Impedance estimation of FEA's grid in fiji islands by V-I measurement by using the synchronous reference frame-PLL

In recent years there has been a significant increase in distributed renewable energy generation feeding into the grid, with resulting detriment of the stability of the network, since present networks have not been designed for this purpose. To feed-in these renewable energy sources with minimum impact, it is essential to know a few grid parameters (voltage, current, grid impedance) at the point in which power supply is convenient. For this purpose in this paper an algorithm is proposed to obtain the estimated network impedance. This algorithm operates in time domain by a synchronous reference coordinate transformation, it requires only the measurement of the phase voltage with no-load and the voltage and current with a recognized load. This method has been applied to determine the grid impedance of the Fiji Electricity Authority (FEA) grid in Fiji (Viti Levu).