The invention relates to the technical field of
power factor correction, in particular to a method for improving the working stability of a PFC (
Power Factor Correction) when an input
voltage drastically drops. According to the method, a 1 / 2 period maximum value detection method is utilized, rapid refreshing of an input
voltage dynamic effective value is achieved through a
software phase-locked loop and a half-power-frequency period maximum value detection method, and the input
voltage dynamic effective value serves as a feed-forward quantity to directly participate in calculation of an input current reference value. Therefore, the input power is compensated instantaneously when
voltage drop occurs,
bus voltage drop and current overshoot are effectively suppressed, and the key problems of slow dynamic response and overlong
system recovery time of a traditional PWM cycle-by-cycle
current limiting scheme and
harmonic distortion,
power factor reduction,
system stability deterioration and the like caused by a
voltage loop bandwidth increasing scheme are solved.