Showing papers on "Flyback converter published in 2022"

A novel dual-leg DC-DC converter for wide range DC-AC conversion

Abstract: This paper proposes DC–AC Dual-leg dual-stage Conversion (DDC) and DC–AC Direct single-stage conversions (DSC). Conventional energy conversion system has only two-stage conversion, so it has some drawbacks such as huge power loss, less conversion range and lower power rating. So direct conversion, dual-leg step-up and step-up conversions are the solutions to get wide voltage conversion efficiently. The proposed converter can perform the power conversion from battery DC supply into AC with 1:1 ratio, step-up AC, and step-down AC in both directions. Also, it can perform rectifier operation from grid AC supply into DC with 1:1 ratio, step-down DC, and step-up DC. Step-up, step-down and ideal operations are possible within a single circuit; its operation is similar to solid-state DC–AC/AC–DC transformer. The ideal operation, Step-down to Step-up conversion and Step-up to Step-down conversion are possible on both sides, so this converter can handle a wide range of voltage. Power distribution is achieved with voltage regulation between battery/DC-load and AC-load/grid using the proposed control strategy with proper modulation. A prototype model of a 2-kW power rating validates the advantages and feasibility of the proposed methodology.

New High-Gain Transformerless DC/DC Boost Converter System

Abstract: This article proposes a new high-gain transformerless dc/dc boost converter. Although they possess the ability to boost voltage at higher voltage levels, converter switching devices are under low voltage stress. The voltage stress on active switching devices is lower than the output voltage. Therefore, low-rated components are used to implement the converter. The proposed converter can be considered as a promising candidate for PV microconverter applications, where high voltage-gain is required. The principle of operation and the steady-state analysis of the converter in the continuous conduction mode are presented. A hardware prototype for the converter is implemented in the laboratory to prove the concept of operation.

New Modulation and Impact of Transformer Leakage Inductance on Current-Source Solid-State Transformer

Abstract: This article presents a novel modulation scheme for device voltage stress mitigation and comprehensive analysis of the impact of transformer leakage inductance in a current-source solid-state transformer (SST). Different from dual active bridge (DAB) SST, the operation of the current-source SST is similar to that of a flyback converter. The device bridge on only one side of the transformer is active to store energy into or release energy from the magnetizing inductance which acts as a current-source dc-link. Such flyback operations with reverse-blocking switches can lead to additional device voltage stress and incomplete zero-voltage switching (ZVS) on the current-source soft-switching solid-state transformer (S4T) under conventional modulation. A new modulation scheme is proposed to address this issue. Moreover, different from the DAB, the leakage inductance of the medium-frequency transformer (MFT) in the S4T is a parasitic element similar to that in a matrix SST and can cause additional device voltage stress. Though the resonant capacitors, originally added to achieve ZVS, can absorb and recycle the leakage energy in the S4T, these capacitors need to be increased with larger leakage inductances to limit the voltage stress. However, large resonant capacitors can result in more lost duty cycles and reduced efficiency. The impact of such leakage inductance on device voltage stress is analyzed comprehensively, which is critical to guide future research and design of the S4T. Experimental results from S4T prototypes for dc–dc, multiport ac–dc, and ac–ac conversion with 1:1 and 4:1 MFT comprehensively verify the proposed concepts. Finally, a case study of a three-phase ac–ac S4T over a power range from 1 to 100 kVA each module reveals that the MFT leakage inductance should be less than 1% of the magnetizing inductance for safe operation.

