Showing papers on "Inertia published in 2023"
TL;DR: In this paper , the impact of integration of inverter-based renewable energy sources (RESs) on grid frequency response through eigenvalue analysis of low-inertia power grids is assessed.
15 citations
TL;DR: In this paper , the authors used the BALEEN II model and the inertia model to assess the eastern North Pacific stock of gray whales and found that catch up to 256 animals per annum will lead to population decline.
Abstract: Bayesian assessments of the eastern North Pacific stock of gray whales are conducted using the standard BALEEN II model and the inertia model developed by Witting (2000; 2001; 2003). The analyses confirm the increase in gray whale population size since 1968, but indicate that catches up to 256 animals per annum will lead to population decline if the inertia model is correct. However, analyses based on the standard BALEEN II model with a starting year of 1930 or 1968 fit the calf count data better than the inertia model, and indicate a population at its (current) equilibrium level and that the current catches are sustainable. The results of both the BALEEN II model and the inertia model are sensitive to the choice of the functional form used to represent density-dependence and those of the inertia model to the starting year for the analyses.
12 citations
TL;DR: In this article , a fuzzy gain scheduling proportional-integral-differential (PID) controller based on dynamic characteristics of a hybrid robot named TriMule is presented, which can reduce the effect of dynamic characteristics on control system, thus ensuring satisfactory control performance under any configuration in the task workspace.
8 citations
TL;DR: In this article , a modified couple stress model was proposed to capture micro-turns due to micro-particles' rotations which could be essential for microstructural materials and/or at small scales.
8 citations
TL;DR: In this article , a unified calculation method was proposed to identify the equivalence of inertia and damping under various ratios of g , and the simulation and experiment results in various cases verify the effectiveness of the proposed equivalent damping and inertia calculation method.
Abstract: Inertia and damping are the core index of the estimation of power system stability. Existing analysis to the support of inertia and damping are focused on the improvement of system stability as well as parameters tuning of virtual inertia and virtual damping but rarely involved in the quantitative calculation of level of inertia and damping under a certain condition. Based on this background, this article puts forward a unified calculation method to identify the equivalence of inertia and damping under various ratios of Rg / Xg . In addition, the quantity of improved inertia and damping support enabled by virtual inductance control are estimated by the derived calculation model of equivalence. The calculated mathematical model of equivalence of inertia and damping is well verified by the overlapped eigenvalues distribution. Besides, the negative synchronous power will inevitably influence the aperiodic loss of synchronization (ALoS) of power system caused by the large virtual inductance. Therefore, a solution should be derived to make a compromise between oscillation damping and ALoS by tuning the value of virtual inductance. Finally, the simulation and experiment results in various cases verify the effectiveness of the proposed equivalent damping and inertia calculation method as well as virtual inductance control.
5 citations
TL;DR: In this paper , the authors comprehensively evaluate the ESS candidates for inertial provisioning and present a comprehensive comparison of the technological economics of various ESSs for inertia emulation, followed by a novel weighted metric to evaluate the suitability of each ESS for inertia provision.
5 citations
TL;DR: In this paper , the local lubrication mechanisms of textures in journal bearings were analyzed from microflow perspective, while considering the interactions between textures and the film formation in the whole bearing, and the results showed that placing textures downstream of the high-pressure region leads to a reduced friction force, with a less severe loss of load-carrying capacity.
Abstract: Adequately designed and positioned surface textures are recognized as a promising way to increase load-carrying capacity and reduce frictional losses of journal bearings. The aim of this work is to analyze the local lubrication mechanisms of textures in journal bearings from microflow perspective, while considering the interactions between textures and the film formation in the whole bearing. For this purpose, hydrodynamic lubrication models of textured journal bearings are built. The results show that placing textures downstream of the high-pressure region leads to a reduced friction force, with a less severe loss of load-carrying capacity. The effects of textures on the load-carrying capacity include the positive micro-hydrodynamic pressure effect and the negative effect caused by the discontinuity of the high-pressure region. The micro-hydrodynamic pressure of textures can be generated on one hand by limiting pressure drop (cavitation) in the divergent gap and on the other hand by the inertia effect. For the friction, the vortex inside textures affects the friction force by influencing the maximum shear stress at the minimum oil film. In turn the vortex is influenced by the bearing lubrication film. The research provides the fundamental reference and theoretical basis for the design and optimization of textured journal bearings.
