Output Operation Research Articles

High‐Energy Lithium‐Ion Batteries: Recent Progress and a Promising Future in Applications

It is of great significance to develop clean and new energy sources with high‐efficient energy storage technologies, due to the excessive use of fossil energy that has caused severe environmental damage. There is great interest in exploring advanced rechargeable lithium batteries with desirable energy and power capabilities for applications in portable electronics, smart grids, and electric vehicles. In practice, high‐capacity and low‐cost electrode materials play an important role in sustaining the progresses in lithium‐ion batteries. This review aims at giving an account of recent advances on the emerging high‐capacity electrode materials and summarizing key barriers and corresponding strategies for the practical viability of these electrode materials. Effective approaches to enhance energy density of lithium‐ion batteries are to increase the capacity of electrode materials and the output operation voltage. On account of major bottlenecks of the power lithium‐ion battery, authors come up with the concept of integrated battery systems, which will be a promising future for high‐energy lithium‐ion batteries to improve energy density and alleviate anxiety of electric vehicles.

A multi-stable ultra-low frequency energy harvester using a nonlinear pendulum and piezoelectric transduction for self-powered sensing

This paper presents the design, theoretical modelling and experimental validation of a quad-stable energy harvester for harnessing ultra-low frequency random motions using a nonlinear pendulum and piezoelectric transduction. The multi-stable pendulum is created by the magnetic forces between magnets on the pendulum and a tip magnet on a piezoelectric cantilever beam. Two attractive and one repulsive magnetic forces in combination with the gravitational force of the pendulum create multiple stable positions for the pendulum. The multi-stable dynamics allow the pendulum to effectively convert low-frequency random kinetic motions from the host, e.g. human motion or wind turbine tower oscillation into the pendulum oscillation, enabling effective plucking of the piezoelectric beam with enhanced output power. A theoretical model, including the magnetic interaction, piezoelectric conversion and pendulum dynamics, is established to describe the electromechanical dynamics of the whole harvester. A prototype is fabricated and tested on a linear shaker at ultra-low frequencies (1–3 Hz) to showcase the capability of the harvester and to validate the theoretical results. Around 8 μW Root-Mean-Square output power was obtained at 2.5 Hz and 0.8 g of excitation. Using the experimentally validated theoretical model, a parametric study was carried out to examine the influence of different structural and operating parameters, such as pendulum mass and length, magnetic coupling strength, excitation frequency and amplitude, on the output power and operating frequency range of the energy harvester. The operation frequency range and output power can be effectively adjusted by changing the above-mentioned parameters. The self-powered sensing capability is then illustrated by integrating the harvester with an off-the-shelf power management circuit and a 22 μF storage capacitor. The capacitor was charged from 2.8 V to 4 V in 90 s, showing its capability of implementing battery-free wireless sensing for different Internet of Things (IoT) applications.

Approximation of infinite-dimensional observer-based state feedback for systems with boundary control and observation

Infinite-dimensional linear systems with unbounded input and output operators are considered. For the purpose of finite-dimensional observer-based state feedback, an observer approximation scheme will be developed which can be directly combined with existing late-lumping controllers and observer output injection gains. It relies on a decomposition of the feedback gain, resp. observer output injection gain, into a bounded and an unbounded part. Based on a perturbation result, the spectrum-determined growth condition is established, for the closed loop.

The Assessment of Fixed Capital Asset-Based Capacity of Fish Farm in Nigeria

The study area of the research work was Jere and Konduga Local Government Area of Borno State, North East Zone, Nigeria. An area that met the environmental requirement for fish farming which have significantly contributed to the development of fish production in the country, Nigeria. The study concerned with the assessment of fixed capital asset-based capacity of fish farm in the study area. Data for the study was collected within the period of thirty-one (31) days from 14th March, to 13th April 2023 through a questionnaire with informal discussion with the fish farmers. Information were also solicited from farmers book of accounts and other organizational official records were used. Thus, both primary and secondary sources of data were employed. The result of the study showed that fixed capital asset-based capacity of concrete fish farm in the study area was below average. Recommendation were made to create an avenue for the fish farmers in the study area to access fixed capital asset adequately for the improvement of fish farm asset-based capacity to expand operation for higher output.

