Faculty of Graduate Studies (Electronic Theses and Practica)

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This community holds theses prepared by graduate students and reviewed by program advisors.

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Browsing Faculty of Graduate Studies (Electronic Theses and Practica) by Author "Abdalaal, Radwa"

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    Power quality conditioning technology for power grids with modern lighting loads
    (2020-06-08) Abdalaal, Radwa; Annakkage, Udaya (Electrical and Computer Engineering) Yuan, Qiuyan (Civil Engineering) Loo, Ka-Hong (The Hong Kong Polytechnic University); Ho, Ngai Man (Carl) (Electrical and Computer Engineering)
    Poor power quality network, including long and short voltage variations, is directly reflected into visual light flickering in light emitting diode (LED) lighting networks. On the other hand, a large scale of LED lighting network injects high harmonic contents that are generated by the internal driver of LEDs. Accordingly, this will distort the quality of the grid leading to high voltage and current total harmonics distortion. This thesis proposes a power electronics apparatus to mitigate major power quality problems in LED lighting networks and improve the overall quality of distribution networks. An active power filter has been proposed as a comprehensive solution to improve grid current and light intensity flickers in a large-scale LED lighting network. The first part of the research study is conducted to gain a better understanding of the characterization of commercial dimmable LED lamps as nonlinear loads. The second part of the research study proposes a single-phase transformerless unified power quality conditioner (TL-UPQC) topology with its controls. The topology provides a stable output voltage for a flicker free lighting network. An active power filter injects harmonic and reactive currents to provide unity power factor. A dynamic voltage restorer quickly supports the load voltage for any voltage dip, swell or flickering in the network. Stability of the designed controllers is analyzed by a small-signal modeling technique. In addition, the proposed topology has been utilized as a central dimmer system for LED lamps while maintaining high voltage and current quality. The TL-UPQC features have been extended to improve the grid voltage profile by designing an ac voltage control loop to achieve reactive power compensation into the input grid. Moreover, the thesis presents a novel approach for a supervisory remote management system to regulate a secondary control system that is based on the available capacity of distributed units connected to the same point of common coupling. The TL-UPQC system topology and its controller methodology have been verified experimentally with a 500VA / 120V prototype. Modularized distributed TL-UPQC systems have been evaluated by implementing a controller hardware-in-the-loop test. All described strategies’ experimental results show good agreements with the theoretical concept.