Direct current converter, control method, direct current combiner box, and photovoltaic power generation system

A control method for a direct current converter, wherein the direct current converter is configured to connect to a direct current power supply, the direct current converter comprises a three-level power switching circuit, a resonant circuit, a first diode, a second diode, and a first capacitor, wherein a first output end of the three-level power switching circuit is connected to an anode of the first diode and a cathode of the second diode by using the resonant circuit, and a second output end of the power switching circuit is connected to a cathode of the first diode, the cathode of the first diode is connected to a positive output end of the direct current converter, an anode of the second diode is connected to a negative output end of the direct current converter, and the first capacitor is connected in parallel between the positive output end and the negative output end, an input end of the three-level power switching circuit is connected to the direct current power supply, an output voltage at an output end of the three-level power switching circuit is used to charge the resonant circuit, and the method comprises:

• controlling power switching components in the three-level power switching circuit, so that when the resonant circuit performs charging or discharging at one half of a direct current voltage, one of the power switching components is connected to a current loop of the resonant circuit, and when the resonant circuit performs charging or discharging at the direct current voltage, two of the power switching components are connected to the current loop of the resonant circuit.