A Novel Hybrid Islanding Detection Method for Grid-Connected Microgrids With Multiple Inverter-Based Distributed Generators Based on Adaptive Reactive Power Disturbance and Passive Criteria

In order to obtain the benefits of both passive and active methods, a well-designed hybrid islanding detection method for grid-connected microgrids with multiple inverter-based distributed generators (IBDGs) is presented in this paper. Considering that IBDGs located at different positions can detect the same frequency variation (FV) characteristics, linear reactive power disturbance (RPD) is utilized, which can guarantee the synchronization of RPDs added on different IBDGs in the microgrid without the need for communication. In addition, the disturbance slope can change adaptively to reduce the disturbance in grid-connected mode and enlarge the reactive power mismatch during islanding for effective and rapid detection. Setting principles of slope values for IBDGs operating at the unity power factor and those generating active and reactive power simultaneously are analyzed in detail. Considering different conditions that may occur after islanding, three passive criteria, including voltage variation, voltage unbalance, and rate of change of frequency, are sufficiently utilized to activate disturbance slope adjustment, further shortening the detection time. Moreover, the correlation factor between the RPD and FV is also designed as another frequency-related criterion, and the slope adjustment logic is provided. This method is simple and easy to implement with excellent performance regardless of the IBDG power factor, parallel number, and connection mode. According to the anti-islanding test system recommended by IEEE Std.929-2000 and IEEE Std.1547-2003, the method effectiveness has been validated with several test cases in the power systems computer-aided design (PSCAD)/electromagnetic transients including DC (EMTDC) environment.