Operating Power Range Research Articles

Thermoelectric installation for lifting objects from shallow reservoirs using the freezing method

Objective. The purpose of the study is to develop the design of a thermoelectric installation for lifting objects from shallow reservoirs using the freezing method, as well as its calculation, analysis of parameters and electrical and thermophysical characteristics. Method. The research is based on the use of methods of thermodynamic analysis, full-scale and computational modeling of cryogenic equipment in order to find optimal solutions for the reliability and service life of low-temperature installations. Result. The installation includes a waterproof probe, on the end surface of which, facing the bottom of the reservoir, thermoelectric modules are installed, heat is removed from the hot junctions of which by means of a heat removal system made in the form of an all-metal heat pipe or in the form of a thermal thermosiphon. The connection between the object lifted from the reservoir and the thermoelectric installation is carried out through a cold wall by freezing. The thermoelectric installation was calculated and its parameters were determined. Graphs were constructed and dependencies were obtained describing the main characteristics of TEMs included in the thermoelectric installation. The graphs are presented at a temperature of the hot junctions of the TEM of 300 K and the achievement of such values of the thickness of frozen water ice on the cold wall of the technical device that would allow lifting objects from a reservoir up to 4 m deep. Conclusion. The installation parameters have been determined: the number of TEMs of the DRIFT-1.2 type is 8, the operating power range of a single TEM of the DRIFT-1.2 type is from 14 to 40 W with an average temperature difference between the junctions of 45 K, the supply current is from 3.8 to 7 .6 A with power consumption from 50 to 200 W, coefficient of performance - from 0.1 to 0.45, minimum temperature of the cold wall of the TU - 248 K, a domestically produced thermal thermosyphon is used as a heat removal system from the hot junctions of the TEM.

Performance prediction and geometry optimization of ejector in PEMFC system using coupled CFD-BPNN and genetic algorithm

The ejector is a promising hydrogen recirculation device in proton exchange membrane fuel cell (PEMFC) systems. However, the limited entrainment performance of the ejector at wide operating conditions hinders its development and widespread application in PEMFC systems. To address this challenge and design a high-performance ejector adapted to the wide power range of PEMFC systems, a backpropagation neural network (BPNN) model with computational fluid dynamics (CFD) simulation data is developed. The sensitivity analysis of geometric parameters based on the CFD model reveals that the nozzle throat diameter and the mixing chamber diameter exert the most pronounced impact on the entrainment performance, with average influence rates of 24% and 57%, respectively. Furthermore, two advanced multi-objective genetic algorithms are applied to improve ejector performance. The linear weighted genetic algorithm (LWGA) method proves effective in elevating the overall ejector performance, achieving a remarkable enhancement in entrainment performance of up to 7.9%. On the other hand, the non-dominated sorting genetic algorithm (NSGA- II) method is favorable for expanding the operational power range of the ejector by 30%, as well as a 4.5% increase in overall ejector performance. This work provides a robust framework for designing and optimizing high-performance ejectors in high-power PEMFC systems.

Design and construction of an affordable optical power meter: micro- to milli-Watt in the 400–800 nm range

This study introduces the design, construction, and evaluation of an affordable optical power meter prototype, AYR (Affordable Yet Reliable) version 1.0, which operates effectively within the 400–800 nm range, using a silicon photodiode. Aimed at bridging the gap in accessibility to precise and reliable photonics instrumentation, especially in resource-constrained settings, AYR 1.0 leverages advancements in photodiode technology, additive manufacturing, and do-it-yourself electronics. The device incorporates a custom-built electronic circuit that facilitates accurate optical power measurement by converting light into electrical current. Through rigorous testing against a reliable commercial optical power meter, AYR 1.0 demonstrated exceptional accuracy and reliability. Sensitivity values ranged from ∼13 μA mW−1 at 405 nm to ∼796 μA mW−1 at 805 nm. The operational power range spanned from 0.003 mW to 242.0 mW, with linearity (R 2) values consistently above 0.9981, indicating high fidelity in measurement. Repeatability percentages varied between 99.4% and 99.9%, and response times ranged up to 55 μs, showcasing the prototype’s rapid and reliable response to changes in optical power. The key components include a low-cost silicon photodiode (2DU10), a differential trans-impedance amplifier circuit for signal processing, and a 3D-printed housing for the sensor head and console, contributing to its cost-effectiveness and robustness. The prototype’s total cost was 116 US dollars, highlighting its affordability and potential for widespread adoption.

