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Grid connected PV systems are becoming increasingly popular due to an exponential energy demand and also due to depletion of fossil fuels and environmental concerns. However, extraction of peak power for such system which reduce cost has always been an area of concern. Many Maximum power point tracking (MPPT) algorithms were proposed for a two stage and single stage grid connected system with some limitations in system performance. A simple strategy to extract peak power from the grid connected PV with nonlinear load at Point of common coupling (PCC) is attempted. To achieve the same task in a single stage Photovoltaic (PV) grid system, two PV emulated virtual DC voltage sources are connected in series with the PV array. The operation of this strategy is tested under low irradiation and Voltage swell at the PCC connected to the grid. A control strategy to achieve dual mode control for MPPT and to regulate DC link voltage is achieved simultaneously by the proposed control. Analysis of the control strategy is carried out using MATLAB and experimentally validated with a TMS320F28335 controller.

In this paper, a new control algorithm for grid connected inverter fed by Photovoltaic array (PV) excited wind-driven induction generator (IG) for unbalanced nonlinear load at point of common coupling (PCC) is proposed. The proposed composite power controller comprises of multi control loops such as power, voltage and current loops. The power control loop generates positive sequence reference current based on the availability of PV power and the average power demand of the load and negative sequence reference currents to compensate the oscillating power component that appears due to the unbalanced nonlinear load at the PCC and further, drop due to non-fundamental power component is compensated by addition of virtual non-linear impedance to the current control loop. The voltage control loop generates the reactive current reference to compensate the drop due to nonlinear magnetizing reactance of IG to eliminate the machine de-rating effect. The current control loop regulates the average and suppresses the oscillating power in dual decoupled double synchronous reference frame to generate modulating signal to the PV sourced inverter. Exhaustive simulations are carried out for the proposed scheme for varying irradiations, wind speed and load variations at the PCC in MATLAB and compared with direct power control scheme.

The effect of rhamnolipid during the formation of initial biofilm (48. h) by Pseudomonas aeruginosa CPCL on polypropylene surface was studied. This strain was isolated from a petroleum contaminated soil and it produces a mixture of rhamnolipids. The nutritional and environmental conditions necessary for optimal production of rhamnolipid, attachment of rhamnolipid and formation of thicker biofilm on the polypropylene surface were found to be different from one another. Comparatively lower pH and temperature, higher concentration of ammonium chloride and rotation velocity of the shaker were required for the biofilm formation and the attachment of rhamnolipid on the polypropylene surface. Screening design showed that the extent of viable cells and rhamnolipid attached to the polypropylene surface was positively correlated (r=0.474; p< 0.01). However, central composite design did not show any such relationship, possibly because of the different experimental ranges used in central composite design. There were considerable variations in the thickness and spatial arrangement of biofilms grown under these three different optimized conditions. Higher substratum coverage and thicker biofilm were observed under the condition optimized for biofilm formation when compared to the other two conditions. This study is essential since P. aeruginosa biofilms are found to have implication in bioremediation of recalcitrant pollutants. � 2011 Elsevier B.V.

The underground storage of carbon dioxide (CO2) requires building, sizing, and coupling the reservoir and distribution network (pipelines and wells) models. Independent designs of the pipeline network, well, and reservoir models do not account for the effects one system has on the others. Coupling the different models is necessary to effectively design the full system. This paper discusses a methodology of jointly optimizing the pipeline network, well, and storage systems. This method uses simple and fast models instead of fully coupled, complex, and integrated models. It is thus applicable in the early phases of projects, when system parameters are not fully characterized (i.e., for scenario building and sensitivity analysis). Two different projects are examined: a single well with a short pipeline and multiple wells with a long pipeline. These cases can be adapted to offshore or onshore conditions. Although vertical wells were considered for this study, the same methodology can be easily extended to deviated and horizontal wells. Depending on conditions, the constraints that will dominate the full system may come from either the reservoir model or the pipeline network and well models.