Dynamic Response Model Research Articles

Dynamic Modeling of Polymer Electrolyte Membrane Water Electrolysis System and Dynamic Response

Water electrolysis to produce hydrogen using electric energy is classified into polymer electrolyte water electrolysis, alkaline water electrolysis, solid oxide water electrolysis, and anion exchange membrane water electrolysis according to the type of electrolyte applied. Among them, polymer electrolyte membrane water electrolysis has a lower operating temperature than other types of water electrolysis, and it is possible to operate high-efficiency, high-power density hydrogen production with high current density. In addition, polymer electrolyte water electrolysis has the advantage of fast response to changes in power supply, so empirical studies for green hydrogen production linked to renewable energy are being conducted most actively compared to other water electrolysis. However, research on coupling polymer electrolyte water electrolysis with renewable energy generation with intermittent and irregular power generation has mainly focused on materials, cells, and stacks. In order to keep the hydrogen production reaction of water electrolysis stack stable under the condition of supply power fluctuation, the peripheral devices should be optimally installed and controlled.In this study, a dynamic model of a polymer electrolyte water electrolysis system was developed using Aspen HYSYS®. To accurately predict the hydrogen production efficiency, a stack model considering electrochemical reactions and crossovers through the electrolyte was developed and internalized in a spread sheet. A heat exchanger model from the model library was used to simulate dynamic changes in the electrolyte temperature flowing through the water electrolysis stack. The developed stack model was extended to a system model by integrating the feed pump, separator, condenser, heater, and cooling system. The developed water electrolysis system model was simulated in connection with power ramp variations and renewable energy output, and the optimal operation strategy of each module unit was derived to ensure the stability of high-purity hydrogen production under transient conditions.

Data-driven estimation of the amount of under frequency load shedding in small power systems

This paper presents a data-driven methodology for estimating under frequency load shedding (UFLS) in small power systems. UFLS plays a vital role in maintaining system stability by shedding load when the frequency drops below a specified threshold following loss of generation. Using a dynamic system frequency response (SFR) model we generate different values of UFLS (i.e., labels) predicated on a set of carefully selected operating conditions (i.e., features). Machine learning (ML) algorithms are then applied to learn the relationship between chosen features and the UFLS labels. A novel regression tree and the Tobit model are suggested for this purpose and we show how the resulting non-linear model can be directly incorporated into a mixed integer linear programming (MILP) problem. The trained model can be used to estimate UFLS in security-constrained operational planning problems, improving frequency response, optimizing reserve allocation, and reducing costs. The methodology is applied to the La Palma island power system, demonstrating its accuracy and effectiveness. The results confirm that the amount of UFLS can be estimated with the mean absolute error (MAE) as small as 0.179 MW for the whole process, with a model that is representable as a MILP for use in scheduling problems such as unit commitment among others.

Dynamic response and constitutive model for coal-rock composite material subjected to impact loading

Comprehensive understanding related to the dynamic responses of the composite materials is critical to prevent natural disasters in underground engineering and mining activities. For this reason, experimental studies were undertaken using dynamic impact tests at different strain rates to explore the failure mechanism using split Hopkinson pressure bar (SHPB) system and Digital Image Correlation (DIC) on composite materials; coal-rock (C-R) and rock-coal (R-C). These results suggest a linear correlation between dissipative energy and fractal dimensions. In addition, they suggest cracks that develop predominantly on the coal side have a dominant influence on the failure process that could be attributed to the interface effects. The damage evolution was established assuming elastic conditions using a three-dimensional coupled FDM-DEM numerical simulation system. Anumerical approach is also developed for interpreting failure mechanism of the composite material based on the fabric tensor and strain energy density. Finally, a constitutiverelationshipis established considering strain rate effect and damage evolution using series element studies. There is a good agreement between the experimental and numerical results, providing justification to the proposed constitutive relationship. The numerical approach in this study is promising for assessing the performance of composite materialstaking account of dynamic loading conditions.