Simulation of distributed photovoltaic power generation system

Combined with the operation characteristics of photovoltaic power generation system, the mathematical model and simulation model are established, and the control strategy of bipolar inverter with wide output characteristics and the maximum power point tracking (MPPT) control method of conductance increment method are designed. The maximum power output and stable operation of distributed photovoltaic power generation system are realized. The simulation results show that the photovoltaic power generation system model established in this paper can effectively reflect the characteristics of distributed photovoltaic power generation and MPPT control. With the change of lighting conditions, the distributed photovoltaic power generation system can accurately adjust the system output, which is of great significance for the research and operation of distributed photovoltaic power generation system.

A space‐time model with temporal cyclostationarity for probabilistic forecasting and simulation of solar irradiance data

To establish a more sustainable future, Saudi Arabia is striving to reduce its dependency on fossil fuels and promote renewable energies. Solar energy is a major resource in Saudi Arabia because of the country's geographical location with year‐round clear skies and plentiful sunlight. However, although solar energy is a clean and safe renewable energy resource, it can be quite unpredictable. Therefore, solar irradiance needs to be forecasted and simulated as accurately as possible on both regional and national scales in the Kingdom to assist in planning for reserve usage, switching sources and short‐term power purchases. Based on an hourly solar diffuse horizontal irradiance (DHI) dataset from 45 different Saudi Arabian solar monitoring stations, this study proposes a novel spatio‐temporal model. We identify the temporal dependency of DHI as cyclostationary and incorporate this key observation in the model. This feature helps yield accurate (i.e. significantly close to the ground truth and with narrow confidence bands) probabilistic forecasts and realistic simulations in near‐future time points and at new locations. Then, the proposed model is compared with a stationary model that fails to recognize the cyclostationarity structure in the data. The proposed model produces significantly better predictions and simulations than the stationary model. Further, we calculate the photovoltaic power outputs using the simulated samples from both the models and the original observations and then compare them. The simulated samples from the proposed model afford photovoltaic power output estimates that are significantly closer to the original observed data than those from the stationary model, and therefore, they can better assist photovoltaic power output operators in assessing solar energy production and operational pre‐planning to mitigate impacts by the uncertain nature of solar irradiance.

Stability properties for two coupled reaction-diffusion equations

This paper studies the stability of the interconnection of two reaction-diffusion equations. We focus on the case where the input and output operators of the interconnection are bounded. Using the spectral decomposition of both equations, we propose a sufficient condition to estimate the exponential stability decay rate of the closed-loop system. This stability test is proposed as constraints of a semidefinite programming. An extension of this condition is also outlined in the form of a Hurwitz criterion. The proposed stability analysis conditions are illustrated with an example of two reaction-diffusion equations with constant couplings terms.

小型多功能农用底盘液压驱动系统的设计与试验

In view of the problems of the output power and operation, when the multi-function machine in hilly and mountainous areas driving in the field, the hydraulic control drive system of small multi-function agricultural hydraulic chassis is designed. The key components of the hydraulic drive system were selected and matched. The hydraulic system simulation model was established in AMESim simulation analysis software, and the dynamic analysis of the hydraulic system operation under different conditions is carried out. The simulation analysis results show that the hydraulic system has a large impact and vibration when it is started instantaneously, and the hydraulic system has smaller impact and vibration when it is started stably. It is consistent with the actual working state of the hydraulic chassis. Under the two starting controls, the maximum flow of the hydraulic pump is 50L/min, the motor torque is about 440N • m, and the motor stable pressure is 6Mpa, the motor speed is 96 r/min, which is within the bearing range of the hydraulic components. The simulation output parameters are basically consistent with the theoretical calculation results, and meeting the design requirements. The chassis performance test results show that the maximum crossing height of the chassis is 200mm, the crossing width is 300mm, the maximum deviation of high-speed straight driving is 2.57m, it can stably pass 20° slope, and the operation is stable and the steering is flexible. All performance parameters can better meet the requirements of chassis operation in hilly and mountainous areas.

