Wide Load Research Articles

A Reconfigurable Phase-Shifted Full-Bridge DC–DC Converter with Wide Range Output Voltage

This paper analyzes, designs and implements a reconfigurable phase-shifted full-bridge (PSFB) converter. It adopts the topology of the traditional PSFB converter and incorporates clamping circuits to solve some fundamental problems of conventional topology. In addition, auxiliary switches are employed for output reconfiguration, which allows expanding the output voltage range without compromising the system efficiency. Single pole double throw (SPDT) mechanical switches are used to realize series and parallel connections. In this paper, the characterization of the PSFB converter with clamping circuit and its design considerations are discussed. A 10 kW prototype with a power density of 0.485 W/cm3, 900 V input voltage and 400/800 V nominal output voltage was manufactured. The experimental results validated the analysis and confirmed the high conversion efficiency for a wide load range; an efficiency of 96.69% was obtained for the full load condition.

Electromagnetic Design and Analysis of a Stator–Magnet Transverse Flux Linear Oscillatory Machine with Yokeless Mover Core

Conventional stator–magnet moving-iron transverse-flux linear oscillatory machines (CSMTLOMs) are widely applied in directly-drive reciprocating devices due to the merits of easy fabrication and robust mover. However, in order to keep the mover vibrating at a certain resonance frequency to save the energy and enlarge the output power, they still suffer from a higher requirement on spring stiffness due to their thick and heavy mover core, which would also narrow the frequency band with a high power factor due to the large inertial energy storage of the heavy mover. Hence, to reduce the mover core weight to reduce the demand of the spring and improve the operation performance, an improved linear oscillatory machine featured by a spoke-type interior permanent magnet inner stator (ISMTLOM) is proposed. Benefiting from its separated two stators, the tangential flux in the radial plane can return through the inner stator core, so that the yoke of the mover core can be eliminated directly. Then, to analytically investigate the influence of the special axial local saturation effect, the segmental equivalent magnetic circuit (EMC) model of the ISMTLOM is established, wherein a saturation coefficient is introduced to quantitatively consider the local saturation effect on the output force. Consequently, several important size parameters are optimally selected when keeping the same outer diameter and copper loss as that of the CSMTLOM. Afterward, the three-dimension finite element algorithm (3D FEA) is adopted for the electromagnetic performance validation and comparison. Finally, it is found that the nonlinear segmental EMC corrected by the saturation coefficient can quickly predict the output force more accurately within the wide load range, and benefiting from the topology improvement, the ISMTLOM has the merits over the CSMTLOM in its smoother output force, much lighter mover core, and less demand of mechanical spring stiffness, whilst preserving the similar output force density.

Experimental study on peak shaving during preheating combustion for different coal ranks: Thermal modification and variable load operation

With the large-scale integration of renewable energy into the power grid, coal-fired power plants shoulder an enormous burden of peak shaving. In this study, the variable load characteristics of different coal ranks were extensively investigated on a 40 kWth down-fired test platform. Moreover, the preheating modification of fuel at ultra-low loads was investigated. A comprehensive evaluation coefficient (Eph) was established to characterize the reactivity of different coal ranks at wide loads. The determination criterion of combustion stability for variable load processes was modified. The results show that the preheating modification of different coal ranks was significant, especially for lower-activity coals such as anthracite and lean coals. The minimum loads after modification were 25 %, 25 %, 35 % and 40 % for ARG (lignite), SM (bituminous), RG (lean coal) and SH (anthracite), respectively. Furthermore, the preheating modification had a positive effect on increasing the variable load rate, which was positively correlated with Eph for different coal ranks. The maximum variable load rates after modification for ARG, SM, RG and SH were 2.78 %/min, 3.13 %/min, 1.79 %/min and 1.15 %/min, which corresponded to the optimum load steps of 25–30 %. The response rate of NO and N2O with time in the low-rank coal is faster than that in the high-rank coal during the variable load process, which is consistent with the trend of the variable load rate. In addition, the conversion of nitrogen oxides decreases and then increases with load, and the inflection points corresponding to AGB, SM, RG and SH are 40 %, 38 %, 70 % and 80 %, respectively. The NOx emissions were less than 335 mg/m3 (@6 % O2) for the different coal ranks during load changes.

