A novel technology for control of variable speed pumped storage power plant

Variable speed pumped storage machines are used extensively in wind power plant and pumped storage power plant. This paper presents direct torque and flux control(DTFC) of a variable speed pumped storage power plant(VSPSP). By this method both torque and flux have been applied to control the VSPSP. The comparison between VSPSP's control strategies is studied. At the first, a wind turbine with the capacity 2.2 k W and DTFC control strategies simulated then a 250 MW VSPSP is simulated with all of its parts(including electrical, mechanical, hydraulic and its control system) by MATLAB software. In all of simulations, both converters including two-level voltage source converter(2LVSC) and three-level voltage source converter(3LVSC) are applied. The results of applying 2LVSC and 3LVSC are the rapid dynamic responses with better efficiency, reducing the total harmonic distortion(THD) and ripple of rotor torque and flux.

The Impact of Land Fragmentation in the Qualitative and Quantitative Aspect of Seeds and Their Production

Due to the pedo-climate conditions in the region of Korca, this area is considered to be one of the most favorable regions for cultivating various kinds of plants such as cereals, vegetables, wood-trees, vineyards, etc. All the factors such as rain, temperature, the impact of sunlight, and the pathological structure of the land, make this region one of the most productive and qualitative among the others. Changing the political systems in Albania during the last decades in Albania had its own impact even in the agricultural aspect. Shifting from communism into a modem, capitalist economy built a huge barrier for farmers in their way to intensifying the agricultural production. Dividing the land according to the law number 7,501, was accompanied by a severe fragmentation of the plot, reducing the degree of mechanization and chemical process. In this paper, the authors will try to analyze the effect of law fragmentation in the regional farmers working process in the region of Korea, and other municipalities such as Bilisht and Maliq, nearby Korea. There were randomly interviewed 150 farmers, from which 30 from the municipality of Bilisht, 22 from Korca municipality and 15 from Maliqi. From each farmer, these were the variables taken into consideration： Total land area, irrigated land, the number of plots, the area planted with wheat, corn, vegetables, fruit, vineyards, and forages. All the data that were gathered and translated into figures have indicated statistic elements such as the average value of each variable, deviation or standard deviation, coefficient of variation, correlation and regression. For instance in the municipality of Bilisht, it has been concluded that between the total variable area and number of plots, the related correlation value of the correlation coefficient is r = ＋ 0.73 and the value of regression coefficient is R = 2.71. In this municipality, correlative links between the variable and the total area planted with wheat area, are of medium category, with a value of the correlation coefficient of r = ＋ 0.52 and the regression coefficient is R = 0.89. Regarding the studies in the municipality of Maliq, it has been a correlation link between the weak variable category： in the surface of the irrigated area and the land planted with vegetables and corn, the value of the correlation coefficient is r = ＋ 0.24 and the regression coefficient R = 2.11. In the municipality of Korea, among the variable of irrigated area and the surface of the land planted with vegetables, there is a weak correlative link with a value of the correlation coefficient r = ＋ 0.17 and the regression coefficient R = 0.58.