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

AC small signal modeling of PWM Y-source converter by circuit averaging and averaged switch modeling technique

© 2016 IEEE and EPE Association. Magnetically coupled Y-source impedance network is a newly proposed structure with versatile features intended for various power converter applications e.g. in the renewable energy technologies. The voltage gain of the Y-source impedance network rises exponentially as a function of turns ratio, which is inherited from a special coupled inductor with three windings. Due to the importance of modeling in the converter design procedure, this paper is dedicated to dc and ac small signal modeling of the PWM Y-source converter. The derived transfer functions are presented in detail and have been verified through simulation and experimental results

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

A Compact Design Using GaN Semiconductor Devices for a Flying Capacitor Five-Level Inverter

Multilevel inverters (MLIs) based on the flying capacitor (FC) concept are beneficial in many renewable energy-based applications due to their compactness, low current stress on semiconductor devices, and reasonable thermal behavior for high-power applications. However, the recently developed FC-based topologies suffer from half dc-link voltage utilization and a variable high-frequency common-mode voltage (HF-CMV). The aim of this paper is to propose an FC-based family of MLIs with a five-level (5L) output voltage, full dc-link voltage utilization, and low HF-CMV. Using redundant states and the phase-shifted sinusoidal PWM technique, the value of the flying capacitor has been reduced significantly. The performance of the converter has been verified using Gallium Nitride (GaN) power switches. Circuit description and a brief comparative study with existing MLIs are given to justify the suitability of the topology

Reproductive and Hormonal Factors in Relation to Lung Cancer Among Nepali Women

Partial funding for Open Access provided by the UMD Libraries' Open Access Publishing Fund.Background: Of the 1.8 million global incident lung cancer cases estimated in 2012, approximately 60% occurred in less developed regions. Prior studies suggest sex differences in lung cancer risk and a potential role for reproductive and hormonal factors in lung cancer among women. However, the majority of these studies were conducted in developed regions. No prior study has assessed these relationships among Nepali women. Methods: Using data from a hospital-based case-control study conducted in B. P. Koirala Memorial Cancer Hospital (Nepal, 2009–2012), relationships between reproductive and hormonal factors and lung cancer were examined among women aged 23–85 years. Lung cancer cases (n = 268) were frequency-matched to controls (n = 226) based on age (±5 years), ethnicity and residential area. The main exposures in this analysis included menopausal status, age at menarche, age at menopause, menstrual duration, gravidity, and age at first live-birth. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using multivariable logistic regression. Results: Among postmenopausal women, those with a younger age at menopause (<45 years; 45–49 years) had an increased odds of lung cancer compared to those with an older (≥50 years) age at menopause [OR (95%CI): 2.14 (1.09, 4.17); OR (95% CI): 1.93 (1.07, 3.51)], after adjusting for age and cumulative active smoking years. No statistically significant associations were observed with the other reproductive and hormonal factors examined. Conclusion: These results suggest that Nepali women with prolonged exposure to endogenous ovarian hormones, via later age at menopause, may have a lower odds of lung cancer

Updated β -decay measurement of neutron-rich Cu 74

The β decay of neutron-rich Cu74 has been studied at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. By using a high-resolution mass separator a purified Cu74 beam was obtained, thus allowing decay through its isobar chain to stable Ge74 without any decay chain member dominating. A total of 170γ rays were associated with Cu74β decay with 111 placed in the Zn74 level scheme. Updated β feeding intensities and estimated log(ft) values are presented, and new Jπ assignments are proposed using shell model calculations. The progression of simulated total absorption γ-ray spectroscopy (TAGS) based on proposed levels and β-feeding values from previous measurements to this evaluation are presented and demonstrate the need for a TAGS measurements for this and similar decays

Reproductive and Hormonal Factors in Relation to Lung Cancer Among Nepali Women

Background: Of the 1.8 million global incident lung cancer cases estimated in 2012, approximately 60% occurred in less developed regions. Prior studies suggest sex differences in lung cancer risk and a potential role for reproductive and hormonal factors in lung cancer among women. However, the majority of these studies were conducted in developed regions. No prior study has assessed these relationships among Nepali women.Methods: Using data from a hospital-based case-control study conducted in B. P. Koirala Memorial Cancer Hospital (Nepal, 2009–2012), relationships between reproductive and hormonal factors and lung cancer were examined among women aged 23–85 years. Lung cancer cases (n = 268) were frequency-matched to controls (n = 226) based on age (±5 years), ethnicity and residential area. The main exposures in this analysis included menopausal status, age at menarche, age at menopause, menstrual duration, gravidity, and age at first live-birth. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using multivariable logistic regression.Results: Among postmenopausal women, those with a younger age at menopause (&lt;45 years; 45–49 years) had an increased odds of lung cancer compared to those with an older (≥50 years) age at menopause [OR (95%CI): 2.14 (1.09, 4.17); OR (95% CI): 1.93 (1.07, 3.51)], after adjusting for age and cumulative active smoking years. No statistically significant associations were observed with the other reproductive and hormonal factors examined.Conclusion: These results suggest that Nepali women with prolonged exposure to endogenous ovarian hormones, via later age at menopause, may have a lower odds of lung cancer

Power Electronics Converters – an overview

The book explores how to manipulate components of power electronics converters and systems to produce a desired effect by controlling system variables

Full Soft-Switching Ultra-High Gain DC/DC Converter Using Three-Winding Coupled-Inductor

This paper presents a new type of non-isolated single-switch step-up DC/DC converter with continuous input current, low voltage stress, and soft-switching performance, and modular scalability. To achieve an ultra-high voltage gain without a large duty cycle, a Three-Winding Coupled-Inductor (TWCI) along with a unit of Voltage Multiplier Cell (VMC) and Voltage Multiplier Rectifier (VMR) are employed. The energy stored in the leakage inductor is recycled by a regenerative clamp capacitor, limiting the maximum voltage stress across the single power switch. Besides, Zero Current Switching (ZCS) at the turn-on time of the power switch is achieved, and by applying a Quasi-Resonance (QR) operation, the switch turn-off current is also reduced significantly. With the help of the leakage inductor of the TWCI, all diodes can operate under the ZCS condition, which eliminates the reverse recovery losses in the proposed converter. Therefore, the introduced circuit can provide an ultra-high voltage gain under high efficiency. Steady-state analysis, comprehensive comparisons with other related converters, and design considerations are discussed. Finally, a 160 W sample prototype with 200 V output voltage is implemented to justify the theoretical analysis's correctness