Nonsynchronous Modes Research Articles

Multistability of synchronous modes in a multimachine power grid with a common load and their global and non-local stability

The purpose of this work is studying the dynamics of the power grid consisting of an arbitrary number of synchronous generators supplying a common passive linear load. We focus on searching the conditions for the existence and stability of synchronous modes, i.e. the main operating modes of a power grid. The possibility of the existence of non-synchronous (quasi-synchronous and asynchronous) modes is investigated. Methods. To study the dynamics of a power grid we use the effective network model in the form of an ensemble of globally coupled nodes-generators. The state of every node is described by the swing equation. The approach for reducing the effective network to the network with a hub topology (star topology) is proposed. We use numerical methods to construct a partition of the parameter space into areas with different operating modes of the power grid. Results. The conditions for the existence, stability and multistability of synchronous modes are obtained. The main characteristics of these modes are considered, such as the power supplied by generators to the grid and the distribution of currents along transmission lines. We constructed the partition of the power gird parameter space into areas with different dynamics. Conclusion. The power grid consisting of an arbitrary number of synchronous generators supplying a common passive linear load has been studied. We shown the presence of two types of synchronous modes: homogeneous and inhomogeneous. The first is characterized by equal powers and currents flowing through all load supply paths except one. The second provides another additional path, which differs from the others in current and transmitted power. Moreover, the currents flowing along the same path, but in various modes, differ. The presence of high multistability of inhomogeneous synchronous modes has been established. The possibility of coexistence of homogeneous and inhomogeneous synchronous modes, as well as quasi-synchronous and asynchronous modes, is shown. In the power grid parameters space we found areas corresponding both the existence of only synchronous modes and their coexistence with quasi-synchronous and/or asynchronous modes.

Bistability of operating modes and their switching in a three-machine power grid.

We consider a power grid consisting of three synchronous generators supplying a common static load, in which one of the generators is located electrically much closer to the load than the others, due to a shorter transmission line with longitudinal inductance compensation. A reduced model is derived in the form of an ensemble with a star (hub) topology without parameter interdependence. We show that stable symmetric and asymmetric synchronous modes can be realized in the grid, which differ, in particular, in the ratio of currents through the second and third power supply paths. The modes of different types are not observed simultaneously, but the asymmetric modes always exist in pairs. A partition of the parameter space into regions with different dynamical regimes of the grid are obtained. Regions are highlighted where only synchronous operating modes can be established. It is shown that the grid can be highly multistable and, along with synchronous operating modes, have simultaneously various types of non-synchronous modes. We study non-local stability of the asymmetric synchronous modes and switchings between them under the influence one-time disturbances and additive noise fluctuations in the mechanical powers of the generators' turbines. The characteristics of one-time disturbances are obtained leading to either return the grid back to the initial synchronous mode or switching the grid to another synchronous mode or some non-synchronous mode. The characteristics of noise fluctuations are obtained, which provide either a more probable finding of the grid in the desirable quasi-synchronous mode, or switching to an undesirable one.

Asynchronous spiking neural P systems with local synchronization of rules

Asynchronous spiking neural P (AsynSN P) systems are a class of distributed and parallel computational models working in a non-synchronized mode, inspired by the mechanism of information processing and communication underlies biological neurons by spikes, where at each computation step, any neuron with applicable rules is not obligatory to execute an applicable rule. It remains an open problem whether AsynSN P systems using standard spiking rules (the execution of the rule only produces a spike) are equivalent in power to Turing machines. In this work, the control mechanism of local synchronization at the rule level is introduced into AsynSN P systems. Namely, there are some given locally synchronous sets of rules; if a rule in such set is executed, then all applicable rules residing in the same set should be executed simultaneously. The computational power of AsynSN P systems with local synchronization of rules is examined. It is demonstrated that with local synchronization of rules, both general and unbounded AsynSN P systems are Turing universal, whereas bounded AsynSN P systems can only characterize the family of semilinear sets of numbers, using standard spiking rules. These results demonstrate the great potential for the local synchronization of rules to improve the computational capability of AsynSN P systems.