Method for calculating a two-stage thermoelectric system for local hypothermia

Abstract. Objective. The aim of the study is to develop a methodology for calculating a two-cascade thermoelectric system (TPS) for local hypothermia, as well as a theoretical analysis of its operation.Method. The model is built on the basis of solving three problems, consisting in determining the parameters of a two-stage thermoelectric module (TEM), thermophysical characteristics of the interface system with a biological object, and heat removal for cooling the hot junctions of the thermomodule.Results. According to the calculation model, the TES was calculated for local hypothermia of soft tissues in the treatment of their inflammation and infectious formations, developed in the laboratory of semiconductor thermoelectric devices and devices of the Daghestan State Technical University. Graphs of the dependence of the change in the cooling capacity of the TEM, the coefficient of performance, the supply voltage on the temperature difference between the junctions for various values of the supply current, as well as the dependence of the voltage on the TEM on the magnitude of the supply current at various values of the temperature difference between the junctions, the change in temperature by cold junction and TEM power from the supply current. The graphs are calculated at a hot junction temperature of 300 K.Conclusion. As a result of the calculations, it was found that the TV-2-(127-127)-1.15 TEM selected as a result of the calculation will have the following characteristics: an operating power range of 8-10 W with an average temperature difference between the junctions of 65 K, the supply current is 4 .4-5.8 A with a power consumption of 45-85 W, the coefficient of performance is 0.2-0.5.

Design and analysis for the SPICE parameters of waveform-selective metasurfaces varying with the incident pulse width at a constant oscillation frequency

In this study, we numerically demonstrate how the response of recently reported circuit-based metasurfaces is characterized by their circuit parameters. These metasurfaces, which include a set of four diodes as a full wave rectifier, are capable of sensing different waves even at the same frequency in response to the incident waveform, or more specifically the pulse width. This study reveals the relationship between the electromagnetic response of such waveform-selective metasurfaces and the SPICE parameters of the diodes used. In particular, we draw conclusions about how the SPICE parameters are related to (1) the high-frequency operation, (2) input power requirement and (3) dynamic range of waveform-selective metasurfaces with supporting simulation results. First, we show that reducing a parasitic capacitive component of the diodes is important for realization of the waveform-selective metasurfaces in a higher frequency regime. Second, we report that the operating power level is closely related to the saturation current and the breakdown voltage of the diodes. Moreover, the operating power range is found to be broadened by introducing an additional resistor into the inside of the diode bridge. Our study is expected to provide design guidelines for circuit-based waveform-selective metasurfaces to select/fabricate optimal diodes and enhance the waveform-selective performance at the target frequency and power level. Our results are usefully exploited to ensure the selectivity based on the pulse duration of the incident wave in a range of potential applications including electromagnetic interference, wireless power transfer, antenna design, wireless communications, and sensing.

Fault supervision of nuclear research reactor systems using artificial neural networks: A review with results

On-line condition supervision of nuclear reactor (NR) is of major concern and high-priority task during operation to ensure safe operation of systems. Usually, faults can occur in different locations at any time. The task of supervision is to monitor the normal operation, and in the case of faults, it has to detect, diagnose them earlier and take appropriate decision, as correction, before they provoke damage to the plant. The actual paper presents the current state of research in the monitoring and decision-making field. It gives a review of fault supervision applications in dynamic, non-linear, complex, and sometimes not well known systems, such as those of NRs; and the important used methods, particularly neural networks (NNs). The aim of this paper is the proposal of a fault supervision application based on NNs of some nuclear and thermo-hydraulic critical variables in Applied Nuclear Energy Laboratory (LENA) NR systems such as the core and hydraulic circuits. The test results show that NN approach estimates successfully the selected variables with early detection, identification and accommodation of faults in real-time, over a wide power range of operation including start-up, shutdown and steady state. Finally, the application of the developed model may be extended to other variables and different NR systems.

Calculation of a thermoelectric unit as part of a system for conducting thermal physiotherapy procedures