Yaw-adjusted wind power curve modeling: A local regression approach

Accurate estimation of wind power curves using field data is instrumental to several wind farm operations including productivity assessment, power output estimation, operations and maintenance, among others. Existing methods for estimating wind power curves mainly rely on environmental variables (e.g., wind speed, direction, density) as inputs to construct the wind-to-power relationship. This paper attempts to integrate yaw misalignment as an additional input to power curve models, constructing what is referred to hereinafter as “yaw-adjusted wind power curves.” Our analysis shows that integrating yaw misalignment into power curves is non-trivial, largely due to the overwhelming impact of environmental variables (mainly wind speed) on a turbine’s power output, which obscures the secondary effect of yaw errors on power production. In response, we propose a local-regression-based method which reconstructs the yaw-to-power relationship conditional on an effective neighborhood of environmental variables. Tested on operational data from two onshore wind turbines in France, our proposed approach achieves significant improvements, in terms of power estimation accuracy, relative to a set of prevalent statistical- and machine-learning-based power curve models.

High Precision Primary Side Regulation Constant Voltage Control Method for Primary and Secondary Resonant Active Clamp Flyback Converter

Active clamp flyback (ACF) converter has been demonstrated that which is better than traditional flyback in high-frequency power-adaptor applications. According to the circuit structure, ACF has two modes, primary resonant ACF (PR-ACF) and secondary resonant ACF (SR-ACF). In order to improve the power density, a high-precision primary side regulation (PSR) constant voltage control method for ACF converter is proposed in this article. The proposed method not only can be effectively adopted in PR-ACF but SR-ACF converter. The high-precision output voltage is predicted by highly accurate sampling points on primary auxiliary voltage. The applied microcontroller environment improves the practicability and increases the power density of the ACF system. To verify the proposed PSR method, a prototype that can be changed into PR-ACF and SR-ACF is designed. The output voltage offset, operation efficiency, and dynamic performance are analyzed. The tested results show that high-precision output is obtained in ACF converter by using the proposed method and the maximum output voltage deviation which are 4% and 3.5% in PR-ACF and SR-ACF converter, respectively. Moreover, SR-ACF has a higher efficiency compared with PR-ACF converter, and a smaller voltage shoot during dynamic process, which needs a larger regulation time since the additional output inductor.

Optimal sizing for a wind-photovoltaic-hydrogen hybrid system considering levelized cost of storage and source-load interaction

Hydrogen energy storage system (HESS) has excellent potential in high-proportion renewable energy systems due to its high energy density and seasonal storage characteristics. After detailing the volatility of wind speed, irradiance and load, this paper proposes a bi-level optimization model to analyze the economic operation of the wind-photovoltaic-hydrogen hybrid system (WPH-HS). First, the relationship between the source-load output matching and operating conditions of HESS is studied, two evaluation indicators are described, which can be adjusted by wind-solar complementarity on the source side and demand response on the load side. Second, considering the levelized cost of storage (LCOS), the total annual cost (TAC) calculation method of WPH-HS is presented, and this paper provides a new hybrid optimization technology of chaotic search, particle swarm optimization and non-dominated sorting genetic algorithm2. Finally, the system is simulated with the MATLAB software to determine the optimal sizing of components and minimize the LCOS while ensuring the optimal TAC. The simulation results are elaborated in detail. In particular, the added source-load interaction reduces the TAC and LCOS by 7.3% and 10.3%. When two indicators reach 0.03 and 0.1745, the system is economically viable with the LCOS of 0.276 USD/kWh. The hybrid optimization algorithm can achieve better result in fewer iterations.

