Papers by Keyword: Self-Oscillation

Abstract: Renewable energy are usually connected to the power grid through an inverter. As the penetration level of such inverter-based distribution generation resources increases, PCC point harmonics become an important concern for grid stability and power quality. In this paper, the PCC-point harmonics in a parallel-inverter-based photovoltaic station were measured and some significant characteristics of such harmonics were presented. These harmonics are stationary; the voltage and current waveforms are lower frequency, power correlation and inter-harmonic. And these harmonics are 3-phase symmetric and contain 3^rd and 6^th harmonic components. The transitions of the PCC harmonic occurrence and vanishing are instantaneous. The analysis indicates that the PCC harmonics are not produced by the resonances related to the linearities of PV inverters but the inverter nonlinearities are the primary reasons. The strategy to eliminate the PCC point harmonics are proposed in this study.

Abstract: In engineering practice, some of the structural elements take the form of a thin planar plate. For such elements, it is sometimes important to consider dangerous condition of resonance. A structural element cannot operate in the range of resonant frequencies. It is therefore necessary to determine natural frequencies and normal modes of vibration of such structural elements. Parts of the paper are the results of the analysis of natural frequencies and normal modes of vibration using FEM program Cosmos. The subject of the analysis was a thin flat circular plate considered in three modifications, i.e. free thin circular plate without hole, a thin circular plate without hole, clamped on the outer periphery, a thin circular plate with a hole, clamped on the outer and inner circumference. At the same time, Chladni patterns were obtained. They were created using the Matlab system and extraction of the outputs of the Cosmos program.

Abstract: A self-oscillating polymer chain consisting of N-ethylacrylamide (NEAAm) and a Ru catalyst of the BelousovZhabotinsky (BZ) reaction was prepared. The polymer chain underwent soluble-insoluble self-oscillation induced by the BZ reaction, originating from the differing solubility of the Ru moiety in the reduced and oxidized states. The amplitude of self-oscillation was small compared to that for the polymer chains prepared from N-Isopropylacrylamide (NIPAAm). The activation energy observed with the novel, NEAAm-based polymer chain was 68 kJ/mol, similar to that found with the NIPAAm-based polymer chain and normal (no Ru catalyst incorporated in the polymer) BZ reaction.

Abstract: Nonlinear differential equations are sometimes found by using harmonic balance principle. If it is based on the complex power balance theory, some much more correct and rational results can be obtained. Non-autonomous circuits sometimes include two components, the forced and the self-excited oscillation, they must satisfy respectively the balancing condition of complex power. When we study the nonautonomous circuit, two notable questions should be considered. On the one hand ,the existence of self-excited oscillation of the circuit which contains the dissipative elements depends on whether or not active power can maintain balance. The existence is closely related to the amplitude of excited current source. When the current source is strong enough, the original self-excited oscillation will thus disappear, leaving only a forced component. On the other hand, the existence of the self-oscillation of the lossless circuit which does not contain the dissipative elements is independent from the current amplitude of the excited source. The forced and self-excited oscillation components can simultaneously coexist unconditionally. chaos can easy be produced by the nonlinear coupling of the two harmonic components. The intrinsic attributes of the chaos can be sufficiently revealed with the help of this kind of lossless circuits.

Abstract: Base on constitution of the self-oscillation linear actuator which is a servo system for a gun launched missile, a nonlinear model was built. Though the experiment, the model is correct. This paper studied the stability, the self-oscillation's frequency and gain on this kind of servo system. On comparing phase-lead compensation and phase-lag compensation, the later is more suitable for this system. After testing, the lag regulator is designed for the system.

Abstract: In this paper, we investigated the influence of the temperatureand the initial concentrations of malonic acid on the transmittance self-oscillation for a novel nonthermoresponsivepolymer chain. The amplitude of the self-oscillation hardly changes while change in the temperature and the concentration of malonic acid. The period of the self-oscillation does not decrease with increase in the concentration of malonic acid at 14, 16 and 18 °C.

Abstract: In this paper, theeffect of the initial concentrationof nitric acidon the soluble-insoluble self-oscillation for a novel polymer chainwith nonthermoresponsive nature was investigated. The self-oscillationoccurs induced by the Belousov-Zhabotinsky (BZ) reaction. In the condition of [HNO₃] = 0.1 M, no transmittance self-oscillation occurs. In addition, in thecondition of [HNO₃] = 0.2 M, the life-time of the self-oscillation is significantly short. This is because the solution pH much affects the BZ reaction. Moreover, we demonstrated that the period of the transmittance self-oscillation decreases with the increase in the temperaturein accordance with the Arrenius equation.

Abstract: In this study, the influence of the temperature on the transmittance self-oscillation of a non-thermoresponsive polymer chain was investigated. The polymer chain was composed of a biocompatible and non-thermoresponsive poly-vinylpyrrolidone (PVP) main-chain covalently-bonded to the 10 wt% ruthenium catalyst moiety (Ru(bpy)3) of the BZ reaction. As a result, the amplitude of the transmittance self-oscillation slightly decreased with the increase in the temperature. The period of the transmittance self-oscillation decreased with increasing the temperature in accordance with the Arrenius equation. Therefore, the period of the self-oscillation can be controlled by the selection of the temperature.

Abstract: In this study, effect of the initial substrate concentrations of the Belouzov-Zhabotinsky (BZ) on a period and transmittance self-oscillating behavior for a polymer chain were investigated under the constant temperature condition (T = 20 °C). The polymer chain was composed of a non-thermoresponsive poly-vinylpyrrolidone (PVP) main-chain covalently-bonded to the 10 wt% ruthenium catalyst (Ru(bpy)3) of the BZ reaction. The transmittance self-oscillation originates from the different solubility of the Ru catalyst moiety in the reduced and oxidized state. The waveform and period of the non-thermoresponsive polymer chain was significantly affected by the initial concentration of the BZ substrates. Moreover, as the concentration of the Ru catalyst increased due to the increase in the polymer concentration, the period hardly changed because of the high solution viscosity.

Abstract: We synthesized a self-oscillating polymer chain with a negatively charged moiety. The polymer chain caused the aggregation-disaggregation self-oscillation under the constant temperature induced by the Belousov-Zhabotinsky (BZ) reaction. In this study, we investigated the influence of temperature and the concentration of sodium bromate on the aggregation-disaggregation self-oscillation of the polymer solution (1.0 wt%) in a strongly acidic condition. As a consequence, we clarified that the life-time of the self-oscillation increased with decrease in the concentration of sodium bromate. On the other hand, the lifetime of the self-oscillation decreased with increase in temperature. In high temperature condition (48 and 60 °C), the amplitude of the self-oscillation was significantly inhomogeneous. Moreover, the frequency of the self-oscillation increased with increasing temperature. On the other hand, the frequency decreased with increase in the concentration of sodium bromate. This tendency was opposite to that in the acid-free condition and the 2.0 wt% AMPS-containing polymer solution.