Output Current Ripple Research Articles

High-Frequency Three-Phase Interleaved LLC Resonant Converter With GaN Devices and Integrated Planar Magnetics

The LLC converter is deemed the most widely used topology as dc/dc converter in server and telecom applications. To increase the output power and reduce the input and output current ripples, three-phase interleaved LLC converter is becoming more and more popular. It has been demonstrated that three interleaved LLC converter can achieve further efficiency improvement at the 3-kW power level. However, the magnetic components for multiphase LLC converter are complex, bulky, and difficult to manufacture in a cost-effective manner. In this paper, a high-frequency gallium nitride (GaN)-based three-phase LLC converter is employed to address these aforementioned challenges. With GaN operating at 1 MHz, all magnetic components, namely, three inductors and three transformers, can be integrated into one common structure while all magnetic windings implemented in a compact four-layer PCB with 3-oz copper. The proposed structure can be easily manufactured cost-effectively in high quality. Furthermore, shielding techniques for full-bridge secondary have been investigated, and additional two-layer shielding has been integrated to reduce common-mode noise. A 1-MHz 3-kW 400 V/48 V three-phase LLC converter is demonstrated, and the peak efficiency of 97.7% and power density of 600 W/in3 (37 kW/L) are achieved.

High-Efficiency Bidirectional Buck–Boost Converter for Photovoltaic and Energy Storage Systems in a Smart Grid

This paper proposes a new bidirectional buck–boost converter, which is a key component in a photovoltaic and energy storage system (ESS). Conventional bidirectional buck–boost converters for ESSs operate in discontinuous conduction mode (DCM) to achieve zero-voltage switching turn- on for switches. However, operation in DCM causes high ripples in the output voltage and current, as well as low power-conversion efficiency. To improve the performance of the conventional converter, the proposed converter has a new combined structure of a cascaded buck–boost converter and an auxiliary capacitor. The combined structure of the proposed converter reduces the output current ripple by providing a current path and the efficiency is increased. A prototype was built and tested to verify the effectiveness of the converter. The proposed converter has a maximum efficiency of 98%, less than ${\text{5.14}}{ \text{V}}_{{\text{p.p}}}$ of output voltage ripple, and less than ${\text{7.12}}{ \text{A}}_{{\text{p.p}}}$ of output current ripple. These results were obtained at an input voltage of 160 V, switching frequency of 45 kHz, output voltage of 80–320 V, and output power of 16–160 W. The experimental results show that the proposed converter has improved performance compared to the conventional converter.

A New Grid-Connected DC/AC Inverter With Soft Switching and Low Current Ripple

This paper presents a new dc/ac inverter for low-power applications (i.e., high-voltage, low-current applications), which offers soft switching of the power semiconductors and low output current ripple. In the proposed power circuitry, a novel ripple steering approach is used that can provide soft switching for the power semiconductors and significantly attenuate the high-frequency current ripple of the inverter. The proposed ripple steering technique utilizes the switching frequency and the duty cycle in order to perform the aforementioned tasks. Basically, the ripple steering technique steers the energy of the ripple to the output capacitances of the power semiconductors in order to provide the soft-switching condition. Theoretical analysis, simulation results, and experimental results verify the feasibility of the proposed technique and demonstrate the superior performance of the proposed inverter.

Design of Digital Control Phase-Shifting Full-Bridge Switching Power Supply

With the development of switching power supply towards miniaturization and high efficiency, digital and soft switching technology has become the research focus of switching power supply. Phase-shifted full-bridge DC/DC converter is commonly used in medium and high power applications due to its advantages of low switching loss, high efficiency and low output current ripple. Based on the existing switching power supply and digital control technology, a digital control phase-shifting full-bridge switching power supply is designed. Its output voltage ranges from 0 to 12 V.The output current ranges from 0 to 50 A. The voltage and current level can be adjusted according to the user’s power demand, and the output mode of steady voltage or steady current can be set. The parallel operation of multiple power supply is realized by RS485 communication protocol.