Second Harmonic Current Reduction Schemes for DC–DC Converter in Two-Stage PFC Converters

Abstract: For the two-stage single-phase power factor correction (PFC) converter, its instantaneous input power pulsates at twice the line frequency, generating the second harmonic current (SHC) at the dc-bus port. The dc–dc stage is used to regulate the output voltage or the dc bus voltage in different applications, and the SHC reduction schemes for the dc–dc stage with different control objectives are discussed in this article. When the dc–dc stage regulates the output voltage, it is pointed out that the control bandwidth of the dc–dc stage is required to be high enough and the dc bus capacitor should be large enough to suppress the SHC, and the design of the dc bus capacitor is given. When the dc–dc stage regulates the dc bus voltage, a virtual impedance is added in series with the input/output of the dc–dc stage to suppress the SHC, and a virtual impedance is added in parallel with the dc bus to improve the dynamic performance. The selection and design of the virtual impedances are also given. Based on that, three specific control schemes are proposed for the dc–dc stage to suppress the SHC, and the parameters design method is also presented. Finally, a 3.3-kW two-stage single-phase PFC converter is fabricated and tested in the lab to verify the effectiveness of the proposed SHC reduction schemes.

Dual-Active-Half-Bridge Converter With Output Voltage Balancing Scheme for Bipolar DC Distribution System

Abstract: Conventional dual-active-bridge dc–dc converters require a dedicated voltage balancer or feedback control when they are used for a bipolar LVdc distribution system. This article proposes a dual-active-half-bridge (DAHB) converter with voltage balancing. The proposed converter is composed of a conventional DAHB converter with an additional inductor and capacitor voltage balancer (LCVB). The LCVB is added between the transformer and the output of the DAHB converter. Although the LCVB increases the switch current, it can balance the two output voltages without additional active switching device and feedback control under unbalanced load conditions. In addition, compared with the conventional DAHB converter, the LCVB can increase the zero-voltage-switching range of the DAHB converter and has no detrimental effect on the operation modes and performances. A 2.8-kW prototype was built and tested to verify the performances of the proposed converter.

PV Microinverter Solution for High Voltage Gain and Soft Switching

Abstract: This article proposes a high-gain flyback-type microinverter for photovoltaic (PV) power generation. The proposed topology integrates a voltage-doubler circuit with the flyback converter to produce the high voltage conversion gain. The solution is effective to minimize the high demand of the winding turns ratio in the flyback transformer. Besides, an active-clamp circuit is employed in the primary side for the resonant operation. The solution reduces the voltage and current stress and supports zero voltage switching of the power switching. The stress reduction achieved by the resonant operation further minimizes the conduction loss of the converter. A prototype is constructed and tested to show the experimental performance, which verified the advantages of the proposed solution for PV microinverter applications.

Control Scheme for Reducing Second Harmonic Current in AC–DC–AC Converter System

Abstract: In the ac–dc–ac converter system, the second harmonic current (SHC) is generated by the ac–dc rectifier and the dc–ac inverter. If the SHC propagates to the intermediate dc–dc converter, the current stress of the power switches will be increased, and the conversion efficiency will be degraded. Therefore, it is necessary to suppress the SHC in the dc–dc converter. In this article, the generation and propagation mechanism of the SHC in the ac–dc–ac converter system is analyzed. Then, from a perspective of control bandwidth and dc bus port impedance, the basic ideas for reducing the SHC in the dc–dc converter with different control targets are proposed. Based on that, the virtual-impedance-based control scheme is proposed to increase both the input impedance and output impedance of the dc–dc converter. In addition, the realization and design guideline of the virtual impedance is presented. Finally, a single-phase 3-kVA ac–dc–ac converter system is fabricated and tested in the lab. The experimental results are provided to verify the effectiveness of the proposed SHC reduction control scheme.

