Detection of islanding and power quality disturbance in micro grid connected distributed generation

Micro grid (MG) is becoming a very good substitution for traditional grid. It is capable of supply DC or AC power with the help of hybrid distributed generator. These are capable maintain good power quality (PQ) and reliable supply with full control over voltage and current. MG could optimize capital resource by reducing maintenances and operating cost. This reduces loss and generation cost and increases efficiency of the power system. MG works in standalone mode and interconnected mode. In standalone mode it operated without any grid connection but in interconnected mode it is coupled with main grid. In case interconnected mode when it operate alone due to grid failure, it is called islanding. It results number of power quality issues and human safety concern. Large variation in frequency, voltage, current and harmonic distortion some time become very harmful for utility and inverter. Non detection zone (NDZ) is a very dangerous condition during islanding. So it is necessary to detect islanding as fast as possible and disconnect the DG from the system. Many different methods have been proposed to detect island previously. In this paper discrete wavelet transform technique (DWT) is used for detection of island and various power quality problem.