Wide Load Research Articles

Design of a Wireless Power Transfer System With Two Inputs With Large Voltage Differences for Missiles Mounted on Maritime Vessels

Missiles mounted on maritime vessels have two types of loads. One is the operating load consumed just before launch, and the other is the safety sensors load that must always be activated for safety. Because the operating load consumes a large power capacity, the power generated by the vessel’s own power generators must be supplied. Meanwhile, the loads for safety sensors are supplied through an energy storage system (ESS) because the safety sensors must be supplied with power even when the generators stop. However, the voltage difference between the generated power and the ESS power reaches ten times or more. Therefore, there is a problem in that the input of the two power sources with a large input difference must be transferred to two loads through only a pair of coils. To solve this problem, a WPT system is proposed to overcome the voltage difference between the generated power and the ESS power. The design method of the proposed system is analyzed mathematically, and it is verified through simulations and experiments. The proposed system has a maximum dc to dc power transfer efficiency of 76.8% with a capacity of 550 W and has the advantage that power is continuously supplied to the sensor loads even if the input voltage source is changed. In addition, by operating the proposed WPT system under a wide load of 200 W to 1000 W, the effectiveness of the proposed WPT system is proved.

Wide Input Variable Mode ZVZCS Converter Design

With the emphasis on energy conservation and emission reduction in various countries, industries such as new energy power generation and electric vehicles have developed rapidly. In many applications, the converter needs to adapt to a wide input voltage range, for example, the input voltage range of electric car charger is 200 ~ 450V. Based on this, this paper proposes a wide-input variable-mode ZVZCS converter for electric vehicles with two operating modes. Before the MOSFETs of the lagging-legs is opened, the primary side current is extinguished by the auxiliary circuit to realize ZCS. Due to the parasitic inductance and diode of MOSFETs, ZVS is realized by MOSFETs on leading-legs. It not only broadens the input voltage range of the traditional phase-shifted full-bridge ZVZCS converter, but also keeps the advantages of the traditional phase-shifted full-bridge ZVZCS converter, such as wide load range and small duty cycle loss. Experimental results with 60 ~ 240 V input voltage are demonstrated to verify the advantages.

Evaluation of the fatigue properties for the long-term service asphalt pavement using the semi-circular bending tests and stereo digital image correlation technique

Reliable assessment of the fatigue resistance of asphalt pavement with a long-term service is critically crucial for the rational formulation of original pavement utilization strategies in reconstruction and expansion projects. Currently, the pavement performance evaluation indicators are mainly used to guide pavement preventive maintenance, and its applicability in reconstruction and expansion projects of the freeway is limited. This paper aims to propose an evaluation method of fatigue resistance of asphalt concrete utilizing semi-circular bending (SCB) tests and stereo digital image correlation (stereo-DIC) techniques. A total of 27 asphalt concrete cores were drilled from the three freeways (K84, K124, and K165) with a service life of more than 20 years, and the SCB specimens were produced to conduct the SCB fracture and fatigue tests. During the SCB test, the stereo-DIC technique was employed to monitor the evolution process of the strain distribution and crack length for the specimens. K-dimension tree neighbor-searching algorithm (K-d tree algorithm) was used to effectively measure the change of crack length corresponding to each fatigue load cycle. Meanwhile, the strain threshold of asphalt concrete crack initiation was determined by the bilinear softening cohesive zone model (CZM) to ensure the accuracy of the crack length calculated by the K-d tree algorithm. Furthermore, the relationship between crack growth rate and stress intensity, which was used to fit the Paris law parameters, was determined. The CZM and DIC results indicated that the strain threshold of asphalt concrete crack should be set as 2000 με when using the K-d tree algorithm to determine the crack length. With the stress ratio increase, the Paris law parameter A increased wavily, and the parameter n decreased steadily, while the threshold of the stress intensity factor increased steadily. The Paris law master curves could characterize the fatigue performance of various road sections at a wide load range. The residual fatigue life of K84, K124, K165 the road sections were 2.13E + 08, 3.57E + 08, and 1.02E + 07, respectively.

