. More output voltage is acquired without imposing any extreme duty cycle and high turns ratio. With the help of a two-phase interleaved technique, the input current ripple is reduced efficiently. The leakage inductance of coupled inductors causes the reverse recovery problem of circuit diodes to be solved and alleviates them. Leakage energy is also absorbed by switched capacitor cells. One of the advantages of this converter is the reduction of voltage stress of power switches, which leads to a reduction of conduction losses. In this way, low-voltage rated power switches can be used. Creating soft-switching conditions on power switches and high efficiency are also the prominent features of this structure. Laboratory and experimental results were produced and presented by making a prototype of 350 W–18 V/480 V. Their analysis indicates the effective performance of the proposed topology.

Soft-Switching High Step-Up DC–DC Converter Based on Switched-Capacitor and Autotransformer Voltage Multiplier Cell for PV Systems

This article introduces a nonisolated, high step-up voltage multiplier cell (VMC)-based dc–dc converter for applications such as module-integrated converter and power optimizers. The VMC combines switched capacitor with autotransformer techniques and active clamp circuit. The autotransformer tertiary winding is employed to increase voltage gain without operating the main switch under extreme duty cycle condition, to reduce the current through the main switch before it turns <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> and to ensure its zero-voltage switching (ZVS) operation on a wide operation range. The auxiliary switch in the clamp circuit provides ZVS for the main switch and vice-versa. Thus, both switches are turned <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> with zero voltage and there is no switching loss. Hence, high switching frequency is used to reduce the passive components’ volume and weight. Besides, the low dc-bias and bidirectional magnetizing current allows a smaller magnetizing inductance in the autotransformer to further minimizing the dimensions of the magnetic core. The leakage inductances are used to provide zero-current switching condition for the diodes, eliminating their reverse-recovery losses. The operation principle, steady-state analysis, and design guidelines are depicted and validated through experimental results obtained from a 350-W prototype of the proposed converter. Efficiency of 96.5% at full load is also reported.

A Step-Up Converter with Large Voltage Gain and Low Voltage Rating on Capacitors

Step-up converters are widely used in many applications, such as renewable energy generation with photovoltaic panels and fuel cell stacks. In many cases, the required voltage gain is larger for those applications than a traditional boost converter can achieve. Several large-voltage gain converters have been recently studied. This paper introduces a converter topology in which the voltage gain is larger than a traditional boost converter. The main advantages of the proposed topology are: (i) it provides a large voltage gain without the use of an extreme duty cycle; (ii) its capacitors require a smaller voltage to be sustained compared with other, similar state-of-the-art converters; (iii) the voltage among the ground input and output is not pulsating; and (iv) it can be synthesized with commercial, off-the-shelf half-bridge packed transistors. The proposed converter can be employed in different applications, such as distributed generation and microgrids. This paper presents the steady-state analysis of the proposed converter in the continuous conduction mode, a short comparison with similar topologies, and their voltage on capacitors. Computer-based simulation results are provided to verify the principle of the proposed converter in different operating conditions.

New Structure of Single-Switch Ultra-High-Gain DC/DC Converter for Renewable Energy Applications

This study introduces a new modified high-gain single-switch single-ended primary-inductor converter-based dc/dc converter. The low input ripple of the proposed converter makes it very suitable for renewable energy applications. In the proposed topology, a three-winding coupled-inductor and a voltage doubler rectifier are used to achieve high voltage gain without needing an extreme duty cycle. This circuit can provide an ultra-high voltage conversion ratio without requiring a large number of the turns ratio of the three-winding coupled-inductor (TWCI). Due to a regenerative clamped circuit, the leakage energy of the coupled-inductor is recycled; thus, the maximum voltage spike across the single-power switch is restricted. Therefore, <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> with a low maximum voltage rating can be utilized, which can alleviate the conduction power dissipations of the converter. Here, the switching power losses have been reduced significantly due to the circuit's soft-switching operation for the switch and all diodes. The steady-state analysis of the proposed converter is discussed thoroughly. Finally, the theoretical analysis is verified through the experimental results from a sample prototype (400-W, 25-400 V).

