Control device and control method during bypassing of power units

A control device during bypassing of power units, being applicable to balance a three-phase output voltage of a cascade inverter, the control device comprising:

• a detection module for detecting the three-phase output voltage;
• a calculation module for calculating a negative sequence component of the three-phase output voltage;
• a compensation module for providing a given negative sequence component and performing closed-loop compensation based on the negative sequence component from the calculation module according to the given negative sequence component, for outputting the compensated negative sequence component;
• and
• an output module for superimposing the compensated negative sequence component with a three-phase output voltage command and outputting a new three-phase output voltage using a modulation way;
• wherein the modulation way is a Sinusoidal Pulse Width Modulation (SPWM) way or a Space Vector Pulse Width Modulation (SVPWM) way, and when the modulation way is the SVPWM way, the calculation module is further used for performing abc/αβ coordinate transformation on the calculated negative sequence component, so as to obtain a negative sequence component in a two-phase static coordinate system, and the compensation module performs the closed-loop compensation on the negative sequence component in the two-phase static coordinate system according to the given negative sequence component to output the compensated negative sequence component.