A hybrid machine learning method with explicit time encoding for improved Malaysian photovoltaic power prediction

Nowadays, with the growing interest in green energy, further improvements in photovoltaic (PV) power systems are needed. In this regard, the main aim is to find an optimal method to predict the output power of PV systems to maintain a sustainable operation. Hence, this work proposes a hybrid Machine Learning (ML) method LASSO-RFR for an hourly PV power output prediction. The model consists of Least Absolute Shrinkage and Selection Operator (LASSO) and Random Forest Regressor (RFR), where the former model makes a prediction and the latter fine tune it by the addition or subtraction of a relatively small value. The proposed model outperformed other models when tested on real data recorded from 2016 to 2019 for three Malaysian PV systems, namely Thin-Film (TF), Monocrystalline (MC), and Polycrystalline (PC). LASSO-RFR attained the lowest root mean square error (RMSE) of 23.7, 18.2, and 20.8 Wh/m2 for the TF, MC, and PC, respectively. This work also highlights the importance of explicit time encoding in improving PV power prediction. Although it is used to be ignored in the literature when developing ML models, the time feature is the second most influencing factor of PV power prediction after solar irradiance, as shown by the SHAP analysis (shapely additive explanation). For the study implications, the developed prediction model can assist the industry in predicting 1 h ahead of PV power output, demand-side management, and building operations and maintenance.

Process Variation Based Electrical Model of STT-Assisted VCMA-MTJ and Its Application in NV-FA

Fast switching speed, low power consumption, and good stability are some of the important properties of spin transfer torque assisted voltage controlled magnetic anisotropy magnetic tunnel junction (STT-assisted VCMA-MTJ) which makes the non-volatile full adder (NV-FA) based on it attractive for Internet of Things. However, the effects of process variations on the performances of STT-assisted VCMA-MTJ and NV-FA will be more and more obvious with the downscaling of STT-assisted VCMA-MTJ and the improvement of chip integration. In this paper, a more accurate electrical model of STT-assisted VCMA-MTJ is established on the basis of the magnetization dynamics and the process variations in film growth process and etching process. In particular, the write voltage is reduced to 0.7 V as the film thickness is reduced to 0.9 nm. The effects of free layer thickness variation (γtf) and oxide layer thickness variation (γtox) on the state switching as well as the effect of tunnel magnetoresistance ratio variation (β) on the sensing margin (SM) are studied in detail. Considering that the above process variations follow Gaussian distribution, Monte Carlo simulation is used to study the effects of the process variations on the writing and output operations of NV-FA. The result shows that the state of STT-assisted VCMA-MTJ can be switched under -0.3%≤γtf≤6% or -23%≤γtox≤0.2%. SM is reduced by 16.0% with β increases from 0 to 30%. The error rates of writing ‘0’ in the NV-FA can be reduced by increasing Vb1 or increasing positive Vb2. The error rates of writing ‘1’ can be reduced by increasing Vb1 or decreasing negative Vb2. The reduction of the output error rates can be realized effectively by increasing the driving voltage (Vdd).

Generalized framework for computing the [formula omitted]-induced norm of sampled-data systems

This paper develops a generalized framework for computing the L∞-induced norm of sampled-data systems, by which we mean those consisting of a continuous-time linear time-invariant (LTI) plant and a discrete-time LTI controller, and such systems have a linear periodically time-varying (LPTV) nature. In the authors’ preceding studies, the input/output relation of sampled-data systems was described in an operator-theoretic fashion, and the kernel and input functions of an input operator and the hold function of an output operator were approximated by piecewise lth order polynomials with l=0,1. This leads to an approximate computation of this norm, where the computation errors were shown to converge to 0 in the order of 1/Ml+1 as the approximation parameter M becomes larger. Along this line, we aim at improving the computation performance compared to the preceding studies by considering the freedom in the point around which the corresponding functions are expanded to a Taylor series. This leads to a generalization of the piecewise lth order approximations, and we show that taking the central point for the Taylor expansion leads to quantitatively improved accuracy than that of our preceding results that take an edge point.Finally, the effectiveness of the developed method is verified through a numerical example.

