Single-stage Converter Research Articles

Direct AC–AC Active-Clamped Half-Bridge Converter for Inductive Charging Applications

In this article, a new direct ac-ac active-clamped half-bridge converter feeding a series-series compensated inductive charging system is proposed. The proposed converter eliminates the rectification stage and bulky life-limited electrolytic dc-link capacitors, resulting in an actual single-stage (ac-to-ac) conversion with low component. The operation principles, steady-state analysis, and design considerations of the proposed converter are presented in detail. Moreover, a new predictive dead-beat technique for input current control and a linear average charging current controller are developed for the proposed converter, which enables the unity power factor and charging current regulation. The performance of the proposed battery charger is validated through experimental results on a 1-kW field programmable gate array (FPGA)-controlled silicon carbide based laboratory prototype.

Efficiency of the Lamm–Honigmann thermochemical energy storage

The Lamm–Honigmann-process is a flexible thermo-chemical energy storage and converter that can be charged and discharged arbitrarily with both heat and electrical power. In this paper, an approximation for the theoretical round-trip efficiency is given for various process configurations. The goal is to predict the process efficiency and storage capacity in dependence of the temperatures of heat sink and source and some easily accessible working fluid properties, namely heat capacities, latent heat of evaporation of the pure working fluid, heat of ab-/adsorption or reaction enthalpy of the working fluid pair, and the boiling point elevation, respectively.The derived approximations are verified by comparing with a detailed calculation using enthalpy data of the working fluid pairs LiBr/H2O and H2O/NH3. The results show a good agreement (deviation less than 11%). The round trip efficiencies are almost independent of temperature and it can be concluded that from a thermodynamic point of view the single stage storage and conversion process should be driven with low temperature heat, e.g. industrial waste or solar thermal heat, and the pure electrical storage process should be driven near ambient temperature to reduce heat losses to the environment.The method is recommended for checking usefullness of further working pairs and is applied exemplary to the adsorption systems Zeolite/H2O and Silica gel/H2O.

Single Conversion Stage Three Port High Gain Converter for PV Integration with DC Microgrid

A high gain three port converter with a unidirectional port for photovoltaic (PV) side and two bidirectional ports one each for the battery and the DC bus for PV integration to DC microgrid is presented. High gain is achieved by a coupled inductor with switched capacitor, whereas single stage conversion is used between the ports to achieve high efficiency. The proposed converter is modelled in PLECS/MATLAB and the simulated results for various operational modes are validated using a 500 W prototype. For main operating mode, i.e., single input single output (SISO), the efficiency is calculated to be as high as 96 %. Similarly, owing to the reduced number of components, the losses are reduced considerably for different operation modes.

A Single-Stage Bidirectional Inductive Power Transfer System With Closed-Loop Current Control Strategy

A conventional two-stage topology that consists of a dc/ac converter, a dc-link, and two ac/dc converter is being used as wireless charging of electric vehicles (EVs). However, the conventional topology contains more conversion stages with a bulky dc-link capacitor, and implementation of control strategies is not easy to transfer power from the primary coil to pickup coil or vice versa. A single-stage, inductive power transfer (IPT) system with a simple control strategy is needed to reduce the conversion stages and to increase the reliability of the system. This article proposes a control strategy for a single-stage conversion topology that is easy to implement and more importantly can achieve unity power factor (UPF) using a single controller. The experimental validation of single-stage conversion topology and steady-state analysis with series–series (SS) compensation scheme is presented in this article. A fixed angle of ±90° in between the output phase of the converters is achieved without estimating any power or current parameters. A hardware prototype working at a lower watt rating is analyzed, and the validation of the proposed system for 3.7-kVA rating as per the international standard is simulated. Furthermore, transient response is also observed to verify the closed-loop control scheme of battery current.

RETRACTED ARTICLE: Improved diode assisted voltage fed three phase quasi z-source inverter for photovoltaic application

In this paper, we propose a design and simulation of improved diode assisted voltage fed three phase quasi z-source inverter for photovoltaic application. Variable shoot through time interval is generated by adding low frequency voltage with constant voltage and the control signal for variable shoot is generated using boost PWM control. The output quality of three phase QZSI is improved by replacing the diode with active power switch in Switch Boost Inverter (SBI). Additionally, we use fuzzy logic controller for optimizing the shoot through duty ratio and modulation index from the source side rectifier, which increases the gain of three phase QZSI. The proposed topology in photovoltaic application increases the input voltage gain and voltage boost property by reducing the number of components, voltage ratings and stress across the switches in three phase QZSI. The proposed method enables improved voltage gain in single stage conversion, which is used for boost function. The simulation of proposed photovoltaic model is built on Simulink. Performance of proposed is evaluated against various metrics including power consumption, delay and power delay product and it is compared against existing VSI.

