Dynamic Equivalent Model Research Articles

Investigation of the Feasibility of the Dynamic Equivalent Model of Large Photovoltaic Power Plants in a Harmonic Resonance Study

In recent years, there have been several harmonic resonance accidents around the world that involve renewable energy power plants. The frequency scanning method is the most widely used technique in engineering practice to evaluate the severity of resonance due to its simple operation and clear physical meaning. However, when establishing electromagnetic transient simulation models and conducting frequency scans, a single generation unit or a few renewable generation units are usually used to represent the original power plant for the purpose of reducing model complexity and improving the simulation efficiency. Such a practice has been found to be effective in dynamic studies around the fundamental frequency. However, its feasibility in harmonic resonance studies has not yet been fully investigated. Because of this research gap, a feasibility study is conducted in this paper by using a real-life photovoltaic power plant. The detailed harmonic model of the plant is first established using the harmonic linearization method, and the equivalent harmonic model is then developed using the power loss conservation method. The feasibility of the equivalent model was investigated in detail, and the impact of the different impedance models on the resonance analysis was analyzed. The results indicate that the conventional dynamic equivalent model can effectively reflect the harmonic resonance characteristics of photovoltaic power plants. Furthermore, a more simplified model that ignores the inductance of the collector line is recommended in this paper to further reduce the modeling complexity.

In Situ Visualization and Analysis of Oil Starvation in Ball Bearing Cages

This article presents an investigation into oil starvation in different cage pocket shapes of a horizontally mounted ball bearing. A counter-rotating angular contact ball bearing test rig (CRACTR) was used to visualize the oil distribution inside specially manufactured transparent bearing cages using detailed images from a high-speed camera. Three different cage types were investigated using various oils dyed with ultraviolet dye. The identification of oil and air regions elucidated the oil distribution in the cage pocket and the formation of oil–air striations on the ball surface under various operating conditions. The experimental results demonstrated that raceway motion, ball submersion level, oil properties, and cage pocket shape influenced oil starvation inside the bearing cage. ANSYS Fluent software was also used to develop an equivalent two-phase computational fluid dynamics (CFD) model for the test bearing. Results from the CFD model corroborate well with the experimentally observed oil distribution for all test cages and establish the strong influence of cage geometry on oil starvation and bearing lubrication.

A study of the Effect of the Weight of a Fixed-Bed Adsorption Column for Removal of Ferrous Iron (Fe2+) in Groundwater using Activated Carbon

The study involves the simulation of a fixed-bed adsorption column with COMSOL Multiphysics software. The bed of the Adsorption column was filled with only activated carbon to absorb the ferrous Iron. The equilibrium and dynamic model equations of the Langmuir adsorption isotherm and fixed-bed adsorption column were used and inputted into the COMSOL Multiphysics software. Line graphs and 2D surface plots were generated from the software after the simulation. Simulated result showed that increase in the weight of the bed could increase the bed performance and indicated that about 28 days’ operative performance of the bed could be achieved for a bed weight of 1500kg and particle size of 0.001m.

Simple parameterization method using differential evolution algorithm to estimate state of charge for Li‐ion batteries and packs for electric vehicles

AbstractAn accurate method is proposed to measure the electrical parameters describing the experimental charge‐discharge curves of Li‐ion batteries and a pack through an equivalent electric dynamic model based on heuristic optimization algorithms (eg, differential evolution approach). The accuracy of these parameters is critical for on‐board state of charge and Health (SOH) estimations of numerous applications and devices. The procedure is constructed, based on the simple Thévenin electrical model. Charge‐discharge experimental curves collected for different chemistry and capacity batteries are described with the model, revealing better estimation results with respect to other algorithms such as impedance‐based methodologies (decreasing the error until 64.19%) and particle swarm optimization based approaches (decreasing the error until 94.02%). The proposal was assessed with different chemistries, capacities and with a 28 battery pack (LiFeMnPO, 100 Ah) used in an electric vehicle.

Cylindrical roller bearing cage pocket lubrication

The objectives of this investigation are to determine the effects of cage pocket conformality on lubrication in a cylindrical roller bearing (CRB) cage. A custom Bearing Cage Friction Test Rig (BCFTR) was configured with a sealed enclosure to emulate a lubricant bath environment. The enclosure was designed to accommodate CRB raceway segments and swappable cage pockets with adjustable roller-pocket clearance. Three transparent cage segments were fabricated with differing pocket conformality with respect to the roller surface. A high-speed camera was used to visualize the in-situ lubricant flow within the roller-pocket contact for all cage types. An equivalent two-phase computational fluid dynamics (CFD) model was developed using Ansys Fluent software. The CFD results corroborated well with the experimentally observed trends of lubricant distribution and cage pocket friction. The findings demonstrated that the impact of pocket conformality was two-fold. The least conformal pocket design experienced minimum pocket friction. However, the same design introduced challenges with retaining lubricant at the roller-pocket contact and increasing air entrapment in the oil.

