Full Load Range Research Articles

Limit states of thin-walled composite structures with closed sections under axial compression

The subjects of the study were thin-walled composite columns with closed cross sections manufactured using the autoclave technique. The composite profiles were characterized by the fact that they had a constant height and arrangement of laminate layers, however, varied cross-sectional shapes. The study was conducted using several interdisciplinary experimental research methods and advanced numerical simulations. In the course of the research, both forms of structural stability loss were registered, and damage to composite structures was assessed. In the course of the research, the influence of the shape of the cross-section on the stability and load-carrying capacity of the structure was evaluated. A measurable effect of the conducted research was the determination of the structure's post-buckling equilibrium paths, which made it possible to determine the structure's behavior in the full range of loading. In addition, the author's numerical models developed enabled validation of parallel experimental studies. The developed numerical models were based on a failure criterion known as progressive failure analysis - which allowed a thorough assessment of the failure mechanism of the composite material.

Dynamic Response Characteristics of Foundation of Mined-out Areas under High-speed Railway Load

To reveal the dynamic response characteristics of the foundation of mined-out areas (MOA) under the high-speed railway (HSR) load is important for predicting settlement and safety assessment of the foundation. Taking MOA of Dianshang under the Taiyuan-Jiaozuo HSR as the engineering background, the model experiments and numerical analysis were employed to reveal the dynamic response of both subgrade and the foundation of the HSR, as well as the attenuation law of the acceleration in the overlying strata of the MOA. Results show that within the full frequency range of the HSR load, the dynamic response of the foundation increases with the increase in load frequency. When the depth exceeds 6 m, the dynamic response of the foundation initially increases and subsequently decreases with the increase in load frequency. Contrasted with single-point loading, the superposition effect and moving effect of the HSR load will form a dynamic response superposition zone within 1-4 m below the subgrade, leading to a significant enhancement of the dynamic response of the foundation. Compared to HSR axle load, the driving speed of HSR has a greater impact on the acceleration of both the subgrade and foundation. The obtained conclusions provide a reference for the safety operation of the HSR crossing the MOA

A Battery Wireless Charger With Full Load Range Soft-Switching Operation and Zero-Switching-Loss Inverter

A Battery Wireless Charger With Full Load Range Soft-Switching Operation and Zero-Switching-Loss Inverter

Paralleled Variable Inductor Phase-Shifted Full-Bridge Converter With Full-Load Range ZVS and Low Duty Cycle Loss

This paper presents a new phase-shifted full-bridge topology using a new variable inductor. In this topology, a variable inductor is connected in parallel with a near-ideal transformer. The ZVS of the switches is achieved over the full load range using the parallel current provided by the variable inductor. And the adjustable parallel current reduces conduction losses. Under the orthogonal DC magnetic potential, the variable inductor has similar characteristics to the saturated inductor, which is beneficial to reduce the conduction loss caused by the parallel current. Since the topology has no series inductor and the leakage inductor is extremely small, the proposed converter has the advantages of extremely small duty cycle loss, larger transformer turns ratio, smaller primary current stress, smaller secondary voltage stress, and smaller output current ripple, which are beneficial to improve the efficiency and frequency of the converter. An experimental platform was established. Theoretical analysis and experimental verification were carried out.

Coupled-Inductor-Based Bidirectional Resonant Converter With Reduced Component Count and Load-Independent Voltage Gain

The bidirectional DC/DC converter (BDC) is a critical part to interface the DC-bus with energy storage system (ESS) in DC microgrid. This paper proposes a coupled-inductor based bidirectional resonant converter with center-aligned pulse width modulation (PWM) modulation method and reduced component count. The structure of dual half-bridges with coupled inductor makes the current analysis more complex than the full-bridge PWM resonant converter. Hence, a method of performance analysis based on the symmetrical pi model is proposed and the corresponding parameter design process is introduced. In addition, fixed switching frequency operation, load-independent voltage gain, full-load range zero-voltage-switching (ZVS), automatic bidirectional power transfer and bidirectional power limitation can be realized in the proposed PWM converter. An experimental prototype with rated power of 1000W is built to demonstrate the operation and performance of the proposed converter.

