Selective harmonic elimination in awide modulation range using modified Newton-raphson and pattern generation methods for a multilevel inverter

Considering the aim of having low switching losses, especially in medium-voltage and high-power converters, the pre-programmed pulse width modulation technique is very useful because the generated harmonic content can be known in advance and optimized. Among the different low switching frequency techniques, the Selective Harmonics Elimination (SHE) modulation method is most suitable because of its direct control over the harmonic spectrum. This paper proposes a method for obtaining multiple solutions for selectively eliminating specific harmonics in a wide range of modulation indices by using modified Newton-Raphson (NR) and pattern generation techniques. The different pattern generation and synthesis approach provide more degrees of freedom and a way to operate the converter in a wide range of modulation. The modified Newton-Raphson technique is not complex and ensures fast convergence on a solution. Moreover, multiple solutions are obtained by keeping a very small increase in the modulation index. In the previous methods, solutions were not obtainable at all modulation indices. In this paper, only exact solutions to the low-order harmonics elimination for Cascaded H-bridge inverter are reported for all modulation indices. Analytical and simulation results prove the robustness and correctness of the technique proposed in this paper. 2018 by the authors.Acknowledgments: This (publication, report, etc.) was made possible by NPRP grant # [X-033-2-007] from the Qatar National Research Fund (a member of Qatar Foundation).Scopu

Fintech and contactless payment: Help or hindrance? The role of invasion of privacy and information disclosure

Purpose: There is always a need to discover how a paradox between a customer’s desire for a more personalized experience and their privacy and security concerns would shape their intention to continue using contactless payment methods. However, personalization–privacy paradox has not been well-covered over the area of contactless payment. Therefore, this study aims to empirically examine the impact of personalization–privacy paradox on the customers’ continued intention (CIN) to use contactless payment. Design: /methodology/approach – The empirical part of the current study was conducted in Saudi Arabia by collecting the primary data using online questionnaire from a convenience sample size of 297 actual users of contactless payment methods. Findings: Based on structural equation modeling, personalization and privacy invasion were approved to significantly impact perceived value of information disclosure (PVD). Strong causal associations were confirmed between perceived severity, structural assurance and response cost with privacy invasion. Finally, both PVD and privacy invasion significantly predict CIN. : There are other important factors (i.e. technology interactivity, technology readiness, social influence, trust, prior experience, etc.) were not tested in the current study. Therefore, future studies would pay more attention regarding the impact of these factors. The current study data were also collected using a convenience sample of actual users of contactless payment methods. Therefore, there is a concern regarding the generalizability of the current study results to other kind of customers who have not used contactless payment. Originality/value: This study has integrated both personalization–privacy paradox and protection motivation theory in one model. The current study holds value in providing a new and complete picture of the inhibitors and enablers of customers’ CIN to use contactless payment, including new types of inhibitors. Furthermore, personalization–privacy paradox has not been fully examined over the related area of Fintech and contactless payment in general. Therefore, this study was able to extend the theoretical horizon personalization–privacy paradox to new area (i.e. contactless payment) and new cultural context (Saudi Arabia)

A smart rig for calibration of gas sensor nodes

Electrochemical gas sensors require regular maintenance to check and secure proper functioning. Standard procedures usually involve testing and recalibration of the sensors, for which working environments are needed. Periodic calibration is therefore necessary to ensure reliable and accurate measurements. This paper proposes a dedicated smart calibration rig with a set of novel features enabling simultaneous calibration of multiple sensors. The proposed calibration rig system comprises a gas mixing system, temperature control system, a test chamber, and a process-control PC that controls all calibration phases. The calibration process is automated by a LabVIEW-based platform that controls the calibration environment for the sensor nodes, logs sensor data, and best fit equation based on interpolation for every sensor on the node and uploads it to the sensor node for next deployments. The communication between the PC and the sensor nodes is performed using the same IEEE 802.15.4 (ZigBee) protocol that the nodes also use in field deployment for air quality measurement. The results presented demonstrate the effectiveness of the sensors calibration rig.Scopu

Employee perceptions of fairness toward IoT monitoring

Purpose: This paper aims to explore Internet of Things (IoT)-enabled monitoring in a multi-national petrochemical organization in Qatar and finds that the technology does not negatively influence employee perceptions of fairness, challenging current propositions on monitoring and highlighting the emerging role of culture, competition and paradoxical leadership in moderating the relationship between IoT-enabled monitoring and perceptions of fairness. Design/methodology/approach: The authors adopted qualitative research as the methodological premise to explore the relationship between IoT-enabled monitoring and perceptions of fairness. They collected data from an oil and gas organization in Qatar to test the validity of the proposed hypotheses. Findings: While I0T-enabled monitoring was perceived as pervasive, tracking every move and recording conversations, the diffusion of the technology throughout Qatar desensitized employees who felt it was the new reality around workspaces. The following three important factors reshaped employees� perceptions toward IoT-enabled monitoring: a culture that is driven by productivity and strongly adheres by policies and standards to reach set goals; a highly competitive job market; and a paradoxical leadership who balances between the competition and lucrative rewards. Research limitations/implications: The limitation of this research is that the authors conducted a case study in similar organizations within the oil and gas industry in the State of Qatar to refute the theory that electronic monitoring of employees in the workspace elicits perceptions of unfairness. Future research can conduct quantitative surveys of employee perceptions in different industries within different cultures to be able to generalize and evolve a universal theory. Practical implications: The research findings shed light on the escalating pressure global competition exerts on employees that nervousness about pervasive monitoring systems is replaced with fear of job loss and analytics on monitoring data is welcomed as a means of readjusting behavior to meet performance expectations. Originality/value: The case study is the first to highlight the desensitization of employees to monitoring and the increasing pressure competition plays in motivating them to exceed expectations. � 2018, Emerald Publishing Limited