Power quality assessment in different wind power plant models considering wind turbine wake effects

Abstract The intense increase in the installed capacity of wind farms has required a computationally efficient dynamic equivalent model of wind farms. Various types of wind-farm modelling aim to identify the accuracy and simulation time in the presence of the power system. In this study, dynamic simulation of equivalent models of a sample wind farm, including single-turbine representation, multiple-turbine representation, quasi-multiple-turbine representation and full-turbine representation models, are performed using a doubly-fed induction generator wind turbine model developed in DIgSILENT software. The developed doubly-fed induction generator model in DIgSILENT is intended to simulate inflow wind turbulence for more accurate performance. The wake effects between wind turbines for the full-turbine representation and multiple-turbine representation models have been considered using the Jensen method. The developed model improves the extraction power of the turbine according to the layout of the wind farm. The accuracy of the mentioned methods is evaluated by calculating the output parameters of the wind farm, including active and reactive powers, voltage and instantaneous flicker intensity. The study was carried out on a sample wind farm, which included 39 wind turbines. The simulation results confirm that the computational loads of the single-turbine representation (STR), the multiple-turbine representation and the quasi-multiple-turbine representation are 1/39, 1/8 and 1/8 times the full-turbine representation model, respectively. On the other hand, the error of active power (voltage) with respect to the full-turbine representation model is 74.59% (1.31%), 43.29% (0.31%) and 7.19% (0.11%) for the STR, the multiple-turbine representation and the quasi-multiple representation, respectively.

Tuned mass damper on spacecraft reaction wheel assembly

Considering the wide frequency range and time-varying characteristics of reaction wheel assembly (RWA) micro-vibrations, an embedded tuned mass damper (TMD) was proposed herein to reduce the influence of the RWA micro-vibration effect on spacecraft. First, dynamics model of the RWA and a mechanical model of the angular contact ball bearing were constructed, and the time-varying characteristics of the RWA were theoretically analyzed. Based on single- and multiple-degree-of-freedom vibration absorption dynamics models, it was shown that the TMD could be applied to the vibration suppression of the RWA’s multi-modal and time-varying state by changing the design parameters of the TMD. Based on the RWA single-degree-of-freedom equivalent dynamics model, the effects of the TMD natural frequency and damping on the displacement amplitude ratio of the RWA were analyzed, and the sensitivities of the RWA resonance peak amplitude and resonance frequency to the two parameters were analyzed by the Sobol sensitivity analysis method. Then, according to the analysis results, the structural design of the TMD in the RWA was guided, and a test platform was built to obtain the RWA micro-vibration data. Finally, a normalized amplitude-frequency response identification algorithm was used to eliminate the effects of non-linearities in the experimental data and to identify the RWA dynamics in a time-varying state, thus obtaining the RWA amplitude–frequency response curve and verifying the results of the theoretical analysis. Theoretical and experimental data showed that the addition of a TMD structure with variable damping and stiffness within the RWA allowed for micro-vibration suppression for arbitrary modes and improved the RWA vibration characteristics. This could provide convenience for different specifications of RWA vibration suppression as well as reference for further research on the effective application of TMDs in RWAs.

A Compact Bandwidth and Frequency-Range Reconfigurable CM Filter Using Varactor-Loaded Dual-Slot-Based Defected Ground Structure

A reconfigurable common-mode (CM) filter with a wide tunable bandwidth and frequency-range is proposed in this article. The filter adopts four compact dual-slot-based defected ground structure (DGS) cells to achieve a wide suppression of CM noise. To simplify the design, only one varactor and one dc-blocking capacitance are loaded on one DGS cell directly, which retains the original structure of the DGS cell. A wide continuously adjustable frequency range and bandwidth can be achieved when different voltages are applied to different varactors. A dynamic equivalent circuit model is built to explain the filter's working principle, which is helpful to obtain the filtering characteristics under different varactor parameters quickly and accurately. In order to verify the feasibility of the scheme, a DGS-based filter with an area of 19 mm × 9.2 mm is implemented under the microstrip line. The simulated results show the filter can achieve a continuously tunable CM suppression of frequency range from 1.9 to 7.3 GHz, and a tunable bandwidth using different voltage supplies. Good agreement between full-wave simulation and measured results is observed.

