Control method and control system of three-level converter

The embodiment of the invention provides a control method and a control system of a three-level converter, and the control method comprises the steps: determining a first vector based on the calculated ideal discharge current and actual discharge current in combination with the switching state of a switching tube in the three-level converter; determining a hexagonal sector graph formed by potentials in the three-level converter; determining a second vector from the hexagonal sector graph, wherein the second vector is obtained by comparing a sector position of a reference vector with an effective vector range; comparing the offset error with a preset offset error result, and determining a corresponding target mode; and in the target mode, generating a hybrid vector based on the first vector and the second vector to realize control of the three-level converter. According to the embodiment of the invention, the problem of midpoint voltage excursion of the direct current side capacitor in the circuit can be solve