Stable Synchronization Research Articles

Synchronization investigation on space vibration system driven by two vibrators with arbitrary direction axes

To reveal the more inclusive vibration synchronization mechanism, investigation is extended to space vibration system driven by two vibrators with arbitrary direction axes. Based on a reliable method for changing the relative rotation direction of vibrators, Lagrange dynamic equation is introduced to obtain vibration responses of the constructed model. Then the electromechanical coupling torque is analyzed through considering load generated by mechanical structure into two vibrators, and synchronization stability is explored by Lyapunov with Kronecker product theory. Next, some important numerical calculations are conducted to analyze synchronization characteristics further. Finally, corresponding experiments are organized to verify the reliability of theoretical and numerical analysis, and the feasibility of detection method through vibration testing displacements for phase differences (PDs) in unstable and stable states is discussed. Results indicate that in arbitrary space or plane patterns a better universality of this study is possessed whether or not identical rotation directions of two vibrators; the PDs can be accurately obtained from vibration displacements.

Stability and multistability of synchronization in networks of coupled phase oscillators

Coupled phase oscillators usually achieve synchronization as the coupling strength among oscillators is increased beyond a critical value. The stability of synchronous state remains an open issue. In this paper, we study the stability of the synchronous state in coupled phase oscillators. It is found that numerical integration of differential equations of coupled phase oscillators with a finite time step may induce desynchronization at strong couplings. The mechanism behind this instability is that numerical accumulated errors in simulations may trigger the loss of stability of the synchronous state. Desynchronization critical couplings are found to increase and diverge as a power law with decreasing the integral time step. Theoretical analysis supports the local stability of the synchronized state. Globally the emergence of synchronous state depends on the initial conditions. Other metastable ordered states such as twisted states can coexist with the synchronous mode. These twisted states keep locally stable on a sparse network but lose their stability when the network becomes dense.

Exploring the effect of voltage amplitude and phase difference on resilient ability for power network with third-order model

Power networks and their ability play crucial role on our modern society. An effective approach to characterize the stability of power network against various disturbances is the resilience, which was presented in recent years. This paper investigates the resilience of power network with third-order model which takes into account voltage dynamics. Firstly, we analyze the local stability of the third order model including the transient dynamics of voltage magnitudes to gain insights into the critical coupling strength of power network. Subsequently, we study the resilience of power network from the view point of synchronous dynamics and voltage stability. Specifically, we focus on two factors: phase angle difference and voltage amplitude. Then, we pin down certain disturbance scenarios in networks with small size simulated according to the third-order model and discuss the transmitted power flow under different conditions. Simulation results show that power network is robust under fixed voltage amplitude. On the contrary, the power network is vulnerable under fixed phase differences. The analysis of the model can further help to understand the dynamics resilience of network in reality, and it is also of practical significance to predict cascading failure and design effective measures to control larger-scale outages.

Composite synchronization of three inductor motors with a circular distribution by a fuzzy proportional–integral–derivative method in a vibration system

Abstract. In this article, the composite synchronization of three inductor motors with a circular distribution by a fuzzy PID (proportional–integral–derivative) method in a vibration system is investigated. The composite synchronization motion is comprised of self-synchronization and controlled synchronization motions. In the self-synchronization section, the electromechanical coupling dynamical model of the vibration system is established by introducing an inductor motor model into the dynamic model. The responses of the vibrating system are calculated, and the synchronous condition and stability criterion are both derived. With the controlled synchronization section, a master–slave controlling strategy and fuzzy PID method are applied on the controlling model. The stability of the control system is proved by the Lyapunov stability theory. A series of simulations are employed to demonstrate the practicability of the designed method. Finally, some experiments are conducted to verify the effectiveness of the proposed control method in practical application. The proposed control method exhibits a superior ability to satisfy the control of multiple motors, to be accurate in targeting the rotational speed arrival, and to be strongly robust against uncertainties and disturbances. The composite synchronization theory introduces a novel concept to design and develop types of vibration equipment.