A Novel Synchronized Multiple Output DC-DC Converter Based on Hybrid Flyback-Cuk Topologies

Abstract: This paper proposes a new hybrid flyback-Cuk (HFC) converter. The new converter consists of a single switch, a single isolated input, and dual output based on flyback and Cuk topologies. The new HFC topology is proposed to reduce switching losses and improve the duty cycle range over which voltage can be stepped down, which would ultimately lead to an increase in efficiency. For step-down capability, the traditional single topologies (flyback or Cuk) require a less than 50% duty cycle. The low duty cycle of conventional converters leads to low operational efficiency. Therefore, the developed HFC can operate at a duty cycle of up to 85% for the same capability. The analysis, derivations, design, and simulation of the proposed HFC are thoroughly discussed for two different applications at two different power levels. The simulation results are obtained using MATLAB 2020a. The developed HFC’s efficiency as a function of the duty cycle is plotted, which reaches 89%, representing a significant efficiency improvement. The proposed converter can supply and absorb power simultaneously, giving it a significant edge over other converters. It is suitable for energy conversion and storage systems, such as renewable energy systems and electric vehicles (EV). To show the effectiveness and validate the new topology proposed, an EV along with battery energy storage (BES), is applied to charge (EV) and recharge (BES) simultaneously. The simulation results of 1.5 kW of HFC-PFC over the universal voltage range show that the proposed HFC can achieve a high power factor up to 97.5% at 260 Vrms. Moreover, the total harmonics distortion is measured between 36.25 and 27.69%. Thus, the results can achieve all required functions efficiently with minimum losses at a high range of duty cycles.

Second Harmonic Current Reduction Schemes for DC–DC Converter in Two-Stage PFC Converters

Abstract: For the two-stage single-phase power factor correction (PFC) converter, its instantaneous input power pulsates at twice the line frequency, generating the second harmonic current (SHC) at the dc-bus port. The dc–dc stage is used to regulate the output voltage or the dc bus voltage in different applications, and the SHC reduction schemes for the dc–dc stage with different control objectives are discussed in this article. When the dc–dc stage regulates the output voltage, it is pointed out that the control bandwidth of the dc–dc stage is required to be high enough and the dc bus capacitor should be large enough to suppress the SHC, and the design of the dc bus capacitor is given. When the dc–dc stage regulates the dc bus voltage, a virtual impedance is added in series with the input/output of the dc–dc stage to suppress the SHC, and a virtual impedance is added in parallel with the dc bus to improve the dynamic performance. The selection and design of the virtual impedances are also given. Based on that, three specific control schemes are proposed for the dc–dc stage to suppress the SHC, and the parameters design method is also presented. Finally, a 3.3-kW two-stage single-phase PFC converter is fabricated and tested in the lab to verify the effectiveness of the proposed SHC reduction schemes.

Non-Isolated DC-DC Converters in Fuel Cell Applications: Thermal Analysis and Reliability Comparison

Abstract: An alternative energy source that has appeared beyond expectations and has seen a lot of progress is the fuel cell. A proton exchange membrane (PEM) fuel cell is chosen for analysis and requires a DC-DC boost converter as an interface between the fuel cell and the load to provide a high-gain regulated voltage. Although great effort towards developing different converter topologies has been made during recent decades, less attention has been devoted to the reliability and thermal performance assessment of the present converters. In this paper, five non-isolated DC-DC converters are analyzed in terms of both thermal behavior and reliability. The temperature estimation of semiconductor devices as a critical part of the thermal analysis has been made via a detailed thermal model and the reliability is evaluated by means of a power cycling test. Finally, a performance score has been attributed using the TOPSIS ranking methodology and considering all the criteria (e.g., the number of components and cost) at the same time. The results indicated that the floating interleaved boost converter is always at the top of the list, even if the weight of the indicators is changed. When the weight of the cost criterion is higher than the reliability criterion, the multi-switch boost converter will be in second place. If the weight of the reliability criterion is greater than cost, the interleaved and multi-switch converter are ranked second and third, respectively. Additionally, the Cuk converter with a closeness coefficient of zero is always associated with the most unfavorable performance.