Modulation of Bidirectional AC/DC Converters Based on Half-Bridge Direct-Matrix Structure

This letter proposes a half-bridge bidirectional isolated matrix-based ac/dc converter for compact ac/dc power conversion applications. The converter can control not only the dc voltage or current, but also the power factor of the ac current with a single conversion stage, which helps to achieve a higher power density with a lower complexity. The converter operates with zero-voltage switching or zero-current switching in all switches. Hence, the switching frequency of the converter can be increased higher, leading to smaller passive components. Besides the simple circuit, the modulation scheme derived from time domain analyses is also easy to implement. The proposed topology has been verified by experimental results for a 2-kW SiC-based prototype. A high efficiency of 96.8% was achieved at a full load condition. The current total harmonic distortion (THD) is lower than 4% and the power density is 1.8 kW/dm3.

Comprehensive Review on Main Topologies of Impedance Source Inverter Used in Electric Vehicle Applications

Power electronics play a fundamental role for electric transportation, renewable energy conversion and many other industrial applications. They have the ability to help achieve high efficiency and performance in power systems. However, traditional inverters such as voltage source and current source inverters present some limitations. Consequently, many research efforts have been focused on developing new power electronics converters suitable for many applications. Compared with the conventional two-stage inverter, Z-source inverter (ZSI) is a single-stage converter with lower design cost and high efficiency. It is a power electronics circuit of which the function is to convert DC input voltage to a symmetrical AC output voltage of desired magnitude and frequency. Recently, ZSIs have been widely used as a replacement for conventional two-stage inverters in the distributed generation systems. Several modifications have been carried out on ZSI to improve its performance and efficiency. This paper reviews the-state-of-art impedance source inverter main topologies and points out their applications for multisource electric vehicles. A concise review of main existing topologies is presented. The basic structural differences, advantages and limitations of each topology are illustrated. From this state-of-the-art review of impedance source inverters, the embedded quasi-Z-source inverter presents one of the promising architectures which can be used in multisource electric vehicles, with better performance and reliability. The utilization of this new topology will open the door to several development axes, with great impact on electric vehicles (EVs).

An Isolated PFC Zeta-forward Single-stage Single-switch for LED Driver Without Electrolytic Capacitor

The high-brightness light-emitting diodes (LEDs) require an AC/DC converter with power factor correction (PFC). The large output electrolytic capacitor, which is used to minimize the low frequency LED current ripple, degrades the operating lifetime of the LED driver. In order to increase the lifetime of an AC–DC LED driver, the electrolytic capacitor should be eliminated without significantly increasing the output current ripple. In this article, an isolated single-stage single-switch AC/DC high power factor LED driver without electrolytic capacitor is proposed in which a zeta power factor (PF) corrector is integrated with a forward converter. The detailed theoretical analysis and design procedure of the proposed single-stage PFC converter is presented. The experimental results of a 110 Vrms, 21 W prototype verify the theoretical analysis. The input PF is 0.99 in the proposed converter that complies with lighting equipment standards such as IEC-1000-3-2 for class C equipment.

Partial Shading, Effects and Solution for Photovoltaic String: A Review

The energy which is generated from natural resources that are abundantly available in nature is called Non-conventional energy sources. Light energy from sun, current of air, storage of water at hilltop, water movement inside sea, heat inside earth is the example of Non-conventional energy sources, etc. The solar energy is based on the conversion of sun rays into electrical voltage and current and it is the single-stage conversion of radiation into electricity. The photovoltaic (PV) power generation is a phenomenon in which photons from sun rays collide on PN junction of semi-conductor material and generates electrical energy. This solar power system uses the string of solar panels distributed over large areas. Power generated by these strings is affected by shadow initiated from different causes. The effect of these shadows is to reduce the power generated by the photovoltaic system. This paper explains the various effect of shadow on PV system and summarizes the different methods for improving the PV performance under shadow conditions. It also covers a wide review of the trends and state-of-art techniques indicated through research to curb the effects of partial shading.

