Method for suppressing periodic fluctuation of output middle point of ship three-phase and four-bridge arm inverter on ground voltage

The invention belongs to the technical field of power electronics, and particularly relates to a method for suppressing periodic fluctuation of an output middle point of a ship three-phase and four-bridge arm inverter on a ground voltage. The method comprises the steps of detecting line voltages of two arbitrary AC incoming lines in a three-phase and four-bridge arm inverter control system by an AC incoming line voltage sensor, converting the line voltages to phase voltages of three phases, locking a phase of an arbitrary phase by a software phase-locked loop, allowing a modulation wave phaseof arbitrary one of A phase, B phase and C phase of the three-phase and four-bridge arm inverter to be same as the phase of an AC incoming line voltage of a certain phase which is detected, and adjusting phases of other two phases so that the phase difference among the A, B and C is 120 degrees. With regard to a A-phase bridge arm, a B-phase bridge arm and a C-phase bridge arm of the three-phase and four-bridge arm invert