| With the consumption of non-renewable resources such as fossil fuels and the increasing air pollution,people have turned their attention to new energy sources.Clean energy represented by photovoltaics has been vigorously developed due to its abundant sources and low pollution,and photovoltaic inverters have received attention as the most important part of photovoltaic power generation systems.After analyzing the topology of the micro-PV inverter,the flyback converter plus the full-bridge inverter stage is determined as the main topology.The main topology of the traditional micro-inverter is the high-end active clamp plus full-bridge circuit.In order to improve efficiency,a quasi-resonant flyback converter plus a full-bridge circuit is used as the main topology.After analyzing the working mode of the flyback converter,the peak current control and DCM/BCM hybrid control mode are introduced in the micro inverter.By controlling the primary current shape of the flyback converter,the secondary side output current is sinusoidal full wave.The shape forms a grid-connected current after the power frequency inverter and the filtering step.It can be seen from the analysis in half grid period and in a single switching cycle that the quasi-resonant flyback inverter has lower main switching voltage stress and voltage than the active clamped flyback inverter.The rising slope is slowed down,and the turn-on frequency of the auxiliary switch is greatly reduced,thereby improving the overall efficiency of the inverter.Then introduce the maximum power tracking and islanding detection technology used by the grid-connected micro-inverter to ensure that the PV module works near the maximum power point to avoid islanding.Finally,through the calculation and design of the main parameters in the inverter,an experiment was carried out on an experimental platform with rated power of 240 W and grid-connected voltage of 220 V.The feasibility of the design was verified by experiments. |
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