5 citations
TL;DR: In this paper , the authors consider a spatial public goods game model where inertia is considered during the imitation process, and they find that inertia hinders cooperation, which can be explained by the decelerated coarsening process under weak selection.
5 citations
TL;DR: In this paper , the authors proposed a kinetic model to describe the condition under which slippage can occur between a slider and a stator, where the transient current absorbed by the multilayer actuators in the stator during slip time defines the sliding behavior of the slider.
Abstract: In an inertia-type motor, a piezoelectric multilayer actuator is espoused to a transient vibration velocity as high as 1.0 m/s during slip time. This vibration velocity makes the inertia-type motors dynamic but not quasi-static. We propose a kinetic model to describe the condition under which slippage can occur between a slider and a stator. The transient current absorbed by the multilayer actuators in a stator during slip time defines the slippage behavior of the slider. A new thickness-mode force factor expression (A33), which is a relation between the transient current and the transient vibration velocity, is described in electrical domain. Impact force acting on a friction coupler produced by the actuators in the stator is proportional to the rate of change in the transient current during the sliding time. Additionally, we present the structure and characteristics of a two-phase inertia-drive-type piezoelectric motor, on which the proposed model was evaluated. Driving the multilayer actuators with truncated and mirrored sawtooth signals enhances the system dynamics. As one actuator expands and the other shrinks, their respective hysteretic nonlinearities are canceled. The motor operating frequency can be as great as 30 kHz and typically load characteristics are unloaded velocity greater than 16.0 mm/s and generated force higher than 3.0 N.
4 citations
TL;DR: Wang et al. as discussed by the authors proposed an improved particle swarm optimization model with dynamic adjustment of inertia weight (DWPSO-SVM) to optimize the parameters of the SVM and achieved better classification performance compared with other state-of-the-art algorithms.
Abstract: Support vector machine (SVM) is a widely used and effective classifier. Its efficiency and accuracy mainly depend on the exceptional feature subset and optimal parameters. In this paper, a new feature selection method and an improved particle swarm optimization algorithm are proposed to improve the efficiency and the classification accuracy of the SVM. The new feature selection method, named Feature Selection-score (FS-score), performs well on data sets. If a feature makes the class external sparse and the class internal compact, its FS-score value will be larger and the probability of being selected will be greater. An improved particle swarm optimization model with dynamic adjustment of inertia weight (DWPSO-SVM) is also proposed to optimize the parameters of the SVM. By improving the calculation method of the inertia weight of the particle swarm optimization (PSO), inertia weight can decrease nonlinearly with the number of iterations increasing. In particular, the introduction of random function brings the inertia weight diversity in the later stage of the algorithm and the global searching ability of the algorithm to avoid falling into local extremum. The experiment is performed on the standard UCI data sets whose features are selected by the FS-score method. Experiments demonstrate that our algorithm achieves better classification performance compared with other state-of-the-art algorithms.
TL;DR: In this article , the authors proposed a kinetic model to describe the condition under which slippage can occur between a slider and a stator, where the transient current absorbed by the multilayer actuators in the stator during slip time defines the sliding behavior of the slider.