Implementation of a viscoplastic substrate creep model in the thermomechanical simulation of the WAAM process

This research work focusses on the implementation of a viscoplastic creep model in the thermomechanical simulation of the wire arc additive manufacturing (WAAM) process for Ti-6Al-4 V structures. Due to the characteristic layer by layer manufacturing within the WAAM process, viscoplastic material effects occur, which can be covered by implementing a creep model in the thermomechanical simulation. Experimental creep tests with a wide temperature, load and time range were carried out to examine short-term creep behaviour in particular. A Norton-Bailey creep law is used to accurately fit the experimental data and describe the base material’s creep behaviour. Subsequently, the fitted Norton-Bailey creep law was implemented in the thermomechanical simulation of the WAAM process. Finally, to determine the effect of creep on global distortion and local residual stress state in the substrate, simulations of a simplified linear, three-layer WAAM structure, with and without applying the implemented creep law, were carried out and compared to experimental data. The thermomechanical simulation with implemented creep model reveals a significant improvement in the numerical estimation of distortion and residual stress state in the substrate. The maximum distortion is reduced by about 13% and respectively the mean absolute percentage error between simulation and experiment decreases by about 34%. Additionally, the estimation accuracy with respect to the local residual stress state in the substrate improved by about 10%.

The Challenges and Emerging Technologies for Low-Power Artificial Intelligence IoT Systems

The Internet of Things (IoT) is an interface with the physical world that usually operates in random-sparse-event (RSE) scenarios. This article discusses main challenges of IoT chips: power consumption, power supply, artificial intelligence (AI), small-signal acquisition, and evaluation criteria. To overcome these challenges, many works recently aimed at IoT system design have emerged. This work reviews the architecture and circuit innovations that have contributed to IoT developments. This paper does not cover security of IoT. Event-driven architectures and nonuniform sampling ADCs significantly reduce the long-term average power. Besides, embedding AI engines in IoT nodes (AIoT) is one critical trend. The computing-in-memory technique improves the energy efficiency of the AI engine. Asynchronous spike neural networks (ASNNs) AI engines show low power potential. In addition to data processing, small-signal acquisition is also critical. The charge-domain analog-front-end (AFE) techniques such as floating inverter-based amplifiers improve energy efficiency. In addition to the above low power and high energy efficiency technologies, energy harvesting can also enhance the lifetime of AIoT devices. This article discusses recent ambient RF and natural energy harvesting approaches and high-efficiency DC-DC with a wide load range. Finally, novel evaluation criteria are introduced to establish benchmark standards for AIoT chips.

Systematic Design and Circuit Analysis of Lightning Impulse Voltage Generation on Low-Inductance Loads

The well-known circuit for the generation of lightning impulse voltage (LIV) on low-inductance loads was introduced by Glaninger in 1975, and the circuit component selection was proposed by Feser. However, the circuit and the approach for the component selection have some difficulties for which further adjustment is required for obtaining the waveform parameters according to the standard requirement. In this paper, an extended Glaninger’s circuit with an additional series resistor is proposed. Furthermore, a systematic design and circuit analysis of LIV generation for low-inductance loads are developed. With the help of a circuit simulator, the circuit analysis for the component selection is described. The validity of the proposed circuit was confirmed by some experimental results in comparison with the simulated ones. The proposed circuit and component selection provide not only the generation waveform according to the standard requirement but also other promising performances in terms of the wide inductance load range from 400 μH to 4 mH, a voltage efficiency of over 80%, an overshoot voltage of below 5%, an undershoot voltage of below 40%, and a maximum charging capacitance of 10 μF. From the simulated and experimental results, the proposed circuit and component selection approach is very useful for the LIV tests on low-inductance loads instead of using the conventional approach based on trial and error.

