Advanced Materials Research Vols. 347-353

Abstract: Output power characteristic of wind generator has different influence on PCC voltage stability, which consists of three kinds wind generator- constant speed induction wind generator, doubly-fed variable speed constant frequency (VSCF) wind generator(DFIG), and direct-driven permanent magnetic synchronous generator ( PMSG).This article establishes simulation model of power grid interconnected by wind farm under Matlab environment, and writes flow calculation procedures. The simulation results show that doubly-fed VSCF wind generator and direct-driven PMSG can improve PCC voltage stability when the fault happened in wind power grid integration.

Abstract: The paper focuses on floating offshore wind turbine (FOWT) and makes a review of famous designs. FOWT foundation is classified into three categories based on the strategy to achieve static stability. In order for utilization, a new concept is proposed and primary design for water depth of 90m is described. Moreover, dynamic analysis of this concept under operational condition is carried out. The thrust force on the rotor is evaluated based on software analysis; the hydrodynamic forces are calculated using Morison equation. The results indicate that the concept is excellent and worth for further development.

Abstract: Agricultural non-point source (NPS) pollution is a growing environmental problem, contributing much to water eutrophication in China as well as in other parts of the world. NPS pollutants are heterogeneously distributed and discharged from agricultural lands and other sources, and extremely hard to control by technical measures. Hence, control of the water quality problems caused by agricultural NPS pollution becomes difficult if recommended best management practices (BMPs) can’t be well implemented. In this paper, current research progress related to distinguishing agricultural NPS pollution sources was reviewed. Three pivotal methods for identifying agricultural NPS pollution sources were introduced and the advantages and disadvantages of each approach were discussed. Finally suggestions were presented on better identifying agricultural NPS pollution sources in China.

Abstract: Nowadays the voltage instability problems occur in the distribution grid due to the integration of more and more fluctuant distributed generators. This paper focuses on voltage stability of distribution networks with wind generation. A voltage stability index is presented, and calculated by an expanding Newton-Raphson power flow method in which the wind power generation nodes are modified according to the P-Q(V) character. In order to obtain the key components of fluctuant wind power, the Hilbert-Huang transform algorithm is utilized to reveal the inherent characteristics of wind power. The extrema extending method based on the mirror periodic is used in the empirical mode decomposition and can handle the end effects. According to the Hilbert spectrum and instantaneous energy of each intrinsic mode functions, the components with lower instantaneous frequency are selected to rebuild the wind power. The new rebuilt series consist of stationary and monotonic components which are smoother, and the rebuilt series can reflect the main fluctuant characteristic of the initial wind power data by comparing the index.

Abstract: Heavy metal pollution is not only damaging to the environment, plant growth, but also harming animal and human health through the food chain. The experimental environment in this paper was coastal sediment, the effects of the biomass and the absorption of heavy metal of Suaeda heteroptera kitagawa by Perinereis aibuhitensis activities were studied by the concentration of Cu and Pb in the body of Suaeda heteroptera kitagawa and the concentration of Cu and Pb, the available N, the available P, the total organic carbon and pH value in the sediment were measured. The results showed that the pH value of sediment was increased, the available N and the available P of sediment were raised and the biomass of the plant were improved in control groups by Perinereis aibuhitensis activities, the difference of fresh weight between with worm and without worm were 134.1. Perinereis aibuhitensis activities raised the concentrations of CaCl2-Cu and DTPA-Pb in the sediment, enhanced metal bioavailability and promoted the Cu and Pb absorption of Suaeda heteroptera kitagawa, the Cu concentrations and the Pb concentrations in the body of plant of under ground with worm was 1.14-2.89 times and 1.33-7.57 times that of without worm. Those provided the basis for improving the efficiency of phytoremediation of the heavy metal contaminated sediment.

Abstract: Water-insoluble chitin betainate was environmentally friendly prepared by esterifying chitin with betaine hydrochloride in the presence of dicyandiamide by dry process. The process achieved free-pollution and easy treatment. The chitin betainate holds potential as an adsorbent by the results of the adsorption experiments.

Abstract: Wind speed forecasting is critical for wind energy conversion systems. Adaptive and reliable methods and techniques of wind speed forecasting are urgently needed in view of the stochastic nature of wind resource, which is varying from time to time and from site to site. Multi-step-ahead speed forecasting is built with empirical mode decomposition (EMD) method and RBF neural network, which makes use of non-linear and non-stationary signal characteristics. Time series of original wind speed data is decomposed by EMD method. And RBF neural network is used to predict the decomposition of the various components. Experimental results show that the method effectively improves the accuracy and the reliability of wind speed forecasting.

Abstract: The microscope characters of flame-retardant PC/ABS by a new kind of phosphate flame retardant, bisphenol-a bis (dipenyl phosphate) (BDP), is carried out in this paper using Scanning Electron Microscope (SEM). The result shows that flame retardant and unflame retardant materials before combustion and after indicate that these lame retardant materials after combustion shape countless closed holes which form sprangly cellular coking char layer, which also make out that BDP play the condensation flame retardant role in PC/ABS resin.

Abstract: Direct-driven permanent magnet synchronous generator (PMSG) has become an important research subject besides the double-fed induction generator. With the increasing of unit capacity, the study of topology of high power converters based on multi-level converter is attracting more and more attention. The study of vector control of the direct-driven permanent magnet synchronous wind turbines based on three-level converter is carried out in this paper. Based on the maximum wind-energy capture control of the PMSG, the unity power factor operation of PMSG is realized by controlling the d-axis current to zero in the generator-side converter. A detailed comparative study of two-level system and three-level system is conducted. The simulation results verify the validity of this algorithm.

Abstract: Catalytic steam reforming of bio-oil is an economically feasible route producing renewable hydrogen. Ni/MgO-La2O3-Al2O3 catalyst was prepared with Ni as active agent, Al2O3 as support and MgO, La2O3 as promoters. The experiments were carried out in a fixed-bed reactor. The content of Ni, calcination temperature, and calcinations time, were investigated with hydrogen yield as index. The optimal preparation conditions were concluded as follows: the Ni content 18%, the calcination temperature 8500C and the calcinations time 6 h.