Research on dynamic characteristics of gun turret under launching load

The purpose of this study is to further study the dynamic characteristics of gun turret under firing load. Firstly, the relative motion between inner ring and outer ring was decomposed into axial translational motion, radial translational motion and rotational freedom in two orthogonal radial planes in order to solve the problem of large number of ball bearings and complex contact calculation in the actual structure of turret ring. Then, the equivalent dynamic mathematical model of turret ring was established. Based on the finite element method, the turret ring is equivalent to Bushing with body-body connection type, Multi-point constraints algorithm and Deformable Behavior attribute. The equivalent stiffness of the turret ring is set as linear stiffness, and the turret dynamic model is established. The dynamic response simulation of the turret under the action of firing load was carried out. The acceleration sensor was arranged at the left trunnion position of the turret, and the acceleration generated by the transient force during firing was measured at the left trunnion position. The results showed that the test value of the acceleration at the left trunnion position was 1304.38m /s2,the simulation value of the turret dynamic model is 1425 m/s2, and the error is 8.46%, which verifies the accuracy of the turret dynamic model and indicates that the turret dynamic model can reflect the dynamic characteristics of the turret well.

Dynamic modeling and analysis of wheeled wall-climbing robot

The dynamic model is very important for the design of a wall-climbing robot and the final realization of its motion performance. The general process of dynamic modeling and expression equations of dynamic models are given for the wheeled wall-climbing robot based on the modeling method of the Udwadia-Phohomsiri equation. Firstly, the dynamic model of an unconstrained four-wheeled wall-climbing robot is constructed. Then, a trajectory constraint is defined, the rationality of the dynamic model for the unconstrained wall-climbing robot is verified by numerical simulation. Again, constraint equations under the conditions of synchronous toothed belt structure, non-lateral motion and nonslip between the driving wheel and the wall surface are established. Finally, the dynamic model of the unconstrained wall-climbing robot is gradually combined with constraint equations, and numerical simulations are implemented. Numerical simulation results verify the correctness of the wall-climbing robot model and constraint models, as well as the effectiveness and advantages of the modeling method.

Optical solitons with DNA dynamics arising in oscillator-chain of Peyrard–Bishop model

In this paper, we introduce the Noether approach for studying the Peyrard–Bishop (PB) DNA dynamic model equation. The Jacobi elliptic function expansion (JEFE) method is used to analyze this model. The obtained soliton solutions are hyperbolic, trigonometric, and rational functions. The dynamics of the obtained solutions conform to the properties of shock waves, periodic waves, solitary waves, double periodic waves, and rational solutions. A comparison between the results obtained by the JEFE method and the results existing in the literature shows that our results are more general, and novel, and have never been reported earlier. The wave profiles are investigated by Wolfram Mathematica simulations for the physical wave behavior.

Evaluation of Equivalent Dynamic Active Distribution Network Models with Individual and Aggregated Consideration of Grid Forming Converters

Detailed active distribution network modeling in the context of stability studies of future power systems can be avoided by applying complexity‐reduced equivalent dynamic models. Previous work developed an approach to derive such equivalent dynamic network models of systems dominated by grid following and grid forming converters. Nevertheless, this approach lacks an investigation of the aggregation of multiple grid forming converters to one equivalent component. Also, the approach needs to be evaluated for a closed ring topology to substantiate its validity independent of the detailed network topology. This work applies and validates the developed approach on active distribution networks in the context of three scenarios. The detailed and equivalent network models are simulated for three events and the results are used to compare the models with respect to accuracy and complexity. The derived equivalent dynamic network models with an individual representation of grid forming converters reproduce the dynamic behavior of the corresponding detailed networks very well. The aggregation of grid forming converters results in an adequate reproduction of the detailed network's dynamic behavior under the constraint of aggregating only neighboring grid forming converters of one branch. This allows for the consideration of the detailed network's topology in the corresponding equivalent dynamic model.

