The demand for renewable energy has been steadily increasing since the start of this century. One of the main stages in converting the renewable energy into electricity is the DC-DC converter. This stage has attracted many researchers to reduce its cost and improve its efficiency. In Photovoltaic (PV) systems, the conventional approach was connecting each PV panel to a single DC-DC converter. To improve the DC-DC conversion stage, Multi-Port Converters (MPCs) can be used to connect multiple PV panels to the same converter reducing size, cost, and achieving higher efficiency. Also, MPCs enable adding energy storage to the PV system to overcome the PV intermittent feature without extra circuitry. This dissertation presents a comprehensive analysis of a dual-input LLC topology for the DC-DC conversion stage of microinverters. It studies the resonant tank behavior under two control techniques: Phase Shift Modulation (PSM) and Frequency Switching Modulation (FSM). Then, the gain characteristics are derived in the normalized form considering the phase shift, switching frequency, and voltage difference between the panels. Then, we explore the control variables impact on solar energy harvesting along with the PV behavior under different conditions. Accordingly, a Maximum Power Point Tracking (MPPT) control algorithm is implemented by adopting the Incremental Conductance (InC) technique. Achieving MPPT for both PV panels of the dual-input LLC converter using the proposed extended InC method is verified by Simulink/MATLAB. In addition, a Four-Port Converter (FPC) is presented by integrating a storage unit to the dual-input LLC converter. The FPC can be easily reconfigured into a TPC realizing seven power flow scenarios, which are analyzed in detail along with their voltage relations. For control, PSM and FSM are used to achieve MPPT for each PV while variable pulse width modulation regulates the battery and load.
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Doctor of Philosophy (Ph.D.)
College of Engineering and Computer Science
Electrical and Computer Engineering
Length of Campus-only Access
Doctoral Dissertation (Campus-only Access)
Alhatlani, Abdullah, "Design and Analysis of Multi-Port Converters Utilizing LLC Resonant Tank" (2021). Electronic Theses and Dissertations, 2020-. 1123.
Restricted to the UCF community until February 2027; it will then be open access.