| 摘要 |
<P>PROBLEM TO BE SOLVED: To suppress a variation in neutral point potential to a preset value or less over an entire operation state. <P>SOLUTION: An offset value where the voltage command of a phase that becomes the maximum value in three-phase voltage commands becomes the maximum value at a positive side is added to the voltage command of all three phases for obtaining a three-phase positive side shift voltage command. Additionally, an offset value where the voltage command of a phase that becomes the minimum value in three-phase voltage commands becomes the minimum value at a negative side is added to the voltage commands in all three phases to obtain a three-phase negative side shift voltage command. Each neutral point current that is generated when PWM control is performed by each of three kinds of voltage commands is calculated. When the potential of a neutral point exceeds a limit value, the three-phase voltage command for generating a neutral point current that can return the neutral point potential within a specified limit value at the highest speed is selected for carrying out three-level PWM control. <P>COPYRIGHT: (C)2003,JPO |