Design of Dual Lower Bound Hysteresis Control in Switched-Capacitor DC–DC Converter for Optimum Efficiency and Transient Speed in Wide Loading Range for IoT Application

Design of Dual Lower Bound Hysteresis Control in Switched-Capacitor DC–DC Converter for Optimum Efficiency and Transient Speed in Wide Loading Range for IoT Application

Analysis and design of an efficient three‐phase voltage source inverter with performance optimization

SummaryThe paper designs a novel efficient three‐phase voltage source inverter with performance optimization. When auxiliary circuits connected in parallel with every bridge arm are involved in working process of the designed inverter, main switches will realize zero‐voltage switching in the wide load range, which is beneficial for further decline of the loss of main switches. Furthermore, the optimized duty cycle of the gate drive signal of auxiliary switches is used to restrict circuiting current loss. Besides, when the designed inverter works in a dead zone, the resonance will occur in the auxiliary circuits to cause the output phase voltage to vary from zero or the DC supply voltage to the DC supply voltage or zero as soon as possible, which is beneficial for further decline of the output phase voltage error and the suppression of dead effect. The paper provides relevant analysis on each working status within a switching period along with design requirements. By analyzing test waveforms, it affirms that main switches realize zero‐voltage switching. The efficiency of the designed inverter reaches 98.8% at rating condition. The experiment affirms that the designed inverter has an edge over another two inverters for comparison in performance optimization.

Anti-Oxidized Self-Assembly of Multilayered F-Mene/MXene/TPU Composite with Improved Environmental Stability and Pressure Sensing Performances.

MXenes, as emerging 2D sensing materials for next-generation electronics, have attracted tremendous attention owing to their extraordinary electrical conductivity, mechanical strength, and flexibility. However, challenges remain due to the weak stability in the oxygen environment and nonnegligible aggregation of layered MXenes, which severely affect the durability and sensing performances of the corresponding MXene-based pressure sensors, respectively. Here, in this work, we propose an easy-to-fabricate self-assembly strategy to prepare multilayered MXene composite films, where the first layer MXene is hydrogen-bond self-assembled on the electrospun thermoplastic urethane (TPU) fibers surface and the anti-oxidized functionalized-MXene (f-MXene) is subsequently adhered on the MXene layer by spontaneous electrostatic attraction. Remarkably, the f-MXene surface is functionalized with silanization reagents to form a hydrophobic protective layer, thus preventing the oxidation of the MXene-based pressure sensor during service. Simultaneously, the electrostatic self-assembled MXene and f-MXene successfully avoid the invalid stacking of MXene, leading to an improved pressure sensitivity. Moreover, the adopted electrospinning method can facilitate cyclic self-assembly and the formation of a hierarchical micro-nano porous structure of the multilayered f-MXene/MXene/TPU (M-fM2T) composite. The gradient pores can generate changes in the conductive pathways within a wide loading range, broadening the pressure detection range of the as-proposed multilayered f-MXene/MXene/TPU piezoresistive sensor (M-fM2TPS). Experimentally, these novel features endow our M-fM2TPS with an outstanding maximum sensitivity of 40.31 kPa-1 and an extensive sensing range of up to 120 kPa. Additionally, our M-fM2TPS exhibits excellent anti-oxidized properties for environmental stability and mechanical reliability for long-term use, which shows only ~0.8% fractional resistance changes after being placed in a natural environment for over 30 days and provides a reproducible loading-unloading pressure measurement for more than 1000 cycles. As a proof of concept, the M-fM2TPS is deployed to monitor human movements and radial artery pulse. Our anti-oxidized self-assembly strategy of multilayered MXene is expected to guide the future investigation of MXene-based advanced sensors with commercial values.

