Stable Synchronization Research Articles

Effect of internal and external chaotic stimuli on synchronization of piezoelectric auditory neurons in coupled time-delay systems.

Hearing impairment is considered to be related to the damage of hair cells or synaptic terminals, which will cause varying degrees of hearing loss. Numerous studies have shown that cochlear implants can balance this damage. The human ear receives external acoustic signals mostly under complex conditions, and its biophysical mechanisms have important significance for reference in the design of cochlear implants. However, the relevant biophysical mechanisms have not yet been fully determined. Using the characteristics of special acoustoelectric conversion in piezoelectric ceramics, this paper integrates them into the traditional FitzHugh-Nagumo neuron circuit and proposes a comprehensive model with coupled auditory neurons. The model comprehensively considers the effects of synaptic coupling between neurons, information transmission delay, external noise stimulation, and internal chaotic current stimulation on the synchronization of membrane potential signals of two auditory neurons. The experimental results show that coupling strength, delay size, noise intensity, and chaotic current intensity all have a certain regulatory effect on synchronization stability. In particular, when auditory neurons are in a chaotic state, their impact on synchronization stability is sensitive. Numerical results provide a reference for exploring the biophysical mechanisms of auditory neurons. At the same time, we are committed to providing assistance in using sensors to monitor signals and repair hearing impairments.

Small-Signal Synchronization Stability of Grid-Forming Converters With Regulated DC-Link Dynamics

The dc-link voltage dynamics can be directly used to synchronize grid-forming (GFM) converters with ac grids. However, such control scheme is prone to unstable low-frequency oscillations (LFO), owing to the constant-power dynamics at the dc link. This paper analyzes first the small-signal stability of dc-link voltage-synchronized GFM converters, and proposes a control method for enhancing the system stability under different operating scenarios. In the approach, a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis voltage-feedforward control is introduced in parallel with the dc-link voltage control for the grid-synchronization purpose. The LFO problem with the conventional dc-link voltage-synchronization control is mitigated. Compared to conventional cascaded/paralleled dc-link voltage- and active power-based synchronization, the method mitigates the synchronous oscillation problem. Experimental tests are performed for the GFM converter operating in both rectifier and inverter modes and with different grid strengths. The results corroborate theoretical analyses and validate the effectiveness of the approach.

Energy controls wave propagation in a neural network with spatial stimuli

Nervous system has distinct anisotropy and some intrinsic biophysical properties enable neurons present various firing modes in neural activities. In presence of realistic electromagnetic fields, non-uniform radiation activates these neurons with energy diversity. By using a feasible model, energy function is obtained to predict the growth of synaptic connections of these neurons. Distribution of average value of the Hamilton energy function vs. intensity of noisy disturbance can predict the occurrence of coherence resonance, which the neural activities show high regularity by applying noisy disturbance with moderate intensity. From physical viewpoint, the average energy value has similar role average power for the neuron. Non-uniform spatial disturbance is applied and energy is injected into the neural network, statistical synchronization factor is calculated to predict the network synchronization stability and wave propagation. The intensity for field coupling is adaptively controlled by energy diversity between adjacent neurons. Local energy balance will terminate further growth of the coupling intensity; otherwise, heterogeneity is formed in the network due to energy diversity. Furthermore, memristive channel current is introduced into the neuron model for perceiving the effect of electromagnetic induction and radiation, and a memristive neuron is obtained. The circuit implement of memristive circuit depends on the connection to a magnetic flux-controlled memristor into the mentioned neural circuit in an additive branch circuit. The connection and activation of this memristive neural network are controlled under external spatial electromagnetic radiation by capturing enough field energy. Continuous energy collection and exchange generate energy diversity and synaptic connection is created to regulate the synchronous firing patterns and energy balance.

