| In order to solve the energy crisis and environment pollution, the renewable energy generation such as wind energy and solar energy has been receiving more and more attentions. Since the wind energy and solar energy are strongly affected by climate and weather, the output voltage varies in a wide range. In general, the grid-connected inverter consists of two stages. The first stage is a dc-dc converter, which converts the variable dc input voltage into a stable dc voltage; and then, the second stage dc-ac inverter converters the stable dc voltage into the ac voltage. This thesis is dedicated to the first stage dc-dc converter.The two-switch buck-boost converter is chosen as the first stage dc-dc converter, which can operate in buck mode and boost mode, thus achieves a high efficiency over the entire input voltage range. In this thesis, a single-regulator two-carrier two-mode control strategy is used, and it can choose the suitable operating mode automatically. In order to depress the output voltage variation when input voltage has a step change, an input voltage feedforward control strategy is proposed in this thesis.The input voltage feedforward functions of buck mode and boost mode are derived, and the feedforward coefficient of the two modes are different. By using two modulating signals,it can choose the corresponding input voltage feedforward branch automatically to regulate the output voltage under different modes, and the output voltage can keep stable no matter the operating mode of the converter changes or not.A 3 kW prototype with input voltage of 250V–500V and output voltage of 360V is fabricated and tested in the lab. The simulation and experimental results are given to verify the effectiveness of the proposed input voltage feedforward control strategy.
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