Impedance Reshaping and Stability Analysis of the Unbalanced Three-phase System Considering the Grid-tied Inverter based Imbalance Compensation

Grid-tied inverters have been adopted both as the interface of renewable energy resources and as a solution to address power quality issues. To compensate the imbalance distortion caused by asymmetric local load, DQ transformation based compensation method is introduced into the control scheme of the grid-tied inverter. Taking both the inverter control scheme and circuit topology into account, the space vector based impedance modelling and stability analysis approaches are proposed in this paper to analyse the dynamic of the asymmetric system with active imbalance compensation. The proposed impedance models indicate that the compensation control method can reshape the output impedance features, and affect the stability of the system. The stability analysis results are verified in this paper by experimental results.

Conditional Symmetry of a Memristive System with Amplitude and Frequency Modulation Control

In this study, we studied the effects of offset boosting on the memristive chaotic system. A system with symmetry and conditional symmetry was constructed, by adding the absolute value function to an offset boosting system. It is proved that the symmetric system or a conditionally symmetric system can be constructed with similar or the same dynamic characteristics by using certain correction and offset boosting in an asymmetric system. In addition to multiple stability, the memristive system can also realize the amplitude and frequency control by introducing a parameter. The simulation circuit verifies the amplitude modulation characteristics of the system.

Compensation for Lateral Misalignment in Litz Wire Based on Multilayer Coil Technology

This study applies a multilayer coil technology that can compensate for a decrease in transfer efficiency due to a lateral misalignment in a practical 100 kHz-band wireless power transfer system and validates its effect on the efficiency of compensation. The effectiveness is investigated using coils fabricated with Litz wires. Three-turn rectangular assistant coils 22.4 × 45.3 mm2 in size were stacked on a five-turn circular primary coil with a diameter of 45.3 mm in a 2 × 1 array. Transfer efficiency between two such coils was measured by producing lateral misalignment, while maintaining the vertical distance between the Tx and Rx coils at 7 mm. The experimental results showed that the transfer efficiency was compensated by approximately 46.1%P maximum in a misalignment state of 30 mm, which corresponded to 67% of the maximum size of the coil, compared to the transfer efficiency of the structure, in which the multilayer coil was not applied. Furthermore, transfer efficiency was compensated by 37.6%P, even in an asymmetric system in which the multilayer structure was applied only to the Tx coil, thereby confirming an excellent multilayer coil technology effect on compensation for lateral misalignment in practical cases.

High Security Optical Encryption based on Sweeping Computational Ghost Imaging

A method for the optical data encryption and decryption based on the sweeping computational ghost imaging is proposed. This method is governed on reconstructing the ghost imaging by one-by-one sweeping of rows or columns of the random generated matrices. Proposed encryption in this paper is defined by these sweeping row and column matrices and basic mathematical operators between them. Introduced encryption can be employed as symmetric and asymmetric encryptions. In the symmetric system, cross-operator and the row and column matrices were assumed as private keys, defining the four basic operators as decryption keys. Whereas, in the asymmetric system, permutation of three possible cases was considered as private keys, leaving cross-operator and row and column selection sequence as public keys. The number of pixel changing Rate (NPCR) as a parameter that evaluates the strength of image encryption versus differential attacks was calculated for each case which show high security data transfer to the user. In the asymmetric systems, even with eavesdropping 50% of data, no useful information was obtained from the image or data. In the symmetric systems, with eavesdropping 100% of data, no useful information was obtained by multiple attacking the encrypted data. Offered high security along with achievable high speeds and compact data packages classify sweeping computational ghost imaging among the best applicable methods for optical data encryption.

Performance Investigation of Stochastic Resonance in Three Types of Asymmetric Bistable System Driven by Trichotomous Noise

This paper proposes a new system whose potential function is with three types of asymmetric potential wells, driven by trichotomous noise. Firstly, the three types of asymmetric bistable system are described in detail, and the changes of asymmetric bistable system potential function under different asymmetric factors are analyzed. Secondly, the effect of potential function parameters, asymmetric factor α , noise intensity D, and the probability of particle transition q is discussed, using numerical simulation. The detection effects of traditional symmetric SR and three types of asymmetric SR are observed and compared under the driving of trichotomous noise and periodic signals. The mean of signal-to-noise ratio gain is the indicator of the system's effectiveness on enhancing weak signal. The results indicate that it can make the detection effect of the asymmetric system better than that of the traditional bistable system by adjusting the parameters of the asymmetric stochastic resonance system and trichotomous noise.