Two-stage low-carbon economic dispatch of an integrated energy system considering flexible decoupling of electricity and heat on sides of source and load

Under the goal of "double carbon", in order to further enhance the level of new energy consumption and solve the problem of restricting the flexibility of the system by "ordering power by heat" of combined heat and power (CHP) units, a low-carbon economic planning strategy with flexible decoupling of electricity and heat is proposed, by introducing a new type of electric-thermal coupling equipment on both sides of the source and load. Firstly, Consideration of the low-carbon and environmentally friendly characteristics of green ammonia production and ammonia-doped combustion technologies, a wind power(WT) – power to ammonia(P2A) - CHP units - thermal power (TH) units joint operation strategy is proposed on the source side. This strategy realizes the conversion of abandoned wind to green ammonia to ammonia coal hybrid generation, the decoupled operation of CHP units and promotes the consumption of wind power and the low-carbon operation of the system. Secondly, A dynamic incentive demand response model is developed to meet the demand of high proportion distributed PV in situ consumption on the load side. The dynamic incentive price guides the distributed power-to-heat load to change the response capacity, tracks the abandonment of wind and light, realizes the flexible conversion of power and heat load, and cooperates with the source side to promote the coupling operation of electric pyrolysis. On this basis, consider the flexible decoupling capability of electric-heat coupling equipment on both sides of the source and load to establish a two-phase low-carbon scheduling model for the day-before and day-after phases. In the day-ahead phase, the source-side electric-thermal-ammonia joint operation strategy is considered, and the electric and thermal energy supply plans are adjusted centrally; In the intra-day phase, the flexible adjustment range of power-to-heat devices and the heat load inertia on the load side are taken into account, and the electricity and heat planning strategies are adjusted in a distributed-centralised manner in conjunction with the source side. Finally, through the simulation of different cases, the results show that compared with the traditional electric heating system, the total cost of the system considering the scheduling strategy proposed in this paper decreases by ￥826,900, the carbon emission decreases by 1.2 t, and basically realises the consumption of wind power and distributed photovoltaic power output. The proposed scheme reduces carbon emissions, promotes the consumption of wind power and distributed photovoltaic output, and is able to reach the goal of low-carbon economic dispatch.

Research on the mechanism of impact of vibrational loads on the bearing capacity of drilling surface conductor

The surface conductor is the first structural pipe in the development of deep-water oil and gas resources, bearing the top load and suspending various casing layers. Vibrational loads can cause soil structural damage and increase pore pressure, reducing the bearing capacity of the surface conductor and threatening the safety and stability of the subsea wellhead. Based on the vertical force analysis of the surface conductor and considering the impact of vibrational loads on soil strength, a model for the vertical bearing capacity of the surface conductor was established. Utilizing the dynamic Winkler model for pile foundation horizontal dynamic response, the surface conductor was simplified as a bending beam subjected to harmonic vibration, and a control equation for lateral deformation of the surface conductor was established. The effects of vibration load amplitude and frequency on the vertical bearing capacity of surface conductors were analyzed through simulation experiments, resulting in an equivalent bearing capacity coefficient for surface conductors ranging from 0.88 to 0.97. Combining the engineering data from a deep-water block in the South China Sea, the reliability of the theoretical calculation model was validated. The analysis indicates that the maximum bending moment of the surface conductor is approximately 6m below the mudline; low-frequency(0.05Hz–0.2Hz) vibrational loads can reduce the ultimate bearing capacity of the surface conductor by 3%–11%, with the effect gradually diminishing over time. This research provides a theoretical basis for the design of surface conductor in deep-water oil and gas wells.

Dynamic response of double-layer rectangular sandwich plates with graded foam cores under blast loading

In this paper, dynamic response of a fully clamped double-layer (DL) rectangular sandwich plate with graded foam cores (GFC) under blast loading is studied theoretically and numerically. Based on the yield criterion, an analytical model for dynamic response of a DL rectangular sandwich plate with GFC is established under blast loading. With the use of the inscribing and circumscribing squares of the exact yield locus, the bound of the analytical solution of the dynamic response of a double-layer rectangular sandwich plate with GFC is obtained. By neglecting the effect of bending moments, the membrane mode solution of a DL rectangular sandwich plate with GFC in large deflection is obtained. Finite element analysis (FEA) is performed using ABAQUS/Explicit software. The effects of interlayer factor, average yield strength of graded foams, and gradient properties of graded foams on the dynamic response of DL rectangular sandwich plate with GFC are considered. The analytical predictions are in excellent accord with the numerical ones. It is demonstrated that the proposed analytical model is effective to predict the blast response of a DL rectangular sandwich plate with GFC.

Feasibility of realizing photothermal, photovoltaic, and radiative cooling with a flexible structure

The escalating energy demands and the imperative of environmental conservation necessitate advanced sustainable energy solutions. This study introduces a novel nanofluid spectrum-splitting photovoltaic/thermal system integrated with radiative cooling (RC) technology, termed NSS-RC-PV/T. This system optimizes solar spectrum utilization, enhances thermal management, and significantly improves the efficiency and flexibility of heat, electricity, and cooling outputs. Employing a reversible PV-Ag panel, the system adapts between PV/T and RC modes based on energy demands. A comprehensive mathematical model is established to evaluate its performance under realistic environmental conditions across China. Results indicate the maximum energy output of the system is 6438 MJ/m2, which is a 33.4% increase in annual energy output compared to the conventional PV/T system. The dynamic power response model also shows an increase of 5.8% (266 MJ/m2) compared to the daylight response model. This research underscores the potential of NSS-RC-PV/T systems in advancing renewable energy technologies and meeting modern energy needs.