The design of the superconducting wiggler power supply system for HEPS-TF

PurposeThis paper describes the design of power supply system for superconducting wiggler in the project of high energy photon source-test facility. It includes three sets of high precision DC stabilized current power supplies for superconducting magnet excitation and three sets of quench protection assembly (QPA). A special magnetic load which has a very large time constant is studied in this paper. In this paper, a stable superconducting excitation power supply is developed, which can adjust the response quickly under the condition of very large load time constant. Meanwhile, the energy dissipation circuit of the QPA is integrated into the power supply in an active quenching protection mode to accelerate the energy release of the superconducting magnet and protect the superconducting magnet.MethodThe main circuit topology, control algorithm, quenching protection circuit and interlocking logic function are designed for the superconducting magnet with large inductance. The upper computer controls the switch of the three main power circuits through the serial port, sets the output current and adjusts the parameters according to the load.ConclusionThrough a series of scientific and rigorous experiments, the rationality of superconducting wiggler magnet power supply scheme is demonstrated. The output current stability test and output voltage ripple test of the power supply meet or exceed the requirements of the magnet system.

Power Factor Improvement in Modified Bridgeless Landsman Converter Fed EV Battery Charger

This work deals with the design and implementation of a new charger for a battery-operated electric vehicle (EV) with power factor improvement at the front end. In the proposed configuration, the conventional diode converter at the source end of existing EV battery charger is eliminated with the modified Landsman power factor correction (PFC) converter. The PFC converter is cascaded to a flyback isolated converter, which yields the EV battery control to charge it, first in constant current mode then switching to constant voltage mode. The proposed PFC converter is controlled using single sensed entity to achieve the robust regulation of dc-link voltage as well as to ensure the unity power factor operation. The proposed topology offers improved power quality, low device stress, and low input and output current ripple with low input current harmonics when compared to the conventional one. Moreover, to demonstrate the conformity of the proposed charger to an IEC 61000-3-2 standard, a prototype is built and tested to charge a 48 V EV battery of 100 Ah capacity, under transients in input voltage. The performance of the charger is found satisfactory for all the cases.

Analysis of the Steady-State Current Ripple in Multileg Class-D Power Amplifiers Under Inductance Mismatches

Multileg Class-D amplifiers (CDAs) with phase-shifted carrier modulation can increase the equivalent switching frequency and reduce the output current ripples, which further reduces the size of the output filter. However, these benefits are degraded by the tolerances in the phase inductance values. The phase inductance mismatches impact the ripple cancelation effects (the harmonic contents at switching frequency and its harmonics appearing in the output current ripple). Therefore, the quality of the output waveform can further be impacted. Current research works dealing with this issue mainly focused on the interleaved dc–dc converters, which does not cover the analysis in multileg CDAs or inverters, especially for the full-bridge configuration. This paper proposes a general analytical method to characterize the steady-state phase and the total current ripple in the multileg CDAs with full-bridge configuration under inductance mismatches. Monte Carlo simulation is used to study the impact of inductance mismatches on the harmonic contents of the total current ripple, and the distribution law of the inductances at the worst case is revealed. The analytical method is verified by simulation and experimental results of a four-leg full-bridge CDA. A design guideline is given to optimize the filter design based on the analytical method.

Literature Survey of Interleaved DC-DC Step-Down Converters for Proton Exchange Membrane Electrolyzer Applications

Recently, the use of electrolyzers for hydrogen production through water electrolysis is of great interest in the industrial field to replace current hydrogen production pathways based on fossil fuels (e.g. oil, coal). The electrolyzers must be supplied with a very low DC voltage in order to produce hydrogen from the deionized water. For this reason, DC-DC step-down converters are generally used. However, these topologies present several drawbacks from output current ripple and voltage gain point of view. In order to meet these expectations, interleaved DC-DC step-down converters are considered as promising and interesting candidates to supply proton exchange membrane (PEM) electrolyzers. Indeed, these converters offer some advantages including output current ripple reduction and reliability in case of power switch failures. In addition, over the last decade, many improvements have been brought to these topologies with the aim to enhance their conversion gain. Hence, the main goal of this paper is to carry out a thorough state-of-the-art of different interleaved step-down DC-DC topologies featuring a high voltage gain, needed for PEM electrolyzer applications.

