Rate of change of superimposed negative sequence impedance based islanding detection technique for distributed generations
In this study, a new islanding detection technique based on the rate of change of superimposed negative sequence impedance (ROCSNSI) is proposed. Due to the presence of non-linear loads in microgrids, a considerable amount of inter harmonic components exist in power system signals. To compute the fundamental frequency component of voltage and current signals, phasors are calculated using a full-cycle least error square technique. The ROCSNSI is considered for the discrimination of islanding and non-islanding events (NIEs). The performance of the proposed technique is evaluated by simulating IEEE 13 and IEEE 34 bus microgrid systems in real-time digital simulator. Islanding and non-islanding scenarios for perfect power match condition, types of distributed generations (DGs) with various control strategies are simulated and the performance of the proposed approach is found to be accurate. It is found that, the technique identifies the islanding even under low active and reactive power mismatches and hence overcomes the non-detection zone problem. Different NIEs, like load switching, faults, tripping of DG, single-pole tripping and reconnection of the DG are considered and the technique discriminates islanding and NIEs within a full cycle from the inception point.
