Performance Evaluation of a 17-Level Octuple Boost Inverter for a Grid-Connected PV System

This paper presents a novel single-phase, 17-level octuple boost switched-capacitor multilevel inverter (OBSC-MLI) for a grid-connected photovoltaic (PV) system. The proposed inverter can boost the low voltage obtained from a small PV source up to eight times at the output to reach the grid voltage level. Thus, the proposed inverter is most suitable for a PV system, as it can eliminate the need for any boost converter or step-up transformer for its grid integration application, resulting in an overall compact system. The inverter consists of a lower number of power electronic components and capacitors. The cost of each switch and diode is lower as the devices’ standing voltages (SV) are only half of the output voltage. Due to its voltage-boosting capabilities, this inverter is a strong contender for transformer-less grid-connected PV systems. A closed-loop dq current control and DC-link voltage control are adopted to manage the active power supplied to the grid and balance the DC-link voltage. A near-sinusoidal output voltage with higher voltage levels is obtained owing to increased efficiency and lower harmonics. Furthermore, the filter size becomes smaller even at a much lower switching frequency. Experimental results for both RL-load and grid-connected modes are presented and analyzed

A Switched-Capacitor Multilevel Inverter With Modified Pulsewidth Modulation and Active DC-Link Capacitor Voltage Balancing

Although switched-capacitor (SC) multilevel inverters (MLIs) offer self-voltage balancing of flying capacitors and voltage gain higher than unity, the advantages come at the cost of high current stress and power loss in the SC circuit and dc source. Moreover, the voltage balancing is often restricted to a limited range of modulation indices. Another problem of MLIs with neutral-point clamped (NPC) front end is with dc-link capacitor voltage balancing under unbalanced load conditions, imploring sensor-based closed-loop control. This article proposes a unity gain five-level active-NPC SC-MLI with inrush charging current attenuation and actively balanced dc-link capacitor voltages under all load conditions and over the entire range of modulation index and power factor. The modified pulsewidth modulation (PWM) results in most switches operating at a low switching frequency, minimizing switching losses in the SC circuit. The proposed MLI attains a maximum efficiency of 98.04% at an output power of 510 W. Experiments on a 2 kVA laboratory prototype validate the theoretical analysis. Results from transformerless grid-connected solar photovoltaic (PV) system show that the proposed MLI can inject power into the grid with a unity power factor under conditions of varying irradiance and provide the grid with reactive power as well

Design, development and verification of a new multilevel inverter for reduced power switches

Due to recent developments in the field of high-power and medium-voltage, the multilevel inverter has raised to such an extent owing to some of its amazing facts regarding harmonic spectrum, ease in control, reduced electromagnetic interference (EMI), filterless circuit, stress on power switches, common-mode voltage. This paper well describes a novel architecture of a single-phase multilevel inverter using a lesser number of overall components, especially the power switches. The proposed topology is generalized in the structure that can generate any number of voltage steps. A 7-level structure of the proposed topology is explained and is elaborately discussed. Simulation is carried out in MATLAB and corresponding experimental results verify the existence of the proposed multilevel inverter. The real-time experimental results were presented and are well verified by the simulation results for 7-level as well for 13-level across RL-Load. The nature of load current is also indicated as per the nature of load voltage. Nevertheless, the topology is further compared with some of the recent literature and found superior in each respect

A comprehensive review on health monitoring of joints in steel structures

Steel-framed structures find extensive application in civil engineering projects, including buildings, bridges, and towers, due to their dependable material characteristics, expeditious construction capabilities, and cost-efficiency. In such structures, beams and columns are interconnected through either welding or bolting methods. However, it is imperative to recognize that joints represent the critical areas susceptible to damage stemming from a variety of factors, both human-induced and environmental, in addition to the effects of aging. Over the past few decades, substantial attention has been dedicated to the field of Structural Health Monitoring (SHM) at the joints of steel structures. This study seeks to comprehensively evaluate various methods employed for SHM at the joints of steel structures, encompassing both bolted and welded connections. While there have been numerous prior review studies that focus on localized and vibration-based techniques for detecting damage at these joints, there is a conspicuous absence of research covering the amalgamation of localized and global approaches across diverse steel structure types. This review paper addresses this gap by offering a thorough examination, incorporating the most recent applications of SHM methodologies employed in research and practical contexts for joint damage detection. Furthermore, it serves as a valuable resource for professionals, engineers, and academics engaged in civil structure design, construction, and maintenance.</p

A randomized two-way crossover comparative pharmacokinetic study of two different tablet formulations containing ilaprazole in healthy human Indian volunteers

Background: Proton Pump Inhibitors (PPI) are observed to be great healer in gastroesophageal reflux disorder (GERD) and duodenal ulcer. Quantification of the drugs in human plasma by validated bioanalytical method are very important to determine pharmacokinetic parameters for undergoing comparative study with standard available formulations to make the newer one commercially available. Objective: The objective of this study was to determine the relative bioavailability of Ilaprazole, a novel PPI comparing the test formulation to the reference one according to standard regulatory guidelines. Materials and Methods: The bioequivalence of two tablet formulations, one as reference and other as test containing 10 mg of ilaprazole [CAS No. 172152-36-2] was studied in 12 healthy Indian volunteers. This was a single dose, twoperiod and randomized crossover study separated with a washout period of one week. Plasma samples for pharmacokinetic analysis were collected before dosing and at pre-specified time points after dosing. The concentration of ilaprazole in plasma was determined by a validated HPLC-UV method using theophylline as internal standard. The formulations were compared using the parameters Area under the plasma concentration-time curve (AUC 0-t ), Area under the plasma concentration-time curve from zero to infinity (AUC 0-͵), Peak plasma concentration (C max ), and time to reach peak plasma concentration (t max ). Results: Mean AUC 0-t of test and reference product were calculated to be 2627.793 ± 154.989 ng h ml−1 and 2555.905 ± 225.916 ng h ml−1 , with a C max of 347.459 ± 48.175 ng h ml−1 . While mean AUC 0-͵ of test and reference product were calculated to be 2733.334 ± 242.438 ng h ml−1 and 2728.716 ± 284.408 ng h ml−1 . Conclusion: The results of this investigation indicated no statistically significant differences between the logarithmic transformed AUC 0-͵ and C max values of the two preparations. The 90% confidence interval for the ratio of the logarithmic transformed AUC 0-t , AUC 0-͵ and C max were 2 within the bioequivalence limit of 80-125% and the relative bioavailability of test formulation was 102.81% to that of reference formulation. The results of this study in healthy human volunteers of 27.92 ± 5.12 yrs (average age), 171.28 ± 6.85 cm (average height) and 66.43 ± 5.21 kg (average weight) support the use of the 10 mg dose tablet newly formulated