Analysis and Design of a Nonisolated High Step-Down Converter With Coupled Inductor and ZVS Operation

This article presents a detailed analysis and design of a high step-down converter. The proposed converter achieves high step-down voltage gain without the need of extreme duty cycles by using coupled inductor. The converter features low switch stresses, which reduces the conduction loss by using low voltage MOSFETs. Moreover, the magnetizing current of the coupled inductor is zero, which reduces the magnetic size. The leakage energy of the coupled inductor is recycled. Zero voltage switching is achieved to reduce switching loss and improve the EMI performance. In addition, continuous output current is achieved; hence, small filtering capacitor can be used. A hardware prototype is built and experimental results verify the feasibility of the step-down converter.

A High Gain DC-DC Converter Based on Coupled Inductor and Switched-Capacitor Cell with Low-Voltage Stress

This paper presents a nonisolated ultrahigh step-up DC-DC converter with an interleaved structure that is suitable for high power and voltage applications. In order to increase the voltage gain, the proposed structure uses coupled inductors and switched-capacitor cells. Achieving this goal is accompanied by avoiding the imposition of any extreme duty cycle or high turns ratio to the converter. The current ripple is reduced due to the use of the interleaved structure. Since the voltage stress of the switches is lower than the output voltage, by selecting the low-voltage rated switches and small RDS(on), the conduction losses are reduced. In addition, alleviating the phenomenon of reverse recovery of diodes and creating soft-switching conditions in MOSFETs, which leads to a reduction of switching losses, are other advantages of the proposed converter. Therefore, there is no need to use clamp circuits in the mentioned structure. The experimental results, using a prototype of 350 W-18 V/400 V, verify the effective performance of the proposed converter.

An Interleaved High Step-Up DC-DC Converter Based on Integration of Coupled Inductor and Built-in-Transformer With Switched-Capacitor Cells for Renewable Energy Applications

This paper proposes an interleaved high step-up DC-DC converter with the coupled inductor (CI) and built-in transformer (BIT) for renewable energy applications. Two double-winding (2W) CIs and one triple-winding (3W) BIT are integrated with the switched-capacitor (SC) voltage multiplier cells (VMCs) to achieve high-voltage gains without extreme duty cycles. The CIs and BIT turns-ratios provide two other degrees of freedom&#x2014;in addition to the duty cycle&#x2014;to adjust the voltage gain that leads to increased design flexibility. The diodes turn off naturally under the zero-current switching (ZCS) conditions because their current falling rates are controlled by the leakage inductances of the CIs and BIT; therefore, the diodes&#x2019; reverse-recovery problems are alleviated. Moreover, employing passive diode-capacitor clamp circuits, the voltage stresses of the switches are limited to a low value far less than the output voltage. Additionally, the leakage inductances energies are recycled and transferred to the output to further extend the voltage gain. Furthermore, due to the interleaved structure, the input current ripple and current stresses of the components are reduced. The proposed converter is analyzed in detail and then compared with similar converters that employed CIs and/or BIT along with passive/active clamp circuits for the MOSFETs. Finally, to verify the feasibility of the proposed converter, the experimental results of a 200 W prototype with output voltage of 400 V and voltage gain of 25 are presented.

A Transformer less Buck Boost Converter with Positive Output Voltage

Some industrial applications require high step-up and step-down voltage gain. The transformer less buck-boost converter has high voltage gain than that of traditional buck-boost converter without extreme duty cycles. A transformer less buck-boost converter with simple structure is obtained by inserting an additional switched network into the traditional buck-boost converter. The two power switches of the buck-boost converter operate synchronously. The operating principles of the buck-boost converter operating in continuous conduction modes are presented. A new buck- boost converter is presented by providing a feedback to the converter. By this, constant output voltage can be maintained under varying load conditions in both buck and boost operation. The output voltage of 40V (step—up mode)/8V (step down mode) is obtained with input voltage 18V and the outcomes are approved through recreation using PSIM MODEL.

