Amplitude-phase correction overmodulation method and system under cascade H-bridge converter sub-module fault

The invention discloses an amplitude-phase correction overmodulation method and system under a cascade H-bridge converter sub-module fault, and the method comprises the steps: obtaining an output level of each phase and a space vector diagram of the output level according to the damage condition of a cascade H-bridge multilevel converter sub-module, and carrying out the quantitative calculation of the coordinates of the vertex of a vector output convex hull and the related parameters of the boundary; applying a corresponding cross multiplication criterion to each boundary vector so as to judge a damaged rectangular region where the vector is located, and obtaining a corresponding rotation transformation vector for amplitude-phase correction; performing coordinate transformation on polar coordinates of each point on the vector diagram and a corresponding rotation transformation vector, specifying a vector amplitude phase correction principle, and solving a value of a reference trajectory circle radius through