A Dual-transformer DC–DC with Variable frequency modulation Technique

For renewable power production systems to use less energy overall, power converters with improved efficiency over a wider load range are crucial. We introduce an unique dual-transformer DC-DC converter with many resonant components. With the right choice of resonance parameters, the converter can achieve a broad DC voltage gain range thanks to several resonance features. More resonance frequencies are included in the proposed converter as well, which will allow the load to receive more of the tertiary active power. Diodes achieve soft-switching or quasi-soft-switching during both the on and off periods, and all power switches are capable of on-soft switching. The proposed and analysis of variable frequency modulation (VFM) are achieved. By providing soft switching throughout the whole load range, the suggested modulation approach can lower switching losses. Additionally, the center-tapped bridge implementation of the synchronous rectifier further reduces conduction losses while the proposed modulation technique ensures soft switching of all devices. We installed a 500W prototype in the laboratory to confirm the theoretical analysis. According to the findings of the experiments, the suggested converter can maintain a relatively high efficiency (95%) throughout a wide load range. Starting with 300W, the highest efficiency is 95.4%.

Non‐isolated high step‐up DC–DC converter based on coupled inductors, diode‐capacitor networks, and voltage multiplier cells

AbstractThis work presents a non‐isolated DC–DC boost converter employing coupled inductors, a diode‐capacitor network, and a voltage multiplier cell (VMC). This converter allows extending the conversion ratio not only by increasing the turns ratio of the coupled inductor, but also by adding more networks and VMCs, resulting in a more flexible design approach. Unlike most coupled‐inductor‐based boost‐type converters reported in the literature, the topology presents an output stage whose current is non‐pulsating, which leads to reduced electromagnetic interference (EMI) levels. Other prominent advantages include the fact that the input current is non‐pulsating with low high‐frequency ripple, as well as the operation of the switch and output diode under soft‐switching condition. Experimental results obtained from a 200‐W prototype are presented and discussed to validate the theoretical assumptions, also showing that the converter has high efficiency over a wide load range.

Flexibility oriented adaptive modeling of combined heat and power plant under various heat-power coupling conditions

The flexible operation of thermal power plant has become a research hotspot for its safety and validity in eliminating power grid fluctuation from large-scale integration of renewable energy. Heat-power decoupling is effective technique to promote flexibility of combined heat and power plant. To address the insufficient dynamics investigation of combined heat and power plant under different heat-power decoupling strategies, an adaptive modeling approach is proposed. This method systematically fuses the mechanism analysis and data-driven fuzzy modeling to prepare for the controller design for rapid and deep load regulation in flexible operation. Firstly, the model structures with unknown parameters are determined by mechanism analyses to reflect the effects of various decoupling techniques on the characteristics of plant. Secondly, in view of the on-site data under wide load operation conditions, corresponding model structure is adaptively matched, and a new Takagi–Sugeno fuzzy modeling scheme depend on biquantum pigeon optimization algorithm is constructed for model parameters acquisition. The effectiveness of the proposed approach is illustrated based on a 350 MW supercritical combined heat and power unit. Simulation results illustrate that the adopted method can rapidly characterize dynamics of plant under different heat-power coupling conditions. All the model identification and verification errors in wide load operation conditions are less than 3.1% plant output, which reveals high modeling precision more than 97%. Thus, the established model provides solid foundation on highly matched controller for ensuring operational flexibility.

Fixed-Frequency Current-Fed LCL Series Resonant Soft-Switching Converter With Capacitive Doubler

Electrification of power take-off (ePTO) system is an effective way to minimize the fossil fuel consumption from heavy duty electric vehicles, where a high gain dc/dc converter is needed to integrate PV/fuel-cell. Popular high-gain dc/dc converters such as PWM type, clamped and unclamped quasi-resonant converters cant serve such applications as they fail to achieve high-efficiency, wide load and input voltage range for soft-switching, constant switching frequency and high transformer utilization (TUF) simultaneously. In this paper, a LCL series resonance based high-gain load resonant dc/dc converter is proposed to eliminate the above-mentioned drawbacks. A series resonant tank in the converter is able to adapt tank current in proportion to load demand leading to minimum losses and high TUF. Further, energy is stored in the series and parallel resonant inductors, in proportion to load demand and constant load voltage respectively, ensures soft-switching of the converter through full load to light load conditions. On the other hand, proposed converter operates with constant switching frequency to adopt simple PWM modulation to regulate load voltage against input and load disturbances. This paper presents operation, analysis, modeling and design of the proposed converter. Hardware setup has been mounted and tested to verify he proposed theory.