High Output Voltage Gain DC/DC Boost Converter Suitable For Renewable Energy Applications

High-voltage gain DC–DC boost converter is very important because it is required in many industrial applications, and therefore becomes the focus of all researches nowadays. Conventional topologies is used to obtain high gain due to its advantages such as simple structure, simple control, and low cost but it must be operated at extreme duty cycle in order to obtain high voltage gain which leads to high semiconductors voltage stress, high switching loss, and diode reverse recovery problems that degrades the system performance, and cause a significant efficiency reduction. Using of Cascaded boost converter and switched inductor converter solve some of the problems appeared with conventional boost converter as they have higher voltage gain without working with high duty cycle like conventional one, but they have some problems such as higher losses, and lower efficiency that also degrades the system performance. This study presents a new non-isolated high voltage gain DC DC boost converter operating with a reasonable duty cycle by integrating dual boost converter with switched inductor structures. The presented converter operates with soft-switching ZVS mode for all switches, high voltage gain, and high efficiency. In order to prove the converter effectiveness, the theoretical analysis, operation principle, and simulation results are presented.

A Novel Nonisolated Buck–Boost Converter With Continuous Input Current and Semiquadratic Voltage Gain

A buck–boost dc–dc converter with semi-quadratic voltage gain is introduced in this article. The proposed converter benefits from continuous input current and common ground characteristic between input–output voltage ports. Due to low ripple input current, the proposed converter is a proper choice for carbon-free power sources such as photovoltaic (PV). Unlike the traditional buck–boost converter, the presented converter offers positive output voltage and large voltage gain without using an extreme duty cycle. In addition, the voltage stresses across the power switches of the proposed converter are very low compared with the output voltage. Hence, power switches with low on-resistance are used in practical implementation, which leads to power loss reduction and efficiency improvement. The performance principles, dc analysis, modeling process, and power loss analysis of the proposed converter are fully described. Finally, a laboratory prototype is implemented so as to evaluate the previously mentioned features of the proposed converter.

Interleaved Ultra-High Step-Up DC-DC Converters With Extendable Voltage Gains and ZVS Performance

This paper introduces eight novel interleaved non-isolated dc-dc converters with ultra-high step-up and zero voltage switching (ZVS) capabilities for renewable energy systems. To increase the voltage gain, the proposed converters benefit coupled inductors, high-frequency (HF) transformer, and voltage multiplier (VM) techniques. In comparison to other converters, which just benefit coupled inductors or HF transformers, these combinations of the techniques make an additional degree of freedom to achieve high voltage gains (more than 25 without extreme duty cycle). Besides, two active clamp circuits, including two stages of switch-capacitor VM cells, not only increase the voltage gain of the proposed converters but also act as an auxiliary circuit to provide ZVS. Moreover, the stored energy in the leakage inductances is absorbed and passed to the output by the clamp capacitors. The input current ripple is reduced by applying the interleaved technique. The voltage stresses across the power switches are clamped to lower values and can be controlled by the turn ratios of the coupled inductors and the HF transformer. The theoretical performance of the proposed converters is fully explained. Also, the proposed converters are compared with more than twenty latest interleaved high step-up and ultra-high step-up dc-dc converters. Finally, a 1 kW, 20 V/500 V laboratory prototype is built to prove the advantages of the proposed converters.

Ultra-High Step-Up Interleaved Converter With Low Voltage Stress

In this paper, a new type of interleaved high step-up converter including a coupled inductor is proposed. The proposed converter has an interleaved configuration on the input side to reduce the ripple of the input current and increase the power level. Moreover, a stacked structure on the output side provides a high input/output (I/O) voltage gain. In addition, the proposed converter can avoid an extreme duty cycle, causing larger conduction losses, by combining a coupled inductor and a lossless clamp circuit with an interleaved method. These increase the efficiency by making the semiconductor device a low voltage stress and allowing the use of components with low voltage ratings. Also, the energy stored in the leakage inductor in the coupled inductor can be recycled to the output side, the MOSFETs can be partially ZCS turned ON, and the diode reverse recovery problem can be alleviated. Finally, a laboratory prototype circuit with an input voltage of 24V, an output voltage of 400V and an output of 500W was implemented to demonstrate the performance of the proposed converter.

