Analysis and Design of Single-Phase Transformerless Inverter for Photovoltaic Applications

University of Technology Sydney. Faculty of Engineering and Information Technology.This thesis provides a comprehensive analysis of different transformerless inverter topologies (TLIs) and their control and modulation techniques. Considering the challenges and merits of the transformerless inverter, four different types of transformerless inverter topologies for PV applications have been investigated, analysed and designed in this thesis. The first topology is H-bridge Zero Voltage Switch Controlled Rectifier (HB-ZVSCR) transformerless mid-point-clamped inverter. 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 better efficiency 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. The second topology is a single-phase switched-capacitor (SC) based (2n+1)-level inverter with reduced number of components and input DC voltage supply magnitude. The total number of output voltage levels can reach up to (2n+ 1) levels, where n ≥ 2 is the number of switching cells consisting of three power switches and two switched-capacitors. The operating principle is presented in detail followed by comparative analysis, thermal modelling and design guidelines. Finally, measurement results are carried out for a 5-level inverter with two SC cells as an example to verify the performance of the proposed (2n+1)-level inverter over different operating conditions. The third topology is a novel dual-mode five-level common grounded type (5L-DM-CGT) transformerless inverter topology for a medium-power application with a wide input voltage range (200 V – 400 V). The theoretical analysis shows the advantages of the dual-mode inverter for various industrial applications. Finally, the laboratory test results are presented to verify the theoretical analysis. The final topology is a novel configuration of switched capacitor multilevel inverters (SCMLIs) with a lower number of power components with inherent voltage boost. The proposed topology is compared with other existing five-level inverter topologies to show its superior capabilities/advantages. The performance of the proposed topology is validated by OPAL-RT. Overall, this thesis provides a comprehensive analysis of all transformerless inverter topologies and their control and modulation techniques and come up with the concept of new single-phase transformerless inverter topologies. The new topologies utilizes minimal components with low voltage stress and offers high power quality output with low total harmonic distortion (THD), high efficiency and power density, low cost and size, and simple modulation techniques

Leakage current paths in PV transformer-less single-phase inverter topology and its mitigation through PWM for switching

The Photovoltaic (PV) is a part and parcel and well known for cost-effective and easy to operate features when it is used with transformer-less inverter based grid-tied distribution generation systems. It reduces the leakage current issue that actually occurs making paths from PV penal to ground. In this paper has been addressed this issue as main problem for reducing leakage current. Moreover, here is compared the proposed topology’s results to AC and DC-based transformer-less topologies. The possibilities of larger number of leakage current paths indicate power loss, which is the focus of work in this paper for different switching conditions. The results on leakage current paths using PSpice with different parasitic capacitance values from inverters of different topologies are compared with the simulation results of the topology proposed in this paper

Leakage current paths in PV transformer-less single-phase inverter topology and its mitigation through PWM for switching

The Photovoltaic (PV) is a part and parcel and well known for cost-effective and easy to operate features when it is used with transformer-less inverter based grid-tied distribution generation systems. It reduces the leakage current issue that actually occurs making paths from PV penal to ground. In this paper has been addressed this issue as main problem for reducing leakage current. Moreover, here is compared the proposed topology’s results to AC and DC-based transformer-less topologies. The possibilities of larger number of leakage current paths indicate power loss, which is the focus of work in this paper for different switching conditions. The results on leakage current paths using PSpice with different parasitic capacitance values from inverters of different topologies are compared with the simulation results of the topology proposed in this paper

Evaluation of various leakage current paths with different switching conditions

The Photovoltaic (PV) panel is the arrangement of solar cells that becoming famous in the world for commercial electric power market via transformer-less topology. However, non-existing galvanic isolation is the biggest problem occurred in the whole system and is known as leakage issue. In this paper, different paths of leakage current were analyzed with various wave shapes and ranges. Furthermore, it was also verified using DC decoupling and AC decoupling with full bridge rectifier. Moreover, the EMC filter and high range load were used to evaluate the performance. Moreover, here also shown the transfer function of EMC filter with its simulated figure

A novel five-level switched capacitor type inverter topology for grid-tied photovoltaic application

This paper presents a novel five-level inverter topology and associated control scheme. The proposed structure consists of a capacitor and eight active switching elements. It requires only one dc source and is capable of generating five voltage levels with double voltage boosting gain. On the other hand, it does not require any control scheme to balance the capacitor in the DC-bus due to inherent voltage balancing capability. As a result, the control complexity reduces a lot. Brief analysis followed by simulation and measurement results of a proposed 5-level inverter using the finite control set model predictive control (FCS-MPC) algorithm is presented. Detail of the analysis with more measurement result and comparison will be presented in the final paper

Factors That Influence Travelers’ Willingness to Adopt Bus Rapid Transit (Green Line) Service in Karachi

peer reviewedBus rapid transit (BRT) system is a sustainable mode choice alternative and traffic management method for traffic congestion problems in urban areas. As an extent of total demand management, BRT has broadly been implemented in many countries. BRT has proven to be progressive in alleviating traffic congestion and the difficulty of finding parking spaces in city centers. Currently, people driving their automobiles to work cause traffic congestion along Karachi’s main corridors. People cannot be persuaded to use public transit until their travel patterns are understood. Therefore, the disparity between public and private transportation must be addressed. This research aimed to develop a model to shift car travelers toward Karachi’s Green Line BRT and investigate the factors that influence car travelers’ decisions. A questionnaire-based survey was carried out on single-occupant vehicle (SOV) users in the Green Line corridor of Karachi. This study investigated the elements that influence SOV users’ willingness to adopt the BRT system and studied the possible ways of attracting car drivers to BRT. Data were examined using descriptive-analytic techniques such as the contingency table approach in conjunction with a Chi-square test of the independence/association model in SPSS. Furthermore, binary logistic regression was applied to the highly mediated associated variables. The research’s outcomes were geared at the imposition of parking fees at workplaces to deter individuals from parking their automobiles there. SOV travelers can be diverted to BRT services using this strategy. The research findings will assist policymakers and serve as a foundation for scientific investigations on the travel demand model for the BRT system.11. Sustainable cities and communitie

State owned enterprises as bribe payers: the role of institutional environment

Our paper draws attention to a neglected channel of corruption—the bribe payments by state-owned enterprises (SOEs). This is an important phenomenon as bribe payments by SOEs fruitlessly waste national resources, compromising public welfare and national prosperity. Using a large dataset of 30,249 firms from 50 countries, we show that, in general, SOEs are less likely to pay bribes for achieving organizational objectives owing to their political connectivity. However, in deteriorated institutional environments, SOEs may be subjected to potential managerial rent-seeking behaviors, which disproportionately increase SOE bribe propensity relative to privately owned enterprises. Specifically, our findings highlight the importance of fostering democracy and rule of law, reducing prevalence of corruption and shortening power distance in reducing the incidence of SOE bribery

Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey

Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10 years; 78.2% included were male with a median age of 37 years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020