Improved QPR Power Controller With Harmonic Compensator For Wind Grid-Connected Inverter

The grid-connected inverter plays an important role in wind turbine grid-connected power generation system. The performance of inverter control strategy directly affects the grid-connected current quality. For quasi-proportional resonant(QPR) control, the output signal step of controller exists owing to the input signal step, and the grid current will be distorted by the low-frequency noise in the input signal. In order to solve these problems, the performance of quasi-PR control should be improved, so a method of constructing quasi-PR controller with two degrees of freedom is adopted, by which the improved controller can effectively suppress the influence of the step and low-frequency noise in the input signal on the grid-connected current. The improved controller is simulated on MATLAB, and the results show that the applied method can effectively improve the property of the existing problems of quasi-QPR controller and the quality of grid-connected current. Keywords: Grid-connected inverter, Harmonic compensator, Matlab/Simulation, 2-DOF,QPR. DOI: 10.7176/CTI/8-0

Geographic Distribution and Risk Factors of the Initial Adult Hospitalized Cases of 2009 Pandemic Influenza A (H1N1) Virus Infection in Mainland China

Background: As of 31st March 2010, more than 127,000 confirmed cases of 2009 pandemic influenza A (H1N1), including 800 deaths, were reported in mainland China. The distribution and characteristics of the confirmed cases in the initial phase of this pandemic in this country are largely unknown. The present study aimed to characterize the geographic distribution and patient characteristics of H1N1 infection in the 2009 pandemic as well as to identify potential risk factors associated with adverse patient outcome in China, through retrospective analyses of 885 hospitalized cases with confirmed H1N1 infection. Methodology/Principal Findings: The proportional hazards model was employed to detect risk factors for adverse outcome; the geo-statistical maps were used to characterize the distribution of all 2668 confirmed H1N1 patients throughout mainland China. The number of new cases increased slowly in May, 2009, but rapidly between June and August of the year. Confirmed cases were reported in 26 provinces; Beijing, Guangdong, Shanghai, Zhejiang and Fujian were the top five regions of the incidence of the virus infection. After being adjusted for gender, age, chronic pulmonary disease and other general symptoms, delay for more than two days before hospital admission (HR: 0.6; 95%CI: 0.5–0.7) and delayed onset of the H1N1-specific respiratory symptoms (HR: 0.3; 95%CI: 0.2–0.4) were associated with adverse patient outcome. Conclusions/Significance: The 2009 pandemic influenza A affected east and southeast coastal provinces and most populous cities more severely than other regions in mainland China due to higher risk of high level traffic-, high population density-, and high population mobility-associated H1N1 transmission.The clinical symptoms were mild in the initial phase of infection. Delayed hospital admission and delayed appearance of respiratory symptoms were among the major risk factors for poor patient outcome. These findings may have significant implications in the future pandemic preparedness and response

Decoupled Land and Ocean Temperature Trends in the Early-Middle Pleistocene

Record of long-term land temperature changes remains ephemeral, discontinuous, and isolated, thus leaving the common view that Pleistocene land temperature evolution should have followed ocean temperatures unconfirmed. Here, we present a continuous land surface temperature reconstruction in the Asian monsoon region over the past 3.0 Myr based on the distribution of soil bacterial lipids from the Chinese Loess Plateau. The land temperature record indicates an unexpected warming trend over the Pleistocene, which is opposite to the cooling trend in Pleistocene ocean temperatures, resulting in increased land-sea thermal contrast. We propose that the previously unrecognized increase of land-sea thermal contrast during much of the Pleistocene is a regional climate phenomenon that provides a likely mechanism in favor of the long-term enhancement of the Pleistocene East Asian summer monsoon

The Sihailongwan Maar Lake, northeastern China as a candidate Global Boundary Stratotype Section and Point for the Anthropocene Series

Sihailongwan Maar Lake, located in Northeast China, is a candidate Global boundary Stratotype Section and Point (GSSP) for demarcation of the Anthropocene. The lake’s varved sediments are formed by alternating allogenic atmospheric inputs and authigenic lake processes and store a record of environmental and human impacts at a continental-global scale. Varve counting and radiometric dating provided a precise annual-resolution sediment chronology for the site. Time series records of radioactive (239,240Pu, 129I and soot 14C), chemical (spheroidal carbonaceous particles, polycyclic aromatic hydrocarbons, soot, heavy metals, δ13C, etc), physical (magnetic susceptibility and grayscale) and biological (environmental DNA) indicators all show rapid changes in the mid-20th century, coincident with clear lithological changes of the sediments. Statistical analyses of these proxies show a tipping point in 1954 CE. 239,240Pu activities follow a typical unimodal globally-distributed profile, and are proposed as the primary marker for the Anthropocene. A rapid increase in 239,240Pu activities at 88 mm depth in core SHLW21-Fr-13 (1953 CE) is synchronous with rapid changes of other anthropogenic proxies and the Great Acceleration, marking the onset of the Anthropocene. The results indicate that Sihailongwan Maar Lake is an ideal site for the Anthropocene GSSP

Research on Hierarchical and Distributed Control for Smart Generation Based on Virtual Wolf Pack Strategy

Nowadays, haze has become a big trouble in our society. One of the significant solutions is to introduce renewable energy on a large scale. How to ensure that power system can adapt to the integration and consumption of new energy very well has become a scientific issue. A smart generation control which is called hierarchical and distributed control based on virtual wolf pack strategy is explored in this study. The proposed method is based on multiagent system stochastic consensus game principle. Meanwhile, it is also integrated into the new win-lose judgment criterion and eligibility trace. The simulations, conducted on the modified power system model based on the IEEE two-area load frequency control and Hubei power grid model in China, demonstrate that the proposed method can obtain the optimal collaborative control of AGC units in a given regional power grid. Compared with some smart methods, the proposed one can improve the closed-loop system performances and reduce the carbon emission. Meanwhile, a faster convergence speed and stronger robustness are also achieved

User-Generated Digital Flashcards Yield Better Learning Than Premade Flashcards

10.1037/mac0000083JOURNAL OF APPLIED RESEARCH IN MEMORY AND COGNITIO

Heat-cured cement-based composites with wet-grinded fly ash and carbide slag slurry: Hydration, compressive strength and carbonation

Fly ash (FA) with high glassy phase content is a pozzolanic material with low activity, while carbide slag is a solid waste with portlandite crystals embedded in the impurity phases. Herein, wet-grinding method was used twice to improve the pozzolanic reactivity of FA and promote the dissolution of embedded calcium hydroxide in the CS as a lime source, respectively. Wet-grinded FA slurry (WFA) with D50 of 2.5 mu m and wet-grinded CS slurry (WCS) with D50 of 3.0 mu m were prepared. It was found that setting times, hydration heat release, early and late compressive strength, carbonation resistance of high volume WFA blended composites were significantly enhanced by WCS, attributed to the pre-dissolved calcium resource and alkali reserve. However, an excessive amount (12 wt%) of WCS addition causes an abnormal decrease in strength, due to the microstructure degradation by coarse portlandite crystals. Higher proportion of C-S-H might be ready for carbonation in high volume WFA blended composites, due to the promoted Al incorporation in C-S-H by wet-grinding.Web of Science307art. no. 12491