A New Active Islanding Detection Method for Microgrids by using Negative Sequence Current Injection

The most important security requirements for the microgrid connected to the network are islanding detection and protection for anti-islanding. In this paper, a new method is presented for islanding detection in a standard microgrid that equipped with wind turbine with double feed induction generator (DFIG), combined heat and power (CHP) and photovoltaic cells (PV) systems. In This method, all control systems of DFIG, CHP and PV cells are modeled. The PV control system is worked for maximum power point tracking (MPPT) of PV system. In this paper, a new method for islanding detection method based on disturbance current injection into the system through the quadrate axis (q-axis) of the DFIG grid side converter is presented. Frequency variation of the wind turbine stator voltage is selected as an index for islanding detection. In this method, wind turbine stator voltage that is index of islanding detection, is fed to a logic circuit and then the frequency of system is evaluated and if frequency violate from threshold (59.9-60.1) Hz, this condition is detected as islanding condition. The proposed method is able to detect islanding condition from transient condition. This capability leads to significant reduction of non detection zone (NDZ) areas. Simulation results using PSCAD/EMTDC software show the effectiveness of the proposed method in islanding detection in a standard microgrid.