Abstract: In an inertia-type motor, a piezoelectric multilayer actuator is espoused to a transient vibration velocity as high as 1.0 m/s during slip time. This vibration velocity makes the inertia-type motors dynamic but not quasi-static. We propose a kinetic model to describe the condition under which slippage can occur between a slider and a stator. The transient current absorbed by the multilayer actuators in a stator during slip time defines the slippage behavior of the slider. A new thickness-mode force factor expression (A33), which is a relation between the transient current and the transient vibration velocity, is described in electrical domain. Impact force acting on a friction coupler produced by the actuators in the stator is proportional to the rate of change in the transient current during the sliding time. Additionally, we present the structure and characteristics of a two-phase inertia-drive-type piezoelectric motor, on which the proposed model was evaluated. Driving the multilayer actuators with truncated and mirrored sawtooth signals enhances the system dynamics. As one actuator expands and the other shrinks, their respective hysteretic nonlinearities are canceled. The motor operating frequency can be as great as 30 kHz and typically load characteristics are unloaded velocity greater than 16.0 mm/s and generated force higher than 3.0 N.
TL;DR: In this article , a general, unified HE dynamic model for the electrolyzer stack circuit, power-electronics interface (PEI), and relevant converter-level control loops is proposed.
Abstract: This article presents the modeling foundations to study the capabilities of hydrogen electrolyzers (HEs) to provide frequency control ancillary services (FCAS), including virtual inertia and primary and secondary frequency response. To do so, we propose a general, unified HE dynamic model for the electrolyzer stack circuit, power-electronics interface (PEI), and relevant converter-level control loops. The equivalent circuit of the stack is derived from its current transfer function, with poles and zero obtained from its step response characteristics (e.g., rise/settling time). The stack model also considers relevant physical nonlinearities and downstream hydrogen buffer/process operational constraints. The PEI control loops account for stack model parameters, hydrogen production operational constraints, stack temperature dynamics, and active power reference generation strategy for contingency and regulation frequency support services. Further, we propose a virtual synchronous machine (VSM) control approach to study the VSM HE capabilities to also provide virtual inertia response. We apply the modeling to both alkaline and proton exchange membrane (PEM) technologies, including design of appropriate control schemes. Finally, we assess the FCAS performance of alkaline and PEM HEs via dynamic simulation of the Australian south-east interconnection in a 50%-renewable scenario, also discussing comparison and cooperation with battery energy storage systems.
TL;DR: In this paper , the authors proposed an adaptive virtual synchronous generator (VSG) control to improve the dynamic characteristic of active power at a certain capacity, and the effect of inertia under grid disturbance by transfer function was analyzed.
TL;DR: In this article , an experimental system was initiated to study the oscillatory Kelvin-Helmholtz (K-H) instability of a planar liquid sheet was experimentally investigated in the presence of axial oscillating gas flow.
Abstract: Abstract The oscillatory Kelvin–Helmholtz (K–H) instability of a planar liquid sheet was experimentally investigated in the presence of an axial oscillating gas flow. An experimental system was initiated to study the oscillatory K–H instability. The surface wave growth rates were measured and compared with theoretical results obtained using the authors’ early linear method. Furthermore, in a larger parameter range experimentally studied, it is interesting that there are four different unstable modes: first disordered mode (FDM), second disordered mode (SDM), K–H harmonic unstable mode (KHH) and K–H subharmonic unstable mode (KHS). These unstable modes are determined by the oscillating amplitude, oscillating frequency and liquid inertia force. The frequencies of KHH are equal to the oscillating frequency; the frequency of KHS equals half the oscillating frequency, while the frequencies of FDM and SDM are irregular. By considering the mechanism of instability, the instability regime maps on the relative Weber number versus liquid Weber number (Werel–Wel) and the Weber number ratio versus the oscillating frequency (Werel/Wel–$\varOmega$s2) were plotted. Among these four modes, KHS is the most unexpected: the frequency of this mode is not equal to the oscillating frequency, but the surface wave can also couple with the oscillating gas flow. Linear instability theory was applied to divide the parameter range between the different unstable modes. According to linear instability theory, K–H and parametric unstable regions both exist. However, note that all four modes (KHH, KHS, FDM and SDM) corresponded primarily to the K–H unstable region obtained from the theoretical analysis. Nevertheless, the parametric unstable mode was also observed when the oscillating frequency and amplitude were relatively low, and the liquid inertia force was relatively high. The surface wave amplitude was small but regular, and the evolution of this wave was similar to that of Faraday waves. The wave oscillating frequency was half that of the surface wave.