Non‐isolated high step‐up DC/DC converter for low‐voltage distributed power systems based on the quadratic boost converter

Abstract: Distributed energy resources have been broadly developed in recent years for supporting DC and AC microgrids. Unfortunately, most of them produce low output DC or AC voltages, and interfacing converters are required. These are implemented either in single‐stage or dual‐stage configurations. Step‐up converters are the essential section in dual‐stage designs, which their producing gain is important. Improving the boost factor and efficiency as well as decreasing the number of required components and electrical stresses on power components are the most critical challenges in designing such topologies. Continuing past efforts, this paper proposes a new non‐isolated step‐up DC/DC converter that can be used in low‐voltage distributed power systems and many other applications requiring step‐up DC/DC conversion. The topology requires only one power switch located on the converter's low voltage (LV) side. Hence, it can be easily selected from LV ratings, low on‐resistance power semiconductors. Besides, the converter operates with a continuous input current, which is a valuable feature in connection with current‐sensitive voltage resources. Compared with the recently proposed topologies, the topology provides better conversion gain and efficiency. In this article, the operating principle of the introduced converter is comprehensively investigated. Also, in order to examine the converter performance, experimental results will be presented and analyzed. For this purpose, a 400 V/400 W prototype has been designed and built. Results confirm the above claims and show that the converter efficiency equals 96.1%, and it produces high output voltage gain about 12 times.

A High-Frequency MMC for DC–DC Applications Using a Three-Winding Transformer With DC Flux Cancellation

Abstract: In this article, a novel high-frequency isolated modular multilevel dc–dc converter is proposed for large step ratio, medium voltage dc–dc applications. The proposed converter is based on the recently introduced class of converters termed the current shaping modular multilevel dc–dc converter (CS-MMC). In the CS-MMC, no string inductors are required and only a fraction of the voltage source modules are switched in each fundamental ac period enabling high effective frequencies to be achieved. The proposed converter builds on this earlier work by introducing a new topology featuring galvanic isolation using only a low voltage, high-frequency, three-winding transformer, and imposing dc flux canceling within the transformer. This article describes the converter architecture, its operating principles, and a control design. Experimental results are provided from a 1250V to 145V, 50 kHz laboratory-scale prototype with a peak measured efficiency of 96.8% at 2.8 kW.

Design and Experimental Study of A High Voltage Gain Bidirectional DC-DC Converter for Electrical Vehicle Application

Abstract: In this paper, a high voltage gain bidirectional DC-DC converter for the Electrical Vehicle (EV) application is proposed. The converter provides the merits of both switched-inductor and switched-capacitor converters. The proposed converter has a wide voltage gain range, low voltage stress on the power semiconductor devices, and a common ground between the grounds of the input and output side. Besides, synchronous rectification is adopted to obtain zero voltage switching (ZVS) during turn on and turn off dead time and thereby, efficiency of the converter is increased. The operating principle of the converter is provided in both step up and step-down mode and then, voltage gains of the converter are derived for two modes. Finally, a 96W converter with a constant high-voltage side (240V) and low-voltage side (18∼24V) has been built to demonstrate the experimental validation of our proposed design.

Ripple-Free Input Current Flyback Converter Using a Simple Passive Circuit

Abstract: This article proposes a new ripple canceling circuit (RCC) to eliminate the pulsating input current of the conventional flyback converter (CFC). The ripple canceling procedure occurs by two capacitors, one transformer, and a winding, which is added to the CFC transformer core. Besides, the proposed RCC acts as a passive snubber to reduce voltage spikes on the power switch of the converter. In comparison to the similar existing topologies, the proposed RCC does not employ additional semiconductors, and a lower number of magnetic components are used. The proposed RCC is verified by simulation and experimental results. The results show that using the proposed RCC, the input current ripple is reduced to 6% with the minimum power losses.

