Abstract: The problems existing in the overcurrent protection circuit of current cascade highvoltage frequency converters and the reasons causing incorrect tripping of the overcurrent protection were analyzed. The hazard of the existing overcurrent protection for normal operation of the converter was expounded. The hardware protection was transformed into a new protection scheme, in which the hardware protection and software protection are used as standby for each other, and an improved full wave Fourier algorithm was put forward. The engineering practice shows that the new overcurrent protection scheme can improve the operation reliability of the cascade highvoltage frequency converter.

Key words: cascade high-voltage frequency converter, over-current protection, full wave Fourier algorithm