Performance analysis intelligent-based advanced PSO algorithm and testing of real-time matrix converter electrical system

The advanced improvements in power electronic switches make the development of power electronic converters. This drastic development results the matrix converter (MC) evaluation. MC is a bidirectional power flow device with single-stage conversion process with variable voltage and variable frequency. The major drawback of MC is harmonic content present due to switching of power electronic devices. To reduce the harmonics present in the MC, lots of research works were carried out, but it is limited to some extent; beyond the limit, the harmonics can be reduced in MC by introducing soft computational algorithm-based controller. The PSO-based controller was implemented in the literature with resistive and inductive loads. In this paper, PSO-, modified PSO-, modified hybrid PSO-based controllers were implemented with induction motor as load. This soft computing-based controller for MC effectively reduces the harmonic content by choosing the optimal switching pulses for each sampling. The simulation results were carried out on the MATLAB/Simulink interface. Both Simulink and hardware results of the MC strongly recommend the soft computing-based controller for MC to improve the behavior.

Investigation of Standalone Solar Photovoltaic Water Pumping System With Reduced Switch Multilevel Inverter

Solar photovoltaic powered water pumping systems are becoming very successful in regions where there is no opportunity for connecting the grid. The photovoltaic technology converts solar energy into electrical energy for operating DC or AC motor-based water pump. In the case of a solar AC motor water pump, it engages two energy conversion stages (DC-DC and DC-AC) in the power conditioning unit. This usually resulted in increased size, cost, complexity and decreases efficiency of the entire system. In addition, the existing two-level inverter (DC-AC) stage generates higher harmonics in output voltage that deteriorates AC motor performance. As a consequence, a single energy conversion stage with more than two-level output voltage could be possible by utilizing multilevel inverters which replaces two-level inversion stage easily to get higher levels of output voltages as well for extracting best results from the motor. Moreover, they can able to operate with reduced switching frequency that certainly reduces switching losses. Still, the increased voltage levels comprise a higher number of power semiconductor switches, cumulative voltage stress and switching losses are making the system more complicated. In this paper an innovative seven-level inverter with five switches had been taken to investigate 0.5 H. P single phase induction motor water pump. This topology ensures minimum switching losses, lowering size along with less installation cost. In order to provide better insight into the working and performance of this proposed topology the simulation results performed in the MATLAB / Simulink environment and hardware implementation are depicted.

Modified multiport Luo converter integrated with renewable energy sources for electric vehicle applications

Purpose Growing concerns about the depletion of fossil fuels and global awareness about the environmental pollution motivate the automobile industries to search for an alternative transportation system such as hybrid vehicular systems, plug-in hybrid vehicular systems and electric vehicular systems. To have carbon emission-free environment, these electric vehicles use renewable sources, such as solar and fuel cell, as primary source of supply. As these renewable sources are intermittent in nature, an energy buffer such as battery or super capacitor is required for the smooth supply and regulation of load power. The current electric vehicle systems use multistage power electronic converters for energy transfer. Therefore, this paper aims to propose a modified multiport converter based on Luo topology. Design/methodology/approach The suggested converter is developed based on Luo topology using voltage lift technique. Findings Most of the research presents buck boost converter as power electronic interface in electric vehicle applications. Whereas the converter proposed in this paper is based on Luo topology. It exhibits the features of single stage conversion between the input output ports, with less ripple, high efficiency, fewer components and centralized control for effective power management. Originality/value The presented converter can work in all possible modes such as buck and boost modes independently or simultaneously during various operating conditions of electric vehicles. During buck/boost mode, the primary source PV (Photovoltaic) in the converter provides the required power for the vehicle and charges the secondary source, i.e. battery, whereas during boost mode the battery supplies the sufficient power to load.

