A New Passive Parameter for Islanding Detection based on Discrete Fourier Transform of Rate of Change of Active Power over Reactive Power

This paper presents a new passive parameter for islanding detection of distributed generation (DG), based on processing the rate of change of active power over reactive power (dP/dQ) parameter with discrete Fourier transform (DFT). During the islanding and non-islanding events, the active and reactive powers at DG output changes. However, in grid-connected mode the voltage and frequency of power system are determined by main grid, therefore, there is no considerable change in the active and reactive powers at DG output. While, in islanding mode the voltage and frequency of the islanded power system are determined by DG units, therefore, if there is significant value of the power mismatch between generation and load demand, the output powers of DG have great changes. However, if there is no difference between the DG generation and total load demand, the power deviations at DG output cannot detect the islanding and other events accurately. Hence, the ratio of rate of change of active power to rate of change of reactive power and for its analysis the DFT is used. The performance of the proposed parameter has been tested on the real power system using MATLAB/Simulink. The understudy DG is synchronous type and installed in the west regional electric company (WREC) network. Simulation results show that, the proposed parameter can precisely differentiate between islanding and transient events and it reduces the non-detection zone (NDZ) up to 0.02 MW and 0.02 MVAr power mismatch. The NDZ of the proposed parameter is very smaller than anti-islanding protection relays of the understudy DG.