Abstract: Provided are a cascaded photovoltaic grid-connected inverter and a control method and control device thereof. The method includes: determining whether at least one of inverter units of the inverter is over-modulated; if yes, calculating a maximum reactive power and a minimum reactive power permitted to be injected to a power grid in a situation that a power factor of a system is not less than a minimum permitted value; simulating an operation state of the inverter after the maximum reactive power is injected to the power grid and determining whether each of the inverter units in the operation state is in a modulating region; if yes, injecting a suitable reactive power to the power grid; and if no, controlling the inverter to exit an operation mode of independently performing maximum power point tracking control on each photovoltaic panel.

Abstract: Provided are a cascaded photovoltaic grid-connected inverter and a control method and control device thereof. The method includes: determining whether at least one of inverter units of the inverter is over-modulated; if yes, calculating a maximum reactive power and a minimum reactive power permitted to be injected to a power grid in a situation that a power factor of a system is not less than a minimum permitted value; simulating an operation state of the inverter after the maximum reactive power is injected to the power grid and determining whether each of the inverter units in the operation state is in a modulating region; if yes, injecting a suitable reactive power to the power grid; and if no, controlling the inverter to exit an operation mode of independently performing maximum power point tracking control on each photovoltaic panel.