| Summary: | 博士 === 國立臺灣科技大學 === 電子工程系 === 98 === This dissertation aims to study and develop two novel grid-connected photovoltaic (PV) systems. The first PV system is parallel-connected to an electric power grid with a power factor corrector (PFC) for supplying DC loads. The balanced distribution of the power flow between the utility and the PV panels is achieved automatically by regulating the output DC voltage of the PFC. The proposed topology, which can effectively transfer the tracked maximum power from the PV system to the DC load, while the unity power factor is obtained at the utility side. The DC-connected Photovoltaic system has the advantages of high reliability and low cost due to its simple topology and easy control.
The conventional AC-connected photovoltaic system consists of a DC/DC converter for tracking the MPP of the photovoltaic panels and a DC/AC inverter for supply AC voltage output. An interesting alternative solution is the application of a single-stage topology. Thus, this dissertation also presents the second PV system that is a single-stage full-bridge inverter topology with maximum power point tracking (MPPT) function. High MPPT accuracy and high conversion efficiency can be achieved by using a simple single-stage configuration. The advantages of the single-stage topology are a high power density, simple configuration and low circuit cost compared with the conventional two-stage structure. The operation principles and design considerations of the proposed DC and AC grid-connected PV systems are discussed and analyzed in details. The laboratory prototypes are implemented and tested. The experimental results are shown to verify the feasibility of the studied schemes.
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