A fuzzy logic based irrigation management system in arid regions applied to the state of qatar

In arid and hyper arid regions like Qatar, the time and duration of irrigation is key to achieving sustainable irrigations. This paper proposes a practical solution based on artificial intelligence where all design and implementation phases are described. First, it describes a microcontroller-based system that collects soil moisture, ambient temperature, and solar radiation. Then the fuzzy logic controller takes these three inputs, and, based on the created rules table for a given crop, it produces the desired time and duration of irrigation. Also, ZigBeebased wireless monitoring is developed in-house in order to monitor the system operation and save sensor readings, irrigation time and during, and amount of water being dispensed. This constitutes the basis for future analysis and economic and environmental studies. Experimental results showed that the developed system rigorously compensates the amount of water that is lost through evapotranspiration as predicted by Penman-Monteith model, which is adapted by the FAO. The deployment of fuzzy control combined with wireless monitoring is found to have a great impact on irrigation management and planning in the near future.Scopu

CMV reduction in a three-to-seven phase direct matrix converter using SVPWM

The pulse-width modulation (PWM)-controlled modern electric drives causes some serious problems such as the generation of common-mode voltage (CMV) and high dv/dt. The CMV might cause high-frequency leakage currents that flow through the possible path that is bearing of the motor. Thus, the flow of current through the motor bearing leads to its premature failure. One of the main challenges in developing PWM methods for control of motor drives is the problem of CMV and its reduction/elimination. In this study, a modulation technique based on space-vector approach is developed to reduce the CMV in a three-to-seven-phase direct matrix converter. CMV reduction becomes possible by selecting suitable zero-voltage vectors for a specific duration and the use of a selected set of active vectors for the output voltage synthesis. The proposed space-vector PWM (SVPWM) for the reduction of CMV is performed with a seven-phase R-L load to show the viability of the proposed technique. The proposed SVPWM technique is implemented experimentally in dSPACE working in conjunction with field-programmable gate array processor board using a system generator. Hardware results that validate the proposed control algorithm are discussed. - The Institution of Engineering and Technology 2019This publication was made possible by the Qatar University internal Grant QUCP-CENG-17\18-2. The statements made herein are solely the responsibility of the authors.Scopu

Towards understanding the effects of climatic and environmental factors on solar PV performance in arid desert regions (Qatar) for various PV technologies

The sensitivity of various solar photovoltaic technologies to dust, temperature and relative humidity is investigated for Qatar's environment. Results obtained show that mono-crystalline PVs have efficiencies as high as 85% compared to 70% for amorphous ones. Also, dust accumulation degrades more critically the efficiency of amorphous and mono-crystalline silicon PVs than the panel's temperature or relative humidity. In addition, the results show that amorphous PVs are more affected by temperature and relative humidity than mono-crystalline PVs. However, amorphous PVs prove to be more robust against dust settlement than mono-crystalline PVs and hence are more suitable for implementation in desert climates like Qatar unless cleaning strategies are devised. It was estimated that 100 days of dust accumulation over mono-crystalline PV panels, caused the efficiency to decrease by around 10%. This limitation makes solar PV an unreliable source of power for unattended or remote devices and thus strongly suggests the challenge of cleaning the panel's surface regularly or injecting technical modifications. Furthermore, the study suggests operating solar PV plants in Qatar from 11:00 am to 02:00 pm to optimize production.Scopu

A resolver converter based upon a novel open-Loop Technique

The paper presents a novel technique for the determination of the angle from slowly-varying quadrature co-sinusoidal signals produced, for example, by position sensors. In the presented scheme applied to a resolver, the separately generated constant-frequency sine wave used for exciting the resolver together with an additional cosine wave are used as reference against which the amplitudes of the angle-dependent demodulated resolver sine and cosine signals are compared. At the instant equality between respective amplitudes of the signals are detected, two sample and hold circuits sample a voltage proportional to the angle of the shaft of the resolver from a triangular waveform generated from the reference signals. In theory, the sample and hold devices produce identical output voltages proportional to the unknown angle of the transducer. In order to improve the precision of the proposed converter, the two sample and hold circuits outputs are fed into a multiplexer to produce a single output that takes full advantage of the accurate comparison outside the peak regions of the signals. With this method, the validated output is obtained from the accurate comparisons involving the alternating pseudo-linear segments of the trigonometric signals. Another important feature of this converter is its robustness to amplitude fluctuations in the trigonometric reference signals which are used for the excitation of the resolver. A converter based on this technique has been successfully implemented using basic electronic components. Theory of operation, computer simulation and experimental results are given

Third Harmonic Operation of Current Fed Resonant Inverters for Inductive Power Transfer Systems

This paper presents Third Harmonic Operation (THO) of Current Fed Parallel Resonant Push-pull Inverter (CFPRPI) for Inductive Power Transfer (IPT) systems. THO is proposed for CFPRPI to achieve higher voltage ratio with lower switching frequency, which is essential for low input voltage IPT systems. The IPT system is considered based on PS compensation method, i.e. parallel compensation for the primary side and series compensation for the secondary side. Moreover, a phase-shift control method is presented based self-oscillating tuning loop for output voltage or power regulations. The tuning loop and IPT system are modeled and formulated in THO mode. To verify the validity of the proposed method, a laboratory prototype with resonant frequency of about 120 kHz and maximum output power of about 50 W has been implemented.ACKNOWLEDGEMENT This publication was made possible by Qatar University Collaborative Research grant # [QUCG-CENG-19/20-5] from the Qatar University. The statements made herein are solely the responsibility of the authors.Scopu