An Islanding Detection Method for Inverter-Based Distributed Generators Based on the Reactive Power Disturbance

In this paper, 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 nondetection zone property. Moreover, the method can be applied to the DG either operating at unity power factor or supplying reactive power as well for its local load. According to the antiislanding test system recommended in IEEE Std.929-2000 and IEEE Std.1547-2003, the effectiveness of the method has been validated with several case studies in the power systems computer-aided design/Electro magnetic transient in DC system environment.