Predicting stability of synchronous nonlinear vibration in vertical rotating shaft system with journal bearing

Journal bearings (JBs) play a vital role in rotating machines across various fields. In vertical rotating shaft systems with JB, synchronous vibration experiences stages of destabilization and stabilization as rotational speed increases due to self-excited vibration. The onset speed of instability (OSI1) can be predicted via conventional eigenvalue analysis around static equilibrium positions. However, conventional analysis cannot determine the stabilizing and destabilizing speeds (OSS and OSI2) at which self-excited vibration disappears and reappears; numerical and experimental methods suffice. No other theory adequately explains these phenomena. This paper proposes an analytical method based on linearizing JB force and generalized eigenvalue analysis to efficiently predict synchronous vibration stability in vertical rotating shaft systems. The extended eigenvalue analysis directly determines synchronous orbit stability. Demonstrating accuracy and efficiency, a characteristic curve representing stability changes within an unbalance range is calculated, compared with numerical results. Our method serves as an input to rotor dynamic software, calculating rotating shaft-bearing stability thresholds.

Using Fe/H2O2-modified biochar to realize field-scale Sb/As stabilization and soil structure improvement in an Sb smelting site

Antimony (Sb) and arsenic (As) released from the Sb smelting activities pose a major environmental risk and ecological degradation in Sb smelting sites. Here the effects of Fe/H2O2 modified biochar (Fe@H2O2-BC) on the synchronous stabilization of Sb/As and the improvement of soil structure in a typical Sb smelting site in Southern China based on a 1-year field experiment were studied. Application of ≥1 % (w/w) Fe@H2O2-BC could stably decrease the leaching concentrations of Sb and As of the polluted soils to Environmental quality standards for surface water Chinese Level III (GB3838–2002). Compared to the untreated soils, the stabilization efficiency of soil Sb and As treated by Fe@H2O2-BC reached 90.7 % ~ 95.7 % and 89.6 % ~ 90.8 %, respectively. The residue fractions of Sb/As in the soils increased obviously, and the bio-availability of Sb/As decreased by 65.0–95.6 % and 91.1–96.0 %, respectively. Moreover, Fe@H2O2-BC addition elevated soil organic carbon content, increased soil porosity, and improved water retention capacity, indicating the positive effects on soil structure and functions. Advanced mineral identification and characterization systems showed that Sb/As usually occurred in Fe-bearing minerals and stabilized by surface complexation and co-precipitation. The findings demonstrated that 1 % (w/w) Fe@H2O2-BC was appropriate to Sb/As stabilization and soil function recovery following field conditions, which provided potential application for ecological restoration in Sb smelting sites.

Controlled synchronization of a vibrating screen driven by two motors based on improved sliding mode controlling method.

With a requirement of miniaturization in modern vibrating screens, the vibration synchronization method can no longer meet the process demand, so the controlled synchronization method is introduced in the vibrating screen to achieve zero phase error state and realize the purpose of increasing the amplitude. In this article, the controlled synchronization of a vibrating screen driven by two motors based on improved sliding mode controlling method is investigated. Firstly, according to the theory of mechanical dynamics, the motion state of the vibrating screen is simplified as the electromechanical coupling dynamical model of a vibrating system driven by two inductor motors. And then the synchronization conditions and stability criterion of the vibrating system are derived and numerically analyzed. Based on a master-slave controlling strategy, the controllers of two motors are respectively designed with Super-Twisting sliding mode control (ST-SMC) and backstepping second-order complementary sliding mode control (BSOCSMC), while the uncertainty is estimated by an adaptive radial basis function neural network (ARBFNN). In addition, Lyapunov stability analysis is performed on the two controllers to prove their stability theoretically. Finally, simulation analysis is conducted based on the dynamics model in this paper.

Hyperbolic function-based fixed/preassigned-time stability of nonlinear systems and synchronization of delayed fuzzy Cohen–Grossberg neural networks

In this article, the fixed-time (FIT) and preassigned-time (PRT) stability of nonlinear models and the FIT/PRT synchronization of discontinuous delayed fuzzy Cohen–Grossberg neural networks (DFCGNNs) are explored, respectively. Firstly, by means of hyperbolic-cosine function and Gudermannian function, a novel FIT stability theorem is established by utilizing Lyapunov method. Then, based on the developed stability theorem, several new discontinuous control schemes with hyperbolic-cosine function are developed to discuss the FIT synchronization of DFCGNNs. Furthermore, the PRT synchronization is also explored by slightly modifying FIT control schemes, where the synchronization time is predetermined. Eventually, two numerical examples are provided to validate the theoretical research.