Objective. The aim of the study is to consider the methodology for calculating a thermoelectric unit as part of a thermoelectric system (TPS) intended for thermal exposure in medical practice, as well as the results of a numerical experiment carried out using it.Method. The calculation model of the thermoelectric block, which is part of the system for conducting thermal physiotherapy procedures, is described. The model is built on the basis of standard expressions for calculating the electrical and geometric parameters of thermoelectric modules (TEM) depending on the thermal and electrical parameters of thermoelement (FC) materials, heat and cooling capacity values, and characteristics of heat removal systems from FC hot junctions.Result. According to the calculation model, the thermoelectric unit was calculated, which is part of the system for conducting thermal cosmetic procedures, developed in the laboratory of semiconductor thermoelectric devices and devices of the Daghestan State Technical University on the temperature difference between the junctions for different values of the supply current, as well as the dependence of the voltage on the TEM on the magnitude of the supply current at different values of the temperature difference between the junctions, the change in temperature at the cold junction and the power of the TEM on the supply current. The graphs are calculated at a hot junction temperature of 320 K.Conclusion. As a result of calculations, it was found that the operating power range of TEMs of the TV-127-1.4-2.5 type is in the range from 8 to 17 W with an average temperature difference between the junctions of 45 K. In this case, the supply current will be 1 .5-3.5 A with a power consumption of 20 to 80 watts. The refrigerating coefficient varies from 0.1 to 0.5. In accordance with the tasks to be solved, the thermoelectric unit of the device should include four TEMs of this type.

Integrated photovoltaic storage joint smoothing strategy based on simultaneous perturbation stochastic approximation algorithm

In order to realize the real-time control of photovoltaic power generation smoothly connected to the grid under the condition that the energy storage equipment can operate safely, a control strategy combining the simultaneous perturbation stochastic approximation (SPSA) algorithm with rule control is designed. Firstly, the photovoltaic data are processed to extract the data characteristics of the power ramp, and then the grid-connected reference power is obtained through SPSA algorithm. Secondly, considering the state of charge (SOC) of energy storage equipment and the safe operating power range of hydrogen storage equipment, 24 hybrid energy storage power allocation rules are formulated by using the rule control method. Finally, according to the sampling data of every 10 s interval in typical day, the simulation is carried out on MATLAB/simulink platform. The results show that, compared with the first-order low-pass filtering algorithm and recursive fuzzy neural network (RFNN) algorithm, the SPSA algorithm has stronger smoothing ability, and the rule control can also complete the allocation according to the characteristics of the hybrid storage device while ensuring its normal operation.

Analysis and research on the influence of multiple factors on the steady operation area of large-capacity MMC-HVDC transmission system

Aiming at the MMC-HVDC (modular multilevel converter based high voltage direct current), this paper studies the influence of multiple factors such as the AC system and converter characteristic limits on the steady-state operating range of the MMC-HVDC transmission system. First, a mathematical model based on the steady-state operation of the MMC-HVDC transmission system is established, and the AC-side power quality requirements and stability limiting factors of the MMC-HVDC system are analyzed and summarized, as well as the constraints of multiple limiting factors on the converter side. Based on this, the power operation range of MMC-HVDC transmission project under different conditions is obtained. Finally, combined with the actual project, the effects of modulation ratio, equivalent reactance between the AC outlets of the converter and AC system equivalent impedance on the steady-state power operating range are analyzed and studied separately.

High efficiency single‐pulse controlled switched reluctance motor drive based on novel multilevel converter

Due to the high back electromotive force and short commutation time at high speed, the phase current of switched reluctance motor (SRM) is difficult to reach a large value, which limits the output performance of the motor in high-speed operation. This paper proposes a novel multilevel converter (MLC) with fast excitation and fast demagnetisation capability, which allows each phase to control independently even in overlapping conduction operation and is suitable for SRM with any number of phases. The excitation current in the rising inductance region is increased by high-voltage fast excitation, thus increasing the phase current level of the motor at high speed; the current tailing in the falling inductance region is suppressed by high-voltage fast demagnetisation, thereby reducing the generation of negative torque. Based on the novel MLC, a maximum torque per ampere (MTPA) control strategy is designed, and closed-loop control of the boost capacitor voltage is developed. By optimising control, the output torque and efficiency of switched reluctance motor drive (SRD) are greatly improved, and the constant power operation range is extended. Simulation study and experimental results verify the effectiveness of the proposed scheme.

Dynamic dv/dt Control Strategy of SiC MOSFET for Switching Loss Reduction in the Operational Power Range

For silicon carbide power <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s, high <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> in switching may bring about a high level of electromagnetic interference. This letter shows that the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dt</i> rate decreases at lower load currents. A dynamic <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dt</i> control strategy is then proposed for switching loss reduction in the whole operating range, by maintaining the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dt</i> at the maximum acceptable level. The effectiveness of the proposed control strategy is verified by an experiment, showing that the total switching loss can be reduced by as much as 22% at 30% load. Furthermore, the simulation shows that a power loss reduction of 11.4% can be obtained for an electric vehicle converter which typically operates at light loads for most of the time.