Solar PV based nanogrid integrated with battery energy storage to supply hybrid residential loads using single‐stage hybrid converter

This study proposes a solar photovoltaic (PV) based nanogrid with integration of battery energy storage to supply both AC and DC loads using single-stage hybrid converter. A boost derived hybrid converter (BDHC) is used as a single-stage converter to supply the AC/DC hybrid loads. The BDHC reduces the number of conversion stages when compared to the conventional solar PV based systems to supply the AC/DC loads. A non-isolated buck–boost bidirectional DC–DC converter is used for charging and discharging of the battery to support the nanogrid. The power reference algorithm proposed in this study provides the proper utilisation of the solar PV in different operating conditions and uninterruptable power supply to the loads along with the battery storage management. A modulation scheme is implemented to operate the BDHC for generation of AC/DC hybrid outputs from a single input. The performance of the proposed system in different modes of operation has been evaluated using PSCAD simulation studies. A laboratory experimental setup is developed and control algorithms are implemented using LabVIEW based FPGA controller for verification of the results.

Enhanced Performance Modified Discontinuous PWM Technique for Three-Phase Z-Source Inverter

Various industrial applications require a voltage conversion stage from DC to AC. Among them, commercial renewable energy systems (RES) need a voltage buck and/or boost stage for islanded/grid connected operation. Despite the excellent performance offered by conventional two-stage converter systems (dc–dc followed by dc–ac stages), the need for a single-stage conversion stage is attracting more interest for cost and size reduction reasons. Although voltage source inverters (VSIs) are voltage buck-only converters, single stage current source inverters (CSIs) can offer voltage boost features, although at the penalty of using a large DC-link inductor. Boost inverters are a good candidate with the demerit of complicated control strategies. The impedance source (Z-source) inverter is a high-performance competitor as it offers voltage buck/boost in addition to a reduced passive component size. Several pulse width modulation (PWM) techniques have been presented in the literature for three-phase Z-source inverters. Various common drawbacks are annotated, especially the non-linear behavior at low modulation indices and the famous trade-off between the operating range and the converter switches’ voltage stress. In this paper, a modified discontinuous PWM technique is proposed for a three-phase z-source inverter offering: (i) smooth voltage gain variation, (ii) a wide operating range, (iii) reduced voltage stress, and (iv) improved total harmonic distortion (THD). Simulation, in addition to experimental results at various operating conditions, validated the proposed PWM technique’s superior performance compared to the conventional PWM techniques.

An Improved Single Stage Phase Shifted Control Based AC–DC PFC Converter for Wireless Applications

Recently, many researchers has more attention in a single stage AC to DC converter features and DC to DC regulator are extensively used into low power applications. When compared with the two stage conventional method over the Single stage converter has a simple design and utilize only less components. Therefore, this task has been used in this paper as a prposed work of AC–DC single stage converters combine a converter front end with DC–DC back end converter. This proposed work has been improved single stage power factor correction (PFC) converter based on phase-shifted controller for wireless Power applications. The proposed technique employed to develop the improved converter for task of an extensive series of voltage outputs with rippleless outcomes in low frequency, that shows the high essential in battery application and the PFC duty ratio restriction is eradicated. Similarly, DC–DC stage operation are designed in a related way of conventional full bridge phase shifted converter. Accordingly, the proposed technique of improved converter of this paper will achieves better efficiency compared with other conventional techniques and it has been prove more efficient for many Industrial applications, it has been discussed in result section clearly. The experimental results of proposed improved converter proves that it is potential to extend high power single stage converter with good power factor, conversion characteristics and efficiency.

A Review on Two-Stage Back End DC-DC Converters in On-Board Battery Charger for Electric Vehicle

Development in the area of Power Electronics leads to a drastic change in transportation from conventional fuel-based vehicles to Electric vehicles. Due to the adverse effects of conventional transportation to the environment, eco-friendly transportation like e-transportation becomes necessary. In e-transportation battery and its charging system plays a major role. The battery charger can be broadly classified into the on-board charger (OBC) and off-board charger. OBC’s can be further branched into a single stage (AC-DC) converter and two-stage (AC-DC & DC-DC) converter. Due to the limitations of the single-stage converter, two-stage topology becomes more popular. Two-stage topology exists with the front end Power Factor Correction (PFC) stage and back end DC-DC regulating stage. Achieving high power quality and regulation is essential for the battery charger. In this paper, an examination of various topologies of the back end two-stage DC-DC converter with isolated and non-isolated configurations in OBC is done with a brief comparison.

