Conventional Converter Topologies Research Articles

Analysis of a High Step-Down DC/DC Converter Topology with a Single Inductor

This paper presents a novel high step-down dc/dc converter topology with a single inductor for 48V data center applications. Distinguished from conventional dc/dc converter topologies with a single inductor, the proposed converter topology is designed by series connecting a step-down cross-connected Fibonacci converter with a buck converter. By combination of these converter modules, the proposed converter topology offers a high voltage gain, viz. 1/48×, without cascade connection. Hence, high power efficiency is provided by the proposed single inductor topology. The characteristics of the proposed converter topology are investigated by theoretical analysis, computer simulations, and experiments. In the given theoretical analysis and the performed simulations, the proposed converter topology demonstrates higher power efficiency than the conventional converter topologies with a single inductor. Furthermore, the validity of the proposed topology is confirmed by the experiments.

Non-isolated conventional DC-DC converter comparison for a photovoltaic system: A review

The output power from a photovoltaic (PV) system varies due to its high dependency on the surrounding irradiance and temperature. To overcome this, a maximum power point (MPP) tracker is used alongside a DC-DC converter to track the varying power. The purpose of the DC-DC converter is to interface the PV system to the load on the grid or a standalone system by balancing the power between them. Selection of the appropriate DC-DC converter is essential because it plays an important role in the overall performance of the PV system. In this paper, various nonisolated conventional DC-DC converter topologies are reviewed, compared, and discussed. The review and discussion of each converter are based on the recent development of converters in terms of efficiency, steady state oscillation, number of components, voltage transfer, and tracking speed. The advantages and disadvantages of the recent topologies within this scope are also highlighted in this paper. A simulation work has been performed to validate the performance of all the reviewed converters using the perturb and observe MPP tracking algorithm under different sets of irradiance and temperature. Finally, this paper also provides a selection method to select the best converter in a stand-alone PV system.

Realization of High-Efficiency Dual-Active-Bridge Converter With Reconfigurable Multilevel Modulation Scheme

Efficiency optimization of dual-active-bridge (DAB) converters involves the minimization of both conduction and switching losses. However, it is challenging to achieve these two objectives simultaneously due to their conflicting nature, i.e., circulating current is required to realize zero-voltage switching (ZVS) but the presence of an excessive amount of the circulating current is the main cause of conduction loss and low efficiency. This dilemma has been common to conventional DAB converter topologies and modulation schemes which cannot provide sufficient degrees of freedom (DoFs) to the design of their operation modes. This paper is an illustration of the merits of utilizing reconfigurability of the operation mode as a new DoF in designing the operation of DAB converters to minimize both conduction and switching losses. The proposed DAB converter is designed to switch between two operation modes. For 25%-100% of the rated output power, a new modulation scheme based on the four-level ac voltages is proposed to achieve zero circulating current, zero backflow power, and full-range ZVS. Below 25% of the rated output power, the new modulation scheme transitions smoothly to the enhanced dual-phase-shift (EDPS) modulation scheme that continues to achieve zero backflow power and full-range ZVS while the incurred circulating current is moderated by operating the ac voltages at half-amplitude. The experimental results obtained from a 2-kW prototype show that, in comparison to conventional modulation schemes, the proposed modulation scheme is capable of maintaining the highest efficiency over the full output power range and greatly improves the reliability of switches due to full-range ZVS operation.

A Non-Isolated Bridge-Type DC–DC Converter for Hybrid Energy Source Integration

The implementation of a non-isolated dual input bridge-type dc–dc converter for hybrid energy source integration is discussed in this paper. The proposed converter accommodates two sources using an inductor, a capacitor, two insulated-gate bipolar transistors (IGBTs) without the anti-parallel diode and two IGBTs with the anti-parallel diode. The different modes of operation of the converter are explained with detailed analytical waveforms and equivalent circuits. From the analysis, the steady-state output equation of the converter is derived. The boundary condition between the continuous conduction mode and discontinuous conduction mode operations is also derived. The dynamics of the converter is analyzed in detail with the help of a small signal model. The step response of different transfer functions is discussed. The computer simulations of the proposed converter topology have been carried out using MATLAB/Simulink. An experimental prototype of the proposed converter is also built and tested successfully in the laboratory environment. Performance comparison of the proposed converter is carried out with the conventional converter topologies in terms of component counts, efficiency, loss breakdown, and power density.