Dynamic response characteristics of optical beam deflection in liquid crystal optical phased array

The beam deflector based on liquid crystal optical phased array (LCOPA) is a crucial component of space laser communication systems. Understanding and mastering the beam deflection characteristics under the dynamic response of LCOPA is essential for achieving real-time acquisition and tracking in space laser communication. This paper thoroughly explores the beam deflection characteristics during the dynamic response process by analyzing the dynamic response and far-field diffraction models of LCOPA. It presents the far-field diffraction patterns under the dynamic response of LCOPA and validates the analysis through experiments. This study not only enhances the understanding of the dynamic performance of LCOPA but also provides a theoretical basis for its control in space laser communication systems.

Participation of wind-storage combined system in the secondary frequency regulation control strategy of power grid

Abstract The secondary frequency modulation of the unit, that is, the automatic generation control (AGC), is the process of increasing or decreasing the power of the power generation unit by the power plant unit according to the dispatching command issued by the power grid dispatching center, and then using the frequency modulator to restore the frequency. Based on the principle of AGC, this paper establishes a frequency dynamic response model of the secondary frequency modulation of the traditional unit and the wind storage participation system including load frequency control (LFC) and traditional proportional-integral-derivative (PID) controllers, determines the frequency modulation control strategy of wind storage, and uses the distribution mode based on Area Control Error (ACE) signal to assist in the secondary frequency modulation. In order to solve the parameter optimization problem of the classical PID controller when the wind-storage combined system participates in the secondary frequency modulation under the large load disturbance, a parameter optimization model of the controller with PID was established, and the ITAE evaluation index was finally selected as the fitness function by comparing different fitness evaluation indexes. To overcome the problem that the conventional Particle Swarm Optimization (PSO) is prone to local extremum, the inertia weights and learning factors are adjusted nonlinearly to balance and optimize the global and local optimization capabilities and improve the search efficiency, and the parameters of the PID controller are optimized by the improved PSO algorithm. The simulation results show that the proposed algorithm improves the secondary frequency modulation effect under the background of a high proportion of renewable energy connected to the power grid.

A 3D nonlinear viscoelastic–viscoplastic constitutive model for dynamic response of an epoxy resin

A 3D nonlinear viscoelastic–viscoplastic constitutive model for dynamic response of an epoxy resin

Thermodynamic analysis and equilibration response time prediction of recuperator in the SCO2 Brayton cycle

The recuperator of supercritical carbon dioxide (SCO2) Brayton cycle significantly affects the system's flexible control due to its thermal inertia. In this study, the structural parameters and operating parameters of recuperator are considered to quantitatively analyze the law of their influence on equilibration response time. Chebyshev spectrum method has been innovatively applied to the one-dimensional dynamic response model of recuperator. The dynamic response time of recuperator under the condition of temperature variation on the hot side is analyzed. The results show that reducing the thermal inertia of solid wall (by increasing the specific surface area of recuperator) can effectively decrease the equilibrium time. Additionally, the rate of inlet temperature variation should not be too large to reduce the thermal inertia of fluid. The zigzag channel demonstrates better dynamic response characteristic than straight channel. A novel dimensionless formula, based on structure and operating parameters, is proposed to quantitatively characterize and predict the equilibrium time for both straight and zigzag channel, the error is within ±20 %. Moreover, a high-precision neural network is trained to predict the equilibrium time directly. The results provide significant theoretical and application support for alleviating the thermal inertia of PCHE and improving the flexibility of SCO2 system.

A steady-state and dynamic response model for working characteristics prediction of the electromechanical transmission system including eddy-current magnetic coupler

In this paper, a steady-state and dynamic response model is proposed to predict the working characteristics of the electromechanical transmission system including eddy-current magnetic couplers. Considering the influence of mechanical characteristics of motor and load device on the performance of eddy-current magnetic couplers, the system is divided into input and output for kinematic analysis. The expressions of electromagnetic torque versus speed are obtained through layer analysis of the eddy-current magnetic coupler during steady-state and then, the dynamic response model of the system is established by combining the kinematic analysis with the motor, the eddy-current magnetic coupler and three typical loads (constant torque load, quadratic rate load and constant power load). The dynamic characteristics during starting and speed-regulation of the system under constant torque loads are analyzed using the proposed model. The variations of the torque and speed with time of input and output are calculated by numerical integration. Finally, the speed and torque during starting and speed-regulation computed with the dynamic response model are compared with those obtained from the experimental results. The result shows a good agreement.