Adaptive on Time Controlled Double-Line- Frequency Ripple Suppressor With Fast Dynamic Response and High Efficiency

Due to the input power and output power do not match in real time, single-stage power factor correction converters have large double-line-frequency ripple at the output voltage. The double-line-frequency ripple voltage will cause some electronic devices to work abnormally, and limit the control loop bandwidth of power factor correction converter. In order to reduce the output double-line-frequency ripple voltage, a single-stage Flyback power factor correction converter with Buck ripple suppressor is used in this paper, the Buck ripple suppressor can generate same magnitude but 180° phase shifted voltage as Flyback power factor correction converter output voltage ripple. Adaptive on-time control is adopted in the Buck ripple suppressor benefiting with its wider bandwidth and fast dynamic response. The switching frequency range and stability of Buck ripple suppressor under constant on-time control and adaptive on-time control are discussed. By establishing the input-output audio susceptibility model, the output double-line-frequency ripple suppression performance is analyzed. Buck ripple suppressor using adaptive on-time control can suppress double-line-frequency ripple voltage effectively with the fast dynamic response and high efficiency. Simulation and experimental results are given to verify the theoretical analysis.

Phase-Shift PWM Converter with Wide Voltage Operation Capability

A soft switching three-level pulse-width modulation (PWM) converter is presented for industrial electronics with wide voltage range operation, such as solar power or fuel cell applications. Phase shift PWM scheme is used on the input-side to accomplish the zero voltage turn-on on power switches and improve the converter efficiency. Three-level diode-clamp circuit topology is adopted in the presented circuit to lessen the voltage ratings on active devices for high voltage applications. Three sub-circuits with the different turns-ratio of transformers can be selected in the presented converter in order to achieve 10:1 (Vin,max = 10Vin,min) wide input voltage operation when compared to the conventional multilevel converter. The proposed circuit is a single-stage converter instead of two-stage converter to realize wide voltage operation. Therefore, the presented converter has less component counts. Finally, the design procedure and experiments with a 300W laboratory circuit are presented and discussed to confirm the circuit analysis and converter performance.

Input Current Quality Parameters Analysis of Modular AC-DC SEPIC Charger Based on Double Fourier Series

Review of AC chargers topologies with active power factor correction are considered in the paper. Single and double-stage charger topologies are highlighted and the feasibility of using the first group of converters is substantiated because of its smaller size and simpler structure. Among single-stage converters, the advantages of modular converters based on SEPIC topologies are emphasized because of minimal dynamic losses, a simple algorithm, and circuit implementation of power factor correction at the boundary condition mode (BCM) of input current and small dimensions. The operation of modular converters is analyzed on the example of a two-cell converter and the principle of improving the shape of the input current under the condition of shifting control pulses of each cell is shown. As a result, the functional dependence of the electricity quality parameters (power factor PF and the total harmonic distortion THD) on the pulse ratio of each converter cell is established. Since it is difficult to comply BCM in real converters, and in continuous mode the shape of the input current is distorted, such converters operate in the discontinuous conduction mode (DCM) of input current. Based on the analysis of equivalent circuits in three intervals of operation of the SEPIC converter - interval of increase of input current, interval of decrease of input current and interval of zero pause - its mathematical model was created. It is shown that the increase of relative zero current interval duration significantly worsens the value of the power factor PF and the total harmonic distortion THD. As a result, the PF and THD parameters are functions of duty cycle and the relative zero current interval duration and have a complex relationship. Therefore, in order to estimate the number of converter cells that provide the required PF and THD values, it is advisable to derive these dependencies in analytical form, based on the use of a Double Fourier series. The obtained dependencies simplify the selection of the number of cells of the converter for a given range of duty cycle and the relative zero current interval duration. PF and THD dependencies for two, three and four cells are constructed on the basis of the derived formulas.

A Novel Hybrid Compensation Method Reducing the Effects of Distorted Input Voltages in Matrix Converters

Matrix converters have the most compact and efficient AC-AC converter structure due to the lack of the DC intermediate components. The matrix converter makes a single-stage conversion directly connecting any terminal of voltage source to any terminal of load. This outstanding feature leads to some problems that must be overcome under the distorted input voltage conditions. A matrix converter has low immunity to power source disturbances, because it has no DC intermediate circuit. Any disturbance in the power source creates a negative effect on the load of the matrix converter and on the current drawn from the source. In this study, a novel compensation method, which provides immunity against input voltage disturbances, is suggested for the matrix converter. The suggested method has a hybrid structure, which includes both feedforward and fuzzy logic controller based feedback methods. The effectiveness and accuracy of the suggested new hybrid compensation approach are proved by the various results obtained.