On Supplying LEDs From Very Low DC Voltages With High-Frequency AC-LED Drivers

This paper studies the driving of white light emitting diodes (LEDs) from very low voltages in the 1.2 to 2 V range. The proposed idea is based on replacing the standard Schottky diode used in conventional converter topologies (i.e., buck, buck-boost, and boost) with an LED while shortcutting the output of the converter. In this configuration, the LED works both as the load and the rectifier diode of the converter, hence switching the LED at high frequencies (>100 kHz). Moreover, a thorough analytical study is carried out for the two topologies proposed in this paper, emphasizing in particular their static analysis and the obtaining of the boundaries between the different conduction modes. Finally, the idea is experimentally validated by means of the boost converter variation (i.e., the DL//S ac-LED driver). The DL//S ac-LED driver was also compared with a dc-dc boost converter, showing a better luminous efficacy while disposing of the Schottky diode and the output capacitor. The analysis was carried out when connected to a Li-ion battery using a simple control and integrated circuit for its development.

An Analysis of Non-Isolated DC-DC Converter Topologies with Energy Transfer Media

As miniaturized mobile devices with various functionalities are highly desired, the current requirement for loading blocks is gradually increasing. Accordingly, the efficiency of the power converter that supports the current to the loading bocks is a critical specification to prolong the battery time. Unfortunately, when using a small inductor for the miniaturization of mobile devices, the efficiency of the power converter is limited due to a large parasitic DC resistance (RDCR) of the inductor. To achieve high power efficiency, this paper proposes an energy transfer media (ETM) that can make a switched inductor capacitor (SIC) converter easier to design, maintaining the advantages of both a conventional switched capacitor (SC) converter and a switched inductive (SI) converter. This paper shows various examples of SIC converters as buck, boost, and buck-boost topologies by simply cascading the ETM with conventional non-isolated converter topologies without requiring a sophisticated controller. The topologies with the ETM offer a major advantage compared to the conventional topologies by reducing the inductor current, resulting in low conduction loss dissipated at RDCR. Additionally, the proposed topologies have a secondary benefit of a small output voltage ripple owing to the continuous current delivered to the load. Extensions to a multi-phase converter and single-inductor multiple-output converter are also discussed. Furthermore, a detailed theoretical analysis of the total conduction loss and the inductor current reduction is presented. Finally, the proposed topologies were simulated in PSIM, and the simulation results are discussed and compared with conventional non-isolated converter topologies.

A Hybrid Structure Dual-Path Step-Down Converter With 96.2% Peak Efficiency Using 250-m$\Omega$ Large-DCR Inductor

A dual-path step-down converter (DPDC) is presented for achieving high power efficiency in the mobile power management ICs (PMICs). Adopting a hybrid structure using one inductor and one flying capacitor, the proposed DPDC supplies a load current via two parallel paths, relieved an intrinsic problem of the conventional buck converter (CBC) topology, which is a significant power loss from a large DCR of the inductor ( ${R}_{\mathrm {DCR}}$ ). Therefore, DPDC achieves a high power efficiency and thus also reduces the heating problem, which is another critical issue in the mobile set. Moreover, DPDC can shrink the volume of the PMIC set with a low manufacturing cost by alleviating an ${R}_{\mathrm {DCR}}$ specification of the inductor. In this paper, although a 250 $\text{m}\Omega $ of large ${R}_{\mathrm {DCR}}$ inductor is used for our measurements, a 96.2% of peak efficiency was achieved and the power loss of total parasitic resistances can be reduced to up to 30% of that of CBC. Moreover, according to our measurement plots, it is verified that DPDC achieves the efficiency notably higher not only in a wide load current ( $I_{\mathrm {LOAD}}$ ) range but also in a wide conversion ratio ( $V_{\mathrm {OUT}}/V_{\mathrm {IN}}$ ) range, compared to CBC.