Unbalanced Three-Phase <inline-formula> <tex-math notation="LaTeX">$LLC$</tex-math> </inline-formula> Resonant Converters: Analysis and Trigonometric Current Balancing

Three-phase $LLC$ resonant converters can handle very high power levels beyond the capabilities of half-bridge and full-bridge $LLC$ topologies. Among other characteristics, three-phase $LLC$ structures reduce output current ripple (small output filter), enable parallel power processing (low peak current), and provide good thermal distribution. However, all these key advantages can be severely compromised due to passive components tolerances, leading to undesired current balance issues in three-phase $LLC$ resonant converters. Tolerances in resonant tank passive components are inevitable and lead to unequal peak currents between phases, uneven temperature distribution, and large output current ripple. This paper investigates the imbalances in three-phase $LLC$ converters and proposes a novel trigonometric current balancing (TCB) technique using phasor analysis. In this strategy, the required input voltage phase angles are calculated to achieve balanced phase currents, even under severe unbalanced conditions. In some cases, the output filter current ripple is reduced to less than half. The methodology is verified with a 3-kW experimental prototype, which validates the analytical framework and effectiveness of TCB.

The Parametric Simulation of the Interleaved Boost Converter for the Electric Transport Vehicle

Abstract This paper deals with the analysis of four phase boost interleaved DC-DC converter with the non-coupled inductors for higher power application in Continuous Conduction Mode. The interleaved topology reduces input and output current ripple, voltage ripple and improves the efficiency of SMPS. The value of capacities and inductances affect the behavior of the converter. The investigation of these parameters is described and supported by parametric simulation in LT spice.

LLC LED Driver Small-Signal Modeling and Digital Control Design for Active Ripple Compensation

This paper presents a new approach for the small-signal modeling of the dc–dc LLC resonant converter aimed to supply high-power light-emitting diodes (LEDs). This small-signal modeling procedure is based on the extended describing function method, where for a reliable small-signal model of the LLC LED driver, the equivalent piece-wise linear circuit of the LED has to be considered under some conditions throughout the model development. Otherwise, the obtained model does not reflect the real dynamic behavior of the converter. Furthermore, a numerical analysis is presented showing the conditions where the proposed model better describes the real dynamic behavior of the converter in relation to the traditional approach where the LED is modeled by an equivalent resistance. From the obtained model, the feedback compensator is designed and implemented in order to track the average current reference and avoid output current ripple, consequently sidestepping output light modulation (flicker). Experimental results show the feasibility of the proposed small-signal model and the active ripple compensation through a dimmable digitally controlled LLC LED driver under closed-loop operation.

Loss Analysis for Efficiency Improvement of the Integrated Buck–Flyback LED Driver

This paper presents a study of the losses in the integrated buck–flyback converter (IBFC) used as high-power-factor LED driver. The aim of the study is to investigate the possibilities of increasing the efficiency of the IBFC converter. The procedure of the improvement is done by obtaining the equations of the current through each component in terms of converter parameters. The current is found in an average value or rms value, depending on the type of the parasitic component, whether it is modeled by a parasitic forward voltage source or by a parasitic resistance, respectively. Using these equations and the parasitic model, the losses of each element of the converter are estimated. This paper proposes a technique to increase the efficiency of the IBFC by redesigning the converter parameters. Furthermore, this paper presents a case of study with a step-by-step efficiency enhancement process of an existing driver. The driver is operating under universal input conditions, and 38 V output, supplying an LED luminary of 26.5 W. The new design shows an improvement of the efficiency from 82% in the old design to 89% in the proposed one. Moreover, the new design shows an improvement in the power factor and the THD and a 50% reduction in the output current ripple. Furthermore, a reduction in the number of components has been achieved, as it is found by the analysis that by adjusting the converter parameters, one diode can be removed. Finally, the presented methodology is explained in detail so that it can easily be applied to other dc–dc converters.