The Concept and Understanding of Synchronous Stability in Power Electronic-Based Power Systems

Synchronous stability in power systems is of essential importance for system safety and operation. For the phase-locked loop (PLL)-based synchronous stability in power electronic-based power systems, which has recently stimulated interest in researchers in the field of electrical power engineering, but is still controversial, this paper divides the topic into two aspects, including the PLL device stability and the system stability. It is found that the PLL device is always stable and the error between the PLL output angle θpll and the terminal voltage angle θt is always finite. Therefore, the synchronization of power electronic-based power systems should be understood as the output synchronization between the electrical rotation vectors (θt or θpll) from each item of grid-tied equipment, rather than the synchronization of the PLL device itself. In addition, it is found that θpll plays an active role in the system synchronization dynamics not only in electromagnetic timescales but also electromechanical timescales and it could be selected as a dominant observable. In this paper, the concept of synchronous stability is well clarified. These findings are well supported by theoretical analyses and MATLAB/Simulink simulations, and thus could provide insights on the synchronous stability mechanism.

Analysis of the synchronisation of energy consumption: Evidence from G7 countries

AbstractGiven differences in the efficiency of oil use of local and foreign technologies across countries, characterising the degree of synchronisation of oil consumption is of great concern and consequence for economic, political, and, not least, climate change reasons. Building on the business cycle theory, we characterise the degree of synchronisation of oil consumption with world consumption among the G7 countries over the period 1890–2017. We provide three crucial points based on the wavelet and phase difference analyses. Firstly, we find that the synchronisation of oil consumption in the largest oil consumers with world consumption was continuous only during periods prior to the great depression of the 1930s, suggesting the lack of a stable synchronisation pattern in oil consumption. In addition, we show that during that period, oil consumption in each G7 country started approaching world consumption. Secondly, the phase relation structure infers a clear pattern of positive correlations (being in phase) between each country's oil consumption and world consumption, mainly during the short run. This strong evidence of interdependency yields beneficial information for monitoring world oil demand by improving the efficiency of oil in the underlying countries. Thirdly, we report that oil consumption patterns in France, the United Kingdom and the United States are the closely synchronised oil consumers with a procyclical pattern after 2010, supporting convergence features in their oil consumption series.

Application of a novel Ca-Fe-Si-S composite for the synchronous stabilization of As, Zn, Cu, and Cd in acidic arsenic slag.

The control of multipleheavy metals (HMs) pollution in solid wastes, especially the co-contamination of As and other heavy metal cations, is of great importance to ecological and environmental health. To address this problem, the preparation and application of multifunctional materials have attracted wide attention. In this work, a novel Ca-Fe-Si-S composite (CFSS) was applied to stabilize As, Zn, Cu, and Cd in acid arsenic slag (ASS). The CFSS exhibited synchronous stabilization ability for As, Zn, Cu, Cd and owned strong acid neutralization capacity. Under simulated field conditions, the acid rain extracted HMs in ASSsuccessfully decreased below the emission standard (GB 3838-2002-IV category in China) after incubated by 5% CFSS for 90days. Meanwhile, the application of CFSS promoted the transformation of leachable HMs into less accessible forms, which was conductive to the long-term stabilization for HMs. There was competitive relation among the three heavy metal cations, following the stabilization sequence of Cu > Zn > Cd during incubation. And the stabilization mechanisms of HMs by CFSS were proposed as chemical precipitation, surface complexation, and ion/anion exchange. The research will be greatly conducive to the remediation and governance of field multipleHMs contaminated sites.

Synchronization stability of power-grid-tied converters.

Synchronization stability is one of central problems in power systems, and it is becoming much more complicated with the high penetration of renewable energy and power electronics devices. In this paper, we review recent work by several nonlinear models for renewable-dominated power systems in terms of multiple timescales, in particular, grid-tied converters within the DC voltage timescale. For the simplest model, a second-order differential equations called the generalized swing equation by considering only the phase-locked loop (PLL) is obtained, which shows a similar form with the well-known swing equation for a synchronous generator in the traditional power systems. With more outer controllers included, fourth-order and fifth-order models can be obtained. The fourth-order model is called the extended generalized swing equation, exhibiting the combined function of grid synchronization and active power balance on the DC capacitor. In addition, a nonlinear model for a two coupled converter system is given. Based on these studies, we find that the PLL plays a key role in synchronization stability. In summary, the value of this paper is to clarify the key concept of the synchronization stability in renewable-dominated power systems based on different nonlinear models, which still lacks systematic studies and is controversial in the field of electrical power engineering. Meanwhile, it clearly uncovers that the synchronization stability of converters has its root in the phase synchronization concept in nonlinear sciences.