Isothermal Amplification Using Temperature-Controlled Frequency Mixing Magnetic Detection-Based Portable Field-Testing Platform.

Sensitive magnetic nucleic acid (NA) detection via frequency mixing magnetic detection (FMMD) requires amplified NA samples for which a reliable temperature control is necessary. The feasibility of recombinase polymerase amplification (RPA) was studied within a newly integrated temperature-controlled sensor unit of a mobile FMMD based setup. It has been demonstrated that the inherently generated heat of the low frequency (LF) excitation signal of FMMD can be utilized and controlled by means of pulse width modulation (PWM). To test control performance in a point of care (PoC) setting with changing ambient conditions, a steady state and dynamic response model for the thermal behavior at the sample position of the sensor were developed. We confirmed that in the sensor unit of the FMMD device, RPA performs similar as in a temperature-controlled water bath. For narrow steady state temperature regions, a linear extrapolation suffices for estimation of the sample position temperature, based on the temperature feedback sensor for PWM control. For any other ambient conditions, we identified and validated a lumped parameter model (LPM) performing with high estimation accuracy. We expect that the method can be used for NA amplification and magnetic detection using FMMD in resource-limited settings.

Research on Variable Speed Variable Displacement Power Unit with High Efficiency and High Dynamic Optimized Matching

For the variable speed variable displacement power unit (VSVDPU), achieving power matching between the permanent magnet synchronous motor (PMSM) and the variable displacement plunger pump (VDPP) is the key to reducing system energy consumption. The control method of adjusting the speed of the PMSM and the displacement of the VDPP is the mainstay of current research and application of the VSVDPU. However, the dynamic properties of the PMSM and VDPP have not been balanced, which affects the control effect of the VSVDPU. This paper proposes a control method of variable speed and variable displacement with low energy consumption and high dynamics. The main idea is based on the efficiency model and dynamic response model of the PMSM and VDPP, and the factors that affect the efficiency and dynamic characteristics of the VSVDPU are analyzed. Guided by the multi-objective optimization algorithm, the optimal combination of speed and displacement under specific working conditions is derived. Simulation and experiment results show that the proposed control method is feasible to improve the efficiency and dynamic characteristics of the VSVDPU.

Stretchable-thickness model for dynamic responses of graphene origami reinforced badminton sport plate

In this article, we organize a stretchable-thickness model to present a frequency analysis for a composite plate applicable in badminton court which is reinforced with origami graphene. A higher order kinematic model is extended in this work including three bending, shear, and stretching functions, where the stretching functions is responsible for satisfying the out of plane shear strains and stresses at top/bottom surfaces of the badminton equipment. The sport or composites plate is manufactured from a copper matrix reinforced with graphene origami where the effective material properties are calculated based on micromechanical models as a function of volume fraction and folding degree of graphene origami, material properties of matrix and reinforcement and temperature. The numerical results are presented with changes of volume fraction, folding degree of reinforcement, and thermal loading along the thickness direction. The main novelty of this work is accounting thickness stretching deformation for the analysis of a graphene origami reinforced plate and investigating the responses of graphene origami as a new reinforcement. A verification investigation is presented for approve of the methodology, and solution procedure. An investigation on the order of deformation is presented for various thickness ratio of the badminton sport plate.

Dynamic mechanical response and constitutive model of (Ti37.31Zr22.75Be26.39Al4.55Cu9)94Co6 high-entropy bulk metallic glass

In this work, the mechanical response and fracture characteristics of (Ti37.31Zr22.75Be26.39Al4.55Cu9)94Co6 high-entropy bulk metallic glass (HE-BMG) were investigated in detail over a wide range of strain rates (10−4–105 s−1). The HE-BMG exhibited a negative strain rate sensitivity under uniaxial compression, with the strength showing more significant rate dependence under dynamic conditions. The shear band behavior translated from the dominance of multiple shear bands propagations under quasi-static compression to the rapid propagation of a single shear band to form cracks under dynamic compression. Under dynamic loading, the shearing velocity increased along an arc-shaped displacement path, and the local stress state on the shear fracture surface shifted from compressive-shear to tensile-shear, accompanied by changes in fracture morphologies. The spall strength of HE-BMG decreased as flyer impact speed increased, while the long-term dependence of spall strength on strain rate may be positive. With the increase of impact speed, the main microstructural features of the spalling surface translated from flat regions accompanied by dimples to cup-cone structures. Furthermore, the complete parameters of the Johnson–Holmquist II (JH-2) model for HE-BMG were obtained based on experimental data. Numerical simulations of planar impact, penetration, and hypervelocity impact are in good agreement with experimental results, demonstrating the validity of the JH-2 model parameters. The current work has important guiding value for the application of HE-BMG in space debris protection.

