Design and Simulation of a Zero Crossing VSC Based Phase Synchronous Inverter for Microgrid System

A microgrid is a system which consists of the transmission line and loads capable of operating in parallel with the national grid and distributed power sources such as power generation, storage and demand management. However, to connect the wind, solar and electrostatic power generation system together with microgrid, a phase synchronisation issue arises. For the electrostatic system, generated DC voltage needs to be converted into AC to connect with the transformer-less microgrid system. This process inherently produces very low output current and also degrades the phase synchronization of the system. To counter these issues, a zero-crossing voltage source controller based phase synchronous inverter system has been designed and implemented in this paper. In addition, an active LCL filter has been designed to reduce the high harmonic distortion. Moreover, to verify the result, MATLAB2014a software has been used. In this design, input DC voltage of 10kV, switching frequency of 1.65 kHz, grid frequency of 50Hz and balanced grid loads of star configuration (00, 1200, and 2400 degree) are considered. The simulated result has shown that inverter inversion efficiency is 96.8% and phase angle error is only 3.50 degrees

Heat stress alters chlorophyll fluorescence, photosynthesis and antioxidative enzyme activities in wheat cultivars

Heat stress becomes one of the most limiting factors to crop growth and yield. To investigate the impact of heat stress on physiological and biochemical responses in wheat cultivars, a pot experiment was conducted in the Depart- ment of Crop Botany, Bangladesh Agricultural University in Mymensingh, during November 2016 to March 2017. The experiment was laid out in a two factorial CRD design with three replications. The factors were (i) four wheat cultivars (BARI GOM-25, BARI GOM-26, BARI GOM-27 and BARI GOM-28) and (ii) heat stress (control and heat). The heat stress (38/25 °C day/night) was imposed to the wheat plants for three days at early grain filling stage in a climate chamber. The control plants were remained in the field at around 20−25 °C. Heat stress declined the leaf greenness (SPAD), the maximum photochemical efficiency of PSII (Fv/Fm), photosynthesis rate (A) and grain weight in all the cultivars in comparison to control. The leaf greenness (SPAD) and Fv/Fm were declined with the progress of heat stress treatment in all four cultivars. In both cases, lowest reduction was observed in BARI GOM-28 whereas, the highest reduction in SPAD and Fv/Fm were observed in BARI GOM-26 and BARI GOM-27, respectively. The percent reductions in photosynthesis and grain weight were significantly higher in BARI GOM-28 in comparison to other cultivars. Increased activities of catalase, peroxidase and ascorbate peroxidase enzymes were observed under heat stress in all four cultivars. Therefore, it may be concluded that the cultivar BARI GOM-28 showed more tolerance to heat stress than the other cultivars based on the measured physiological and biochemical traits. [Fundam Appl Agric 2019; 4(2.000): 858-866

Characterization of Maize Hybrids (<i>Zea mays</i> L.) for Detecting Salt Tolerance Based on Morpho-Physiological Characteristics, Ion Accumulation and Genetic Variability at Early Vegetative Stage

Increasing soil salinity due to global warming severely restricts crop growth and yield. To select and recommend salt-tolerant cultivars, extensive genotypic screening and examination of plants’ morpho-physiological responses to salt stress are required. In this study, 18 prescreened maize hybrid cultivars were examined at the early growth stage under a hydroponic system using multivariate analysis to demonstrate the genotypic and phenotypic variations of the selected cultivars under salt stress. The seedlings of all maize cultivars were evaluated with two salt levels: control (without NaCl) and salt stress (12 dS m−1 simulated with NaCl) for 28 d. A total of 18 morpho-physiological and ion accumulation traits were dissected using multivariate analysis, and salt tolerance index (STI) values of the examined traits were evaluated for grouping of cultivars into salt-tolerant and -sensitive groups. Salt stress significantly declined all measured traits except root–shoot ratio (RSR), while the cultivars responded differently. The cultivars were grouped into three clusters and the cultivars in Cluster-1 such as Prabhat, UniGreen NK41, Bisco 51, UniGreen UB100, Bharati 981 and Star Beej 7Star exhibited salt tolerance to a greater extent, accounting for higher STI in comparison to other cultivars grouped in Cluster-2 and Cluster-3. The high heritability (h2bs, >60%) and genetic advance (GAM, >20%) were recorded in 13 measured traits, indicating considerable genetic variations present in these traits. Therefore, using multivariate analysis based on the measured traits, six hybrid maize cultivars were selected as salt-tolerant and some traits such as Total Fresh Weight (TFW), Total Dry Weight (TDW), Total Na+, Total K+ contents and K+–Na+ Ratio could be effectively used for the selection criteria evaluating salt-tolerant maize genotypes at the early seedling stage

Characterization of Maize Hybrids (Zea mays L.) for Detecting Salt Tolerance Based on Morpho-Physiological Characteristics, Ion Accumulation and Genetic Variability at Early Vegetative Stage

