Phase modifier frequency conversion starting process short circuit fault protection method and device

The invention discloses a phase modifier frequency conversion starting process short circuit fault protection method and device. The method comprises the following steps of acquiring a phase modifiermachine end side voltage, a phase modifier neutral point side current, a computer end side voltage amplitude and frequency, and a ratio of the machine end side voltage to a frequency per unit value, and calculating a neutral point side current amplitude and a neutral point side current amplitude variation; in an initial constant magnetic flux starting stage, when the ratio of the phase modifier machine end side voltage to the frequency per unit value is reduced to exceed a setting value and a neutral point side current amplitude is increased to exceed the setting value, determining to be a short-circuit fault; or in a constant-voltage starting stage, when the machine end side voltage is reduced to exceed the setting value and the neutral point side current amplitude is increased to exceedthe setting value, determi