Synchronization and vibration absorption analysis of a dual-body vibrating screen driven by multiple motors with double-frequency actuation

Vibrating screen is the pivotal equipment of solid control in drilling mud purification system. With the continuous upgrading of rapid drilling technology, the conventional single-body vibrating screen with the same-frequency excitation is difficult to satisfy the needs of current drilling operations. Therefore, a newly dual-body vibration absorption system model with double-frequency excitation is proposed to improve the mechanical performance of screening equipment. To grasp the dynamic characteristics of the vibration system, the synchronization mechanism and stability criterion are theoretically studied by modified small parameter average method and Poincare-Lyapunov method. Meanwhile, the vibration absorption ability, coupling torque and synchronization state of the system are numerically discussed. Lastly, the electromechanical coupling model of system is established by Runge-Kutta method to verify the reliability of theoretical analysis and numerical calculation. According to the results of research, the synchronous characteristics are mainly determined by the installation position of motors and the mass ratio of eccentric rotors. Besides, the synchronization ability between identical-frequency motors is stronger than different frequency motors. The present work can provide theoretical direction for designing of new screening equipment.

The complementary contribution of each order topology into the synchronization of multi-order networks.

Higher-order interactions improve our capability to model real-world complex systems ranging from physics and neuroscience to economics and social sciences. There is great interest nowadays in understanding the contribution of higher-order terms to the collective behavior of the network. In this work, we investigate the stability of complete synchronization of complex networks with higher-order structures. We demonstrate that the synchronization level of a network composed of nodes interacting simultaneously via multiple orders is maintained regardless of the intensity of coupling strength across different orders. We articulate that lower-order and higher-order topologies work together complementarily to provide the optimal stable configuration, challenging previous conclusions that higher-order interactions promote the stability of synchronization. Furthermore, we find that simply adding higher-order interactions based on existing connections, as in simple complexes, does not have a significant impact on synchronization. The universal applicability of our work lies in the comprehensive analysis of different network topologies, including hypergraphs and simplicial complexes, and the utilization of appropriate rescaling to assess the impact of higher-order interactions on synchronization stability.

Synchronization Stability of Grid-Following VSC Considering Interactions of Inner Current Loop and Parallel-Connected Converters

In the grid-following (GFL) voltage source converter (VSC), the synchronization process of phase-locked loop (PLL) can be seriously affected by the interactions from the inner current loop and other parallel-connected VSCs. In this paper, we focus on the influences of these interactions on the synchronization stability of GFL-VSC. Firstly, these interactions are classified into static and dynamic interactions by the mechanism of how they affect the dynamic of PLL. Then, their influence on the synchronization stability is estimated based on a novel Lyapunov stability criterion, which is derived from the extended invariance principle. On this basis, in terms of the physical mechanism, we reveal how the VSC exhibits the non-asymptotic synchronization (i.e., limit cycles) and cascading synchronization instability. In addition, we get the maximum range of static and dynamic interactions that the VSC endure, which can provide the practical design guidance for the VSC. Finally, simulations and experiments are performed to verify the theoretical findings.