Magnetic Design and Experimental Evaluation of a Commercially Available Single Integrated Transformer in Three-Phase <italic>LLC</italic> Resonant Converter

Multiphase topologies are preferably employed in power conversion systems to lessen the per-phase circuit current, conduction losses, devices thermal stresses, and to reduce the output current ripples. A multiphase LLC resonant dc/dc converter usually possesses a number of magnetic cores equal to the number of phases. These magnetic cores are the major contributors to supply volume, weight, and size. For these reasons, circuit designers tend to select the topologies that have a minimal number of magnetic cores. In this paper, the authors aim to promote the industrial applications of the three-phase LLC resonant converter by integrating three transformers into a single commercially available magnetic core to reduce the volume, weight, and cost of the power converter. A comprehensive magnetic analysis for the three-phase-integrated transformer is conducted. Finite element method (FEM) simulation and experimental tests are carried out to validate the proper operation of the integrated transformer utilized in a 390-/12-V to 500-W prototype. Furthermore, the power losses distribution has been presented. The proposed integrated transformer has been proven effective, and it realized a uniform thermal distribution along the core compared to the three-discrete transformers.

REDUCTION OF INVERTER OUTPUT CURRENT RIPPLE IN CONNECTION OF FUEL CELL TO THE POWER NETWORK

In this paper, a method is introduced which reduces the harmonicdistortion of the inverter output current, connecting the fuelcell to the AC load. Using FUZZY LOGIC-PI (FLPI), the controllingmethod is engaged in optimum tuning of the PI controllercoefficients of this converter. This converter has only one DC-ACboost inverter and simultaneously has the task of increasingvoltage level and generating the AC power. In order to control theinverter output voltage, an internal current control loop and anexternal voltage control loop are used. Designing the control ofeach loop is done separately based on FLPI controller. Simulationresults for proposed fuel cell energy system in the presence ofthis controller imply good performance of FLPI and suitablemitigation of inverter output current ripple.

Bidirectional dc to dc Converters: An Overview of Various Topologies, Switching Schemes and Control Techniques

Bidirectional dc to dc converter is used as a key device for interfacing the storage devices between source and load in renewable energy system for continuous flow of power because the output of the renewable energy system fluctuates due to change in weather conditions. In electric vehicles also, bidirectional converter is used between energy source and motor for power supply from battery to motor. Thus, bidirectional dc to dc converters are getting more and more attention in academic research and in industrial applications. Bidirectional dc to dc converters work in both buck and boost mode and can manage the flow of power in both the direction between two dc sources and load by using specific switching scheme and phase shifted control strategy and hence generated excess energy can be stored in batteries/super capacitors. Therefore, the basic knowledge and classification of bidirectional dc to dc converters on the basis of galvanic isolation, the comparison between their voltage conversion ratio and output current ripple along with various topologies researched in recent years are presented in this paper. Finally, zero current and zero voltage soft switching schemes and phase shifted controlling techniques are also highlighted.

Design of solar‐powered agriculture pump using new configuration of dual‐output buck–boost converter

This paper proposed a new structure of single switch dual output Zeta derived DC-to-DC converter for an efficient harvesting of photovoltaic (PV) power for a 4-phase switched reluctance motor (SRM) driven agriculture pump. The system is essentially developed to minimise both cost and complexity, while synchronously guaranteeing optimal operation of the PV array. The proposed converter is derived from a hybrid of a ‘Zeta’ and Landsman converters and so it contains all the benefits of both converters including balanced outputs. Due to an identical instantaneous duty cycle, the switching node is shared by both Zeta and Landsman converters. The proposed converter offers continuous power to drive, a low ripple in output current, and balanced dual output supply. The PV power optimisation and to deliver smooth start of SRM, are the two major objectives of proposed DC-to-DC converter. A new maximum power point tracking (MPPT) technique is also used in the system to optimise the performance of PV array. Moreover, the proposed MPPT control has an additional advantage of regulating the flow rate of water pumping by adjusting the duty cycle of DC-to-DC converter. The motor speed is smoothly regulated through the variable DC link voltage of a mid-point converter.