Mobility simulation modelling of wheeled military vehicles under off-road traffic conditions

Ensuring the mobility of military vehicles (MV) is especially urgent in the conditions of modern hybrid wars and determines the growth of requirements for their designs. The influence of cross-country ability indicators, suspension and tire characteristics on limiting the maximum possible off-road speeds was analyzed. It is shown to limit the maximum speeds depending on the maximum permissible values of the vibrational loads level on the human body, disturbed by irregularities, the off-road micro-profile and the corresponding transmission functions of the suspension and tires.
 An analysis of literary sources, as well as standards regarding the methods of evaluating the movement mobility, determining the limit vibrational loads from the point of view of limiting the maximum speed of movement of the MV sample, was carried out. To study the influence of the suspension on the vibro-oscillatory properties of the MV sample, taking into account that vertical vibrations are the determining factors in the formation of vibro-oscillatory loads (the specific significance of longitudinal and transverse vibrations in total is within 20%), a dynamic equivalent model adequate to the physical process was built for a car with a 4x4 wheel formula. According to the specified model, the structure of simulated computer modeling of the wheeled vehicles movement in the MATLAB Simulink software environment was worked out.
 The possibility and parameters of the deterministic setting of the heights of irregularities of the off-road micro-profile with the possibility of operational change of both the characteristics of the suspension/tires and the type and condition of the off-road were worked out. Adequacy of the model was previously evaluated by evaluating the degree of reproduction of known experimental studies and determines the feasibility of forming a typical section of the off-road micro-profile for evaluating the effectiveness of the suspension.

Research on Dynamic Modeling and Parameter Identification of the Grid-Connected PV Power Generation System

With the increasing proportion of renewable energy in the new power system, the grid-connected capacity of photovoltaic (PV) units shows an obvious upward trend, but its dynamic behavior under different penetration rates significantly affects the transient stability of the power system, so it is crucial to establish a dynamic model that meets the actual working conditions and select a suitable parameter identification method. Therefore, in this paper, based on the electromechanical transient characteristics of the grid-connected PV power generation system, the corresponding dynamic discrete equivalent model is established, and the simulation platform of the grid-connected PV power generation system is built in MATLAB/Simulink to study the adaptability of the dynamic discrete equivalent model of the grid-connected PV power generation system from the single and multiple scenarios using the ordinary least squares (OLS) and bat algorithm (BA) while comparing the generalization ability of the parameters identified by the two methods to the model. The simulation results show that the generalization ability of the parameters identified by the OLS and BA for the model in the single scenario is better, indicating that the model has good adaptability; the generalization ability of a set of general parameters identified by the BA for the model in the multiple scenarios is better than that of the OLS, indicating that the parameters identified by the BA have better adaptability. In conclusion, the dynamic discrete equivalent model of the grid-connected PV power generation system proposed in this paper can accurately reflect the dynamic characteristics of the grid-connected PV power generation system, and the parameters identified by the BA are more generalized than the OLS.

Development of a Dynamic Gray‐Box Model of a Fermentation Process for Spore Production

AbstractFermentation processes are difficult to describe using purely mechanistic relations as the underlying biochemical phenomena are complex and often not fully understood. In order to cope with this challenge, we developed an approach to augment standard dynamic model equations by data‐based components that are fitted to data using machine learning techniques, which results in dynamic gray‐box models. This methodology is applied here to the batch fermentation process of the sporulating bacterium Bacillus subtilis, using experimental data from a lab‐scale fermenter. The key step in developing the model is the estimation of a training set for the machine learning submodels. The quality of the resulting model is analyzed, and the predictions are compared with real data.

Enhanced multi-state estimation methods for lithium-ion batteries considering temperature uncertainties

Due to their high energy density and minimal emissions, lithium-ion batteries are frequently employed in electric vehicles (EVs). Accurate estimation of the micro-parameters, state of charge (SOC), and state of health (SOH) are a few primary monitoring functions of the battery management system (BMS) to increase the battery's efficiency and safety under various operating conditions. This paper proposes a SOC and SOH co-estimation method by adopting an ensemble empirical mode decomposition method with adaptive noise and an autoencoder (EEMDA) to extract, decompose, and reconstruct the full-scale charging voltage and current data for a dual extended Kalman filter (DEKF) with multi-parameter and time-scale updates for accurate estimation based on a variable forgetting factor limited memory recursive least squares (VFF-LMRLS) method. The VFF-LMRLS method is used to solve the data saturation phenomenon and identify the battery's characteristic micro-parameters based on a proposed dynamic migration second-order resistor-capacitor equivalent circuit model under different operating states. Battery tests are conducted at temperatures ranging from −10 to 50 °C under complex working conditions. Using the VFF-LMRLS method, the effects of different temperatures on the micro-parameters are discussed. The SOC and SOH results of the proposed EEMDA-DEKF method based on the dynamic migration battery model show that the mean absolute error and root mean square error metrics have the least values of 0.0233% and 0.0252%, which signify an optimal performance improvement of 93.26% and 93.66%, respectively, compared to the conventional DEKF method. Based on the experimental results and analyses, the proposed method has a high degree of accuracy and robustness, which makes it feasible for battery monitoring and prognostic BMS applications.

