Improved dynamic reconfiguration strategy for power maximization of TCT interconnected PV arrays under partial shading conditions

In photovoltaic (PV) systems, partial shading is a major issue that may cause power losses, hot spots, and PV modules damage. Thus, PV array dynamic reconfiguration approaches based on irradiance equalization (IEq) between rows have been proposed to alleviate the shading effect thereby improving PV power production. However, the existing IEq-based reconfiguration techniques focus only on the minimization of row current error, without taking into consideration the voltage effect, which in turn, may result in power losses. In this regard, an improved reconfiguration strategy is proposed in the present paper to maximize the power production of a TCT interconnected PV array operating under partial shading conditions. The proposed strategy aims to achieve a PV array reconfiguration that mitigates the droop voltage issue by considering irradiance levels in both rows and columns. An in-depth investigation of a typical PV module and TCT module is provided, demonstrating that there are cases where the partial shading does not affect the PV module current but the operating voltage. In addition, an analysis highlighting the limitations of the IEq technique regarding the droop voltage issue is presented. Furthermore, mathematical development is established for deriving the objective function of the proposed strategy. The efficiency of the proposed reconfiguration strategy is assessed through experimental tests carried out on a 20 MWp PV station in Ain El-Melh, Algeria. The obtained results reveal that the proposed method overcomes the weaknesses of the existing IEq strategy and ensures power production higher than the TCT and IEq configurations by 17.25% and 19.34%, respectively

A new estimation method of irradiance on a partially shaded PV generator in grid-connected photovoltaic systems. Renewable Energy

Abstract A new method for estimating the irradiance on a partially shaded photovoltaic generator system is proposed. The basic principle of this method consists of two parts: firstly, an approximation of the obstacles' outline or the local horizon by a set of linear functions. Here, a survey of the surroundings is based on the reading of the topographic coordinates of the only significant points of all the objects surrounding the photovoltaic generator. Secondly, the irradiance on the photovoltaic plane is estimated using an accurate model such as the Perez et al. model and assuming that the shading affects both the direct radiation and a part of the diffuse component (circumsolar component). The aim of this paper is to present the principles of the proposed method and the algorithm used for calculating the irradiance on shaded planes. In addition, the results of the comparison between the simulated and measured values of this method are presented.

Power Transformers Differential Protection Using the p-q Power Theory

Part 11: EnergyInternational audienceThis paper describes the application of the p-q power theory to the differential protection of power transformers. The information provided by the harmonic content of the differential active and reactive power components is used to detect winding insulation failures and to distinguish them from magnetizing inrush current transients. A variety of test cases is presented in the paper, demonstrating the effectiveness of the protection strategy

Isolation of Multiple Subspecies of Bacillus thuringiensis from a Population of the European Sunflower Moth, Homoeosoma nebulella

Five subspecies of Bacillus thuringiensis were isolated from dead and diseased larvae obtained from a laboratory colony of the European sunflower moth, Homoeosoma nebulella. The subspecies isolated were B. thuringiensis subspp. thuringiensis (H 1a), kurstaki (H 3a3b3c), aizawai (H 7), morrisoni (H 8a8b), and thompsoni (H 12). Most isolates produced typical bipyramidal crystals, but the B. thuringiensis subsp. thuringiensis isolate produced spherical crystals and the B. thuringiensis subsp. thompsoni isolate produced a pyramidal crystal. Analysis of the parasporal crystals by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the crystals from the B. thuringiensis subsp. kurstaki and aizawai isolates contained a protein of 138 kDa whereas those from B. thuringiensis subsp. morrisoni contained a protein of 145 kDa. The crystals from B. thuringiensis subsp. thuringiensis contained proteins of 125, 128, and 138 kDa, whereas those from B. thuringiensis subsp. thompsoni were the most unusual, containing proteins of 37 and 42 kDa. Bioassays of purified crystals conducted against second-instar larvae of H. nebulella showed that the isolates of B. thuringiensis subspp. aizawai, kurstaki, and thuringiensis were the most toxic, with 50% lethal concentrations (LC(inf50)s) of 0.15, 0.17, and 0.26 (mu)g/ml, respectively. The isolates of B. thuringiensis subspp. morrisoni and thompsoni had LC(inf50)s of 2.62 and 37.5 (mu)g/ml, respectively. These results show that a single insect species can simultaneously host and be affected by a variety of subspecies of B. thuringiensis producing different insecticidal proteins