High-Efficiency WPT Systems for Potable Electronics Based on DC-Bias-Voltage- Controlled Variable Capacitor

The power density of wireless power transfer (WPT) systems employed in portable electronics can be enhanced by increasing the operating frequency, but at the expense of lower efficiency due to increased switching and parasitic losses. This paper proposes a method, based on the DC-bias-voltage-controlled variable capacitor (VC) and variable frequency (VF) regulation, to improve the overall efficiency of the WPT system for portable electronics. The method uses VC on the primary side to detune the resonant tank and dynamically regulate the output power, while VF is employed to improve the system efficiency using a look-up table based on a power loss model. A DC bias voltage control module with self-supply ability is employed to control the equivalent capacitance of the VC. A control strategy is proposed to regulate both VC and VF. Experimental results of a 150W prototype are presented to demonstrate that constant output voltage can be maintained despite a wide load range, with an overall efficiency range of 82.1% (@25W) and 92.2% (@150W).

Enhanced On-Off Keying Modulation for Wireless Power Transfer Systems to Improve Efficiency Over a Wide Load Range

Enhanced On-Off Keying Modulation for Wireless Power Transfer Systems to Improve Efficiency Over a Wide Load Range

Analysis and Design of Configurable Rectifier With Compensated Near-Zero Impedance Angle for Megahertz Wireless Power Transfer

Adapting to wide load range variations is always one of the main goals pursued by megahertz (MHz) wireless power transfer (WPT) systems. For this, the nonlinear phenomenon of the rectifier has become a problem that must be solved. Compared with the method of optimizing the efficiency around the maximum power point in the traditional design, this paper proposes a global load optimization method. Meanwhile, a novel configurable compensated near-zero impedance angle rectifier (NIAR) is proposed to take full advantage of the global optimization method. The NIAR not only realizes the compression of a wide range of impedance angles, but also solves the classic problems of Class E rectifiers such as large stress, voltage asymmetry, and low real part of input impedance. The configurable design allows the system to adjust the rectifier unit according to the output index, thereby fully improving the coil efficiency, and providing a solution for the application of high-voltage and high-power MHz WPT systems in the future. To verify the effectiveness of the proposed NIAR and design method, a 60 W prototype was built, and a traditional full-wave rectifier was used for comparison. The results show that the proposed NIAR system exhibits better characteristics in terms of system efficiency, voltage stress, and symmetry.

Performance enhancement and optimization of primary frequency regulation of coal‐fired units under boundary conditions

AbstractUnder the dual‐carbon goal, due to the long‐term operation of thermal power units under wide load and frequent fluctuating load after heat supply transformation, the dynamic process of subcritical units is modeled, and a frequency modulation optimization technology based on frequency signal accuracy is proposed to ensure the accuracy of the speed signal and improve the qualification rate of primary frequency modulation action. At the same time, the frequency regulation technology of steam engine side control optimization under boundary working conditions is proposed, so as to realize the sensitivity and rapidity of the digital electric hydraulic control system. The coordination optimization technology under boundary working conditions is proposed, and the primary frequency regulation performance of the unit is improved through a series of optimization adjustments. Finally, the engineering application is carried out and the optimization effect is analyzed.

A Wearable All-Printed Textile-Based 6.78 MHz 15 W-Output Wireless Power Transfer System and Its Screen-Printed Joule Heater Application

While research in passive flexible circuits for Wireless Power Transfer (WPT) such as coils and resonators continues to advance, limitations in their power handling and low efficiency have hindered the realization of efficient all-printed high-power wearable WPT receivers. Here, we propose a screen-printed textile-based 6.78 MHz resonant inductive WPT system using planar inductors with concealed metal-insulator-metal (MIM) tuning capacitors. A printed voltage doubler rectifier based on Silicon Carbide (SiC) diodes is designed and integrated with the coils, showing a power conversion efficiency of 80-90% for 2-40 W inputs over a wide load range. Compared to prior wearable WPT receivers, it offers an order of magnitude improvement in power handling along with higher efficiency (approaching 60%), while using all-printed passives and a compact rectifier. The coils exhibit a simulated Specific Absorption Rate (SAR) under 0.4 W/kg for 25 W received power, and under 21 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> C increase in the coils' temperature for a 15 W DC output. Additional fabric shielding is investigated, reducing harmonics emissions by up to 17 dB. We finally demonstrate a wirelessly-powered textile-based carbon-silver Joule heater, capable of reaching up to 60 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> C at 2 cm separation from the transmitter, as a wearable application which can only be wireless-powered using the proposed system.