An Interleaved Zero-Voltage Zero-Current Switching High Step-Up DC-DC Converter

An interleaved zero-voltage zero-current switching (ZVZCS) high step-up DC-DC converter is proposed for modern photovoltaic power generation systems. The proposed converter can achieve high voltage conversion gain without operating under extreme duty cycles. The voltage conversion gain can be readily adjusted by selecting different numbers of the diode-capacitor multiplier (DCM) cells in the circuit at the design stage. Moreover, with the passive snubber circuit in the proposed converter, all power switches and diodes in the DCMs can achieve zero-voltage turn-off and zero-current turn-on, which effectively reduces switching losses and increases the overall converter efficiency. The operational principles and analysis of the performance analysis with two DCMs are presented for demonstrative purpose. The effectiveness of the proposed ZVZCS DC-DC converter is validated using an 800W experimental prototype.

Design, analysis, and implementation of a new high step‐up DC–DC converter with low input current ripple and ultra‐high‐voltage conversion ratio

In this study, the analysis and design of a coupled-inductor (CL)-based ultra-high step-up single-switch DC–DC converter are presented. With the aid of the CL and voltage multiplier cell, the suggested topology can obtain ultra-high-voltage gain without a large turn ratio and extreme duty cycle. A passive clamp circuit is utilised in the structure of the introduced converter for not only alleviating voltage spike on the main switch effectively but also recycle the leakage inductance energy. So low-voltage rating and low on-state resistance metal oxide semiconductor field-effect transistor is allowed to increase efficiency and lower the conduction losses. The input current ripple of the suggested topology is very low due to connecting an inductor to the suggested structure input section, which is very friendly and desirable to the photovoltaic and fuel cell applications. The suggested converter steady-state analysis, operation principle, theoretical efficiency analysis, and design procedure are described comprehensively in this study. Furthermore, the suggested converter superiority is illustrated over various alike recently introduced the most important DC–DC structures in the comparison study. Finally, a laboratory prototype is fabricated with a 225 W output power to confirm the theoretical analysis of the introduced converter.

A generalized common‐ground single‐switch continuous input‐current boost converter favourable for DC microgrids

SummaryThe conventional DC‑DC converters have limited voltage gain at moderate duty cycles. In theory, the large duty cycles should be adopted to reach large boosting factors. But in reality, at extreme duty cycles, the effect of parasitic components become dominant, which leads to increased voltage drops on devices, increased total loss and reduced efficiency. This paper proposes a single‐switch (requiring single gate‐driver circuit) diode‐inductor‐capacitor (DLC) cell‐based basic boost configuration that can solve the abovementioned issues. The employment of single‐switch has led to only two operational modes (in continuous conduction mode [CCM]) and easy control strategy. The continuous input‐current and large step‐up capability make the proposed configuration favourable for renewable or hybrid energy systems in DC microgrids. The simple configuration, modularity, moderate blocking voltage on semiconductors, wide duty‐cycle range, large voltage gains at low duty cycles, common‐ground between source and load are some profits of suggested configuration. The basic topology can be expanded by addition of DLC cells. Based on comparative analysis, the proposed configuration has larger step‐up capability per required components and lesser average normalized blocking voltage on semiconductors compared with other single‐switch topologies. This leads to smaller and cheaper structure with fewer losses. The configuration and operational modes of proposed basic topology (and its extended version) have been explained. Then, the design considerations and small‐signal modelling of basic topology have been investigated. Finally, the effectiveness and correct operation of proposed topology have been certified by comparative analysis and experimental results.