Input parallel–output parallel connected modular nonisolated DC‐DC converters with current self‐sharing capability operating in discontinuous conduction mode

AbstractThis paper covers the self‐sharing analysis of dc‐dc nonisolated converters with input parallel–output parallel (IPOP) configuration and operating in discontinuous conduction mode (DCM). The main contribution of the proposed system is its capability of providing self‐sharing of the currents on both sides of each individual converter, without average current sharing control, even in the face of parametric variations. This self‐balance only occurs for DCM. When the addressed converters operate in continuous conduction mode (CCM), the self‐sharing does not occur naturally under parametric differences among them, requiring the use of additional control loops. The use of self‐sharing converters in nonisolated converters simplifies the control system, it makes the modular solution being attractive for many applications, and it increases the power range that the DCM converters may be applied. This paper brings the theoretical study of self‐sharing of the current mechanism to six basic nonisolated converters operating in DCM. The self‐sharing is verified by experimental results, which are obtained from three modules of dc‐dc SEPIC converters. Both converters were designed to operate with 200‐V input voltage, 125‐V output voltage, 1500‐W rated power (500 W each module), and switching frequency at 30 kHz.

Implementation of radial basis function network-based maximum power point tracking for a PV-fed high step-up converter

This research offers a maximum power point tracking (MPPT) algorithm for photovoltaic (PV) systems based on neural networks (NNs) and a rapid step-up converter configuration. An improved variable step size-radial basis function network (RBFN) in the NN algorithm is accomplished in the proposed system to track the maximum power point (MPP) with high convergence speed and obtain maximum power with reduced oscillations. Under various irradiance and temperature conditions, the performance of the recommended algorithm was compared to that of particle swarm optimization (PSO), modified perturb and observe (P&O) MPPT technique, artificial neural network (ANN), and multilayer perceptron feed-forward (MPF) NN-based MPPT method. In this system, a new interleaved non-isolated large step-up converter with the coupled inductor technique is suggested to compensate for the discord in PV devices to enable a continuous and independent power flow. The proposed PV-fed converter system is validated under partial shading conditions (PSCs) and uniform solar PV, and the results are experimentally verified with the use of a programmable direct current (DC) source. The obtained results indicate that the proposed converter produces output with high gain, continuous input current, low voltage stress on switches, minimal ripple, high power density, and extensive input and output operations. Finally, a prototype has been implemented to verify the functionality of the presented converter in continuous conduction mode operation with an input voltage range of 20 V and an output voltage of 200 V.

Polishing the Lead-Poor Surfacefor Efficient Inverted CsPbI3 Perovskite Solar Cells.

Triiodide cesium lead perovskite (CsPbI3 ) has promising prospects in the development of efficient and stable photovoltaics in both single-junction and tandem structures. However, achieving inverted devices that provide good stability and are compatible to tandem devices remains a challenge, and the deep insights are still not understood. This study finds that the surface components of CsPbI3 are intrinsically lead-poor and the relevant traps are of p-type with localized states. These deep-energy-level p traps induce inferior transfer or electrons and serious nonradiative recombination at the CsPbI3 /PCBM interface, leading to the considerable open-circuit voltage (Voc ) loss and reduction of fill factor (FF). Compared to molecular passivation, polishing treatment with 1,4-butanediamine can eliminate the nonstoichiometric components and root these intrinsically lead-poor traps for superior electron transfer. The polishing treatment significantly improves the FF and Voc of the inverted CsPbI3 photovoltaics, creating an efficiency promotion from 12.64% to 19.84%. Moreover, 95% of the initial efficiency of the optimized devices is maintained after the output operation for 1000 h.