Stability and Chaos Analysis of Nonlinear Roll Motion of Trimaran Ship With Variable Lay-Out Under Wind and Waves

The combined action of wind and waves has a great influence on the dynamic stability of roll motion of a trimaran ship, which may get into chaotic situation even capsizing. The lay-out of the trimaran is the main factor influencing the roll performance and its dynamic stability. In order to study the stability performance of the roll motion, firstly, the nonlinear roll motion equations under transverse wind and beam waves are established, in which the main coefficients are obtained by CFD method combined with model test. Then, the Hamilton system is used to analyze the phase portraits of the homoclinic and heteroclinic orbits under different transverse spacing. Finally, the Melnikov function is used to calculate the critical wave threshold of the asymmetric system under the combined action of wind load and wave force, and the Lyapunov exponent based on RHR algorithm was used to verify it. A series of significant conclusions are obtained by comparing the calculation models of different transverse spacing, which can provide references for the design of the trimaran ship.

Dynamic Behaviors Analysis of Asymmetric Stochastic Delay Differential Equations with Noise and Application to Weak Signal Detection

This paper presents the dynamic behaviors of a second-order asymmetric stochastic delay system with a Duffing oscillator as well as through the detection of weak signals, which are analyzed theoretically and numerically. The dynamic behaviors of the asymmetric system are analyzed based on the stochastic center manifold, together with Hopf bifurcation. Numerical analysis revealed that the time delay could enhance the noise immunity of the asymmetric system so as to enhance the asymmetric system’s ability to detect weak signals. The frequency of the weak signal under noise excitation was detected through the ‘act-and-wait’ method. The small amplitude was detected through the transition from the chaotic to the periodic state. Theoretical analysis and numerical simulation indicate that the application of the asymmetric Duffing oscillator with delay to detect weak signal is feasible.

Radiation instability in a split-cavity resonator

The interaction of an electron beam with the electromagnetic field of a split resonator that consists of a hollow cylindrical resonator and a conducting grid dividing it into coupled sections was considered. In the small-signal approximation, taking into account the space charge of the beam for an asymmetric resonator, the expression for the energy loss by the electron passing through the system was obtained. Within the chosen approximation, it was shown that a resonator with equal length sections provides greater efficiency in the transfer of energy from a charged particles beam to an electromagnetic field in comparison with an asymmetric system configuration. It was found that the interaction of an electron with a space charge in a split resonator leads to the increase of the radiation beam instability with the increase of its density. The effect of current modulation of the electron beam passing through the system was studied. It was shown that the resonator size increase leads to the increase of the amplitude of the beam current variable component at the system output. The increase of the current density of the beam entering the interaction region also leads to the increase of the modulation efficiency. The possibility of increasing the modulated current amplitude in a system with unequal sections was considered.

Research and application of weak fault diagnosis method based on asymmetric potential stochastic resonance

Because fault characteristics are often difficult to extract from a strong noise background, it is essential for mechanical fault diagnosis to extract a weak characteristic signal with a very small signal-to-noise ratio from a noisy interference. Therefore, this paper proposes a new method for diagnosing weak faults in asymmetric potential stochastic resonance. Compared with the existing methods, the asymmetric potential stochastic resonance method not only has characteristics common to the symmetric potential stochastic resonance, but can also change the inclination of the barrier and slope of the wall to obtain a better model structure. The proposed method solves the local adjustment problem of the existing method from the perspective of potential structure and optimizes the asymmetric system shape to better target frequency detection during much interference from noise. After simulation, a bearing failure test, and rolling mill gearbox bearing failure experiments, we concluded that the asymmetric potential stochastic resonance detection technology can effectively identify faults. Compared with the symmetric potential stochastic resonance method, the proposed method has better recognition.