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47 results on '"Aly, Mokhtar"'

40. A New Single-Phase Five-Level Inverter Topology for Single and Multiple Switches Fault Tolerance.

Author

Aly, Mokhtar, Ahmed, Emad M., and Shoyama, Masahito

Subjects
*FAULT tolerance (Engineering), *ELECTRIC inverters, *AEROSPACE engineering, *COST effectiveness, *ENGINEERING economy
Abstract

Reliability of power inverters is of dominant importance in various applications, including industrial, military, aerospace, and commercial applications. Therefore, developing fault tolerant (FT) power inverters is extremely needed from the viewpoints of system availability and avoiding harmful consequences. Tolerating various types of faults, preserving full output ratings after the fault, and being cost-effective represent the main challenges for most of existing FT solutions. In this paper, a new FT single-phase five-level inverter topology is proposed. The proposed topology can effectively tolerate both of single or multiple switches faults whether they are of open- or short-circuit fault types. Moreover, the proposed topology does not deteriorate system efficiency in postfault operation compared to the previously developed FT solutions. Evaluation of the effectiveness and robustness of the proposed topology is verified in both of simulation and experimental environments. Different case studies are investigated in order to cover various types and locations of switches’ faults. Moreover, comprehensive comparisons are provided to validate the superiority of the proposed topology over the previously addressed techniques. [ABSTRACT FROM AUTHOR]

Published
2018
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44. Thermal Stresses Relief Carrier-Based PWM Strategy for Single-Phase Multilevel Inverters.

Author

Aly, Mokhtar, Ahmed, Emad M., and Shoyama, Masahito

Subjects
*THERMAL stresses, *ELECTRIC inverters, *PULSE width modulation, *ENERGY storage, *CAPACITORS
Abstract

Enhancing power cycling capability of power semiconductor devices is highly demanded in order to increase the long-term reliability of multilevel inverters. Ageing of power switches and their cooling systems leads to their accelerated damage due to excess power losses and junction temperatures. Therefore, thermal stresses relief (TSR) is the most effective solution for lifetime extension of power semiconductor devices. This paper presents a new TSR carrier-based pulse width modulation (TSRPWM) strategy for extending the lifetime of semiconductor switches in single-phase multilevel inverters. The proposed strategy benefits the inherent redundancy among switching states in multilevel inverters to optimally relieve the thermally stressed device. The proposed algorithm maintains the inverter operation without increased stresses on healthy switches and without reduction of the output power ratings. In addition, the proposed algorithm preserves voltage balance of the dc-link capacitors. The proposed strategy is validated on a single-phase five-level T-type inverter system with considering different locations of thermal stresses detection. Experimental prototype of the selected case study is built to verify the results. Moreover, comparisons with the most featured strategies in literature are given in detail. [ABSTRACT FROM PUBLISHER]

Published
2017
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47. Thermal and Reliability Assessment for Wind Energy Systems With DSTATCOM Functionality in Resilient Microgrids.

Author

Aly, Mokhtar, Ahmed, Emad M., and Shoyama, Masahito

Abstract

Different functionalities can be incorporated into wind energy conversion systems (WECSs) in resilient microgrids in order to reduce the total system cost and to assist their self-healing capability. Meanwhile, wind industry-based reliability surveys have addressed that power electronics components are the most vulnerable parts in WECS. Therefore, thermal stresses and lifetime consumption of WECS are critical factors for evaluating the added functionalities and for developing new control strategies as well. Almost all of the previous methodologies in the literature tackle the problem of lifetime assessment of WECS using only the behavior of wind generation profiles and reactive power injection, which is limited by grid codes. Subsequently, these approaches cannot efficiently achieve lifetime assessment in case of resilient microgrid operation and different load demands. This paper proposes a more convenient approach for thermal behavior, and lifetime assessment for WECSs that considers the influence of the added DSTATCOM functionality, and various modes of resilient microgrids operation. Moreover, the proposed approach utilizes a joint probability distribution function (JPDF) that combines both of the collected field data of wind generation and load demand levels as well. The feasibility of the proposed approach has been verified analytically and compared to the previously addressed approaches. It can be concluded that thermal behavior and reliability assessment of WECS are highly impacted by the added DSTATCOM functionality. [ABSTRACT FROM PUBLISHER]

Published
2017
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