One cycle control (OCC) is widely used for grid current control owing to least number of sensors used, reduced complexities and cost. A proportional multi-resonant controller within the OCC is ...implemented in this paper for the purpose of further improvement in grid current THD. A trapezoidal PWM is proposed to reduce the DC voltage requirement for a grid-connected inverter as well as to reduce the switching losses of the inverter and hence improve the efficiency. No extra sensors are used for the implementation of trapezoidal modulation. Overall, the proposed modulation and control strategy for the inverters not only further reduces the DC voltage requirement, the number of sensors and the total switching loss, but also improves the grid current THD. Three cases are compared and verified experimentally. In Case I, a traditional PMR controller is used for the purpose of current control. In Case II, a trapezoidal PWM along with PMR control technique is proposed, whereas in Case III, trapezoidal modulation along with PMR-OCC is proposed. Experimental results and analysis show the superior performance of trapezoidal PWM along with the proposed PMR-OCC compared to that with the other two techniques.
This work focuses on a new topology-control-based D-STATCOM solution with reduced DC bus voltage requirement and with an excellent grid side performance. The proposed solution consists of a main ...inverter and auxiliary inverter along with a transformer and LCL filter network to achieve the required DC bus reduction. A new controller structure with two proportional-multi resonant controller for the converters with only one of the inductors current as a controlled variable ensures the active damping of the LCL resonance. The power circuit configuration assists the controller to generate a difference in the modulation signal due to non-equal gains in two controllers and helps to achieve the resonance damping without capacitor current sensor. Hence, the corresponding capacitor current sensor can be eliminated. The converter operates for any point of common coupling (PCC) loading conditions and the performance of the controller is immune to the grid impedance variation. A detailed stability study is carried out for the proposed controller. The proposed controller can achieve a very fast dynamic response with an excellent stability margin. The proposed solution is verified through simulation studies and through a scaled-down experimental prototype.
WHO defines malnutrition as severe if the z-scores are less than - 3 Standard deviation (SD), moderate if between - 2 and - 3 SD and mild if between - 2 SD to - 1 SD. This study was aimed to assess ...nutritional aspects of Indian children suffering from EB and to evaluate the effect of severity of EB on the severity of malnutrition. In this study, pediatric EB patients were evaluated prospectively for baseline nutritional status using anthropometric parameters and WHO growth charts, and its correlation with disease severity using instrument for Scoring Clinical Outcomes for Research of Epidermolysis Bullosa-iscorEB. In second phase, an individualized diet chart was given to meet the energy, protein and micronutrients needs and its effects were observed after 6 months. The median age of participants was 3 years (IQR-9). Of 57 patients, malnutrition was seen in 40.35% patients (22.81%-moderate and 17.54%-severe), and significantly correlated with iscorEB (r = 0.45, p < 0.0001). On bivariate regression analysis, iscorEB was independently associated with moderate-to-severe malnutrition (p = 0.047; OR 1.038, CI 1.011-1.066). iscorEB enabled the identification of patients with moderate-to-severe malnutrition with an Area Under Receiver Operating Curve (AUROC) of 0.72 (95%CI 0.58-0.85; p < 0.005). In phase 2, there was significant improvement in nutritional status in children with recessive dystrophic EB (RDEB) and dominant dystrophic EB (DDEB) subtype (p < 0.0001). The severity of malnutrition in EB children significantly correlates with disease severity, and is an independent predictor of moderate-to-severe malnutrition.
This paper focuses on sliding mode controller (SMC)-based master–slave parallel operation of DC–DC converters using a modified sliding manifold to achieve a fast dynamic response and very low ...steady-state error. The converter performance is analyzed in a novel way starting from a simple case of paralleling of two converters and then concept is extended for parallel operation of multiple converters. An investigation of the choice of the sliding surface on the performance of parallel converter is carried out in detail, and a mathematical design guideline for sliding coefficients for the proposed manifold for the master converter is derived to achieve stable operation. The proposed manifold ensures an improved dynamic response with an excellent steady-state accuracy in stand-alone mode. However, when it is incorporated with master–slave control for parallel operation with finite tie wire impedance, there is a degradation in the steady-state accuracy. In order to improve the steady-state performance of the sliding mode controller, two new hybrid (SMC + PI) controllers are proposed and implemented for parallel connected DC–DC converters. Finally, the proposed SMC techniques are verified through simulation study and through a scaled down experimental (laboratory) prototype.
