A hybrid active islanding detection technique for single-phase inverter-based distributed generation system

Islanding detection is mandatory for grid connected inverter-based distributed generation systems. At present, there are passive, active, hybrid and communication based islanding detection techniques. The effectiveness of these methods depends on the Non-Detection Zone (NDZ), cost, complexity and degradation in inverter output power quality. This paper analyses various possibilities of active/reactive power mismatch during grid disconnection and its impact on voltage amplitude and frequency at the Point of Common Coupling (PCC). An inverter-based Distributed Generation (DG) system operating in constant power mode, interconnected with local RLC load and the grid is considered for analysis. An active islanding detection technique based on the combination of Reactive Power Variation (RPV) and Positive Feedback Frequency Shift (PFFS) is proposed in this paper. This technique eliminates NDZ and accelerates the speed of islanding detection without degrading the inverter power quality. A detailed simulation study of the proposed islanding detection technique with several case studies of active/reactive power mismatch is carried out using MATLAB/Simulink. The proposed islanding detection technique is verified on Hardware in Loop (HIL) system implemented using Real Time Windows Target (RTWT) of MATLAB/Simulink, NI PCIe-6251 Data Acquisition Card (DAC) and TMS320F28335 controller.