Investigation of the part load behavior for the R-Graz cycle with pure oxygen and hydrogen fuel

ABSTRACT In order to address the future demands for large-scale and efficient hydrogen storage and utilization, while considering the need of power dispatch and peak shaving, in this article, based on the cycle part load models and the conceptual design of the main components, the R-Graz cycle design parameters have been reoptimized, and subsequently, an analysis of the part load behavior and performance characteristics was conducted. The results show that within the load range discussed in this paper, i.e., 50% to 100%, the components of the R-Graz cycle are well matched, enabling high-efficiency operation. The net cycle efficiencies are 64.4% and 71.0% for 50% and 100% load respectively. Within this wide load range, the performance of the R-Graz cycle surpasses that of the Graz cycle consistently. When the load decreases, key parameters of the R-Graz cycle’s main components, such as rotational speed, pressure, temperature, mass flow rate and split ratio also decrease. Performance analysis under varying load conditions reveals that the maximum temperature in the cycle is a critical parameter affecting the efficiency of the R-Graz cycle. The research findings of this article lay the foundation for the practical application of the R-Graz cycle.

An Improved Three-Level Full-Bridge Soft-Switching DC/DC Converter with Wide Load Range for Energy Storage System

An Improved Three-Level Full-Bridge Soft-Switching DC/DC Converter with Wide Load Range for Energy Storage System

Design of Multi-Input Multi-Output Non-linear Model Predictive Control for Main Steam Temperature of Super Critical Boiler

Flexible operation of coal-fired power plants is becoming increasingly necessary for successful integration of large-scale renewable power generation into the power grid. The maximum ramp rate and the number of load cycles are generally limited by the thermal stress experienced by the boiler pressure parts, turbine metallurgy and creep and fatigue of critical thick-walled components Main steam temperature is a critical operating parameter that must be controlled within acceptable limits for safe operation. Main steam temperature deviation beyond acceptable limit has impact on boiler pressure parts and turbine material of construction due to creep and fatigue effect. Base load operating units do not require steep ramp rate and hence recommended ramping rates are kept low within the safe operating zone in comparison to the flexible operation of the units with wide range load change width. Thermal stresses are caused by the temperature changes inside the thick-walled components and turbine steam admission parameters. Hence, the quality of main steam temperature control plays a vital role in flexible operation of the coal fired units. Conventional cascaded PID temperature control loop architecture performs well at steady state condition within a limited variation of load change at low ramp rate but it acts slowly and performs poorly at transient operating conditions of flexible operation of the boiler turbine with wide range load variation and load cycle with high ramp rate and remains far from rated conditions. In this paper, a Multi-Input Multi-Output (MIMO) Non-linear Model Predictive Control (MPC) design for regulation of the main steam temperature of a Once-Through supercritical Boiler is proposed. The controller is based on a non-linear dynamic model which incorporates dynamics of the variables of interest. It has the capability to operate effectively across a wide load range while maintaining main steam temperature within acceptable limits. A notable advancement in this design of MPC is the incorporation of coal flow demand and feedwater flow demand as additional control inputs alongside primary and secondary spray flows. In simulation test cases, the MPC controller demonstrates satisfactory performance and computational efficiency.

A high-efficiency and wide-load current range LDO with dynamic loop gain control technique

The design proposes a low-dropout regulator incorporating dynamic loop gain control to accommodate a wide load current range. It introduces a multi-phase error detection mechanism, a tri-state damping selector, and a dynamic integration shift register. These elements predict load variations and dynamically increase loop gain when the load variation is significant, all without increasing the input clock. This approach achieves a fast response and low power consumption simultaneously. The chip was implemented in 0.18 μm CMOS, with an input operating voltage of 1.2 V and an output voltage of 1 V. The measured results revealed that it could provide output currents from 0.5 to 150 mA, indicating that it had a 300 times wider current range. The maximum current efficiency was 99.93%, and the core area was 0.198 mm2.