High-Order Compensated Capacitive Power Transfer Systems With Misalignment Insensitive Resonance

A well-performed capacitive power transfer (CPT) system highly depends on its compensation to achieve load-independent (LI) output and zero phase angle (ZPA) operation. It is particularly meaningful to maintain these objectives under various misalignments. This paper is devoted to a general and comprehensive method to study and explore all the potential high-order compensations. The coupler parameter variation is evaluated under different types of misalignment, and misalignment-insensitive (MI) parameters are properly designed for MI resonance. A general and straightforward decomposition and synthesis method is then proposed to generate the high-order resonant tanks. With the help of inverse ABCD parameters, all tank candidates are further judged by their capability for LI output and ZPA operation. Finally, two example CPT systems are built to verify the LI output and ZPA operation under misalignment.

Design and implementations of high step‐up non‐isolated DC‐DC converters for electric vehicles application

AbstractAn effective hybrid energy system that connects with a fuel cell, solar, and battery system is described as a renewable energy (RE) source powered electric vehicle. The consequences of designing multi‐input DC‐DC converters for various sources are thoroughly studied. The fuel cell (FC) is utilized as the major source of energy, with photovoltaic (PV) livings utilized to recharge the battery, enhance efficiency, and diminish fuel consumption. By selecting a suitable coupled inductor turn ratio, the proposed structure efficiently enhances the rate of output voltage. A coupled inductor's created leakage inductance energy can be reclaimed, resulting in a reduction in the recommended converter's power losses. Variability in RE power production and load demand are both taken into account for maintaining the power balance. In addition, a power management technique is developed and implemented in a control technique. High gain, continuous input current, low voltage stress on switches, and extensive input and output operations are some of the interesting features of the proposed converter. The converter's results are also experimentally verified with the use of a programmable DC source.

Realistic operation of two residential cordwood-fired outdoor hydronic heater appliances—Part 2: Particle number and size

ABSTRACT The use of wood as a fuel for home heating is a concern from an environmental health and safety perspective as biomass combustion appliances emit high concentrations of particulate matter. Wood burning significantly contributes to wintertime particulate matter concentrations in many states in the northern United States. Of particular concern are outdoor wood-fired hydronic heaters. These devices are concerning as they tend to have very large combustion chambers and typical use patterns can result in long periods of low output, which result in an increased particulate matter emission rate relative to high heat output operating conditions. In this study, the performance of two hydronic heaters operating under different combustion conditions, including four different heat output categories approximately corresponding to categories I–IV denoted in Environmental Protection Agency Method 28 Outdoor Wood-fired Hydronic Heaters, and during start-up and reloading events were investigated. Measurements of flue gas particulate number concentration and size for particles with aerodynamic diameters between 0.006 and 10 µm were made using a dilution sampling system. The measured particle number concentration in the flue gas was between 0.71 and 420 million particles per cubic centimeter and was dependent on fuel loading and heat output. For each hydronic heater tested, the highest average particle concentration was found at the beginning of each test during the cold-start condition. Additionally, the majority of the particles had aerodynamic diameters less than 0.100 µm (particles of this size made up between 64% and 97% of all particles) and less than 1% of all particles had aerodynamic diameters greater than 1 µm for all phases. For particles in the accumulation mode, between 0.100 and 1 µm, the mean particle diameter was dependent on fuel loading and heat output. Implications: In this work, we provide information on the particle number concentration and particle size of emissions from outdoor cord- wood-fired hydronic heaters. Wood-fired hydronic heater data is sparsely available compared to wood stove data. Thus, additionaldata from this source help to inform the work of modelers and policy makers interested in hydronic heaters. The test method used in this work is also novel, as it is more inclusive of real-world use cases than the current certification method. Our data helps to validate the test method and allows for comparisons between real-world use case scenarios, and idealized test cases.