Switched-capacitor integrated single-phase (2n+1)-levels boost inverter for grid-tied photovoltaic (pv) applications

© 2019 IEEE. This paper presents a switched-capacitor integrated (2N+1)-level (N≥2) boost inverter for single-phase photovoltaic (PV) applications. It consists of N modular switching cells, where each cell consists of two switched capacitors and three active switching elements. A boost converter at the front side of the switching cells helps to maintain the capacitor voltage balance during different operation modes. With this arrangement, the inverter is capable to generate 2N+1 output voltage levels, and able to accommodate a wide range of input voltage. Detailed analysis followed by simulation and experimental results of a 5-level inverter as an example is presented to verify the proposed concept. Further, comparison with other multilevel inverter topologies is presented to show the merit of the proposed concept

Novel High Efficiency H-Bridge Transformerless Inverter for Grid-Connected Single-Phase Photovoltaic Systems

© 2018 IEEE. This paper proposes a new H-bridge type transformerless inverter for grid-connected photovoltaic (PV) application. The proposed H-bridge zero voltage switch controlled rectifier (HB-ZVSCR) inverter uses additional switches and diodes at the AC side with voltage clamping feature to the DC midpoint. Main characteristics of the proposed inverter are the high conversion efficiency and low leakage current, which make it a suitable candidate for grid-connected PV applications. The analysis and operating principles of the proposed inverter are discussed in details. This theoretical findings has been simulated using PLECS software to verify the common mode voltage (CMV) and leakage current behaviors and the results are compared with similar existing midpoint voltage clamping inverter topologies (i.e. HB-ZVR and HB-ZVR-D). Furthermore, power loss and efficiency of the proposed inverter have been evaluated and compared with existing topologies

H-Bridge Zero-Voltage Switch Controlled Rectifier (HB-ZVSCR) Transformerless Mid-Point-Clamped Inverter for Photovoltaic Applications

A single-phase transformerless mid-point clamped H-bridge zero-voltage switch-controlled rectifier inverter topology is proposed in this paper for photovoltaic (PV) systems to address the issue of common mode (CM) voltage and leakage currents. Apart from the full H-bridge inverter, the proposed voltage clamping circuit consists of two switches and a full-bridge diode which clamps the AC terminal to the DC midpoint (consisting of two DC-link capacitors) during the freewheeling period. As a result, the common mode voltage is held constant which makes it suitable for the grid-connected PV system. The operating principle and CM effect of the proposed topology are analysed and compared with the conventional topologies. This is followed by the thermal analysis and loss calculation, which shows that the proposed circuit is more efficient over the conventional topologies. Validation is carried out using MATLAB-Simulink using the PLECS toolbox followed by a scale down prototype of 1.5 kW. It is shown that the proposed inverter has the 98±1% efficiency over a wide range of loads with a peak efficiency of 98.96%, and the total harmonic distortion of the output current relatively low (≤1.8 %). The leakage current (icm) is measured for different values of parasitic capacitance that reaches a maximum of 16.65 mA for 330 nF capacitor under consideration which is well below the limit set by different safety standard

A Classification of Single-Phase Transformerless Inverter Topologies for Photovoltaic Applications

© 2018 IEEE. In Photovoltaic (PV) applications, a transformer is often used to provide galvanic isolation and voltage ratio transformations. However, a transformer based inverter is bulky and has high conduction losses, therefore lead to a reduction in the inverter efficiency. To overcome this issue, the transformerless inverter topologies are addressed widely, but the main challenge of a transformerless inverter is common mode issue. Numerous topological modifications with their control and modulation techniques makes them difficult to follow, generalize and highlight the advantages and disadvantages. To address the issue, this paper gives an overview on transformerless inverter and classify them into subsection to discuss the merit and demerit of some of the major topologies. Five subsections based on common mode behavior, voltage clamping and decoupling techniques have been demonstrated (i.e., common ground, mid-point clamping, AC-decoupling, DC-decoupling and AC+DC decoupling). To verify the finding and for general consensus, major transformerless topologies are simulated using PLECS. A general summary is presented at the end to stimulate readers to acknowledge the problems and identify solutions

Evaluation of Antihypertensive Effect of Aqueous Methanol Extract of Caralluma tuberculata N.E.Br in Sprauge Dawley Rats