Transient Synchronization Stability of Grid-Following Converters Considering Nonideal Current Loop

Transient Synchronization Stability of Grid-Following Converters Considering Nonideal Current Loop

Constant-Coupling-Effect-Based PLL for Synchronization Stability Enhancement of Grid-Connected Converter Under Weak Grids

The Phase-Locked Loop (PLL)-caused couplings on the grid-connected converter (GCC) are strengthened by increasing its bandwidth and then incur synchronization instability. This paper proposes a constant coupling effect-based PLL (CCE-PLL) to resolve the aforementioned issues. Initially, the feature of the PLL-caused couplings on GCC is explored. It exhibits that the couplings are varied along with the PLL bandwidth hence jeopardizing the system's stability. Subsequently, the CCE-PLL with a constant and low coupling regardless of its bandwidth on the GCC is proposed. It illustrates that the CCE-PLL bandwidth does not influence the GCC's impedance response, bringing the GCC and CCE-PLL can be designed separately. Lastly, the experiments confirm that using CCE-PLL, the system has high robustness against grid impedance variation, and the GCC is capable of injecting/absorbing 1.0 per unit active power in a very weak grid. Moreover, the system attains good anti-interference ability and transient performance under system disturbances thanks to the permission usage of the high CCE-PLL bandwidth.

Synchronizability of Discrete Nonlinear Systems: A Master Stability Function Approach

In recent times, studies on discrete nonlinear systems received much attention among researchers because of their potential applications in real-world problems. In this study, we conducted an in-depth exploration into the stability of synchronization within discrete nonlinear systems, specifically focusing on the Hindmarsh–Rose map, the Chialvo neuron model, and the Lorenz map. Our methodology revolved around the utilization of the master stability function approach. We systematically examined all conceivable coupling configurations for each model to ascertain the stability of synchronization manifolds. The outcomes underscored that only distinct coupling schemes manifest stable synchronization manifolds, while others do not exhibit this trait. Furthermore, a comprehensive analysis of the master stability function’s behavior was performed across a diverse range of coupling strengths σ and system parameters. These findings greatly enhance our understanding of network dynamics, as discrete-time dynamical systems adeptly replicate the dynamics of continuous-time models, offering significant reductions in computational complexity.

Synchronous Generator Stability Characterization for Gas Power Plants Using Load Rejection Tests

For power grid operators, knowing the transient response of the synchronous generators (SGs) included in their grids is important in order to simulate and monitor faults and other contingencies. However, the time constant of the automatic voltage regulator (AVR) and speed governors of SGs are not fast enough to show their transient dynamics in the case of a fault in the grid. This paper presents a fieldwork carried out in more than 60 gas power plants, where the response of their controllers was studied. These power plants are running and supplying electricity to the Spanish grid. The study consists of recording some SG responses in different situations, varying the AVR or the speed governor setpoints while the generator is running at no-load conditions, and also performing load rejection tests, achieving a real fault emulation. Once all the data are gathered, a fitting of the SG parameters is performed by computer simulations using GENSAL, GAST and SEXS models replicating the performed field tests. This work allows us to build an accurate network model for the whole power system and check which plants are having trouble in the case of contingencies in the grid.

The influence of noise and frequency distortions in the communication channel on a communication circuit based on a hyperbolic chaos generator.

The analysis of the possibility of using a chaotic communication scheme based onsynchronization of the receiver and transmitter, which used hyperbolic chaos generators. It is shown that useful information nonlinearly mixed into the transmitter signal can be detected by the receiver if it is in stable synchronization with the transmitted signal. Research has been conducted to confirm the hypothesis that the roughness, strong chaotic properties and noise-like broadband spectrum of this type of generator provide greater reliability and stability of transmission. The influence of noise and frequency distortions of the signal in the communication channel on the quality of information detection by the receiver is also shown.

Influence of Noise and Frequency Distortions in a Communication Channel on a Communication Scheme Based on a Hyperbolic Chaos Generator

The article analyses the effectiveness of a chaotic communication scheme based on synchronization of hyperbolic chaos generators used as a receiver and a transmitter. It is shown that useful information nonlinearly mixed into the transmitter signal can be detected by the receiver if the receiver has stable synchronization with the transmitted signal. Research, aimed to confirm the hypothesis that robustness, strong chaoticity and noise-like wideband spectrum of this type of oscillators provide reliability and stability of transmission, has been carried out. This study also shows the effect of noise and frequency distortion of the signal in a communication channel on the quality of information detection.

