Power converter and power supply system

A control method, applied to a power converter, wherein a positive electrode of a direct current side of the power converter is configured to connect to a positive direct current busbar, a negative electrode of the direct current side is configured to connect to a negative direct current busbar, and the power converter comprises a power conversion circuit, a filter circuit, and a control circuit;

• the power conversion circuit comprises an inverter circuit and a direct current busbar capacitor, the direct current busbar capacitor is connected between the positive direct current busbar and the negative direct current busbar, and the direct current busbar capacitor comprises a positive busbar capacitor and a negative busbar capacitor that are connected in series;
• the inverter circuit comprises a bridge arm, an output end of the bridge arm is electrically connected to the filter circuit, the bridge arm comprises a plurality of switching transistors, and the bridge arm is configured to convert an input direct current into an alternating current;
• and
• the method comprises:
• obtaining a voltage between both ends of the positive busbar capacitor, a voltage between both ends of the negative busbar capacitor, and an output current of the bridge arm;
• and
• controlling, based on the voltage between both ends of the positive busbar capacitor, the voltage between both ends of the negative busbar capacitor, and the output current of the bridge arm, the bridge arm to switch between a first modulation mode and a second modulation mode, wherein
• in the first modulation mode, a level output by the bridge arm in one switching cycle comprises a co-directional level, a zero level, and a reverse level;
• and
• in the second modulation mode, a level output by the bridge arm in one switching cycle comprises the co-directional level and the zero level, wherein
• the co-directional level is a level in a direction that is the same as a direction of an equivalent voltage output by the inverter circuit, and the reverse level is a level in a direction that is opposite to the direction of the equivalent voltage output by the inverter circuit.

A power supply system, comprising:

• a power supply, a positive direct current busbar, a negative direct current busbar, and a power converter, wherein the power converter comprises:
• a direct current side having a positive electrode connected to the positive direct current busbar and a negative electrode connected to the negative direct current busbar;
• a power conversion circuit, comprising:
• a direct current busbar capacitor connected between the positive direct current busbar and the negative direct current busbar, wherein the direct current busbar capacitor comprises a positive busbar capacitor and a negative busbar capacitor connected in series, and
• an inverter circuit having a bridge arm, wherein an output end of the bridge arm is electrically connected to a filter circuit, the bridge arm comprises a plurality of switching transistors, and the bridge arm is configured to convert an input direct current into an alternating current;
• and
• a control circuit configured to switch between a first modulation mode and a second modulation mode, based on a voltage between both ends of the positive busbar capacitor, a voltage between both ends of the negative busbar capacitor, and an output current of the bridge arm, wherein
• in the first modulation mode, a level output by any bridge arm in one switching cycle comprises a co-directional level, a zero level, and a reverse level;
• and
• in the second modulation mode, a level output by any bridge arm in one switching cycle comprises the co-directional level and the zero level, wherein
• the co-directional level is a level in a direction that is the same as a direction of an equivalent voltage output by the inverter circuit, and the reverse level is a level in a direction that is opposite to the direction of the equivalent voltage output by the inverter circuit;
• the power supply is connected to a positive input end of the power converter via the positive direct current busbar, and is connected to a negative input end of the power converter via the negative direct current busbar;
• and
• the power converter is configured to convert a direct current input by the power supply into an alternating current, and output the alternating current to a load.