Comparative Evaluation of Silicon and Silicon-Carbide Device-Based MMC and NPC Converter for Medium-Voltage Applications

The neutral-point-clamped (NPC) converter and the modular multilevel converter (MMC) are among the most popular converter topologies for medium- and high-voltage applications. This article investigates the impact of silicon-carbide (SiC) switches on the performance of MMC and NPC converters for medium-voltage (MV) applications. Furthermore, two different cases of the circulating current control schemes are considered for the MMC configuration. The experimental prototypes of three-level configurations for both of these topologies are developed to compare and analyze their performances. Furthermore, the double pulse test (DPT) setup is constructed to obtain the device loss characteristics of the switching devices. These characteristics are then used to compute the device losses using the derived loss models. Moreover, in order to generalize the results for wide power range of operation, two sets of devices are considered for the loss analysis of the considered converter configurations. The obtained results for conduction and switching losses are compared for both the converter configurations at various loading conditions. These results provide the operating range for the considered converters to achieve reduced converter losses. Finally, a comparative analysis for the selection of converter configuration based on the obtained results is presented.

Wide-Range Light Harvesting Module for Autonomous Sensor Nodes

A large number of autonomous devices is nowadays supported by renewable and green energy sources. A vital sub-circuit in such systems is the power converter circuit, which should efficiently transform and store the available energy. In order to obtain the maximum efficiency under varying energy conditions, various maximum power point tracking (MPPT) methods are used. In this work a complete harvesting module with battery management and MPPT is presented, suitable for a plethora of autonomous applications. A novel, low-complexity and ultra-low power consumption design is proposed, which offers very wide operating voltage and power range with high MPPT efficiency and very low power consumption. It can be combined with different harvesters, such as thermoelectric generators or photovoltaic panels and is able to work under widely varying energy conditions. As supported by experimental results, the proposed module covers a very wide working input power range, from 40 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> up to 4 W, as well as a very wide input voltage range, from 650 mV up to 2.8 V with 96.5% average MPPT efficiency and a total power consumption of 3.9 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> at 3.6 V. The module relies on an embedded ultra-low power microcontroller unit (MCU) to perform the power management and MPPT operations, which can also be used for extra tasks (e.g., sensor reading). Using the proposed module, an autonomous sensor node was built, able to acquire acceleration measurements, and wirelessly communicate with a remote user in order to send an alert or stream the acquired sensor data in real time.

A Hybrid Class-E Topology With Constant Current and Constant Voltage Output for Light EVs Wireless Charging Application

Traditional Class-E circuit features fewer components, high reliability, and soft switching. However, due to the unidirectional excitation, the application of such a topology circuit is limited, i.e., usually used in low-power applications. To relieve this issue, this article proposes a switched-capacitor-based Class-E circuit, to extend the operating power range of the Class-E circuit. With the proposed new circuit, both constant current (CC) and constant voltage (CV) output modes can be achieved by switching the branch once without changing the switching frequency or compensation network. Compared with the existing CC and CV charging strategies, the proposed circuit has the advantages of fewer components, simpler implementation, and higher reliability. Moreover, the studied compensation network can also be extended to other inverter topologies. The working principle of the proposed circuit is described in detail, and the variable zero-voltage switching (ZVS) margin is introduced to make an accurate design of parameters. Subsequently, the influence of high-order harmonic components on the circuit and the sensitivity of parameters are analyzed. Finally, the proposed circuit is simulated and experimented on a 180–450-W prototype with CC and CV characteristics to verify the feasibility of the circuit and the accuracy of theoretical analysis.

A Novel DC-Biased Current Dual PM Vernier Machine

In this article, a novel electric machine having permanent magnets (PMs) in both stator and rotor parts, and fed with dc biased phase current is proposed. The innovative characteristic of the proposed machine is that it contains multiple field excitation sources including stator PM, rotor PM. and dc component in the phase current. Thus, the exciting field can be greatly strengthened. What is more, the exciting field is flexible and adjustable thanks to the variable dc component. Therefore, the proposed machine is expected to exhibit high torque density, wide constant power operation range. This article first illustrates the basic operation principle, slot/pole combination equation, and the topology. Then, performance of six machines with different slot/pole combination is analyzed. After that, effects of several key design parameters on machine performance are researched theoretically and by finite-element method and genetic algorithm. And neural network is applied to verify the correctness of torque and torque ripple. Finally, the electromagnetic performance including flux density, back electromotive force, torque quality of an optimized machine is illustrated.