Self-tuning vibration reduction study of magnetic fluid rolling-ball damper based on PSO-FUZZY-PID

For towering structures under complex time-varying excitation, the tuned magnetic fluid rolling-ball dampers (TMFRBD) cannot achieve self-tuning damping. In this paper, considering the operating characteristics of the TMFRBD, a damper self-tuning control algorithm, namely particle swarm optimization (PSO)-FUZZY-PID, is proposed for real-time adjustment of the intrinsic frequency of TMFRBD, which can greatly improve the damping effect, namely self-tuning magnetic fluid rolling-ball dampers (STMFRBD). Firstly, the equivalent dynamics model of the damping system is established, deriving the structural dynamic amplitude response as a function of the excitation frequency to structural frequency ratio. Different frequency tracking schemes of the damper are compared and analyzed. Then magnetic field simulations and magnetic fluid magnetic property measurements are performed for the dampers, respectively. Secondly, the self-tuning PSO-FUZZY-PID control algorithm is designed to improve the damping performance of STMFRBD under time-varying excitation by optimizing factors of the FUZZY-PID controller with PSO. To confirm the effectiveness of the damper self-tuning control algorithm, the frequency tracking of dampers with different control algorithms under time-varying excitation is compared. The results show that the damper’s frequency can be tuned quickly and accurately tracking excitation frequency by PSO-FUZZY-PID. Finally, the simulation and experimental results of STMFRBD and passive mass damper (PMD) under different loads are analyzed, and the structural amplitude response is analyzed using the Hilbert-Huang transform (HHT). In addition, the damping of STMFBD and TMFBD under different loads is compared. The results show that STMFRBD has better vibration-damping performance than PMD and TMFRBD.

Multi-harmonic equivalent dynamic model of the gyroelastic repetitive truss with nonlinear joints

Multi-harmonic equivalent dynamic model of the gyroelastic repetitive truss with nonlinear joints

Performance-based model-free adaptive finite-time control for shape memory alloy actuated swing platform

Shape memory alloy (SMA), a kind of smart material, can be used as an actuator in many fields; however, its strong nonlinearity and parameter uncertainty hinders its application in high-tracking accuracy tasks. This paper addresses the tracking control problem of the SMA actuated swing platform suffering from completely unknown nonlinear model information and prescribed finite-time error constraints. First, the equivalent dynamic linearization model of the swing platform is established, and the unknown disturbance is estimated and compensated by the extended state observer. Meanwhile, a novel discrete-time performance function is proposed, and the prescribed finite-time tracking error constraints are transformed into a new equivalent unconstrained task. Second, the model-free adaptive sliding mode controller is designed using the unconstrained error, and the complete control law, including sliding mode control law and equivalent control law, is derived. Third, the stability of the closed-up swing platform is guaranteed by employing the Lyapunov method. Finally, experiments reveal that the proposed method is preferable.

Design and modeling of a novel triple-magnet magnetic dynamic vibration absorber

A novel Triple-magnet Magnetic Dynamic Vibration Absorber (TMDVA) with Eddy Current Damping (ECD) and Coulomb damping is proposed in this paper. A multi-storey structure is selected as the vibration reduction object. First, the equivalent dynamics model of the TMDVA multi-storey structure vibration reduction system is established. Then the nonlinear magnetic force model is built according to the magnetizing current theory. Next, an ECD accurate calculation model is developed and derived based on Faraday’s law of electromagnetic induction. Because of the model, the ECD coefficient can be designed and adjusted arbitrarily. The full text indicates that adjusting the ECD coefficient properly can not only improve the vibration reduction effect of the TMDVA, but also reduce the sensitivity of the vibration reduction effect to the excitation amplitude as well as enhance the broadband vibration reduction performance and the robustness of the TMDVA. With its simple structure, the TMDVA is easy to be implemented and miniaturized. And the low frequency vibration reduction effect of the TMDVA is better than other existing magnetic dynamic vibration absorbers. Taken together, the TMDVA has potential application value in passive vibration reduction of engineering structures.