Optimal time-varying coupling function can enhance synchronization in complex networks.

In this paper, we propose a time-varying coupling function that results in enhanced synchronization in complex networks of oscillators. The stability of synchronization can be analyzed by applying the master stability approach, which considers the largest Lyapunov exponent of the linearized variational equations as a function of the network eigenvalues as the master stability function. Here, it is assumed that the oscillators have diffusive single-variable coupling. All possible single-variable couplings are studied for each time interval, and the one with the smallest local Lyapunov exponent is selected. The obtained coupling function leads to a decrease in the critical coupling parameter, resulting in enhanced synchronization. Moreover, synchronization is achieved faster, and its robustness is increased. For illustration, the optimum coupling function is found for three networks of chaotic Rössler, Chen, and Chua systems, revealing enhanced synchronization.

Configurable Pseudo Noise Radar Imaging System Enabling Synchronous MIMO Channel Extension.

In this article, we propose an evolved system design approach to ultra-wideband (UWB) radar based on pseudo-random noise (PRN) sequences, the key features of which are its user-adaptability to meet the demands provided by desired microwave imaging applications and its multichannel scalability. In light of providing a fully synchronized multichannel radar imaging system for short-range imaging as mine detection, non-destructive testing (NDT) or medical imaging, the advanced system architecture is presented with a special focus put on the implemented synchronization mechanism and clocking scheme. The core of the targeted adaptivity is provided by means of hardware, such as variable clock generators and dividers as well as programmable PRN generators. In addition to adaptive hardware, the customization of signal processing is feasible within an extensive open-source framework using the Red Pitaya® data acquisition platform. A system benchmark in terms of signal-to-noise ratio (SNR), jitter, and synchronization stability is conducted to determine the achievable performance of the prototype system put into practice. Furthermore, an outlook on the planned future development and performance improvement is provided.

Synchronization of power systems under stochastic disturbances

The synchronization of power generators is an important condition for the proper functioning of a power system, in which the fluctuations in frequency and the phase angle differences between the generators are sufficiently small when subjected to stochastic disturbances. Serious fluctuations can prompt desynchronization, which may lead to widespread power outages. Here, we model the stochastic disturbance by a Brownian motion process in the linearized system of the non-linear power systems and characterize the fluctuations by the variances of the frequency and the phase angle differences in the invariant probability distribution. We propose a method to calculate the variances of the frequency and the phase angle differences. For the system with uniform disturbance-damping ratio, we derive explicit formulas for the variance matrices of the frequency and the phase angle differences. It is shown that the fluctuation of the frequency at a node depends on the disturbance-damping ratio and the inertia at this node only, and the fluctuations of the phase angle differences in the lines are independent of the inertia. In particular, the synchronization stability is related to the cycle space of the network. We reveal the influences of constructing new lines and increasing capacities of lines on the fluctuations in the phase angle differences in the existing lines. The results are illustrated for the transmission system of Shandong Province of China. For the system with non-uniform disturbance-damping ratio, we further obtain bounds of the variance matrices.

Phase synchronization between neurons under nonlinear coupling via hybrid synapse

Biological neurons and nonlinear circuits contain certain inner field energy, and an equivalent Hamilton energy function can be obtained to discern the dependence of firing modes on the energy flow. In this paper, a voltage-controlled resistor is used to connect two neural circuits, and hybrid synapse is activated to control the synchronization stability and mode transition in neurons under phase lock. Realistic stimuli can be combined signals within certain frequency band rather than simple periodic stimulus, and the firing patterns will show multiple modes by applying mixed signals. Similar coherence resonance is detected in an isolated neuron driven by the filtered signals. Therefore, chaotic signals are encoded to represent filtered waves with finite frequency band, and then the mixed signals are used to excite two neural circuits via nonlinear coupling. Hamilton energy for the coupled neurons via hybrid synapse is estimated to detect the controllability of synchronization between neurons. The nonlinear resistor along the coupling channel can reproduce the biophysical property of hybrid synapse accompanying with field coupling, which mainly contributes the energy exchange between neurons. It is confirmed that this hybrid synapse is effective to control the synchronization stability and phase lock even the neurons presenting with different firing patterns/modes. The results confirmed that nonlinear coupling via specific components is helpful to design hybrid synapse, and it is effective to block the bursting synchronization between neurons driven by filtered chaotic signals. Therefore, activation of this hybrid synapse can prevent the occurrence of seizure in nervous system.