Investigation of Fault-Tolerant Capabilities in an Advanced Three-Level Active T-Type Converter

A novel fault-tolerant three-level power converter topology, named advanced three-level active T-Type (A3L-ATT) converter, is introduced to increase the reliability of multilevel power converters used in safety-critical applications. This new fault-tolerant multilevel power converter is derived from the conventional T-Type converter topology. The topology has significantly improved the fault-tolerant capability under any open circuit or certain short-circuit faults in the semiconductor devices. In addition, under healthy condition, the redundant phase leg can be utilized to share overload current with other main legs, which enhances the overload capability of the converter. The conduction losses in the original outer devices can be reduced by sharing the load current with the redundant leg. Moreover, unlike other existing fault-tolerant power converters in the literature, full output voltages can be always obtained in this proposed A3L-ATT converter during fault-tolerant operation. A 13.5-kW ATT-A3L converter prototype was developed and constructed using silicon carbide MOSFETs. Simulation and experimental results were obtained to substantiate the theoretical claims of this new fault-tolerant power converter.

Resonant Converter with Voltage-Doubler Rectifier or Full-Bridge Rectifier for Wide-Output Voltage and High-Power Applications

This paper presents a resonant converter with the benefits of wide output voltage, wide soft switching characteristics for power devices and high circuit efficiency. Since the series resonant circuit is adopted on the primary side, the power switches are turned on under zero voltage switching and power diodes on the secondary side can be turned off under zero current switching. To overcome the drawback of narrow voltage operation range in the conventional resonant converter, full-bridge rectifier and voltage-doubler rectifier topologies are employed on the secondary side for low-voltage output and high-voltage output applications. Therefore, the voltage rating of power devices on the secondary side is clamped at output voltage, rather than two times output voltage, in the center-tapped rectifier circuit. Synchronous power switches are used on the secondary side to further reduce the conduction losses so that the circuit efficiency can be further improved. To verify the theoretical analysis and circuit performance, a laboratory prototype with 1 kW rated power was built and tested.

A Family of High Frequency AC-LED Drivers Based on ZCS-QRCs

A family of dimmable ac light-emitting-diode (LED) drivers fed from dc voltages, is presented in this paper based on zero-current-switching quasi-resonant converters. The proposed family of drivers is based on replacing the diode in the conventional converter topologies (i.e., buck, boost, or buck-boost) by a string of high-brightness LEDs (HB-LEDs). Hence, the HB-LED string will be working as the rectifier diode and the load, switching at the same frequency of the main switch. In this case, the output current, which is experimentally validated, shows a negative current peak due to the reverse-recovery effect of the HB-LEDs. In order to reduce the reverse-recovery effect on the HB-LEDs, the main switch of the proposed topologies is replaced with a full-wave resonant switch, which makes possible to reduce the di/dt during the turn-off of the HB-LED string, therefore the reverse-recovery effect is eliminated. Moreover, the dimming of the HB-LEDs is done by means of changing the switching frequency of the converter by varying the turn-off, while keeping a constant turn-on time. The proposed converters are suggested to be used in a postregulator stage of an ac-dc converter or as the interface between the low-voltage bus and the HB-LED string in a dc nanogrid. In order to validate the analysis, the proposed topologies have been experimentally tested on a constructed prototype with an output power of 7.5 W, that is able to achieve an electrical efficiency of 94.5% and a luminous efficacy of 110 lm/W at full load. Moreover, the analysis has been extended to a comparison in terms of reliability with the conventional topologies on a 700-h test.

Novel multi‐terminal MMC‐based dc/dc converter for MVDC grid interconnection

Multi-terminal modular multilevel converter (MMC)-based dc/dc converter with the medium-frequency ac-link transformer is an attractive and feasible solution for interconnecting medium-voltage direct-current (MVDC) grids. This study proposes a novel multi-terminal dc/dc converter which features significantly reduced number of components compared with the conventional converter topology. The proposed dc/dc converter is capable of interconnecting multiple MVDC grids with different voltage levels as well as controlling the power flow between them. A combination of sine wave modulation scheme and phase disposition level-shifted pulse-width modulation is developed and employed for voltage balancing and controlling the power flow in the proposed converter. Several simulations, experimental and real-time hardware-in-the-loop case studies are carried out to demonstrate the dynamic response and capacitor voltage balancing capability of the proposed MMC and dc/dc converter under the developed control strategy.

