Three-phase photovoltaic inverter anti-islanding method based on phase angle deviation positive feedback

The invention relates to a three-phase photovoltaic inverter anti-islanding method based on phase angle deviation positive feedback, which comprises the steps as follows: carrying out disturbance to a power grid phase with T being used as a cycle, a disturbance phase angle for each time is delta theta under a grid synchronization condition of the inverter; and beginning to accumulate when a power grid voltage phase angle is 0 degree and assuming total accumulating n times within T, namely a current phase leading voltage is n*delta theta degrees, and calculating an error value delta f of the current frequency and the last periodic frequency of the power grid voltage, so that the error value is adopted as phase angle deviation positive feedback quantity. When islanding happens, the frequency of the current voltage is more than that of the last period, the delta f is positive, a control loop leads the plosive value into the positive feedback, the disturbance quantity is changed into n*delta theta+delta f at the moment, and equivalently, the forward disturbance is increased, so that the more the phase disturbance is, the more the voltage frequency deviation is, so as to form a forward deviation positive feedback system; and the system reports an overfrequency error until the frequency exceeds standard, so as to achieve the islanding protection purpose.