Purpose: To evaluate the phytochemical profile and antihypertensive effect of Caralluma tuberculata N.E.Br (AMECT).Methods: The antihypertensive effect of the aqueous methanol extract of (AMECT) was evaluated in both normotensive and hypertensive rats. In normotensive rats, various doses (100, 300 and 500 mg/kg body weight, p.o.) were administered at 0, 1, 3 and 6 hr intervals. Anti-hypertensive activity of the crude extract was investigated in three experimental hypertensive models, viz, egg-fed diet, glucose-induced and cadmium-induced hypertensive rats. Cardiovascular parameters, including systolic blood pressure (SBP), diastolic blood pressure (DBP), mean blood pressure (MBP) and heart rate (HR) were measured by tail cuff method using non-invasive blood pressure apparatus (NIBP) attached. AMECT was also investigated for its phytochemical profile.Results: The results indicate that AMECT produced a dose-dependent, significant (p < 0.05) decrease in SBP, DBP, MBP, and HR (p < 0.01) of normotensive rats, when compared to control groups, at all test doses. The 500 mg/kg dose produced a highly significant effect (mm Hg, p < 0.001) in SBP (85.9 ± 7.2), DBP (71.86 ± 12.1), MBP (75.1 ± 11.7) and HR (238.08 ± 8.3 beats/min), in comparison to 100 and 300 mg/kg doses; therefore, 500 mg/kg was selected for antihypertensive test in egg-fed, glucose-induced and cadmium-treated hypertensive rats. Significant (p < 0.05) antihypertensive and negative chronotropic effects were observed in hypertensive models compared to their respective normal controls. Phytochemical analysis revealed the presence of tannins, alkaloids, phenolic compounds, cardiac glycosides and flavonoids.Conclusion: The findings indicate that Caralluma tuberculata possesses significant anti-hypentensive activity in rats.Keywords: Phytochemical profile, Antihypertensive, Cardiovascular, Caralluma tuberculata N.E.Br, Blood pressur

A novel single source three phase seven-level inverter topology for grid-tied photovoltaic application

This paper presents a novel single-source three-phase multilevel inverter structure with voltage boosting capability, which is suitable for medium-voltage photovoltaic (PV) applications. The proposed structure consists of switched-capacitors (SCs) based multilevel dc-link stages that boost-up the input DC-source voltage significantly. It reduces the dc-link voltage requirements by 75% compared to the traditional neutral point clamped (NPC), flying capacitors (FCs), active NPC (ANPC), hybrid and hybrid clamped ANPC and cascaded h-bridge (CHB) topologies, and 50% compared to advanced ANPC topologies. The proposed structure also reduces the number of required switches and capacitors as well as their voltages stresses compared to these state-of-the-art topologies. A robust control scheme based on finite control set model predictive control (FCS-MPC) is derived to control the converter. The capacitor voltage balancing is inherent of the proposed topology, and thus, eliminates the need for additional voltage balancing circuit and reduces the control complexity

Determinants of Increasing Trend of Self-Medication in a Pakistani Community

Purpose: To determine the major reasons, sources, diseases and drugs responsible for increasing trend of self-medication.Method: A community-based cross-sectional survey was carried out in the district of Faisalabad in Pakistan. Respondents (1488) were classified on the basis of age, sex, education, lifestyle and their economical level. A questionnaire was distributed among the sample population to collect data.Results: Majority of respondents involved in self-medication were aged between 15 and 20 years. Family members (N = 717, 48 %) were considered the major source of information for self-medicated drugs. Lack of time (N = 504, 37 %) while economic issues (N = 485, 33 %) were the major reasons for self-medication. Medical stores were the source of drug purchase by 1087 (73 %) respondents. Headache (N = 772, 52 %) and fever (N = 600, 40 %) were the main indications for self-medication while 694 respondents reported that they engage in single-dose self-medication. Paracetamol (N = 689, 46 %), other analgesics (N = 488, 33 %),  non-steroidal anti-inflammatory (N = 680, 46 %) were reported to be used frequently for self-medication.Conclusion: Self-medication is prevalent in the Pakistani community due to easy access to over the counter (OTC) and prescription-only medicines  (POM). This may lead to untoward effects in consumers of the products. Special interventions by relevant regulatory agencies regarding the sale of the drugs are therefore required.Keywords: Self-medication, OTC drugs, Pharmacist

Antihypertensive Activity of Aqueous-Methanol Extract of Berberis Orthobotrys Bien Ex Aitch in Rats

Purpose: To investigate the hypotensive potential of Berberis orthobotrys Bien Ex Aitch (Family: Berberidaceae) in both normotensive and hypertensive rats.Methods: Aqueous-methanol (70:30) extract of Berberis orthobotrys at doses of 25, 50, 75 and 100 mg/kg was evaluated for its effect on blood pressure and heart rate using non-invasive blood pressure measuring apparatus. After initial screening, 100 mg/kg dose that produced a maximum effect was selected for the antihypertensive study. Median lethal dose (LD50) and sub-chronic toxicity of the extract were also determined. Various biochemical parameters and organ weight were measured usingstandard procedures.Results: The extract produced a significant (p < 0.01) decrease in systolic blood pressure (SBP), mean blood pressure (MBP), diastolic blood pressure (DBP) and heart rate of normotensive rats at all test doses with maximum effect at 100 mg/kg. Similarly, a significant antihypertensive and negative chronotropic effect was observed in both hypertensive models. LD50 of the extract was 200 mg/kg in mice. The extract also exhibited a reduction (p < 0.05) in serum alanine transaminase (ALT), aspartate aminotransaminase (AST), alkaline phosphatase (ALP), triglycerides and low density lipoprotein (LDL) levels while a significant (p < 0.05) increase in high density lipoproteins (HDL) level was observed.Conclusion: It seems that the aqueous-methanol extract of Berberis orthobotrys possesses active compounds which may be responsible for the antihypertensive and negative chronotropic effects in rats.Keywords: Berberis orthobotrys, Antihypertensive, Egg feed diet, Blood lipid