A Modulation Method for Capacitance Reduction in Active-Clamp Flyback-Based AC–DC Adapters

Abstract: Recent developments of fast-charging power delivery protocols are driving ac–dc adapters to 100-W power ranges. Conventional solutions in this power range employing a two-stage topology and a big twice-line frequency buffer capacitor are generally costly and bulky. This article presents a patent-pending modulation method for an active-clamp flyback converter, allowing for a single-stage adapter design with reduced capacitance requirements and higher efficiency. This is achieved by exploiting the inherent energy storage capability of the clamping capacitor while turning it into an active power buffer. No hardware modifications are needed, while all salient features of active-clamp flyback converter, i.e., soft switching and leakage recycling, are retained. Operating principles and detailed controller design are discussed, and a 100-W laboratory prototype is built. The prototype achieves 94% peak efficiency and up to 92% size reduction of the buffer capacitor. The experimental evaluation shows that the new single-stage solution enabled by the proposed modulation method is superior to the conventional two-stage and single-stage solutions in terms of cost, conversion efficiency, and power density.

Low-Stress and Optimum Design of Boost Converter for Renewable Energy Systems

Abstract: This paper examines the design and analysis of DC–DC converters for high-power and low-voltage applications such as renewable energy sources (RESs) and comparisons between converters based on switch stresses and efficiency. The RESs including photovoltaic arrays and fuel cell stacks must have enhanced output voltages, such as 380 V DC in the case of a full bridge inverter or 760 V DC in the case of a half bridge inverter, in order to interface with the 220 V AC grid-connected power system. One of the primary difficulties in developing renewable energy systems is enhancing DC–DC converters’ efficiency to enable high step-up voltage conversion with high efficiency and low voltage stress. In the present work, the efficiency, current, and voltage stress of switches of an isolated Flyback boost converter, simple DC–DC Boost converter, and an Interleaved boost converter, are explored and studied relatively. The most suitable and optimized options with a high efficiency and low switching stress are investigated. The more suitable topology is designed and analyzed for the switch technology based on the Silicon-Metal Oxide Semiconductor Field Effect Transistor (Si-MOSFET) and the Gallium Nitride-High Electron Mobility Transistor (GaN-HEMT). The Analytical approach is analyzed in this paper based on efficiency and switching stress. It is explored that GaN HEMT based Flyback boost converter is the best. Finally, the future direction for further improving the efficiency of the proposed boost converter is investigated.

Monopolar Symmetrical DC–DC Converter for All DC Offshore Wind Farms

Abstract: All dc offshore wind farms are gaining popularity for long-distance and high-power offshore wind energy conversion. It calls for high-power dc–dc converter with high step-up ratio for interconnecting the medium-voltage dc collection and the high-voltage dc transmission systems. This article proposes a monopolar symmetrical dc–dc converter, which is featured with partial-power processing and presents less installed capacity of components, low cost, low power loss, lightweight, and small footprint. Moreover, a modified phase-shifted carrier pulsewidth modulation with variable carrier frequency is developed to further reduce the switching loss and keep the dynamic current tracking performance. The effectiveness of the proposed converter has been verified by a simulation study of a 400 MW, ±25 kV/±250 kV model and experimental results of a 5.4 kW, ±60 V/±320 V scaled-down prototype.

Revisiting the Partial Power Processing Concept: Case Study of a 5-kW 99.11% Efficient Flyback Converter-Based Battery Charger

Abstract: This article proposes an analytical methodology to evaluate the performance of the main partial power processing (PPP) architectures in terms of the improvements in the system’s conversion efficiency. This analysis considers the influence of the system’s voltage gain, the auxiliary dc/dc converter’s efficiency, and the possibility of bidirectional power flow. Herein, the key PPP architectures are, thus, modeled and benchmarked. The presented results attest to the series configuration as the most efficient PPP circuit solution, with no limits on the system voltage gain, contrary to the generalized results found in today’s literature. To assess these results and the significance of the proposed analysis, a well-known, simple, and cost-effective flyback topology has been designed and tested for a series PPP circuit solution able to effectively interface a 5-kW battery energy storage system (BESS) to a 700-V dc grid. A relatively high power conversion efficiency and compact hardware are achieved due to the reduced size requirements on the input and output filtering stages. Above all, while explaining the PPP concept, this study shows that even converter circuits known for their low power efficiency can be used to derive highly efficient systems. A design approach is, thus, provided to facilitate the design of the presented PPP circuit, and measurements are, finally, carried out to compare the obtained results with the expected ones derived from the developed analytical models.