TL;DR: In this paper , the effects of the magnetic field and inertia on the onset of thermal convection in a horizontal bidispersive porous layer, rotating about a vertical axis, are analyzed.
Abstract: Effects of the magnetic field and inertia on the onset of thermal convection in a horizontal bidispersive porous layer, rotating about a vertical axis, are analyzed. The Darcy equation with same temperature in the micro- and macrophases is used to characterize the fluid motion. The Vadasz number is taken into account in a generalized Darcy equation for the macrophase. The eigenvalue problem obtained from the linear stability analysis is solved analytically for free–free boundaries. Moving one step further from the traditional linear stability analysis, machine learning tools are introduced in this paper to include the effect of multiple parameters on the marginal state of the system. Machine learning techniques have been implemented to identify the mode of instability with respect to different parameters. In particular, classification algorithms, namely, Artificial Neural Networks (ANN) and Support vector machine, are used to examine the onset of oscillatory convection and stationary convection. The required data for training of the algorithms are generated from the results of linear stability analysis. It is found that ANN with the sufficient number of hidden layers along with good choice of training dataset can predict the mode of instability even on the small variation in a given parameter. The combined effect of rotation, magnetic field, and inertia is to reduce the oscillatory mode of instability; hence, the system exhibits the steady mode of instability for a significant region in the three dimensional space comprising the Taylor number, the Hartman number, and the Vadasz number.
TL;DR: In this paper , the authors analyzed the influence of thermal pipelines inertia on a small-scale solar concentrator of 20 kW with a phase-change material thermal storage, and they found that the pipeline inertia conveyed delays in the start-up sequence of the system and decreased the temperatures of heat transfer fluids until the steady state is reached.
Abstract: Solar Heat for Industrial Processes (SHIP) is one of the most promising alternatives to decarbonize the industry. The present work aims to analyze the influence of thermal pipelines inertia on a small-scale solar concentrator of 20 kW with a phase-change material thermal storage. Two dynamic simulations for this SHIP system integrated into a tube steel factory in Romania were developed with Dymola software: one of them considered the thermal inertia of the pipelines and the other did not. By comparing the simulation results, we have found that the pipeline inertia conveyed delays in the start-up sequence of the system and decreased the temperatures of heat transfer fluids until the steady state is reached. Furthermore, the thermal inertia decreased the total energy produced. Other researchers have also found delays due to the inertia of the pipelines, but the delays were lower than ours. The difference in the delays may be due to the small scale of the SHIP system analyzed in the present work. Finally, we can conclude that dynamic simulation became important in SHIP systems because of the difference found with the non-inertia simulation.
TL;DR: In this paper , the effects of virtual inertia and reactive damping values on the small signal stability of the system were investigated, and an optimal allocation model and method for virtual inertia used to improve the small disturbance stability was proposed, and the results showed that the optimization procedure could improve the damping ratio of the interval oscillation mode while ensuring the system frequency.
Abstract: Abstract The doubly-fed induction generator (DFIG) with virtual inertia control and reactive damping control gives a renewable energy generation system inertia and damping characteristics similar to those of a thermal power plant, and the parameters of the control strategy have a direct impact on the small-signal stability of the system. This paper firstly introduces the operating characteristics and control strategies of DFIG-based damping control and virtual inertia control, establishes a small-signal model of the control-based DFIG integrated interconnected system, and investigates the effects of virtual inertia and reactive damping values on the small-signal stability of the system; then, the maximum damping ratio of the interval oscillation mode in small disturbance analysis is taken as the optimization objective, and the control parameters are the optimization variables. An optimization method of inertia and damping parameters is established for improving the small disturbance stability of the system. The results show that the optimization procedure could improve the damping ratio of the interval oscillation mode while ensuring the system frequency. The effects of virtual inertia and reactive damping values on the small signal stability of the system are investigated, and an optimal allocation model and method for virtual inertia used to improve the small disturbance stability of the system is proposed.
