SVPWM SWITCHING PATTERN FOR Z-SOURCE INVERTER, SIMULATION AND APPLICATION

The voltage source inverter (VSI) and current voltage source inverter (CSI) are widely used in industrial application. But the traditional VSIs and CSIs have one common problem: can’t boost or buck the voltage come from battery, which make them impossible to be used alone in Hybrid Electric Vehicle (HEV/EV) motor drive application, other issue is the traditional inverter need to add the dead-band time into the control sequence, but it will cause the output waveform distortion. This report presents an impedance source (Z-source network) topology to overcome these problems, it can use one stage instead of two stages (VSI or CSI + boost converter) to buck/boost the voltage come from battery in inverter system. Therefore, the Z-source topology hardware design can reduce switching element, entire system size and weight, minimize the system cost and increase the system efficiency. Also, a modified space vector pulse-width modulation (SVPWM) control method has been selected with the Z-source network together to achieve the best efficiency and lower total harmonic distortion (THD) at different modulation indexes. Finally, the Z-source inverter controlling will modulate under two control sequences: sinusoidal pulse width modulation (SPWM) and SVPWM, and their output voltage, ripple and THD will be compared

Social Obligations of Land Rights on Chinese Collective-Owned Land

This article critically examines social obligations on Chinese collective-owned land. Current social responsibilities on Chinese collective-owned land are inadequate, ineffective, and distorted. Rural property right holders do not owe sufficient social burdens to society. As rural land regulators, rural collectives should have the authority to regulate and manage agricultural land use. Because of the vague and weak identity of rural collectives, collectives have limited authority and resources in restricting and regulating rural land use rights. As rural landowners, collectives violate their social responsibilities by misusing agricultural land and harming society. This article argues that for agricultural land, where physical characteristics of the land are better used in farming, the use restriction serves as a social obligation that conforms to the physical characters of the land. Thus, it is justifiable for collectives or the state to impose restrictions upon the land use rights of agricultural land, especially basic agricultural land—land that is most suitable for farming. The restrictions, however, must be imposed according to physical characteristics of the land, not according to the identity of landowners

Confronting brane inflation with Planck and pre-Planck data

In this paper, we compare brane inflation models with the Planck data and the pre-Planck data (which combines WMAP, ACT, SPT, BAO and H0 data). The Planck data prefer a spectral index less than unity at more than 5\sigma confidence level, and a running of the spectral index at around 2\sigma confidence level. We find that the KKLMMT model can survive at the level of 2\sigma only if the parameter $\beta$ (the conformal coupling between the Hubble parameter and the inflaton) is less than $\mathcal{O}(10^{-3})$, which indicates a certain level of fine-tuning. The IR DBI model can provide a slightly larger negative running of spectral index and red tilt, but in order to be consistent with the non-Gaussianity constraints from Planck, its parameter also needs fine-tuning at some level.Comment: 10 pages, 8 figure

Master of Science

thesisA method for producing pure titanium dioxide with controlled particle size and morphology has been developed. The TiO2 powder produced by this method can be used as the starting material to produce pure Ti metal powder. In this method, the upgraded Ti-slag (UGS) is used as the starting material. Upgraded Ti-slag is first roasted with NaOH to produce sodium titanate. The roasted product is washed by water to remove alkaline soluble impurities like Si and Al. The titanate is then dissolved into HCl solution and filtered to prepare the solution for hydrolysis of titanic acid. Hydrolysis of titanic acid is performed at different temperatures with varied free acid concentration and equivalent TiO2 concentration. The titanic acid is then calcined to remove combined water to produce TiO 2 powder. The particle size and morphology of the titanic acid particles produced by this method depend strongly on factors including temperature, free acid concentration, equivalent TiO2 concentration, and agitation. To optimize the parameters of the hydrolysis process, a systematic parametric study was conducted. TiO2 powders with different morphology and particle size were obtained. The desired morphology of TiO2 powder is determined to be around 30µm, with a round shape and smooth surface. Porosity was found on the surface of TiO2 particles after calcination. The dependence of particle size and morphology of solid titanic acid particles on those process parameters was studied. The effect of the process parameters on the kinetics of the hydrolysis process were also studied. The mechanisms of nucleation and growth of titanic acid particles during hydrolysis was discussed

Minkowski Brane in Asymptotic dS5_5 Spacetime without Fine-tuning

We discuss properties of a 3-brane in an asymptotic 5-dimensional de-Sitter spacetime. It is found that a Minkowski solution can be obtained without fine-tuning. In the model, the tiny observed positive cosmological constant is interpreted as a curvature of 5-dimensional manifold, but the Minkowski spacetime, where we live, is a natural 3-brane perpendicular to the fifth coordinate axis.Comment: 6 pages, Latex fil