Partition Variable Frequency and EPS Hybrid Control to Achieve Full Load Range ZVS for Dual Active Bridge Converters

Partition Variable Frequency and EPS Hybrid Control to Achieve Full Load Range ZVS for Dual Active Bridge Converters

Bidirectional ZVS Operation of All Switches for a DAB Converter Over a Full Range of Loads With Optimized Current Stress

Bidirectional ZVS Operation of All Switches for a DAB Converter Over a Full Range of Loads With Optimized Current Stress

Hybrid-Level Modulation Scheme for Dual-Bridge Series-Resonant Converter

This paper proposes a hybrid level modulation (HLM) scheme to achieve full load range zero voltage switching (ZVS) over various voltage gains for dual-bridge series-resonant converter. According to the load conditions, HLM includes two parts. At heavy load, a variable-frequency symmetrical level modulation (VFSLM) scheme is offered to ensure the complete commutation of the bridge legs with soft-switching operation. In addition, the optimal root mean square (rms) of the inductor current can be achieved, which further benefits the transfer efficiency. At light load, the switching frequency demanded by VFSLM is much higher than the resonant frequency. So, a dual asymmetric level modulation (DALM) scheme is proposed to prevent devices from hard-switching operation within a moderate range of changes in frequency. Furthermore, the method of identifying control variables with DALM is analyzed for overall efficiency optimization. The developed approach is validated on a 6.6kW on-board-charger whose output voltage varies from 220V to 470V.

A high efficiency buck converter based on PLL for frequency stabilization

A high efficiency Buck converter circuit based on Phase-locked loop (PLL) to achieve frequency stabilization is proposed to solve the problems of reduced converter efficiency, unstable output and high electromagnetic interference caused by unstable switching frequency. Since the increase of load current increases the switching frequency in the conventional adaptive on-time (AOT) control, a phase-locked loop is designed to achieve the switching frequency stabilization by forming a negative feedback. In addition, a bootstrap high-voltage gate driver circuit is designed to drive the dual NMOS power tubes in order to achieve high conversion efficiency and optimize the chip area. The proposed Buck circuit is simulated and verified based on SMIC 0.18 μm CMOS 2P4M process, with an input voltage of 2.5V–5.5V, an output voltage of 0.8V–4V, a switching frequency variation rate of only 8.5 kHz/A over the load range of 0.5A–3A, and a peak efficiency of 94.8 % over the full load range is achieved, and the undershoot/overshoot recovery time of the load transient response is only 5.4μs and 6.9μs.

Modified Voltage Matching Control and Inductor Current Injections for Hybrid-Bridge-Based DAB Converter

In this paper, a modified voltage matching control and current injections method are proposed for the hybrid-bridge-based dual active bridge (DAB) converter, which is aimed at achieving full load range zero voltage switching (ZVS) with consideration of all the switch junction capacitors. With the proposed modified voltage matching control, the non-ZVS region under backward power transfer (even without the junction capacitors) is eliminated. The analysis of the operation principle, ZVS model analysis considering junction capacitors and current injection method are discussed in detail. In addition, the problem of discontinues ZVS region with consideration of the switch junction capacitors is solved through injecting two current sources with paralleling one inductor to the transformer. Finally, the effectiveness of the proposed solution is verified by experimental results on a 100kHz, 1kW converter prototype.

Magnetizing Current Injection Based Push-Pull Dual Active Bridge Converter With Optimized Control to Achieve Full Load Range ZVS for the Distributed Generation System

To reduce greenhouse gas emissions, the distributed generation system is an approach worth investigating. With fewer switches, the push-pull circuits are suited for low-voltage and high-current applications, such as the distributed generation system. In this paper, a modified push-pull dual active bridge (PPDAB) dc-dc converter and its optimized control are proposed to achieve full load range zero voltage switching (ZVS). Considering the switch junction capacitors, the added current is injected by the magnetizing inductance to achieve full load range ZVS. Based on the RMS value of transformer current, the optimized control strategy is proposed to enhance the system efficiency with the precondition of achieving full load range ZVS of all switches. The working principles, ZVS region analysis, and design of key parameters are discussed in detail. Finally, the effectiveness of the proposed method for the PPDAB converter is verified by the results of a laboratory prototype.

Cyclic loading induces anabolic gene expression in ACLs in a load-dependent and sex-specific manner.

Anterior cruciate ligament (ACL) injuries are historically thought to be a result of a single acute overload or traumatic event. However, recent studies suggest that ACL failure may be a consequence of fatigue damage. Additionally, the remodeling response of ACLs to fatigue loading is unknown. Therefore, the objective of this study was to investigate the remodeling response of ACLs to cyclic loading. Furthermore, given that women have an increased rate of ACL rupture, we investigated whether this remodeling response is sex specific. ACLs were harvested from male and female New Zealand white rabbits and cyclically loaded in a tensile bioreactor mimicking the full range of physiological loading (2, 4, and 8 MPa). Expression of markers for anabolic and catabolic tissue remodeling, as well as inflammatory cytokines, was quantified using quantitative reverse transcriptionpolymerase chain reaction. We found that the expression of markers for tissue remodeling of the ACL is dependent on the magnitude of loading and is sex specific. Male ACLs activated an anabolic response to cyclic loading at 4 MPa but turned off remodeling at 8 MPa. These data support the hypothesis that noncontact ACL injury may be a consequence of failed tissue remodeling and inadequate repair of microtrauma resulting from elevated loading. Compared to males, female ACLs failed to increase anabolic gene expression with loading and exhibited higher expression of catabolic genes at all loading levels, which may explain the increased rate of ACL tears in women. Together, these data provide insight into load-induced ACL remodeling and potential causes of tissue rupture.