TL;DR: In this article , the dynamical critical exponent of swarms of insects is calculated using the renormalization group to order 4-d, where d = 1.35, in agreement with both experiments and numerical simulations.
Abstract: The dynamical critical exponent $z$ of natural swarms of insects is calculated using the renormalization group to order $\epsilon = 4-d$. A novel fixed point emerges, where both activity and inertia are relevant. In three dimensions the critical exponent at the new fixed point is $z = 1.35$, in agreement with both experiments ($1.37 \pm 0.11$) and numerical simulations ($1.35 \pm 0.04$).
TL;DR: In this paper , a moving mirror analog of the electron is presented, whose worldline possesses asymptotic constant velocity with corresponding Bogoliubov β coefficients that are consistent with finite total emitted energy.
Abstract: We present a moving mirror analog of the electron, whose worldline possesses asymptotic constant velocity with corresponding Bogoliubov β coefficients that are consistent with finite total emitted energy. Furthermore, the quantum analog model is in agreement with the total energy obtained by integrating the classical Larmor power.
TL;DR: In this article , a novel function is developed for implementing synthetic inertia in smart inverters as a combination of several control modes, and the operating curves of these control modes are varied to investigate their impact on the synthetic inertia's performance and stability.
TL;DR: In this article , the negative sequence voltage and the rate of change of frequency are handled by a logistic regression method to identify the events of improper action in the UFLS scheme.
TL;DR: In this article , the authors discuss experimental efforts on Taylor-Couette (TC) flows of viscoelastic fluids and provide a map of flow transitions to EIT as a function of the key fluid parameters.
Abstract: Since the seminal work of Taylor in 1923, Taylor–Couette (TC) flow has served as a paradigm to study hydrodynamic instabilities and bifurcation phenomena. Transitions of Newtonian TC flows to inertial turbulence have been extensively studied and are well understood, while in the past few years, there has been an increasing interest in TC flows of complex, viscoelastic fluids. The transitions to elastic turbulence (ET) or elasto-inertial turbulence (EIT) have revealed fascinating dynamics and flow states; depending on the rheological properties of the fluids, a broad spectrum of transitions has been reported, including rotating standing waves, flame patterns (FP), and diwhirls (DW). The nature of these transitions and the relationship between ET and EIT are not fully understood. In this review, we discuss experimental efforts on TC flows of viscoelastic fluids. We outline the experimental methods employed and the non-dimensional parameters of interest, followed by an overview of inertia, elasticity and elasto-inertia-driven transitions to turbulence and their modulation through shear thinning or particle suspensions. The published experimental data are collated, and a map of flow transitions to EIT as a function of the key fluid parameters is provided, alongside perspectives for the future work. This article is part of the theme issue 'Taylor–Couette and related flows on the centennial of Taylor’s seminal Philosophical Transactions paper (part 1)'.
TL;DR: In this article , a hybrid virtual machine is proposed to augment the inertia fulfillment of a weak power grid by concurrently introducing a flexible virtual DC inertia, which is composed of a virtual AC machine and two virtual DC machines wherein the converter dynamics and real machine swing equation are incorporated altogether using the small signal linearization technique.