A 240-nA Quiescent Current, 95.8% Efficiency AOT-Controlled Buck Converter With A2-Comparator and Sleep-Time Detector for IoT Application

An ultralow-quiescent current dc-dc buck converter with a single controller is presented to achieve high efficiency over a wide load range for Internet of Things application, which is achieved by utilizing adaptive on-time control topology. An on-demand modulation strategy and sleep-time detector are proposed to attain sub-μA quiescent current consumption under ultralight load condition. The adaptive-bias and adaptive-gain (A <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) comparator is presented to improve the loop stability caused by the inherent propagation delay of the low-power comparator. Moreover, a novel on-time generator is proposed to fix the switching frequency in continuous conduction mode. The proposed buck converter was implemented by using a 0.18-μm CMOS process with an area of 1.092 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . It achieves a peak efficiency of 95.8% and >90% efficiency from 10 μA to 300 mA. A 240-nA quiescent current, including bandgap voltage and current reference, is achieved. With a low output ripple of less than 20 mV, the input voltage range and regulated output voltage are 2.1-5.5 and 1.8 V, respectively.

Modified cohesive zone model for soft adhesive layer considering rate dependence of intrinsic fracture energy

The cohesive zone model (CZM) has been extensively utilized to investigate the cohesive failure of the soft adhesive layer. This paper has proposed a modified CZM considering the rate dependence of the intrinsic fracture energy as well as the dissipative energy. The evolution of the intrinsic fracture energy with loading rate was established based on Chaudhury’s model, and the dissipative energy was described by the Maxwell model. After implemented into FEM, the proposed CZM was validated by the double cantilever beam (DCB) debonding test data and the effect of the rate-dependent intrinsic fracture energy on the cohesive failure of soft adhesive layer was further investigate. The limitation on the wide loading rate range was solved by introducing the rate-dependent intrinsic fracture energy. The phenomenon that the dissipative energy is affected by the evolution of the intrinsic fracture energy can be described. The experimental observable fibrillation zone of the soft adhesive layer can be taken as the criterion for whether considering the rate dependence of intrinsic fracture energy or not. The modified CZM is a promising approach for describing the cohesive failure of the soft adhesive layer.

Collaborative optimization of fuel composition and operating parameters of gasoline compression ignition (GCI) engine in a wide load range

Through the integration of three-dimensional computational fluid dynamics (CFD) simulation and genetic algorithm, the operating parameters and fuel composition of a gasoline compression ignition (GCI) engine were simultaneously explored in the full load range. The blends of n-heptane, iso-octane, and toluene were utilized as the substitute for real gasoline fuels, in which toluene can efficiently diminish the heat release rate so that excessively high ringing intensity (RI) can be avoided at high load by extending combustion duration. The synergistic effects of fuel properties and operating parameters on combustion and emissions were analyzed. In addition, the fuel composition requirements of GCI combustion were further discussed. The optimization results indicate that the collaborative optimization can achieve low nitrogen oxides (NOx) emissions, near-zero soot emissions, and satisfactory fuel consumption under the GCI strategy. The combustion procedure was dominated by initial temperature and pressure at low load, and the effect of fuel characteristics is strengthened with higher load. The optimal combustion phasing of the GCI engine is postponed with the increase of load, which can enhance the temperature and fuel stratifications in the cylinder to prevent unacceptable RI. To minimize NOx emissions, a high proportion of n-heptane is preferred at low load and the contents of iso-octane and toluene approach to zero. Fuel research octane number (RON) has an inconspicuous impact on GCI at low load, and the fuel with higher RON can perform well at low load, except for the slightly higher NOx and soot emissions for high RON fuels. With the increase of load, the proportion of n-heptane decreases, which is compensated by the higher proportion of iso-octane. At high load, a certain amount of toluene is required, and high soot emissions are the main factor to limit the adoption of low RON fuels. Overall, GCI engine can utilize the fuel with RON between 70 and 80 in a wide load range.