Combustion of LPG / DME gas mixtures in an SI engine with correction of the ignition advance angle

The paper presents the results of tests on a SI engine fueled with an LPG/DME blends of various composition. A number of experimental studies and calculations using a mathematical model were carried out to examine the suitability of this fuel. These tests allowed for the analysis of the changes taking place in the combustion process and the assessment of the main operating parameters of the engine. The results of the analysis of the combustion process make it possible to observe how the heat is released and how the indicated pressure changes, depending on the share of DME in the fuel mixture. The scope of the tests performed included engine and vehicle tests on a chassis dynamometer and a series of simulation tests conducted on the basis of the obtained results. The engine was powered by an LPG/DME fuel mixture with different proportions of components. The share of DME ranged from 0% to 30% of the fuel mass. The obtained results reflect the operation of the engine in the full load range and selected rotational speeds. Measurement series were made for different settings of the ignition advance angle. Based on the obtained results, a corrected map of the ignition advance angle was developed. The obtained results confirm the usefulness of using the LPG/DME mixture to power the SI engine.

A Scalable Electronic-Embedded Transformer, a New Concept Toward Ultra-High-Frequency High-Power Transformer in DC–DC Converters

The demand for high-power and high-density isolated dc-dc converter is driven by the rapid development of energy storage system, data center power supplies and transportation electrification. However, designing a high-power and high-frequency transformer presents significant challenges due to the trade-off between thermal management, leakage inductance minimization, and insulation requirements. In order to overcome this trade-off between power rating and operation frequency, a scalable electronic-embedded transformer (EET) is proposed with a low voltage bridge integrated into the transformer windings. The EET addresses the challenge through its simple open-loop control and natural current sharing, enabling easy parallel connection and scaling to different power ratings. Based on this concept, a bi-directional EET-based dc transformer (EET-DCX) is proposed to solve the transformer-level paralleling and resonant point shift issues in traditional LLC-DCX designs. By employing the embedded full bridge, the EET-DCX effectively cancels out the impedance of the leakage inductance, ensuring optimal operation at any frequency. Additionally, the EET-DCX retains the inherent advantages of the LLC-DCX, such as load-independent voltage gain, simple open-loop control, full load range zero voltage switching (ZVS), and low circulating current. Leveraging these advantages, the proposed EET-DCX solution has the potential to push the boundaries of transformer performance to the MHz operation frequency range with hundreds of kilowatts power capability. To validate these merits, a 12 kW 500 kHz EET-DCX with four planar EET units was built. This article is accompanied by two videos demonstrating the dynamic load changing and frequency changing test.

Modeling, Simulation and Digital Control of Full-Bridge LLC Resonant Converter

In order to demonstrate the performance of an LLC resonant converter with digital control, in this paper, we analyze the operating principles of the full-bridge LLC resonant converter. According to the operating characteristics of the full-bridge LLC resonant converter at different frequency bands, a simulation model was established using MATLAB Simulink software, and simulations were carried out. The digital control system of full-bridge LLC resonant converter was then designed based on the STM32 microcontroller. The simulation and experimental results demonstrated that the LLC resonant main circuit was always operating within the zero voltage switching (ZVS) state of the primary MOSFET and the zero current switching (ZCS) state of the secondary rectifier diode, while soft-switching was achieved in the full load range. The digital control of the full-bridge LLC resonant converter was ideally realized based on STM32. The input disturbance load test result validated the closed-loop concept of the proposed LLC resonant converter. The step response results in both simulation and load tests show that the power supply system has the desired dynamic response characteristics with low overshoot, short rise time and settling time, while the load step response results in both tests showed that the system has a strong anti-interference ability and robustness.

Programmable 1 A ultra-low dropout LDO regulator for high-resolution camera sensors

In this article, design and realization of a high-performance linear low dropout regulator (LDO) capable of supplying 1 A of output current, designed and fabricated in 180 nm BCD technology of STMicroelectronics company, is described. The main purpose of this device is providing a stable output voltage for supplying high-resolution sensors of cameras in cellphones. The LDO is equipped with a big N-channel power transistor allowing an ultra-low dropout voltage around 50 mV at the maximal load current of 1 A even with a very low level of the output voltage of only 0.4 V. These features make the device suitable as a block following buck switching converters. Emphasis has been laid on assuring 1% accuracy of the output voltage across full temperature range and line and load conditions, very low quiescent current around 32 μA, necessary for battery powered applications such as cellphones, good transient response and a high power supply rejection ratio (PSRR) of more than 85 dB at 1 kHz. This combination of high-level parameters stands for an extraordinary device. The proposed LDO is a programmable device which means that the output voltage (up to 100 voltage versions in total) and other functions can be set via post-package electrical trimming. Last but not least, an efficient design for testability (DFT) is implemented in order to reduce the failed parts to a very low level, guaranteeing the highest quality level needed in the market.