Hybrid-DC Electric Springs for DC Voltage Regulation and Harmonic Cancellation in DC Microgrids

DC electric springs (DCES) are emerging technologies for the (i) regulation of mains voltage against the intermittent renewable generations and (ii) harmonic cancellation in dc microgrids. When conventional converter topologies (e.g., half-bridge or full-bridge converter) are adopted as DCES, the battery storage of the DCES has to process both the dc power and the ac harmonic power. The pulsating ac power can severely reduce the lifetime of the battery. To address this issue, a hybrid-DCES (H-DCES) is proposed in this paper to perform (i) and (ii) in a decoupled manner. With a modified topology and control method, the H-DCES can divert the ac current to the ground and retains the function of manipulating noncritical load for dc voltage regulation. The immediate benefits of this H-DCES are the reduction of storage capacity and a prolonged lifetime of the battery. Both the operating principle and the mathematical model of the proposed H-DCES are analyzed in this paper. A prototype of the H-DCES is practically tested in a 48-V dc grid. The experimental results show that the H-DCES can realize the decoupled operation of dc voltage regulation and harmonic cancellation. Simulation studies further demonstrate that the H-DCES requires less storage capacity than its counterparts.

High-Order Resonant Converter Topology With Extremely Low-Coupling Contactless Transformers

Although a large number of typical resonant converter topologies have been developed for use in contactless power transfer applications, these topologies need to be precisely optimized to obtain maximum efficiency and maximum power transferring capacity. High-order resonant power converters with flexible designs are invariably required to develop energy-efficient and cost-effective converter systems. An ideal converter topology can contribute toward realizing efficient converter systems if it is capable of providing an optimized output that is insensitive to load variations, coupling coefficient, type of the wireless transformer used, and other operating conditions. This paper presents a new contactless power converter topology for a low-coupling (0.14) ferrite-core transformer that has low cost, small size, high efficiency, and a wide gap (20 mm). In addition, the merits and demerits of conventional converter topologies are studied herein, and results for these topologies are compared with those for the proposed converter topology.

A General Method for Analyzing Resonant and Soft-Charging Operation of Switched-Capacitor Converters

Traditionally, switched-capacitor (SC) converters have suffered from high transient currents, which limit both the efficiency and power density of such converters. Soft-charging operation can be employed to eliminate the current transients and greatly improve the power density of SC converters. In this approach, a second-stage magnetic converter is cascaded with the SC stage to act as a controlled current load. Another approach is to use resonant SC converters with zero-current switching. This paper shows that resonant and soft-charging operations of SC converters are closely related, and a technique will be proposed, which achieves either operation by adding a single inductor to existing SC topologies. In addition, since most preexisting resonant or soft-charging SC converters were devised in an ad-hoc manner, this paper formulates an analytical method that can determine whether an existing conventional SC converter topology is compatible with the proposed approach. A number of common SC topologies are analyzed, including Dickson, series-parallel, ladder, Fibonacci, and doubler configurations. Through comparison to simulated results, as well as experimental work, the proposed method is validated and a family of high-performance SC converters is obtained.

Multilevel Inverter Scheme for Performance Improvement of Pole Phase Modulated Multiphase Induction Motor Drive