Electromagnetic‐Thermal Bi‐directional Coupling Analysis of IEF‐DDPMM Under Different Operation Conditions and Cooling System Optimization Design

Compared with the traditional single stator permanent magnet (PM) direct‐drive motor, the direct‐drive PM motor with inner enhance force (IEF‐DDPMM) has the advantages of high‐torque density, strong heavy‐load starting ability and flexible operation mode, so it is especially suitable for the occasions such as mine winches with a wide load range, frequent heavy‐load starting, light‐load operation, and limited use environment space. It is very important to check the temperature rise of IEF‐DDPMM according to its different operating conditions, including transient temperature rise during heavy‐load starting and steady‐state temperature rise during rated operation, so as to optimize the electromagnetic and thermal performance at the same time. Based on the bi‐directional coupling method (BDCM) of the electromagnetic field and temperature field, the thermal analysis of IEF‐DDPMM and the transient temperature field analysis of the inner motor as a torque motor for short‐term operation are carried out, and then the rated power of inner motor in S1 working system and the maximum operation time of output peak power are determined. The fluid–solid coupling analysis method is used to optimize the design of the cooling system, and the influence of the number of water channels and inlet water velocity on the heat dissipation effect of the motor is analyzed. A cooling system with strong heat dissipation ability is obtained, which can achieve higher power or torque output within the temperature range of winding insulation or demagnetization limitation of PM. Finally, a prototype is developed and equipped with a temperature rise experimental platform, and the experimental results provided a good verification of the simulation results. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

High Efficiency Isolated On-Board EV Battery Charger Using LLC Resonant Converter

In this study, high efficiency design of an on-board Electrical Vehicle (EV) battery charger is presented. The presented charger has two stages where the first stage is conventional front-end boost converter and the second stage is LLC resonant converter. The basic principles of both stage are discussed and the detailed design procedures are presented in terms of wide range output voltage regulation, wide range load condition, high efficiency and high power density. The presented design approach is tested with a prototype implemented with 2.5 kW output power at 250 V-450 V output voltage range. The peak efficiency of system is obtained as 95.53% at full load condition.

Isolated DC–DC Boost Converter for Wide Input Voltage Range and Wide Load Range Applications

A current-fed dual-inductor resonant full-bridge dc–dc isolated boost converter is proposed. The converter is most suitable for applications that demand wide input voltage and load ranges. It can be used as a front-end dc–dc converter that can boost variable low voltage from a power source [battery (home/industrial inverter/industrial UPS application), fuel-cell, or solar-PV] and interface it to a high-voltage dc-link, which typically feeds an inverter. It removes all major drawbacks of conventional current-fed isolated dc–dc converters, namely high-voltage spikes across the switches due to transformer leakage inductance, need for additional start-up circuit, and difficulty in converter tripping in case of faults. Soft-switching of rectifier didoes and clamping power switches is load independent leading to good efficiency over entire load range. Converter can be operated with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> < 0.5, making it suitable for wide input voltage range applications. A detailed comparative analysis with state-of-the-art converters for wide input voltage range applications considering the major important factors, such as power device utilization, transformer utilization, inductive energy requirement, and dc capacitors utilization, confirms the superiority of the proposed converter. Experimental results for a 2.5 kVA inverter application with an input dc voltage range of 90–160 V and output ac voltage of 230 V are provided.

