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Your search keyword '"Khajehoddin, Sayed Ali"' showing total 23 results
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23 results on '"Khajehoddin, Sayed Ali"'

1. Continuous Input Current Isolated Resonant LED Driver With Wide Input Voltage Range

Author

Molavi, Navid, Askari, Shirin, Farzanehfard, Hosein, and Khajehoddin, Sayed Ali

Abstract

In this article, an isolated resonant light-emitting diode (LED) driver featuring inherent constant output current characteristic at fixed frequency operation is presented. The LED current is regulated using the main switches operating duty cycle within a wide input voltage range variation while the integrated step-up structure brings continuous input current with low current ripple suitable for battery operation. The proposed isolated CLLC resonant network incorporates the transformer magnetizing and leakage inductances as the main resonant components leading to a lower number of magnetic components while improving the power density. Also, the zero-voltage-switching operation for the main switches and zero-current switching of the rectifier diodes are realized in the entire input voltage range. A detailed theoretical analysis of the proposed LED driver is presented. To verify the analysis and effectiveness of the proposed topology, a 100-W laboratory prototype with input voltage range of 35–60 V dc is designed and implemented for 48-V dc automotive applications which delivers 1 A current to a high brightness light emitting diode string including 30 series LEDs.

Published
2024
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9. A High Step-Up/Step-Down LVS-Parallel HVS-Series ZVS Bidirectional Converter With Coupled Inductors.

Author

Mohammadi, Mohammad Reza, Amoorezaei, Afshin, Khajehoddin, Sayed Ali, and Moez, Kambiz

Subjects
ZERO voltage switching, HIGH voltages, LOW voltage systems
Abstract

This article introduces a nonisolated bidirectional converter with high-voltage conversion ratio. In the proposed converter, by integrating the two-phase low-voltage-side (LVS)-parallel high-voltage-side (HVS)-series bidirectional converter with the coupled inductors, features, such as high voltage gain, low voltage stresses, current sharing, and current ripple cancelation, are achieved. Due to the proposed converter's operation in triangular conduction mode, the desirable benefits of zero voltage switching, diode reverse recovery elimination, and reduction of converter filter inductors and, consequently, leakage inductors are obtained. To recycle the leakage inductors’ energy and to solve the related difficulties for both operation modes, a simple passive clamp with the minimum number of elements is utilized. Also, to improve the light-loads’ efficiency, the variable frequency control is developed. The proposed converter is comprehensively analyzed, and to verify the analysis, the experimental results are provided. [ABSTRACT FROM AUTHOR]

Published
2022
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23. Resonant Micro-Inverters for Single-Phase Grid-connected Photovoltaic Systems

Author

Queen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.)), Khajehoddin, Sayed Ali Jr, Queen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.)), and Khajehoddin, Sayed Ali Jr

Abstract

This thesis addresses the design and implementation of micro-inverters for grid-connected single-phase photovoltaic (PV) systems. Despite the existing research issues concerning Micro-inverters, they have recently become very attractive due to their modularity and capability of independent maximum power point tracking (MPPT). The complexity in the design of micro-inverters stems from strict grid connection standards and high expectations of compactness, large amplification gain, high efficiency over a wide range of operating conditions and excellent output power quality. Moreover, since micro-inverters are exposed to a wide temperature range, the reliability and life-time of this technology are major problems. The main limiting factor in the life-time of micro-inverters is the use of large electrolytic capacitors for power decoupling. New circuit configuration and control structures to design a compact and efficient micro-inverter with high quality and robust output power injection capabilities are introduced in this thesis. In the proposed topology electrolytic capacitors are eliminated, removing the obstacles in achieving a durable and reliable design. To achieve a compact design, the proposed micro-inverter consists of a soft-switching high frequency resonant converter at the input and a hard-switching lower frequency inverter with a high order filter at the output. Small and large signal models of the resonant converter are obtained to design controllers. A new optimal controller and a design method are also proposed for the inverter that yield robust performance with a high quality output in the presence of grid voltage harmonics, impedance uncertainties and frequency changes. Furthermore, using a new nonlinear control strategy, a direct instantaneous power control method is proposed to achieve fast active and reactive power injections into the grid without using the measurement or calculation of active and reactive powers. A comprehensive steady state analysis, Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2010-04-29 13:57:39.306

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