Pole-phase modulation (PPM) is one of the effective speed and torque control techniques for multiphase induction motor (MIM) drives. Performance of the drive in low-pole high-speed mode for steady run is good even with two-level voltage excitation due to the inherent advantages of high phase number. The drive operation under high-pole high-torque starting mode suffers degradation in performance due to reduction in phase number in a way to increase number of poles. Extending conventional multilevel converter topologies for performance improvement of MIMs increases the device count and control complexity considerably. In this paper, a simple technique to generate multilevel voltage across the phase of a pole-phase-modulated induction motor (PPM IM), for improving the performance of the drive under high-pole operation is presented. The technique requires least changes in the control scheme and no additional switches for the power circuit. Exploiting the advantages of equal voltage profile coils (EVPCs) for carrier phase-shifted PWM control is the main focus of this paper. In addition, generalization of PPM is revisited in this paper to add a small constraint on the pole ratio to avoid unequal pole width for some pole-phase combinations. The effectiveness of the proposed scheme is shown through simulation with finite-element method (FEM) model of nine-phase squirrel cage induction motor and two-level nine-phase inverter cosimulated in Ansys Maxwell two-dimensional (2-D) and Simplorer environment. Experimental validation is also done on 5 hp nine-phase two-level induction motor drive controlled using Spartan6 FPGA board.

Grid Connected Multilevel Inverter for Renewable Energy Applications

Abstract Electrical energy generation from renewable energy sources such as sun, wind etc., are widely adopted due to the increase in electricity consumption. The integration of renewable energy sources with the grid plays an important role in energy utilization. It is difficult to utilize electricity from renewable energy sources directly for the injection of power into the grid. Hence the system needs power electronic converters as an interface between renewable energy sources and grid/load. This paper discusses about the integration of three phase six level voltage source inverter into the grid. Three phase 2000 VA inverter is designed by using three , single phase eight switch six level inverters (in quarter cycle) and each single phase inverter uses three DC voltage sources which can be derived from renewable energy sources such as solar, wind and fuel cell. The pure sinusoidal 415 V three phase voltage is obtained from inverter to inject the power into grid and to the three phase resistive load. The proposed three phase Multi Level Inverter (MLI) is compared with the conventional three phase inverter and the observed THD of the conventional MLI is 31%. THD of the proposed MLI output voltage is analyzed which is 0.13% and found to be very less compared to six and 12 pulse conventional converter topologies. The simulation on the proposed inverter topology is done in MATLAB/Simulink and the results are verified.

Generation, Analysis of Switched Mode Dc to Dc Converters by the Use of Converters Cells

The conventional PWM converter topologies limit the operation to lower switching frequencies because of the minimum ON-time of the transistor switch. The quadratic feature is interesting for application where a wide voltage range is necessary, a quadratic buck-boost converter is presented. The converter cell is showed, the quadratic buck converter with the converter cell can convert to the quadratic buck-boost converter without increasing elements.

New approach to SRM drive with six-switch converter

This paper presents novel topologies implementation for Switched Reluctance Motor (SRM) drive used in commercial applications. For effective utilization of the developed system, a novel direct current controlled PWM scheme is designed and implemented to produce the desired dynamic speed characteristic. In comparison to conventional asymmetric converter topology, it can minimize entire system costs by reducing numbers of power semiconductors. Therefore, it may open up investigation of a new way for SRM to compete with other ac motors such as induction motors, brushless dc motors, etc. The validity of the proposed method is verified through theoretical explanation and experimental results.

A simple single-switch single-stage AC/DC converter with harmonic current correction

A simple single-switch single-stage AC/DC converter based on the flyback topology with the high power factor correction, high efficiency and small size is proposed and implemented. It complies with IEC 61000-3-2 for low frequency harmonics under a power range (20-50W) at 110VAC input. The proposed converter introduces the auxiliary winding of the transformer to replace the bulk inductor of the conventional converter topologies. The voltage of the bulk capacitor is (1) clamped under the rectified line voltage and (2) not influenced by the output load. The efficiency reaches 89∼90% and the power factor is between 0.94 and 0.95.

Novel Topologies Implementation for SRM Drive with Conventional Type Structure

This parer presents novel topologies implementation for Switched Reluctance Motor (SRM) drive used in commercial applications. For effective utilization of the developed system, a novel direct current controlled PWM scheme is designed and implemented to produce the desired dynamic speed characteristic. In comparison to conventional asymmetric converter topology, it can minimize entire system costs by reducing numbers of power semiconductors. Therefore, it may open up investigation of a new way for SRM to compete with other ac motors such as induction motors, brushless dc motors, etc. The validity of the proposed method is verified through theoretical explanation and experimental results.