Synchronization of directed uniform hypergraphs via adaptive pinning control

In recent years, higher-order networks have been gradually investigated, and uniform hypergraph is one of their typical expressions. In this paper, in addition to undirected uniform hypergraphs, directed uniform hypergraphs with newly defined hyperedges are proposed by equipping each node with identical chaotic oscillator. In order to realize global synchronization of proposed uniform hypergraphs, two kinds of adaptive pinning control schemes with and without desired synchronized states are designed. By newly defining Laplacian tensor of the uniform hypergraphs, several sufficient conditions of globally stable synchronization are obtained by applying the Lyapunov stability theory. The Laplacian tensor is supersymmetric when considering undirected structures and asymmetric when considering directed structures. Based on the stability condition, an algorithm for determining the pinned nodes is developed. The result further shows that the directionality of uniform hypergraphs can restrain the realization of synchronization. Numerical examples are presented to illustrate the theoretical results.

Secure Communication in Complex Dynamical Networks via Time-Delayed Feedback Control

In this article, a synchronization method of complex dynamical networks (CDNs) with time-varying delay feedback control is proposed to secure communication between the command system and each node of CDNs. To advance the security of the communication between the command system and each node of CDNs, the original information signal transmitted from the command system is encrypted with the techniques of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathcal {N}$ </tex-math></inline-formula> -shift cipher and public key. Based on the Lyapunov stability sense and linear matrix inequality (LMI) framework, a new delay-dependent synchronization criterion is established to restore the original information signal on each node of the CDN as well as to ensure stable synchronization for secure communication of all nodes of the command system and CDN. With the support of numerical simulation, the validity of the proposed method is verified.

Energy-guided synapse coupling between neurons under noise.

From a physical viewpoint, any external stimuli including noise disturbance can inject energy into the media, and the electric response is regulated by the equivalent electric stimulus. For example, mode transition in electric activities in neurons occurs and kinds of spatial patterns are formed during the wave propagation. In this paper, a feasible criterion is suggested to explain and control the growth of electric synapse and memristive synapse between Hindmarsh-Rose neurons in the presence of noise. It is claimed that synaptic coupling can be enhanced adaptively due to energy diversity, and the coupling intensity is increased to a saturation value until two neurons reach certain energy balance. Two identical neurons can reach perfect synchronization when electric synapse coupling is further increased. This scheme is also considered in a chain neural network and uniform noise is applied on all neurons. However, reaching synchronization becomes difficult for neurons in presenting spiking, bursting, and chaotic and periodic patterns, even when the local energy balance is corrupted to continue further growth of the coupling intensity. In the presence of noise, energy diversity becomes uncertain because of spatial diversity in excitability, and development of regular patterns is blocked. The similar scheme is used to control the growth of memristive synapse for neurons, and the synchronization stability and pattern formation are controlled by the energy diversity among neurons effectively. These results provide possible guidance for knowing the biophysical mechanism for synapse growth and energy flow can be applied to control the synchronous patterns between neurons.

The effects of fertility and synchronization variation on seed production in two Chinese fir clonal seed orchards

Variations in fertility and synchronization information is fundamental to seed orchard management. Our objective was to determine clonal variation and stability in strobili production, phenology, synchronization, and seed production in two generation clonal seed orchards (CSO) of Chinese fir. The number of female and male strobili and the phenology of 42 clones in both the 2.0- and 2.5-generation clonal seed orchards were investigated and recorded to calculate the variation and stability of fertility and synchronization. In both seed orchards, an obvious variation in gamete contribution was found among clones, indicating deviation from random mating. Female receptivity was in the pollen shedding stage, which is favorable to pollination. However, low synchronization (mean POij = 0.283) between clones indicated low overlap between female receptivity and pollen shedding. A higher POij value within clones than within outcrossing combinations indicated a high risk of selfing in two seed orchards, particularly for early- and late-flowering clones. The number of female strobili and POij (as female) significantly influence seed production. Overall, fertility and synchronization variation had notable consequences for seed production. Scientific genetic management is indispensable for promoting fertility uniformity and synchronization to obtain maximal genetic gain.

