Method and device for adjusting output voltage of three-level frequency converter

The embodiment of the invention provides an output voltage adjusting method and device of a three-level frequency converter, and belongs to the technical field of three-level frequency converters. The method comprises the following steps: determining capacitance midpoint potential offset according to a first voltage of a first capacitor and a second voltage of a second capacitor; starting a first modulation mode when the maximum voltage amplitude of the three-phase modulation wave is less than a first threshold voltage and the capacitance midpoint potential offset is greater than a second threshold voltage, determining a first modulation strategy according to a PWM waveform generation algorithm, and obtaining a corresponding output PWM waveform according to the first modulation strategy; and if the capacitor midpoint potential offset is smaller than a third threshold voltage, starting a second modulation mode, in the second modulation mode, determining a second modulation strategy according to a PWM waveform