POWER CONVERSION APPARATUS

A power conversion apparatus provided in this application includes a direct current end, a positive direct current bus, a negative direct current bus, a positive bus capacitor, a negative bus capacitor, at least three inverter bridge arms, a switch unit, a controller, and filter inductors, filter capacitors, and alternating current ends that correspond to the at least three inverter bridge arms. A third end of each inverter bridge arm sequentially passes through a filter inductor, a filter capacitor, and a switch unit that correspond to each inverter bridge arm, and is connected to a bus midpoint. The controller is configured to: when a voltage of a power grid is less than or equal to a first voltage threshold, control the switch unit to be turned off or impedance of the switch unit to be increased; and after the switch unit is turned off or the impedance of the switch unit is increased, control a modulated wave of each inverter bridge arm to be a modulated wave obtained by superimposing a first common-mode modulation signal on an initial modulated wave of each inverter bridge arm, to increase amplitude of the modulated wave of each inverter bridge arm. In this way, this can balance losses of switching transistors of the inverter bridge arms, and improve common-mode oscillation caused by a change of the modulated wave.