Method for controlling photovoltaic grid-connected inverter

The invention discloses a method for controlling a photovoltaic grid-connected inverter. The method includes the steps that a connecting switch of a photovoltaic array and the grid-connected inverter is controlled to be switched on or off by judging the relation between the output voltage of the photovoltaic array and a preset range, according to working conditions of the photovoltaic array, the active current instruction value and the corresponding reactive current instruction value of the grid-connected inverter are acquired, the acquired active current instruction value and the acquired corresponding reactive current instruction value of the grid-connected inverter are correspondingly converted, adjusted and calculated, and PWM signals for controlling the switch of the grid-connected inverter to be switched on or off are acquired. According to the different working conditions of the photovoltaic array, the grid-connected inverter is switched and operated among three different modes that only the active power of the photovoltaic array is output, the active power of the photovoltaic array and part of reactive power needed for an alternating current bus side are output and the grid-connected inverter only serves as a reactive power compensator, the situation that the grid-connected inverter cannot be fully loaded and even unloaded is avoided, the utilization rate of the inverter is increased, and stability of the alternating current side voltage is improved.