Grid Monitoring for Distributed Power Generation Systems to Comply with Grid Codes

This paper investigates the possibility of using the phase-locked loop (PLL) algorithms for grid monitoring. The main interest is on the ability of the PLL to determine accurately other grid variables except the phase angle. The main focus is set on the voltage amplitude and frequency estimation but other attributes of the PLL systems such as the possibility to detect unbalance and to extract the positive and negative sequence from the grid voltages are also discussed. A detailed description of standards for wind turbine (WT) and photovoltaic (PV) systems regarding grid monitoring is given and the simulation results of the proposed PLL are compared with the values stated in these standards. Based on this comparison, it can be concluded that PLL system can be used with success for grid monitoring