Design, Validation, and Economic Behavior of a Three-Phase Interleaved Step-Up DC–DC Converter for Electric Vehicle Application

Abstract: Due to the increasing number of direct current (DC) loads in electric vehicles (EVs), DC–DC converters are widely used in EV applications. Hence, a DC distribution system with DC–DC converters is more efficient. A three-phase interleaved step-up DC–DC converter (ISC) has been proposed for use in electric vehicles. Other uses of the proposed ISC converter include aircraft, satellites, industrial, and traction drives. The proposed converter is subjected to a thorough frequency response study, which is explained in detail. The design technique recommends the proper quantity of switches to be used in the system. The reduction in the number of switches results in a 94% increase in the efficiency of this converter. The economic aspects of ISC, such as cost analysis and its procedure, have been discussed. Design models were checked using MATLAB/Simulink, which was interfaced with the real-time simulator OPAL-RT (OP5700) to ensure that they were appropriate. The results have been presented in detail.

MHz-Driving Current-Fed Snubberless Soft Switching DC-DC Converter

Abstract: This paper presents a novel current-fed step-up DC-DC converter that is suitable for the front-end high-frequency link DC-DC converter (DC-X) in a grid-tied inverter of a fuel cell interface. The proposed DC-DC converter features the snubberless zero current soft-switching (ZCS) commutation with high-frequency switching by adopting quasi-resonance and parallel load resonance; the multi resonance while minimizing the number of additional circuit components. The switch-mode transitions of the proposed DC-DC converter are explained in detail for revealing the principle of snubberless ZCS due the multi resonance. In order to analysis the proposed DC-DC converter more precisely, a time-domain analysis is employed to examine the high-order harmonics in the three-level stepwise voltage of the quasi-resonant high frequency inverter, which is superior to a conventional sinusoidal AC analysis. The effectiveness of the proposed converter and the analytical strategy is demonstrated by comparing the theoretical and simulation results, after which the feasibility is verified by experiment of a 1 MHz-55 W class prototype with Gallium Nitride (GaN) high-electron-mobility-transistor (HEMT).

A New Non-Isolated High-Gain Single-Switch DC–DC Converter Topology with a Continuous Input Current

Abstract: An ultra-high step-up, non-isolated DC–DC converter with a continuous input current was developed as a result of this research. This converter’s architecture consists of a voltage multiplier cell (VMC), a positive output super lift Luo converter (POSLLC), and a quadratic boost converter (QBS) (also referred to as a cascaded boost topology (CBT)). Thus, the bold points of the topologies mentioned earlier enhance the voltage gain of the proposed topology. It is important to note that when the duty cycle is at 50%, the converter attains a voltage gain of ten. Additionally, the constant input current of the topology reduces the current stress on the input filter capacitor. This converter’s topology was investigated and studied under various operating conditions: ideal and non-ideal modes, as well as continuous and discontinuous current modes (CCM/DCM). The converter’s efficiency and voltage gain were also compared to those of newly proposed converters. PLECS and MATLAB software tools were used in the investigation of the proposed topology. A 200 V/200 W prototype was constructed. The experimental results validated the theoretical study and the simulation results. The extracted efficiency was 91%.