Machine learning predictive model for dynamic response of rising bubbles impacting on a horizontal wall

The integrated behavior of the fluid flow, encompassing variation of some specific response, has received more attention than mere examination of velocity and pressure distributions. A machine learning framework is introduced for the first time to elucidate and predict the complex fluid dynamic responses across varying time scales. For the same class of fluid processes, the dynamic response curves with varying time durations can be defined in terms of time scales and curve shapes. The former is predicted by a single-objective regression model, and the curves are normalized and recovered using time scaling and uniform interpolation. The latter are downscaled by Principal Component Analysis (PCA) and then predicted by a multi-objective regression model. As a novel application, this framework is employed to analyze small bubbles in a Newtonian fluid as they impact a horizontal wall, predicting the velocity, aspect ratio, and position dynamic response of the bubbles. Both Random Forest and Gaussian Process models, based on PCA-driven data processing, exhibit remarkable accuracy in describing and predicting complex dynamics of rising bubbles. Notably, PCA's principal components demonstrate independence and are set through rigorous cross-validation of the training set, rather than dependence on the Cumulative Variance Explained (CVE) values. Furthermore, our framework adeptly extends to predict the complex behavior of multiple bubble bounces by concatenating individual bounce predictions with high efficiency and precision. The proposed framework proves to be a catalyst for comprehending the dynamic response of fluids.

Viscoelastic Rheological Modelling of the Lateral Dynamic Response of Ballasted Railway Tracks

This article presents a novel methodology for evaluating the response of ballasted railway tracks under train-induced loading along lateral directions. The main focus of this study is the development of a computational technique that can capture the lateral response of ballasted railway tracks, which has been ignored in past studies. The proposed approach employs a viscoelastic rheological track model in which three substructure layers are simulated using discrete masses, Hooke’s (springs) and Newtonian elements (dampers). The methodology is successfully validated against the data from experimental and analytical investigations published in the literature. Subsequently, parametric investigations are conducted to study the influence of axle load, train speed, and granular layer thickness on the track response. The results indicate that as the axle load (20 to 40 t) and train speed (70 to 200 km/h) are increased, there is a corresponding increase in track displacements (both lateral and vertical) by 100% and 26.2%, respectively. However, an increase in the granular layer thickness (0.1 to 0.75 m) reduces ballast top displacement (lateral and vertical) by 20–30%. The results demonstrate the capability of the proposed computational approach to capture the transient response of railway tracks and the influence of neighbouring layer properties on the track response. The proposed methodology can be helpful to practising railway engineers for assessing the performance of ballasted railway tracks along lateral directions.

Novel analytical approach for vertical dynamic response of floating pile groups based on a fictitious soil pile model

A novel analytical model for the vertical dynamic response of floating pile groups is established based on a fictitious group soil pile model (FGSP). Analytical solutions of the pile-to-pile interaction factor and dynamic impedance for the FGSP are obtained by combining the superposition and matrix transform methods. The obtained solutions are then validated by comparison with model test results and published analytical solutions. A numerical analysis is further performed to examine the effects of pile and soil parameters on the dynamic response of the FGSP. Results indicate that the effects of pile end soil on the pile-to-pile interaction factor and dynamic impedance of the FGSP are significant. Consequently, the established novel analytical model has better applicability to the dynamic problems of floating pile groups due to its consideration of the effects of pile end soil.

KT-Biologics I (KTB1): A dynamic simulation model for continuous biologics manufacturing

The pharmaceutical industry's shift towards biological therapeutics has led to a transition from conventional batch production to continuous manufacturing. This change highlights the crucial need for effective process monitoring and control strategies to ensure consistent product quality and stability. Open-source benchmark simulation models have become essential tools for refining these processes, offering a platform for testing research hypotheses. This study uses the production of Lovastatin as a case study for continuous biopharmaceutical production. A comprehensive dynamic model covering upstream and downstream components provides an integrated perspective of the production process. The study introduces a basic control system emphasizing realistic sensor and actuator integration to enhance simulation accuracy. It assesses the benchmark through open-loop and closed-loop simulations, offering an in-depth analysis of the KTB1 model's dynamic response and functionality. KTB1 represents a model-driven decision support tool that enables the evaluation of monitoring strategies, process design, process optimization, and control for biomanufacturing.