Photovoltaic grid-connected power generation device based on multilevel technique

The invention discloses a photovoltaic grid-connected power generation device based on a multilevel technique. The photovoltaic grid-connected power generation device comprises a photovoltaic power input unit, a direct-current bus capacitor unit, a three-phase square wave inverter unit, a transformer unit and an output filter reactor unit, wherein the photovoltaic power input unit consists of N groups of photovoltaic cell arrays and direct-current/direct-current (DC/DC) converters which realize maximum power point tracking and step-up functions; the direct-current bus capacitor unit realizes direct-current bus voltage supporting and alternating-current and direct-current energy decoupling functions; and the direct-current/alternating-current (DC/AC) conversion of the three-phase square wave inverter unit adopts a square wave superposition multilevel technique, the transformer unit is used for synthesizing the output voltage of the three-phase square wave inverter unit, unit power factor control and low distortion rate of grid-connected current are realized through the output filter reactor unit, and the islanding protection of the photovoltaic grid-connected power generation device is realized through the combination of detection voltage, detection frequency and reactive power disturbance. Therefore, the photovoltaic grid-connected power generation device can be used for high-voltage high-capacity photovoltaic grid-connected power generation systems.