Multi-variable Multi-constraint Optimization of Triple Active Bridge DC-DC Converter with Conduction Loss Minimization

Abstract: This paper presents the design and development of an isolated three-port bidirectional DC-DC converter composed of three full-bridge modules and a high-frequency planar transformer. Besides the phase shift control, optimized power flow management along with the utilization of the duty cycle control for minimization of the system conduction losses are discussed and the control laws ensuring the minimum overall system losses are thoroughly studied. In order to calculate the accurate circuit RMS currents and to obtain the multi-variable optimized operating condition, a frequency domain analysis using generalized harmonic approximation (GHA) technique is employed for formulating the bridge voltage and current expressions that are key ingredients for the conduction loss minimization problem in the triple active bridge (TAB) converter. A 600 W TAB converter proof-of-concept has been built to verify all theoretical considerations and model-oriented analysis. While the converter has an input DC bus voltage of 160V, the two output ports of the converter can deliver 400W and 200W at voltage levels of 110-130V and 18-26V, respectively. The circuit topology is particularly relevant to multiple bus voltage electrical systems in space applications as well as in electric vehicles. With the implementation of proposed optimal phase-duty control, the experimental results show a full load efficiency increment of 0.8% compared to the conventional modulation technique with phase-control alone.

Partial-Power Post-Regulated LLC Resonant DC Transformer

Abstract: This article presents a partial-power postregulated LLC resonant converter. In the proposed topology, the input power is first transferred to the secondary side of the transformer through the LLC-DC transformer converter to achieve galvanic isolation and voltage conversion functions. Then, most of the power is directly transmitted to the load side, and only a small portion of the power is converted to the output side by the partial-power processing converter. Therefore, unlike the two-stage solution, the converter proposed in this article achieves output voltage regulation while minimizing the efficiency loss caused by the two-stage conversion. The operating principle of the proposed converter is analyzed, and the system prototype is constructed. Experimental result validates the correctness of the analysis and proves the feasibility of the proposed converter.

A New Continuous Input Current Nonisolated Bidirectional Interleaved Buck-Boost DC-DC Converter

Abstract: In this paper, a new interleaved bidirectional buck-boost DC-DC converter is proposed. The input current of this converter is continuous and has a low ripple, that cause reduction in the size of the input filter of the converter. Because of these features, this converter is appropriate for renewable applications such as fuel cells and photovoltaic (PV) panels for obtaining maximum power in which the continuity of the input current is essential. The operation principle of this converter is detailed, and its power losses calculation shows the positive effects of the low input current ripple on its efficiency. The input current ripple of the proposed converter and conventional interleaved buck-boost converter has been calculated in detail. In addition, the comparison results of this converter with conventional interleaved buck-boost converters and other similar structures confirm that the proposed converter without utilizing extra components achieves continuous input current with low ripple. Compared with other buck-boost structures, the low input current ripple in the presented converter causes an improvement in its efficiency. An experimental prototype is implemented in the laboratory to confirm the correctness of theoretical analyses.

An Analysis-Supported Design of a Single Active Bridge (SAB) Converter

Abstract: Currently, due to its various applications, the high-performance isolated dc-dc converter is in demand. In applications where unidirectional power transfer is required, the single active bridge (SAB) is the most suitable one due to its simplicity and ease of control. The general schematic of the SAB converter consists of an active bridge and a passive bridge, which are connected through a high-frequency transformer thus isolated. The paper summarizes the behavior of this converter in its three operation modes, namely the continuous, discontinuous, and boundary modes. Later, the features of this converter, such as its input-to-output and external characteristics are discussed. Input-to-output characteristics include the variation of converter output power, voltage, and current with an input control variable i.e., phase-shift angle, whereas the external characteristic is the variation of the output voltage as a function of output current. In this discussion, the behavior of this converter in its extreme operating conditions is also examined. The features of the characteristics are elucidated with the help of suitable plots obtained in the MATLAB environment. Afterward, the specifications of a SAB converter are given and, based on the results of the analysis, a detailed design of its electrical elements is carried out. To validate the features and the design procedures presented in this paper, a prototype is developed. An element-wise loss estimation is also carried out and the efficiency of the converter has been found to be approximately equal to 93%. Lastly, the test was executed on this prototype, confirming the theoretical findings concerning this converter.