An Si MOSFET-Based High-Power Wireless EV Charger With a Wide ZVS Operating Range

This article proposes a new digitized modulation scheme suitable for a high-power wireless electric vehicle charger employing an integrated boost multilevel converter (IBMC) as its primary-side converter. Using the proposed modulation scheme, an IBMC can generate a boosted square-wave-shaped ac voltage with a controllable amplitude, enabling it to regulate the power efficiently over a wide load and/or coupling range while achieving zero voltage switching for all switches. This article focuses on the steady-state operating principles of the proposed digitized modulation scheme. Key practical considerations, such as capacitor voltage balancing and semiconductor device selection, are highlighted. To verify the benefits of the proposed modulation scheme, an SAE J2954 WPT2/Z2 compliant wireless EV charger prototype that uses an IBMC as the primary converter is designed and built. 200 V Si MOSFETs are employed in the 12 submodules (SMs) that compose the IBMC. The secondary side employs a passive rectifier, and the power flow is controlled using only the IBMC. This system maintains an efficiency between 90% and 93% when regulating power transfer at 7.7 kW under a 220% variation in coupling factor (i.e., 0.14–0.31) and a 150% variation in battery voltage (i.e., 280–420 V).

A Wide-Load-Range and Compact MHz Wireless Power Transfer System Based on Novel Reactance Compression Design and Edge Inductor

In megahertz (MHz) wireless power transfer (WPT) systems, a varying reflected reactance due to a changing final load deteriorates the overall system performance, such as efficiency and output voltage stability. This article aims to achieve a compact and robust MHz WPT system working over a wide range of load. A novel concept of reactance compression design is proposed to compress the variation of the reflected reactance through positioning of a “reactance window.” Efficient receiving-side parameter design procedures are then developed to best compress the reactance variation and satisfy maximum output power requirement in a wide load range but without adding any other hardware. This makes it possible to directly apply the existing voltage-source design using a modified Class E power amplifier (PA) and current-source design using an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> transformation network. An edge inductor also becomes worthy to replace the bulky air-core infinite inductor required by the modified Class E PA, thereby further improving circuit compactness. Finally, the receiving-side design concept and the edge inductor are experimentally implemented to verify their performance over a 5–50- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Omega$</tex-math></inline-formula> load and with the maximum final output power of 20 W. The results well validate the improved reactance compression, output voltage stability, efficiency, and harmonic distortions over the wide load range.

Buck Circuit Design With Pseudo-Constant Frequency and Constant On-Time for High Current Point-of-Load Regulation

This paper introduces an accurate frequency regulation method based on a constant on-time (COT) buck regulator designed for point-of-load (POL) regulation with a fast load transient requirement and wide load range. Traditional COT regulators suffer from frequency shift due to load variations. The proposed frequency adjustment circuit helps the COT control engine to reach its target frequency of operation by adjusting the on-time pulse under varying conditions. This circuit includes a phase detector and a voltage-to-current converter block. The phase error between the target clock signal and the PWM is directly used to adjust the width of the on-time pulse. This will fine-tune the bandwidth of the frequency regulation loop, which can help to improve the transient performance of the COT as well. The fabricated chip has been tested under 20A/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> load transient speed with a 10A load step condition. The measured silicon performance shows that the error of the switching frequency is less than 0.16% in the 400kHz to 1MHz range during steady-state operation.

Analysis and Design of a Nonisolated Bidirectional DC–DC Converter Based on CLC Network

This article proposes a nonisolated bidirectional dc–dc converter based on the π type resonant network for renewable energy sources. The circuit consists of a front-stage boost inverter, a CLC resonant network and a poststage voltage doubled rectifier. The proposed converter has simple structure and smaller volume without conventional transformer, easier to achieve modularity and integration. Under bidirectional power flow, the switches can achieve zero voltage turn- on and the rectifier diodes can achieve zero current turn- off with the wide load range. In this article, the operation modes, output power characteristics, soft-switching conditions, and the optimization design of the circuit are analyzed. A 200 W prototype based on GaN device is implemented and tested to verify validity of the proposed converter. The prototype can achieve a peak efficiency 95.4% in boost mode and 94.1% in buck mode.