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2. Fault-Tolerant SRM Drives—A Review

Author

Ali, Nasir and Narimani, Mehdi

Abstract

Fault tolerance in electric motor drives has been extensively studied due to their widespread usage in safety-critical applications, including more/all-electric aircraft and electric vehicles. Switched reluctance motors (SRMs) are renowned for their high robustness and excellent fault tolerance. However, they are not immune to faults, and a potential fault in any part of the motor drive could have serious implications for the system, even may lead to unexpected shutdown if the fault is not promptly remedied. The power converter is a key component and the most vulnerable to failure, as reported for 35% of the drive faults. Fault tolerance has typically been achieved through a combination of hardware and software reconfigurations. However, due to the simple structure of the standard asymmetrical half-bridge converter, hardware reconfiguration is more commonly used to remediate converter faults. Consequently, fault tolerance adds cost and complexity to a standard SRM drive system. This article presents an instructive survey of the recent research on fault-tolerant SRM drives. Moreover, the postfault performance, implementation costs, and fault-tolerant capabilities of advanced fault-tolerant converters are systematically quantified, evaluated and compared. Finally, the article is concluded with an investigation on the future research trends in fault tolerance in SRM drives.

Published
2024
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5. Integrating OFDM Into Switching Power Supplies for Visible Light Communications

Author

Barmaki, Alireza, Narimani, Mehdi, and Hranilovic, Steve

Abstract

Visible light communications (VLC) is a promising technology that combines the ubiquity of illumination devices with broadband communication to provide connectivity. The most recent VLC communication standards specify orthogonal frequency division multiplexing (OFDM) as the underlying modulation due to its spectral efficiency and compatibility with existing broadband modems. However, a key challenge remains in realizing VLC modulators capable of generating OFDM signal compatible with the primary illumination function, while ensuring the efficacy of the luminaires. In this paper, a novel method is proposed to integrate OFDM modulation into a switching power supply. Commutating diodes in the DC/DC converter are replaced by light-emitting diodes (LEDs) which are used for communication while the larger illumination string of LEDs is left unmodulated preserving the quality of illumination and luminaire lifetime. Biasing the switching MOSFET to its saturation region during its off states allows for the MOSFET to act as an amplifier, amplifying the OFDM communication signal and injecting it to the light-emitting commutating diode (LECD). As a result, energy efficient LED drivers capable of OFDM signal transmission are realized. Both simulation and experimental results are provided to demonstrate the feasibility of this approach, showcasing superior performance compared to existing literature in terms of component count, efficacy, illumination quality, and reliability. Notably, based on simulation results, the efficacy of our approach surpasses the bias-T approach by approximately 6.25%.

Published
2024
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18. A New Active Front-End Control for Regenerative Cascaded H-Bridge Motor Drives With Filter- Less Interfacing Capability

Author

Abuelnaga, Ahmed H., Ni, Zhituo, Badawi, Sarah, Narimani, Mehdi, Sayed-Ahmed, Ahmed, and Zargari, Navid R.

Abstract

This article proposes a new active-front-end (AFE) control method for regenerative cascaded H-bridge (CHB) motor drives. Conventional CHB converters have dominated the market for the medium-voltage industrial motor drives. However, conventional CHB converters cannot provide regenerative capability. To enable regeneration; diode-front-ends in power cells are replaced with insulated-gate bipolar transistor (IGBT)-based pulsewidth modulation (PWM) AFEs. Despite the appealing dynamic performance of PWM AFEs, their integration to the CHB converters is not optimal. First, they introduce more semiconductor losses due to the high-frequency switching. Second, they introduce switching harmonics that are not cancelled by phase-shifting transformers. Therefore, they require additional harmonic filtering solutions to comply with grid harmonic standards. To resolve these challenges, this article proposes a new AFE control for regenerative CHB converters based on fundamental frequency switching (FFE) to reduce switching frequency and thus power losses. The operation of FFEs at nominal and sag voltage conditions is presented, in addition to the capability of filter-less interfacing to the transformer. Finally, the performance of the proposed control is validated experimentally on a seven-level regenerative CHB drive.

Published
2023
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40. Light-Emitting Commutating Diodes for Optical Wireless Communications Within LED Drivers.

Author

Pawlikowski, Warren, Barmaki, Alireza, Narimani, Mehdi, and Hranilovic, Steve

Abstract

Although visible light communication (VLC) systems provide high density links for use in Internet-of-Things (IoT) devices, the design of high rate VLC transmitters that maintain luminaire efficacy is an open problem. In this article, a novel approach to the integration of VLC within light-emitting diode (LED) drivers is proposed through the replacement of freewheeling/blocking diodes with light-emitting devices termed a light-emitting commutating diodes (LECDs). In this manner, communications and illumination can be provided using a simple, cost effective design while employing no additional components. The subtle change of LED driver control signals facilitates the transmission of data from LECDs while simultaneously supporting illumination functions. Lighting controls such as dimming are maintained and combined with modulation through the use of overlapping pulse position modulation (OPPM) and performance is quantified. Prototype buck and boost converters with LECDs are implemented and their efficacy is measured. Though current commercial LEDs are not intended for such signalling applications, we experimentally demonstrate their feasibility in this application and suggest methods to make such converters reliable. It is demonstrated that the addition of an LECD improves the efficacy of the luminaire as compared to conventional LED drivers while simultaneously enabling a VLC downlink. [ABSTRACT FROM AUTHOR]

Published
2020
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49. Low Power AC-DC and DC-DC Multilevel Converters

Author

Narimani, Mehdi

Subjects
Single-Phase AC-DC Rectifiers, Three-Phase AC-DC Rectifiers, DC-DC Converters, Single-Stage Converters, Power and Energy, Power Factor Correction, Multilevel Converters
Abstract

AC-DC power electronic converters are widely used for electrical power conversion in many industrial applications such as for telecom equipment, information technology equipment, electric vehicles, space power systems and power systems based on renewable energy resources. Conventional AC-DC converters generally have two conversion stages – an AC-DC front-end stage that operates with some sort of power factor correction to ensure good power quality at the input, and a DC-DC conversion stage that takes the DC output of the front-end converter and converts it to the desired output DC voltage. Due to the cost of having two separate and independent converters, there has been considerable research on so-called single-stage converters – converters that can simultaneously perform AC-DC and DC-DC conversion with only a single converter stage. In spite of the research that has been done on AC-DC single-stage, there is still a need for further research to improve their performance. The main focus of this thesis is on development of new and improved AC-DC single-stage converters that are based on multilevel circuit structures (topologies) and principles instead of conventional two-level ones. The development of a new DC-DC multilevel converter is a secondary focus of this thesis. In this thesis, a literature survey of state of the art AC-DC and DC-DC converters is performed and the drawbacks of previous proposed converters are reviewed. A variety of new power electronic converters including new single-phase and three-phase converters and a new DC-DC converter are then proposed. The steady-state characteristics of each new converter is determined by mathematical analysis, and, once determined, these characteristics are used to develop a procedure for the design of key converter components. The feasibility of all new converters is confirmed by experimental results obtained from proof-of-concept prototype converters. Finally, the contents of the thesis are summarized and conclusions about the effectiveness of using multilevel converter principles to improve the performance of AC-DC and DC-DC converters are made.

Published
2012

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