An improved control strategy for current source converter-based HVDC using fundamental frequency modulation

When pulse width modulation (PWM) is applied in a high-voltage current source converter (CSC) based on fully controlled devices, there are some concerns arising, such as large DC voltage fluctuations, high switching losses, and a narrow power operation range. To solve these problems, the CSC-based HVDC using fundamental frequency modulation (FFM-CSC) is proposed. First, the topology of the CSC is introduced. Then, an independent control strategy for FFM-CSC is presented, which can be used to realize univariate control of DC voltage or DC current. The mathematical model of CSC is also analyzed, and on this basis, a coordinated control strategy is proposed for FFM-CSC to decouple the active and reactive power. An outer loop power controller and an inner loop current controller are designed, and the power operation range is investigated. Finally, an FFM-CSC simulation model is built in PSCAD/EMTDC. The simulation results show that there are smaller DC voltage fluctuations, lower switching losses, and a wider power operation range under the proposed FFM-CSC control strategy.

A Novel Baseband Generation Method for Modeling RF Power Amplifiers for Bit Error Rate Computations

In this article, we present a novel method for modeling radio frequency (RF) power amplifiers (PAs). The proposed method for baseband data generation introduced in this paper, enables us to specify operational power range and bandwidth criteria of the PA, yielding a generic power amplifier model, which includes both memory effects as well as non-linearity of the PA. Further, we show that, the modeling approach is useful for bit error rate (BER) computations with PA distortions for any digitally modulated signal. Estimated BER using the proposed PA model for the test case of QPSK and 16-QAM, shows a significant difference in BER at high input back-offs due to memory effects, compared to the conventional non-linear PA models.

Optical memories and switching dynamics of counterpropagating light states in microresonators.

The Kerr nonlinearity can be a key enabler for many digital photonic circuits as it allows access to bistable states needed for all-optical memories and switches. A common technique is to use the Kerr shift to control the resonance frequency of a resonator and use it as a bistable, optically-tunable filter. However, this approach works only in a narrow power and frequency range or requires the use of an auxiliary laser. An alternative approach is to use the asymmetric bistability between counterpropagating light states resulting from the interplay between self- and cross-phase modulation, which allows light to enter a ring resonator in just one direction. Logical high and low states can be represented and stored as the direction of circulation of light, and controlled by modulating the input power. Here we study the switching speed, operating laser frequency and power range, and contrast ratio of such a device. We reach a bitrate of 2 Mbps in our proof-of-principle device over an optical frequency range of 1 GHz and an operating power range covering more than one order of magnitude. We also calculate that integrated photonic circuits could exhibit bitrates of the order of Gbps, paving the way for the realization of robust and simple all-optical memories, switches, routers and logic gates that can operate at a single laser frequency with no additional electrical power.

Optimal Design of a Dual-Active-Bridge DC–DC Converter

This article presents a systematic design procedure for a dual-active-bridge (DAB) dc-dc converter. Design of a DAB converter involves determination of two key parameters, i.e., transformer turns ratio and the series inductance value. Existing literature addresses this problem through numerical optimization, which is computation intensive and does not provide much insight. In general, loss is minimized by applying equal weightage to all operating conditions, which may not be practical. Given an operating power range, terminal voltage range, and switching frequency, this article presents a way to optimally select the design variables through analytical solution of a constrained optimization problem. Analysis is carried out in the time domain, and an optimal triple-phase-shift modulation strategy is considered that ensures minimum inductor rms current and soft switching. The choice of the design parameters results in minimization of the worst-case inductor rms current over the entire operating range of the converter, which leads to both efficiency and size optimization. A procedure for selection of devices and filter capacitors and design of magnetics is given. A 2.6-kW experimental prototype is designed to validate the theoretical analysis.

Performance analysis and parametric studies on the primary nozzle of ejectors in proton exchange membrane fuel cell systems

ABSTRACT Ejectors are used for anode hydrogen recirculation in proton exchange membrane fuel cell (PEMFC) systems, and the geometric parameters of the primary nozzle of ejectors have essential effects on the ejector performance. A 3D numerical model was established to investigate ejectors, and the reliability of the numerical model was verified by experiments. The operating characteristics of ejectors in the PEMFC system were analyzed by numerical simulation. Moreover, the effects of four geometry parameters (throat diameter, convergent angle, divergent angle, and length) on entrainment performance were studied. The results showed that the angle and length of the divergent zone have a significant influence on entrainment performance. A larger divergent angle may cause over-expanded under low power conditions, resulting in lower entrainment performance. For PEMFC systems with stable operating conditions or high entrainment requirements, a supersonic ejector with an appropriate divergent angle and length is recommended. Conversely, a convergent primary nozzle is suggested to be employed for the PEMFC systems with the wide operating power range. This study may provide a helpful reference for the design of ejectors used in fuel cell systems.