Bullous pemphigoid (BP) and mucous membrane pemphigoid (MMP) sometimes have overlapping clinical, histopathological, and direct immunofluorescence (DIF) features in the early stages. Complement ...deposition is an intrinsic component of the patho-mechanism of BP in contrast to MMP. Hence immunohistochemistry (IHC) for C3d and C4d may be helpful in differentiating the two disorders. Seventy-four patients of BP and 18 patients of MMP along with 10 negative controls were enrolled in this study. C3d and C4d IHC was performed in formalin-fixed skin biopsy specimens. C3d IHC staining in BP/MMP had a sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 59.2%/41.2%, 100%/100%, 100%/100%, 25.6%/50.0%, respectively. C4d IHC staining in BP/MMP had a sensitivity, specificity, PPV and NPV of 26.8%/17.6%, 100%/100%, 100%/100% and 16.1%/41.7%, respectively. Receiver operator analysis showed utility of C3d in diagnosing both BP Area under curve (AUC) = 0.8, p = 0.0001 and MMP (AUC = 0.71; p = 0.001). C4d was useful in diagnosis of BP (AUC = 0.5; p = 0.0001), but not MMP (AUC = 0.6; p = 0.064). Hence, C3d is a better diagnostic modality for BP as compared to C4d, whereas C3d and C4d have lower diagnostic importance in MMP. C3d IHC can be employed in diagnosing BP when a second biopsy for direct immunofluorescence (DIF) is not possible or where a facility for IF microscopy does not exist.
Life expectancy is gradually increasing due to continuously improving medical and nonmedical interventions. The increasing life expectancy is desirable but brings in issues such as impairment of ...quality of life, disease perception, cognitive health, and mental health. Thus, questionnaire building and data collection through the questionnaires have become an active area of research. However, questionnaire development can be challenging and suboptimal in the absence of careful planning and user-friendly literature guide. Keeping in mind the intricacies of constructing a questionnaire, researchers need to carefully plan, document, and follow systematic steps to build a reliable and valid questionnaire. Additionally, questionnaire development is technical, jargon-filled, and is not a part of most of the graduate and postgraduate training. Therefore, this article is an attempt to initiate an understanding of the complexities of the questionnaire fundamentals, technical challenges, and sequential flow of steps to build a reliable and valid questionnaire.
Glucocorticoids are the mainstay of treatment for pemphigus vulgaris (PV). However, the requirement of high doses for long durations often leads to serious adverse events. Methotrexate as an adjuvant ...has shown potential in retrospective studies but randomized trials are lacking. The objective of the study was to assess the adjuvant potential of methotrexate in mucosal/limited mucocutaneous PV. In this randomised prospective study, 44 patients with mucosal/limited mucocutaneous PV were randomised (1:1) to receive either prednisolone 1 mg/kg/day (later fixed at a maximum dose of 60 mg/day) alone or with methotrexate 0.3 mg/kg/week for 9-months study period. Prednisolone dose was tapered once there was an 80% reduction in Pemphigus Disease Activity Index. Outcome measures were total cumulative dose of prednisolone, the proportion of patients achieving disease control, time taken for disease control and remission on minimal treatment, and adverse effects. No significant difference in the total cumulative dose of prednisolone among the groups was observed (p = 0.68). Disease control was achieved in 95.5% and 86.4% of patients in the prednisolone alone group, and prednisolone and methotrexate group respectively (p = 0.61). No statistically significant difference was observed among the groups with respect to the proportion of patients achieving remission, time taken for disease control and remission, and the number of adverse events. Our study showed no additional benefit of methotrexate to prednisolone in the treatment of mucosal/limited mucocutaneous PV.Trial registration: CTRI/2018/07/015002; Registered on 23/07/2018; Trial Registered Retrospectively. http://ctri.nic.in/Clinicaltrials/pdf_generate.php?trialid=24964&EncHid=&modid=&compid=%27,%2724964det%27 .
A hybrid passive-active damping solution with improved system stability margin and enhanced dynamic performance is proposed for high power grid interactive converters. In grid connected active ...rectifier/inverter application, line side LCL filter improves the high frequency attenuation and makes the converter compatible with the stringent grid power quality regulations. Passive damping though offers a simple and reliable solution but it reduces overall converter efficiency. Active damping solutions do not increase the system losses but can guarantee the stable operation up to a certain speed of dynamic response which is limited by the maximum bandwidth of the current controller. This paper examines this limit and introduces a concept of hybrid passive-active damping solution with improved stability margin and high dynamic performance for line side LCL filter based active rectifier/inverter applications. A detailed design, analysis of the hybrid approach and trade-off between system losses and dynamic performance in grid connected applications are reported. Simulation and experimental results from a 10 kVA prototype demonstrate the effectiveness of the proposed solution. An analytical study on system stability and dynamic response with the variations of various controller and passive filter parameters is presented.
PDF