Corrected complex torque coefficient method for synchronization stability analysis of grid‐connected VSC

AbstractSub‐synchronous oscillation of grid‐connected voltage source converter (VSC) dominated by phase locked loop (PLL) is an important stability issue in nowadays power systems. The complex torque coefficient method has been used to investigate the issue because of its advantage of giving insights into source of damping and contributions of different components on damping. However, it is found that the classic complex torque coefficient method is not entirely applicable for stability analysis of VSC because of the proportional term in PLL. This paper proposes a corrected complex torque coefficient method and defines synchronous and damping coefficients. Based on the proposed method, a small‐signal stability criterion is obtained, in which the system stability depends on the sign of corrected damping coefficient. The impacts of different elements on system damping can be quantitatively evaluated through the method. It is drawn that current control loop and line dynamics contribute negative damping, whereas power control loop contributes positive damping. Moreover, the impacts of operating conditions and controller parameters on damping of different elements are analysed. The eigenvalue analyses and electromagnetic transient simulations have verified the theoretical analysis.

Revealing the buildup of dynamic mode-switchable frequency-shifted feedback laser based on photon–phonon interaction

Photon-phonon interaction (PPI) is an intriguing physical phenomenon in which the dynamic photon-phonon energy transfer allows the manipulation of acousto-optic properties in the media. Recently, there has been significant interest of PPI as it accompanies the conservations of energy and momentum processes. Mode-locking is a process in which temporal and spatial resonant modes establish stable synchronization through non-linear interactions. Here, we propose and reveal the buildup of a dynamic mode-switchable frequency-shifted feedback laser in which frequency shift and mode conversion are achieved based on PPI. Moreover, dynamic switching between LP11a/b mode and stable donut mode output is achieved and precisely controlled by PPI. Finally, by using the time-stretch dispersive Fourier transform (TS-DFT) detective system, we observe the transient dynamics established in frequency-shifted feedback (FSF) fiber laser, such as the direct evolution from continuous wave (CW) state to mode-locked state, CW state to multipulse state and subsequently to stable mode-locked state. All these findings would unveil the buildup of mode-locking mechanisms of dynamic mode-switchable FSF fiber lasers based on PPI with more degrees of freedom and unlock new possibilities in ultrafast laser-based technology, optical communication and light control.

Improving the Synchronous Stability Control Strategy of Virtual Synchronous Generators

The microgrid dominated by new energy has small inertia and weak damping, while a virtual synchronous generator (VSG) is an effective means to enhance inertia and damping to improve the stability of the microgrid. However, it also introduces power angle oscillation problems similar to that of synchronous machines. This paper is based on the current inner loop and voltage outer loop control of the three-phase LCL inverter. It introduces the virtual inertia and damping coefficient of the virtual synchronous generator, achieving a good grid connection effect. While a significant change in active power occurs, the system can lose synchronization and stability. Therefore, the paper proposes an improved synchronization stability control strategy for virtual synchronous generators by introducing a frequency-proportional integral feed-forward link in the reactive power loop to suppress power angle oscillation and improve system synchronization stability. Theoretical analysis was conducted on the synchronous stability of the improved control strategy in case of sudden changes in active power load. The effectiveness of the strategy was verified through simulation.

On the Impact of the Grid on the Synchronization Stability of Grid-Following Converters

The research on the synchronization stability of Grid-Following Converter (GFL) is of great significance for the stable operation of inverter-based resources. Existing literature mainly focuses the stability factors from the point of view of the converter and assumes the grid to be an infinite-bus with constant frequency. However, faults cause the grid to experience interdependent variations of grid voltage amplitudes and phases, as well as of its frequency. The impact of these variations on the synchronization stability has not been systematically and comprehensively studied yet. Here we study the combined effect on GFL synchronization stability of all these quantities following a large disturbance. The theoretical appraisal shows that phase-angle jump affects the initial perturbance of the GFL while the grid frequency affects the following transient responses and the stability boundary. Simulation results also show that the variation of the frequency with higher RoCoF may be beneficial for the stability of the GFL, and that the effects of the various of the voltage and frequency can be studied separately.