Abstract: An islanding detection method for inverter-based distributed generators (DGs) is presented, which is based on perturbing reactive power output. Two sets of disturbances are configured in this method, which have different amplitudes and duration time. The first set of reactive power disturbance (FSORPD) is periodic with small amplitudes to break the reactive power balance during islanding, whereas the magnitude of the second set of reactive power disturbance (SSORPD) is sufficient to force the frequency to deviate outside its threshold limits. Considering all the possible frequency variation characteristics with the FSORPD after islanding, three criterions are designed for switching the disturbance from the FSORPD to the SSORPD. Since DGs located at different positions have the same frequency variation characteristics, the SSORPDs can be added on different DGs at the same time without the need of communication. Therefore, synchronization of the SSORPDs can be guaranteed for the system with multiple DGs and the method can detect islanding with a zero non-detection zone (NDZ) property. According to the anti-islanding test system recommended in IEEE Std.929-2000 and IEEE Std.1547-2003, in the effectiveness of the method has been validated with several case studies in mat lab simulation.

Keywords: Inverter based distribution generation, reactive power disturbance, islanding detection, circuit breaker.