A Dual-Mode Step-Down Converter with Automatic Mode Switch Circuit for System-on-Chip Applications

In this paper, a dual-mode step-down DC-DC converter with an automatic mode-switching circuit is implemented in a 28 nm digital CMOS process and embedded in an RF transceiver chip to power the digital part. The proposed automatic mode-switching circuit includes a frequency-voltage conversion circuit that is designed according to the principle of charge redistribution on capacitance. The converter can switch modes according to the load without external intervention. This converter, along with a PMU sequencer, can also provide a solution for low-power design for system-on-chip applications. The IC occupies a total die area of 0.378 mm2. The input voltage of the converter is 3.3 V, the output voltage is 1.05 V, and the maximum load current can reach 1 A. The converter shows a conversion efficiency of not less than 81% at a full load range and can achieve a peak conversion efficiency of 91% when the load current is 100 mA. The load range of the PWM mode is 1 A to 50 mA, and that of the PFM mode is 100 mA to 1 mA. The combination of zero-crossing detection circuitry and freewheel switches can reduce energy loss and eliminate additional electromagnetic interference.

Hybrid Control for Three-Level LLC Resonant Converter of Dual-Bridge for Wide Output Range

A three-level (TL) LLC resonant converter of dual-bridge (DB) with hybrid control modulation strategy is proposed for the wide output-voltage range and high input-voltage applications. The topology integrates two neutral-point-clamped arms (NPCs) through an auxiliary transformer, which forms a new controllable double-voltage structure and makes all MOSFETs hold half of the input voltage. Based on the characteristics of the new topology, a hybrid modulation strategy is proposed corresponding to three gain modes, which include conventional pulse frequency modulation (PFM) and fixed frequency phase shift modulation (FF-PSM). Compared to conventional modulation strategies, the proposed hybrid modulation strategy, which improves the output voltage gain range, achieves zero-voltage switching (ZVS) of all the MOSFETs and zero-current switching (ZCS) of rectifier diodes under wider operating voltage and full load range. To minimize the frequency window and improve the efficiency of the converter, the parameter optimization method is designed, which based on the characteristics of the modulation strategy and the relationship among the maximum output voltage gain, resonant current and turned-off current. At last, the experimental results of the 600W prototype are presented to confirm the theoretical and characterization analysis.

Synthesis and Analysis of Primary High-Order Compensation Topologies for Wireless Charging System Applying Sub-Harmonic Control

Sub-harmonic control (SHC) is an excellent method for wireless charging system because it is easy to achieve full-load range soft switching and unity power factor. However, in existing works, SHC is only applied to the system with primary series compensation topology (PSCT), which has the drawbacks of low degrees of design freedom, high sensitivity to misalignments and no open-circuit protection. To overcome these issues, in this paper, systematic synthesis of primary high-order compensation topology (PHCT) for WPT is identified in terms of general T-branch structure. Afterwards, the applicability of PHCT to SHC is explored by gaining insight into their filter characteristics. It reveals that when SHC is applied, four kinds of PHCTs are superior over other candidates in performance because the unity power factor and soft switching can be achieved without limitation on pulse distribution. Then, six kinds of PHCTs exhibit a moderate performance as they may nullify the strengths of SHC under some specific pulse distributions. The rest of PHCTs are not applicable to SHC no matter what the pulse distribution. Finally, the experimental results on prototype with jointly applying SHC and PHCT are examined.

An Attempt to Analytically Determine Course of the Continuous Q-S Curve in Case of Changed Pile Length or Diameter

Abstract In this paper authors have described the analytical method of continuous static load test Q-s curve conversion for any given pile. Authors have used data sets from static load tests conducted by Energopol Szczecin S.A. in a full range of loads which allows to use of measured values of pile maximum bearing capacity and determine relation between it and pile length and diameter. All the piles used in this paper were CFA piles bored in mostly loam soil conditions. The research described in this work was based on the Meyer-Kowalow method (M-K method) of static load test interpretation. The M-K method allows for a full description of the load-settlement relation, as a continuous curve (M-K curve) using three parameters that described pile-soil interaction. As a result of conducted research relations between parameters describing M-K curve and pile dimensions were established, which allows for a practical application of the proposed method. In this paper, the authors presented an example of the practical use of curve conversion to analyze the impact of changes in geometric dimensions on pile-soil interaction. The proposed method allows for a curve conversion of the total resistance curve, as well as a curve describing base and skin resistances.