Analysis of performance parameters for wireless network using switching multiple access control method

The developments of wireless networks have directed to search for opportunities of a broad diversity of improved and new networking contributions. Wireless Asynchronous Transfer Mode (ATM) is a non-synchronous or random mode of transferring information. The advantages of circuit switching include dedicated connections and guaranteed traffic parameters and the benefits of packet switching are the efficiency at the physical layer and a more cost-effective design. ATM is the only protocol that offers the best of both communication methods. Although the Variable Bit-Rate (VBR) transmission presents a promising prospective of stable data quality, it is usually accompanied by network traffic overload and cell packet loss, which extensively weakens that potential. This work overcomes these concerns by developing a switching-based multiple access control model to improve the data transmission performance of wireless ATM. Therefore, this work discusses the effectiveness of the developed approach to minimize the cell packet losses and network traffic overload in wireless ATM. Three control access is processed; polling, token passing, and reservation algorithms for collision avoidance. The reservation stage reserves the data before sending, which includes two timeline intervals; a fixed-time reservation period, and variable data transmission interval. Using OPNET 10.5, the results show that the presented switching-based multiple access control model can achieve a throughput value of 98.3 %, data transmission delay of about 40.2 ms, and 0.024 % of packet losses during data transmission between the source and destination. It is demonstrated that the introduced method effectively transmits information without creating any network complexity and delay

Phase synchronization of fluid-fluid interfaces as hydrodynamically coupled oscillators

Hydrodynamic interactions play a role in synchronized motions of coupled oscillators in fluids, and understanding the mechanism will facilitate development of applications in fluid mechanics. For example, synchronization phenomenon in two-phase flow will benefit the design of future microfluidic devices, allowing spatiotemporal control of microdroplet generation without additional integration of control elements. In this work, utilizing a characteristic oscillation of adjacent interfaces between two immiscible fluids in a microfluidic platform, we discover that the system can act as a coupled oscillator, notably showing spontaneous in-phase synchronization of droplet breakup. With this observation of in-phase synchronization, the coupled droplet generator exhibits a complete set of modes of coupled oscillators, including out-of-phase synchronization and nonsynchronous modes. We present a theoretical model to elucidate how a negative feedback mechanism, tied to the distance between the interfaces, induces the in-phase synchronization. We also identify the criterion for the transition from in-phase to out-of-phase oscillations.

Dynamic event-based reliable dissipative asynchronous control for stochastic Markov jump systems with general conditional probabilities

The paper concerns the problem of reliable dissipative asynchronous controller design for a type of stochastic Markov jump systems (MJSs) with general conditional probabilities in the presence of the dynamic event-triggered rule. Since the mode information of the stochastic MJS is impossible to obtain, a reliable asynchronous controller is established such that the phenomena of nonsynchronous modes between the original stochastic MJS and the developed controller is formulated as a hidden Markov model. A novel dynamic event-triggered strategy is constructed to further decrease the data transmission frequency over the communication network. By taking the internal dynamic variable into account, the criteria of stochastically stable with the reliable dissipativity performance for the resulting closed-loop stochastic MJS are provided based on a collection of linear matrix inequalities. Further, the designs of reliable dissipative asynchronous controller and the dynamic event-triggered strategy are developed simultaneously. Lastly, a numerical instance is supplied to elucidate the superiority of proposed method.

Finite-time asynchronous ℋ∞ filtering for discrete-time Markov jump systems over a lossy network

Summary This paper is concerned with the problem of finite-time asynchronous filtering for a class of discrete-time Markov jump systems. The communication links between the system and filter are assumed to be unreliable, which lead to the simultaneous occurrences of packet dropouts, time delays, sensor nonlinearity and nonsynchronous modes. The objective is to design a filter that ensures not only the mean-square stochastic finite-time bounded but also a prescribed level of performance for the underlying error system over a lossy network. With the help of the Lyapunov–Krasovskii approach and stochastic analysis theory, sufficient conditions are established for the existence of an admissible filter. By using a novel simple matrix decoupling approach, a desired asynchronous filter can be constructed. Finally, a numerical example is presented and a pulse-width-modulation-driven boost converter model is employed to demonstrate the effectiveness of the proposed approach. Copyright © 2016 John Wiley & Sons, Ltd.

タービン動翼回転非同期モードの強制加振方法の開発（回転非同期モードの減衰比計測）

タービン動翼回転非同期モードの強制加振方法の開発（回転非同期モードの減衰比計測）

Design and performance analysis of a novel parallel servo press with redundant actuation

The large capacity servo press is traditionally realized by means of simultaneous actuation of multiple motors. But there exist the over-constraint problem and interference among actuators, which increases the control difficulty and product cost. This paper proposed a novel parallel servo press with redundant actuation, which can avoid the over-constraint and actuation interference. The kinematic and dynamic model of the present servo press are established and thus the kinematic and dynamic performances are obtained under three working modes, i.e. the same and opposite direction modes and non-synchronous mode. The prototype of the active mechanism with the redundant actuators has been manufactured. The kinematic experiments are carried out by using API laser tracking system and the theoretical calculation results agree with the measured data very well, which validates the theoretical model and the present press mechanism.