Analysis and Design of a Unidirectional Resonant Switched-Capacitor Step-Up Converter for OLED Lamp Driving Based on Variable Inductor

This paper presents an analysis and design of a unidirectional resonant switched-capacitor (URSC) step-up converter for organic-lighting-emitting-diode (OLED) lamp driving. The URSC converter includes a very small inductor in series with the SC to improve the switching behavior. Also, the URSC converter presents the advantages of high power density, higher efficiency compared to other SC converters, low output voltage and current ripples, and low electromagnetic interference noise, which make it adequate for driving OLED lamps. URSC is designed to operate in closed loop with constant current variable inductor (VI) control technique. By working the resonant inductor as a VI, the OLED current can be regulated and dimmed because of resonant frequency change. Simulation and experimental results of the VI inductor, which are in a good agreement, and the results of a URSC step-up converter design example for a 21.8-W OLED lamps array supplied from 48 Vdc are presented, where a maximum 92.97% efficiency is obtained.

A Modular-Designed Three-Phase High-Efficiency High-Power-Density EV Battery Charger Using Dual/Triple-Phase-Shift Control

In this paper, an enhancement-mode GaN high-electron mobility transistor (HEMT)-based 7.2-kW single-phase charger was built. Connecting three such single-phase modules to the three-phase grid, respectively, generates a three-phase ∼22-kW charger with the $>{\text{97}}\% $ efficiency and $>{\text{3.3}}-{\rm{kW}/ \rm{L}}$ power density, superior to present Si-device-based chargers. In addition to GaN HEMTs with fast-switching transitions yielding high efficiency, the proposed charger employs the dc/dc stage to control the power factor and power delivery simultaneously, yielding little dc-bus capacitance and thereby high power density. To secure the soft switching for all switches within full voltage and power ranges, a variable switching frequency control with dual phase shifts was adopted at high power, and a triple phase shift was employed to improve the power factor at low power. Both control strategies accommodated the wide input range (80–260 VAC) and output range (200–450 VDC). A closed-loop control for the three-phase charger was realized to minimize the output current ripple and balance the power among three single-phase modules. Experimental results validated this design.

New Modeling Method and Design Optimization for a Soft-Switched DC–DC Converter

High-performance cloud computing enables many key future technologies such as artificial intelligence (AI), self-driving vehicle, big data analysis, and the Internet of things (IoT), using clustered CPU and GPU servers in the datacenter. To improve the power efficiency and the infrastructure flexibility, the computing industry is adopting 54 VDC to power the servers in the open compute racks. In this paper, a new modeling technique for a soft-switched dc–dc converter is presented and suitable to guide optimal design in different applications, for example, 54 V to point of load (PoL) for the new open compute rack. To improve the model accuracy and reduce the complexity, this paper proposes a reduced-order linear differential equation (LDE) based modeling technique to discover the following: 1) the tank resonance involving the output inductor; 2) the output current ripple and its impact on power efficiency; 3) the proper on-time control for soft switching; 4) the unique bleeding mode under the heavy load; 5) the output power capability of the converter; and 6) component tolerance analysis and impact on the performance of the converter. With the power loss estimation, design guidelines are provided for a reference design and design improvement based on this new modeling technique. Using the proposed method, great accuracy can be expected in the efficiency estimation. Simulation and experimental results are provided to verify the modeling technique in a 54–1.2 V 25 A dc–dc converter prototype.

Voltage Gain Improvement of a High-Step-Down Converter With Coupled-Inductor Core Size Reduction Based on Flux Linkage

As compared with the buck converter, the ultrahigh step-down converter can achieve a much higher step-down gain, which can be determined by not only the duty cycle, but also the turns ratio of the coupled inductor. However, this converter suffers from some problems, such as pulsating output current and large dc magnetizing inductance current, which will degrade the core utilization. As compared with the ultrahigh step-down converter, the coupled-inductor-based high step-down converter features a nonpulsating output current and a zero dc magnetizing inductance current. Therefore, the output current ripple is lower and the core utilization can be upgraded. Since the core size is proportional to the square of the applied flux-linkages, an improved coupled-inductor-based high step-down converter is presented herein. By employing an auxiliary circuit, consisting of a small capacitor and a mosfet , the flux linkage of the coupled inductor can be decreased, and hence the required core size can be reduced. In addition, due to the auxiliary circuit, the voltage spike across the tapped switch can be reduced. Above all, the step-down gain can be improved. Finally, detailed theoretical analyses and experimental results are provided to verify the feasibility and effectiveness of the proposed converter.