A power converter includes a power conversion circuit, a bus capacitor, and a controller. A direct current input end of the power conversion circuit is configured to connect to a direct current power supply through a direct current bus. An alternating current output end of the power conversion circuit is configured to connect to an alternating current power grid through a point of common coupling (PCC). The controller is configured to: in response to that a difference between a voltage across two ends of the positive bus capacitor and a voltage across two ends of the negative bus capacitor is greater than a specified threshold, control the power converter to inject a second harmonic current into the alternating current power grid, to reduce the difference between the voltage across the two ends of the positive bus capacitor and the voltage across the two ends of the negative bus capacitor.