Li S.,Hubei University for Nationalities
Solar Energy | Year: 2014
In this paper, a unified model of three basic DC/DC converters is firstly proposed under certain conditions. This model is named as inductance-capacitor-diode (LCD) circuit and consisted of an inductance, a capacitor and a diode. Based on LCD circuit, a maximum power point tracking (MPPT) control strategy with variable weather parameter is proposed for photovoltaic (PV) generation systems with DC bus. In this strategy, through using LCD circuit instead of DC/DC converter, the MPPT performance of PV system is not influenced by the choice of different DC/DC converter topologies and the configuration of PV system is simplified, which makes the overall cost lower and the system integration, modularization and miniaturization more convenient. Finally, the accuracy of LCD model, and the feasibility and availability of proposed MPPT control strategy are verified by some simulated experiments conducted under random weather conditions; the effect of non-uniform weather on proposed MPPT strategy is tested by some experiments under non-uniform weather conditions; the output transient-state performance of proposed MPPT strategy is analyzed by one experiment under a varying irradiance condition and the performance comparison with conventional P&O method is made by another experiment under a given weather condition. © 2014 Elsevier Ltd.
Zeng X.-X.,Chongqing Jiaotong University |
Liu X.-M.,Hubei University for Nationalities |
Liu W.-B.,Beijing Normal University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2015
Gravitational collapse of a shell of dust in noncommutative geometry is probed by the renormalized geodesic length, which is dual to probe the thermalization by the two-point correlation function in the dual conformal field theory. We find that the larger the noncommutative parameter is, the longer the thermalization time is, which implies that the large noncommutative parameter delays the thermalization process. We also investigate how the noncommutative parameter affects the thermalization velocity and thermalization acceleration. © 2015 The Authors.
Liu H.,Hubei University for Nationalities
Journal of Nanoparticle Research | Year: 2010
Iron phosphate nanorods were synthesized via a novel facile route. The structure, composition, and morphology of the prepared material were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM), respectively. The diffraction lines were indexed to the hexagonal structure. The diameter of these nanorods is about in the range of 20-30 nm and the length 50-100 nm. The preferential growth direction of the prepared material was the . The reaction mechanism for the synthesis of FePO4 nanorods was also primarily discussed. Compared to the bulky and the irregular nanoparticles, the nanometer ones will be more fascinating for application in many areas. © 2010 Springer Science+Business Media B.V.
Li S.,Hubei University for Nationalities
Solar Energy | Year: 2015
To improve the tracking speed of maximum power point (MPP) of photovoltaic (PV) system, some maximum power point tracking (MPPT) algorithms or their improved algorithms have been studied in depth. However, these algorithms are usually the improvement for a certain MPPT method, now there still exists no common method for improving the rapidity of the MPP tracking. To solve this question, in this paper, the conceptions of load-variable-weather-parameter (RVWP) optimization interval and variable-weather-parameter (VWP) optimization interval are proposed. Meanwhile, on the basis of them, a VWP optimization strategy, which can optimize the tracking speed of most MPPT algorithms, is proposed. In this strategy, the control signal of PV system has been quickly contracted within RVWP interval or VWP interval before a MPPT method which will implement the MPP tracking is operated. Therefore, the essence of this strategy is that the MPP tracking speed is increased by contracting the optimizing range-in other words, the global optimization is converted into local optimization. Finally, in this paper, the conventional perturb and observe (P&O) method is selected as the optimized object to study the MPP tracking speed under constant load, changing load, constant weather and changing weather conditions. The results of simulated experiments show that the MPP tracking speed can be greatly optimized by VWP optimization strategy with RVWP interval in any case and can be optimized by VWP optimization strategy with VWP interval in most cases, and that the output power stability can be also optimized by proposed optimization strategy for PV system with output power oscillating. © 2014 Elsevier Ltd.
Ma D.-Z.,Hubei University for Nationalities |
Cao Y.,Beijing Normal University |
Wu J.-P.,Beijing Normal University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011
In this Letter we construct the Stückelberg holographic superconductor with Weyl corrections. Under such corrections, the Weyl coupling parameter γ plays an important role in the order of phase transitions and the critical exponents of second order phase transitions. So do the model parameters cα, α and c4. Moreover, we show that the Weyl coupling parameter γ and the model parameters cα, α, c4 which together control the size and strength of the conductivity coherence peak and the ratio of gap frequency over critical temperature ωg/Tc. © 2011 Elsevier B.V.