Islanding Detection Scheme for Inverter-Based Distributed Generation Systems Using Cumulative Reactive Power Harmonics

In this paper, a new islanding detection scheme using cumulative reactive power harmonics (CRPH) for inverter-based distributed generation (DG) systems is presented. In the proposed method, first, any changes in the system are detected using a change detection index. Desired harmonic components of the voltage and current signals at DG terminals are extracted by a discrete Kalman filter (DKF). Then, a criterion based on CRPH is defined using the extracted harmonic signatures. The change detection index is based on the difference of measured current and its estimated fundamental component. At the initial moments of any events, reactive power controller of the inverter is disabled just for a short time interval. Since the main grid as the main source of reactive power loses in islanding condition, the reactive harmonic power of the system experiences significant variations. Then, islanding can be discriminated from other similar conditions by processing the captured signals of the mentioned time interval. Performance of the proposed method is assessed using plenty of simulations. Moreover, the superiority of the proposed method is confirmed by performing a comparison with other similar techniques.