Abstract: One of the drawbacks of the virtual inertia emulation process for AC power systems is to not consider the simultaneous effect of DC power control in the DC-link side interfaced power converters in presence of energy storage systems. In this paper, a Hybrid Virtual Machine is proposed to deal with this gap by augmenting the inertia fulfillment of a weak power grid by concurrently introducing a flexible virtual DC inertia. In this regard, the proposed hybrid virtual machine is composed of a virtual AC machine and two virtual DC machines wherein the converter dynamics and real machine swing equation are incorporated altogether using the small-signal linearization technique. Moreover, a multi-objective function is commensurately assigned attempting to meet the desirable responses for virtual machine currents under optimal virtual inertia and damping factors. Before starting optimization process, appropriate constraint areas are achieved for the virtual inertia and damping factor of both virtual AC and DC machines through a comprehensive analysis of second-order transfer functions. In addition, the AC and DC virtual inertia are concurrently altered to distinguish the non-synchronous variation effects of virtual inertia consistent with the optimization process for constraint affirmation and also further stability analysis. The significant performance of the proposed optimized hybrid virtual machine is verified through the simulation of a two hybrid virtual machines-based system in presence of PV unit variations in MATLAB/SIMULINK environment. The simulation results exhibit the stable and robust responses for power sharing, DC-link voltages, and also the frequency and voltage magnitude of the weak power grid. The data times-span of the MATLAB simulation performance will be [0 s, 0.4 s] with the sample time 1 μs wherein the dynamic change occurs at t = 0.2 s. As a future work, authors suggest that the proposed hybrid virtual machine can be extended to the electric vehicles-based microgrids in a multi-bus IEEE standard system in presence of energy storage systems.
TL;DR: In this article , a mathematical model of the nonlinear shaft centerline orbit of auxiliary support bearing in the cylinder block bore during hydraulic axial piston pump (SHAPP) operation is analyzed accurately.
TL;DR: In this article , a chance-constrained stochastic unit commitment model with inertia requirements is proposed to calculate equilibrium energy, reserve and inertia prices using convex duality.
Abstract: Maintaining the stability of renewable-dominant power systems requires the procurement of virtual inertia services from non-synchronous resources (e.g., batteries, wind turbines) in addition to inertia traditionally provided by synchronous resources (e.g., thermal generators). However, the pricing of inertia provision has not been studied in a stochastic electricity market, where the uncertainty characteristics of renewable energy sources (RES) are considered. To fill in this research gap, this paper formulates a chance-constrained stochastic unit commitment model with inertia requirements and computes equilibrium energy, reserve and inertia prices using convex duality. Numerical experiments on an illustrative system and a modified IEEE 118-bus system show the performance of the proposed pricing mechanism. By allowing new virtual inertia providers to contribute to system inertia requirements, the total operating cost reduces. Moreover, the proposed stochastic electricity market internalizes RES uncertainty, which yields additional cost reductions by co-optimizing energy, reserve and inertia procurement.
TL;DR: In this paper , a neural network compensation sliding mode control (SMC) strategy mixed with the angle independent method (AIM) is proposed to suppress the vibration of the TSVFL.
Abstract: The two-inertia system with variable-length flexible load (TSVFL) is a typical dynamic model uncertain system. It is affected by transmission flexibility, flexible load length variation, and inaccurate friction torque, in which the flexible load will vibrate during rotation. In this study, a neural network compensation sliding mode control (SMC) strategy mixed with the angle-independent method (AIM) is proposed to suppress the vibration of the TSVFL. Among them, the AIM is proposed to design the fluctuating desired input of the motor. The vibration of the flexible load is offset by the speed fluctuation of the motor. The RBF neural networks are proposed to recognize the uncertain term in the TSVFL's dynamic model. First, the nonlinear mathematical model of the TSVFL is deduced based on the assumed mode method. Then, the Lyapunov stability theorem is proposed to design the weight coefficients’ adaptive law in neural networks and the robust term in the control law. Finally, simulation and physical experiments on output speed control are implemented. The results show that the proposed strategy is able to effectively decrease the error and weaken the vibration.
TL;DR: In this paper , the authors considered the general form of the damping fractal Duffing oscillator and showed that there is an agreement with the numerical solution when the fractal of the two scales becomes identical to the continuous space.