Generative team learning in Web 2.0 environments

Purpose – The purpose of this paper is to examine how teams work and learn in Web 2.0 environments. Web 2.0 technologies enable geographically dispersed teams to work in synchronous and nonsynchronous modes of interaction in dynamic, self‐directed ways, within and across team boundaries, thereby avoiding some of the limitations of earlier generations of electronic communication.

Synchronization and complex oscillations in a two-ring system with phase control

Modes of dynamic behavior in a coupled system with phase control are studied. The system is intended for tracking estimation of a complex signal’s parameters. The case is considered when both subsystems individually exhibit both regular and chaotic dynamic states. The boundaries of the region where the system is switched to a tracking mode are determined, and scenarios for transformation of dynamic parameters when the system leaves this area are studied. Application of complex filters in the circuits controlling the subsystems and coupling via the control circuits is shown to enable excitation of various regular and chaotic non-synchronous modes.

A Novel Technique for Steam Turbine Exhaust Pressure Limitation Using Dynamic Pressure Sensors

In this paper, a novel approach is presented to increase the operational flexibility of steam turbines. Exhaust pressure at the exit of the last-stage blades is one of the most important parameters that limit the operation of a steam turbine, especially on days with hot ambient conditions. The main concern in these off-design high-exhaust pressure operating conditions is that it can result in flow separation, which can lead to aeromechanics instabilities and thus to blade failure because of high-cycle fatigue. In the method proposed in this paper, dynamic pressure transducers are placed around the perimeter of the last-stage blade to measure the pressure variations caused by vibrating last-stage blades. This approach, which is applicable to condensing turbines only, will provide increased exhaust pressure limits through realtime monitoring of the pressure signal and thereby enable the power plant to produce more power during times of peak demand. Finite elements analysis was performed to predict the natural frequencies of the row of blades to distinguish between the synchronous and nonsynchronous modes of vibration. Strain gauges were placed on the blades to obtain the experimental frequency information of the system. Response from the dynamic pressure transducers was compared with responses from the strain gauges. An excellent agreement between the two sets of results proved the validity of the proposed method.

The Dynamics of a Frequency- and Phase-Controlled Oscillator

We study the dynamic regimes of a phase/frequency-locked loop with second-order filter. The appearance and evolution of synchronous and nonsynchronous modes are analyzed as functions of the parameters of the control circuits and of the initial frequency mismatch. We focus on the influence of the frequency-control loop on the dynamic modes of the controlled oscillator.

Part transfer mode selection in a cyclic mixed-model line

Considers the transfer mode selection problem (TMSP) in a mixed-model assembly line which is operated under a cyclic scheduling policy. Assembly lines are mostly designed for the synchronous transfer mode. There is a change in the assembly technology toward the nonsynchronous transfer mode which offers higher production rates than its synchronous counterpart. In the paper, a model for determining the cycle time of a mixed-transfer mode assembly line is presented. The TMSP in a mixed-model assembly line is then formulated as a mixed-integer program. Computational results on performance comparisons of different transfer mode configurations are presented.

Mode competition in fourth-harmonic magnicon amplifiers

In the magnicon RF amplifier, the drive and gain cavities are cylindrical deflection cavities which operate in a rotating TM/sub 110/-mode and spin up an electron beam to high transverse momentum. As a result of the rotating-mode interaction, the electron beam entry point into the output cavity rotates about the axis at the drive frequency. The gyrotron-like output cavity can be operated at m times the drive frequency by using a mode with an azimuthal index of m, as this mode rotates at m/sup -1/ times its RF frequency, thus maintaining synchronism with the electron beam. Previous frequency-multiplying magnicons have used m=2; in this paper it is shown that magnicons with m=4 may be practical, provided one also operates the output cavity at the m/2 harmonic of the cyclotron frequency. Operation at higher harmonics lowers the frequency of the deflection cavities allowing lower RF fields, reducing cavity breakdown problems; lower magnetic fields, reducing magnet cast and complexity; and a larger electron beam, relaxing beam quality constraints. On the other hand, higher order azimuthal-index magnicon modes interacting at higher order cyclotron interactions are subject to competition with nonsynchronous (gyrotron) modes and are more sensitive to electron beam scanning angle spread. A time-dependent multimode gyrotron code has been modified to examine competition in the output cavity between the phase-synchronous operating mode and other nonsynchronous modes which interact via the conventional gyrotron interaction. Calculations have been carried out for fourth-harmonic magnicons with TM/sub 410/ and TE/sub 411/ mode output cavities and include the effects of mode competition with nonsynchronous modes as well as a spread in entry-point angles of the scanning electron beam.

