Photovoltaic converter string, control method, and system

A photovoltaic converter string, comprising a plurality of photovoltaic converters, wherein output ends of the plurality of photovoltaic converters are connected in series, and an input end of each of the photovoltaic converters is connected to a corresponding photovoltaic module;

• wherein each photovoltaic converter comprises a buck/boost circuit and a controller, an output capacitor is connected between a positive output end and a negative output end of the buck/boost circuit, and both ends of the output capacitor are connected in parallel to a bypass diode;
• wherein the controller is configured to:
• based on the buck/boost circuit being in an off state and an output voltage of the buck/boost circuit being greater than or equal to a preset voltage, control energy of an output end of the buck/boost circuit to be reversely leaked to the correspondingly connected photovoltaic module, to reduce a voltage that the bypass diode withstands;
• and
• wherein the off state indicates that the controller included in the photovoltaic converter has not received a start instruction sent by a host computer, and the host computer is a controller of an inverter.

A method for controlling a photovoltaic converter string, wherein the photovoltaic converter string comprises a plurality of photovoltaic converters, output ends of the plurality of photovoltaic converters are connected in series, an input end of each of the photovoltaic converters corresponds to a connected photovoltaic module, each photovoltaic converter comprises a buck/boost circuit and a controller, an output capacitor is connected between a positive output end and a negative output end of the buck/boost circuit, and both ends of the output capacitor are connected in parallel to a bypass diode;

• and
• the method comprises:
• determining whether the buck/boost circuit is in an off state:
• based on the buck/boost circuit being in the off state, controlling, one of switching transistors in the buck/boost circuit to be conducted, wherein the switching transistors are connected in parallel to the bypass diode;
• and controlling the other switching transistors in the buck/boost circuit to be cut off, so that a voltage that the bypass diode withstands is less than or equal to a breakdown voltage of the non-conducted switching transistor;
• further based on a condition that an output voltage of the buck/boost circuit is greater than or equal to a preset voltage, controlling energy of an output end of the buck/boost circuit to be reversely leaked to the correspondingly connected photovoltaic module, to reduce a voltage that the bypass diode withstands;
• and
• wherein the off state indicates that the controller included in the photovoltaic converter has not received a start instruction sent by a host computer, and the host computer is a controller of an inverter.