Increasing soil salinity due to global warming severely restricts crop growth and yield. To select and recommend salt-tolerant cultivars, extensive genotypic screening and examination of plants&rsquo; morpho-physiological responses to salt stress are required. In this study, 18 prescreened maize hybrid cultivars were examined at the early growth stage under a hydroponic system using multivariate analysis to demonstrate the genotypic and phenotypic variations of the selected cultivars under salt stress. The seedlings of all maize cultivars were evaluated with two salt levels: control (without NaCl) and salt stress (12 dS m&minus;1 simulated with NaCl) for 28 d. A total of 18 morpho-physiological and ion accumulation traits were dissected using multivariate analysis, and salt tolerance index (STI) values of the examined traits were evaluated for grouping of cultivars into salt-tolerant and -sensitive groups. Salt stress significantly declined all measured traits except root&ndash;shoot ratio (RSR), while the cultivars responded differently. The cultivars were grouped into three clusters and the cultivars in Cluster-1 such as Prabhat, UniGreen NK41, Bisco 51, UniGreen UB100, Bharati 981 and Star Beej 7Star exhibited salt tolerance to a greater extent, accounting for higher STI in comparison to other cultivars grouped in Cluster-2 and Cluster-3. The high heritability (h2bs, &gt;60%) and genetic advance (GAM, &gt;20%) were recorded in 13 measured traits, indicating considerable genetic variations present in these traits. Therefore, using multivariate analysis based on the measured traits, six hybrid maize cultivars were selected as salt-tolerant and some traits such as Total Fresh Weight (TFW), Total Dry Weight (TDW), Total Na+, Total K+ contents and K+&ndash;Na+ Ratio could be effectively used for the selection criteria evaluating salt-tolerant maize genotypes at the early seedling stage

Biological Nitrification Inhibition (BNI) Potential in Sorghum

The biological oxidation of ammonia (i.e. nitrification), results in the transformation of relatively immobile NH4+ into a highly mobile NO3-, which is vulnerable to losses through leaching and denitrification, resulting in low nitrogen-use efficiency in agricultural systems. The ability of certain plants to suppress soil nitrifier function by releasing inhibitors from roots is termed 'biological nitrification inhibition' (BNI). Using a recombinant luminescent Nitrosomonas europaea, we developed an assay to detect and quantify the inhibitory effects in plant soil systems termed, 'BNI activity', expressed in ATU (allylthiourea unit). Sorghum roots released (into water-based medium, hereafter referred to as root exudates) substantial amount of BNI activity. The BNI capacity (ATU g-1 root dry wt d-1) of roots changed with growth stage, from 60 ATU at 3 week old to 20 ATU at 45 day stage. In addition, sorghum roots released hydrophobic compounds, which can be recovered by washing with dichloromethane (hereafter referred to as DCM-root wash). One of the active constituents with BNI activity in root exudates, isolated by activity-guided HPLC fractionation, was a flavonoid, identified as sakuranetin. Using a similar approach, the major active constituent with BNI activity in DCM-root wash was isolated and identified as sorgoleone. Both sakuranetin and sorgoleone inhibited Nitrosomonas activity in a dose-response manner. Substantial genetic variability for sorgoleone production capacity was detected in sorghum. Some wild-sorghum species showed high-BNI capacity under field conditions. Potential implications of BNI in inhibiting nitrification and in reducing the nitrogen footprint from agricultural systems will be discussed

Biological Nitrification Inhibition (BNI) Potential in Sorghum

The biological oxidation of ammonia (i.e. nitrification), results in the transformation of relatively immobile NH4+ into a highly mobile NO3-, which is vulnerable to losses through leaching and denitrification, resulting in low nitrogen-use efficiency in agricultural systems. The ability of certain plants to suppress soil nitrifier function by releasing inhibitors from roots is termed 'biological nitrification inhibition' (BNI). Using a recombinant luminescent Nitrosomonas europaea, we developed an assay to detect and quantify the inhibitory effects in plant soil systems termed, 'BNI activity', expressed in ATU (allylthiourea unit). Sorghum roots released (into water-based medium, hereafter referred to as root exudates) substantial amount of BNI activity. The BNI capacity (ATU g-1 root dry wt d-1) of roots changed with growth stage, from 60 ATU at 3 week old to 20 ATU at 45 day stage. In addition, sorghum roots released hydrophobic compounds, which can be recovered by washing with dichloromethane (hereafter referred to as DCM-root wash). One of the active constituents with BNI activity in root exudates, isolated by activity-guided HPLC fractionation, was a flavonoid, identified as sakuranetin. Using a similar approach, the major active constituent with BNI activity in DCM-root wash was isolated and identified as sorgoleone. Both sakuranetin and sorgoleone inhibited Nitrosomonas activity in a dose-response manner. Substantial genetic variability for sorgoleone production capacity was detected in sorghum. Some wild-sorghum species showed high-BNI capacity under field conditions. Potential implications of BNI in inhibiting nitrification and in reducing the nitrogen footprint from agricultural systems will be discussed