Theory of competition between synchronous and nonsynchronous modes in a magnicon output cavity

In the magnicon amplifier, a scanning electron beam drives a synchronous fast-wave interaction in a cylindrical output cavity. The output cavity is designed to support a synchronous transverse magnetic (TM) waveguide mode, usually the TM210 mode. However, a number of other transverse electric (TE) or TM modes can be excited in the cavity via a nonsynchronous, gyrotron-type interaction. To investigate the possibility of competition from these nonsynchronous modes, a multimode gyrotron simulation theory and code have been adapted to the magnicon configuration. The gyrotron theory and corresponding code have been generalized to include a synchronous TM mode as well as nonsynchronous TE modes. Proper phase averaging between the modes, and between the modes and the beam electrons, is critical to accurate mode competition calculations. In nonsynchronous interactions this is achieved by averaging with respect to electron entrance time and the orbit guiding center angle. The synchronous mode interaction is invariant with respect to these two averages; however, it is affected by the scanning angle spread, which is included via a third average over scanning angles. Calculations have been carried out to model a second-harmonic X-band magnicon experiment, which is currently underway at the Naval Research Laboratory (NRL). The output cavity has been optimized for the TM210 mode at 11.4 GHz or twice the drive frequency (ωd=5.7 GHz). The principal competing mode is the TE121 mode. The simulations show that nonsynchronous mode interactions are suppressed by the synchronous interaction if the scanning angle spread is sufficiently small (≤90° in the NRL configuration).

Computer modeling of theoretical structures of monoacid triglyceride α‐forms in various subcell arrangements

AbstractSix theoretical triarachidin space‐filling α‐form structures were examined using a computer modeling technique that simulated restricted oscillations of carbon zigzag planes in synchronous and nonsynchronous modes. Intermolecular minimization procedures determined best‐fit positions around a centralized molecule, which enabled calculation of total lattice energy values for nine different hexagonal subcell arrangements. Subcell arrangement had a greater effect on the energy of the system than did the configuration of the triglyceride. The analysis thus far indicates several equally preferred structure‐sub cell arrangement combinations for triglyceride α‐forms rather than a single crystalline entity.

Thermochemical kinetics of nitrogen compounds. V. The unimolecular thermal decomposition of diallylamine in the gas phase

AbstractThe kinetics of the thermal decomposition of diallylamine to propylene and prop‐2‐enaldimine have been studied in the gas phase in presence of an excess of methylamine over the temperature range of 532.7 to 615.6°K, using a static reaction system. Methylamine reacted with the unstable primary product prop‐2‐enaldimine, forming the thermally stable N‐methyl prop‐2‐enaldimine.First‐order rate constants, based on the internal standard technique, fit the Arrhenius relationship log k(s−1) = (11.04 ± 0.13) − (37.11 ± 0.33 kcal/mole)/2.303 RT. They were independent on the initial total pressure (46–340 torr), the initial pressure of diallylamine (9.2–65 torr), or methylamine as well as the conversion attained. Despite an apparent surface sensitivity, the reaction is essentially homogeneous in nature as demonstrated by experiments carried out in a packed reaction vessel.The observed activation parameters for the title reaction together with those observed earlier for triallylamine and allylcyclohexylamine are consistent with the proposed concerted reaction mechanism involving a cyclic 6‐center transition state. The observed substituent effects suggest a nonsynchronous mode of bond breaking and bond formation.

Wave propogation and transient beam loading in alternating periodic structures

The exact response of beperiodic accelerating structures to transient excitations is derived. Numerical examples of the field build-up are given, and the effect of the second nearest neighbour coupling on the wave propogation and on the phase and amplitude stability during transients is investigated. A comparison is drawn of the performances of biperiodic structures and of monoperiodic structures operating in the π mode. The effect of transient beam loading is expressed in terms of a drive in each accelerating cell. Computations are carried out to assess the effect of the nonsynchronous modes on the beam during, and after, the beam has filled the structure.