High PSR external capacitor‐less LDO with adaptive supply‐ripple cancellation technique

AbstractThis work presents an external capacitor‐less low‐dropout regulator (CL‐LDO) with high power supply rejection (PSR) over a wide frequency and load current ( ) range. The high PSR is implemented with an adaptive supply‐ripple cancellation (ASRC) technique. The proposed ASRC circuit consists of a buffer with diode‐connected structure and an adjusting unit. The novel buffer introduces the supply ripple through the diode‐connected transistor to the gate of the pass transistor, enhancing the PSR in the range of 1 MHz. Additionally, the adjusting unit trims the current of the buffer continuously according to the magnitude of to optimize the PSR adaptively. Designed in a 55 nm CMOS process with an input voltage of 1.4 V, the proposed LDO achieves −69 dB and −55 dB PSR at 100 KHz and 1 MHz for 50 mA of , respectively. Moreover, the maximum current efficiency of the LDO is 99.8% at a full of 50 mA.

Analysis and implementation of feedback linearisation controller for fuel cell-fed boost converter

ABSTRACT Fuel cell needs to be integrated with dc-dc boost converters to supply load at elevated voltages. Due to the presence of right half plane zero (RHPZ) in the output voltage to duty cycle transfer function of the boost converter and the nonlinear V-I characteristics of the fuel cell, it necessitates the usage of nonlinear controllers. This paper proposes an effective stabilising feedback linearisation (FDBKLN) controller for fuel cell-fed boost converter to provide improved dynamic performance and tight voltage regulation for wide load variation. Performance of the controller has been tested in simulation using the developed tunable minimal order fuel cell model and validated through experiments for fuel cell-fed 600W boost converter. Stability of the proposed controller is also verified using Lyapunov theorem.

Ultra-wideband rectenna with the dual ground plane for wide dynamic input power and load range

ABSTRACT The ultra-wideband rectenna is designed to have a fractional bandwidth of more than 100%, allowing it to work from 1.4 GHz to 5.4 GHz, with a bandwidth of 4 GHz. The proposed design involves a square patch antenna that incorporates an inverted L-slot and utilises dual ground planes in the form of rectangular and semi-octagonal shapes. The intended rectenna simultaneously harvests energy from various frequency bands, including GSM 1800 MHz, UTMS 2100 MHz, ISM 2450 MHz, 2800 MHz, and 3600 MHz. The proposed rectifier circuit incorporates three impedance-matching (IM) branches, which effectively mitigate the nonlinear attributes of the rectifier system and ensure favourable IM across a broad spectrum of frequencies. The DC combining technique is employed to attain favourable conversion efficiency. The CE in the GSM 1800 MHz band was measured to be 74%. The CE in the UTMS 2100 MHz band was measured to be 66%. In the ISM2450 MHz frequency band, a CE of 76% was measured. The CE in the 2800 MHz frequency band was determined to be 67.5%. At 3600 MHz, the measured CE is recorded as 67%. The obtained optimal load value is 470 Ω and it provides more than 65% conversion efficiency (CE) at all the intended frequency bands. The proposed rectenna demonstrates an CE exceeding 50% across the entire range of input power level (IPL) variations from 0 to 11 dBm. Furthermore, it achieves an efficiency surpassing 60% when subjected to load variations ranging from 270 Ω to 750 Ω.

4 MHz Electrosurgical Generator System for Wide Load Impedance Range With SiC-Based Full-Bridge Inverter

A power conversion system to drive a high-frequency electrosurgical generator (ESG) is proposed. The proposed system consists of a 4 MHz full-bridge (FB) inverter capable of ensuring power in a wide load impedance range and implementing energy control functions in accordance with the ESG characteristics. Unlike conventional inverter systems, ESG cannot deliver energy directly to the load, but through an instrument, which makes it difficult to ensure power. Thus, impedance matching is essential to ensure power in ESG. For ensuring power, impedance matching is realized using a resonance filter while considering instrument induced parasitic components that cannot be ignored at high frequencies. The inverter is composed of silicon carbide (SiC) suitable for the MHz switching operation. A prototype is to validate the proposed system. Experimental test of the prototype that it can provide a load power of more than 100 W for a tissue model with impedance range of 5-to-800 Ω.

A Fully Integrated, Automatically Generated DC–DC Converter Maintaining &gt;75% Efficiency From 398 K Down to 23 K Across Wide Load Ranges in 12-nm FinFET

A Fully Integrated, Automatically Generated DC–DC Converter Maintaining &gt;75% Efficiency From 398 K Down to 23 K Across Wide Load Ranges in 12-nm FinFET