Synchronous stabilization of As, Cd, and Pb in soil by sustained-release of iron-phosphate

Anionic arsenic (As) exhibits geochemical behavior opposite to those of cationic cadmium (Cd), and lead (Pb), which makes the synchronous remediation of As, Cd, and Pb challenging. The synchronous stabilization of As, Cd, and Pb to form Cd/Pb-phosphate and iron‑arsenic precipitates is a promising strategy. However, the effectiveness of soluble phosphate or iron-based materials is limited by the activation of Cd, Pb, or As, while low mobility hinders insoluble particles. In this study, we developed an amorphous structure that releases iron and phosphate at a sustained rate. Thus, the stabilization efficiencies of NaHCO3-extractable As, DTPA-extractable Cd and Pb reached 44.6 %, 40.8 %, and 48.1 %, respectively. The proportion of residual fraction of As, Cd, and Pb increased by 12.1 %, 14.5 %, and 36.4 %, respectively, after 28 d. Ferrihydrite was chosen as the soil component to monitor the chemical behavior and speciation transformation of As, Cd, and Pb in the reaction. During the process, the released iron directly reacted with dissolved As to form iron‑arsenic precipitation and phosphate directly reacted with Cd/Pb to form Cd/Pb-phosphate precipitation. Simultaneously, phosphate replaced the adsorbed As and transformed into a dissolved state, which could be re-precipitated with the released iron ions. Thus, this study provides a reliable strategy for the remediation of As, Cd, and Pb combined pollution in soil.

Основные тенденции развития современного немецкого языка (в сравнении с русским языком)

The purpose of the study is to determine themain trends in the development of theGerman language (in comparison with theRussian language) in the context of socio-political transformations, changing social norms, communication conditions, and rethinking of values. The scientific novelty of thework is to establish the factors that determine changes in theGerman language. The article proposes an analysis of norms and values of theGerman society in terms of their synchronous stability and diachronic variability. The development of theGerman language in themodern period is influenced both by global processes (globalization, pandemic, conflicts, etc.), and by the peculiarities of the life of theGerman nation in the context of increasing migration, struggle for gender equality and gender diversity. The authors give examples of neologisms and borrowings in theGerman language that have arisen under the influence of various forms of political correctness, as well as examples of other lexical and speech innovations due to the new value hierarchy. As a result of considering the specifics of social norms and values of theGerman society, the universal and original trends in the evolution of themodern German language, the features of the language policy of theGerman state are determined.

Input-to-state stable synchronization for delayed Lurie systems via sampled-data control

&lt;p style='text-indent:20px;'&gt;This paper focuses on the input-to-state stable (ISS) synchronization issue for delayed Lurie systems via sampled-data control. Two time-dependent Lyapunov functionals are constructed for delay functions without and with differentiability restrictions, respectively. Sufficient conditions on the ISS synchronization are established via using the proposed Lyapunov functionals, the reciprocally convex-combination approach, and a few integral inequalities. The gain matrix of the needed sampled-data controller can be attained through solving a couple of linear matrix inequalities, which is numerically easy to handle. Furthermore, the present conditions are capable of ensuring the exponential synchronization of the considered Lurie systems in the absence of external disturbances. In the end, two examples are employed to demonstrate the effectiveness of the established ISS synchronization conditions.&lt;/p&gt;

Improvement of Power System Frequency Stability With Universal Grid-Forming Battery Energy Storages

Large-scale integration of inverter-based renewable generation leads to the reduction of power systems’ natural inertia. Therefore, the dynamics of the future power systems will be more sensitive than in the traditional systems with high-inertia rotating synchronous generators. This development is a potential risk for frequency stability and requires utilization of rapidly controllable resources for dynamic frequency stability support. Simultaneously, development of new synchronization and control methods for inverter-based resources is needed in order to ensure the frequency and synchronization stability of future power systems. In this paper, a grid-forming and supporting universal frequency-locked-loop -based control and grid synchronization for inverter-based resources is utilized to improve the frequency stability of a small high-voltage network. The simulations are done with PSCAD software and the main focus is on the battery energy storages to evaluate the effect of their location, enhanced control schemes as well as operation mode on frequency stability. In the studies, for example, the effect of battery storages location, active power response related control parameters, communication time delay and input frequency determination on frequency support are studied during charging and discharging of the batteries. Based on the simulations, also new solutions to improve the frequency stability of future variable inertia power systems with universal grid-forming battery storages are proposed.