Two-Stage Hybrid Isolated DC–DC Boost Converter for High Power and Wide Input Voltage Range Applications

Abstract: A two-stage hybrid isolated dc–dc boost converter for high power and wide input voltage range applications is proposed. It can be used as a front-end dc–dc converter that can boost variable low voltage from a power source [battery (home/industrial inverter/industrial UPS application), fuel-cell or solar-PV] and interface it to a high-voltage dc-ink, which typically feeds an inverter. A detailed comparison among the different family of converter topologies for isolated dc–dc boost application is carried out that can prove to be useful for power electronics engineers to choose the correct topology for a given input voltage range. The quantitative comparison takes into account the power device utilization, transformer utilization, capacitance utilization, and inductive energy requirement. Based on the comparison, it is shown that with input voltage variation greater than ±20%, two-stage hybrid isolated dc–dc boost converter is superior compared to other family of converters. Design details for the two-stage converter are provided. The converter is developed and tested for a 5 KW inverter application with an input dc voltage range of 90–170 V and output ac voltage of 230 V. Theoretical analysis for loss calculations is also provided which closely matches the experimental results.

Sliding-Mode Control of a Photovoltaic System Based on a Flyback Converter for Microinverter Applications

Abstract: A method to design a sliding-mode control of a photovoltaic system based on a flyback converter is proposed. First, the photovoltaic system is modeled to design the sliding-mode controller and to select the parameters of a maximum power point tracking algorithm. Then, the detailed design of the sliding-mode controller is presented, which includes the establishment of the sliding surface. The transversality, reachability, and equivalent control tests are also developed. Because the power extraction of the PV system is carried out through a P&O MPPT algorithm, the selection of the perturbation magnitude, the perturbation period, and the maximum switching frequency is integrated into the control design. Additionally, since the derivative of the MPPT output could prevent the achievement of the reachability test, a filter to limit that derivative is also integrated into the design process. The whole method is illustrated in an application example where the data of a BP585 PV module and a real flyback converter are used. Once the parameters were obtained, circuital simulations performed in PSIM validated the intended operation of a PV system composed of a PV module and a flyback converter, which is connected to a source that produces the perturbations of an AC grid.

Modernisation of DC-DC converter topologies for solar energy harvesting applications: A review

Abstract: Solar photovoltaic (PV) power generation has become increasingly important as a renewable source of energy due to the many benefits it offers. These benefits include the ease with which it can be allocated; the absence of noise; the longer life; the absence of pollution; the shorter amount of time required for installation; the high mobility and portability of its parts; and the capability of its output power to meet peak load requirements. DC-DC converters are typically incorporated into solar energy harvesting systems because they allow for the more efficient exploitation of solar cells. One of the difficulties is in the selection of a suitable converter since this has an effect on the operation of the PV system. This study discusses the modernisation of several different DC-DC converter topologies for solar energy harvesting systems. Some of these topologies are boost, buck-boost, single-ended primary-inductance converter (SEPIC), Cuk, and flyback. The topologies have been compared so that detailed information on the complexity of the hardware, the cost of implementation, the efficiency of the energy transfer elements, the tracking efficiency, and the efficiency of the converters can be provided. This paper will be useful as a handy reference in choosing the best converter topology for solar energy harvesting applications.

A Non-isolated Buck-Boost DC–DC Converter with Continuous Input Current and Wide Conversion Ratio Range for Photovoltaic Applications

Abstract: In this paper, a non-isolated buck-boost dc–dc converter is presented which benefits from broad range of conversion ratio. The designed topology, contrary to the classic buck-boost converter, has continuous input current. In addition, the introduced converter delivers high step-up voltage gain, making it a good candidate for industrial, electric vehicle and remarkably, renewable energy applications. Operation basis of the introduced converter is discussed thoroughly. The presented converter is compared with similar topologies in respect of several measures, such as the element number, voltage gain, switch voltage stress and continuity or discontinuity of the input current. By taking into account of the merits of the given converter, it is possible to utilize this converter in renewable energy implementations, distinctively in photovoltaic systems.