Issues of inertia response and rate of change of frequency in power systems with different penetration of variable speed wind turbines

Variable speed wind turbines (VSWTs) have been widely used in recent years. Due to the usage of power electronics the electrical coupling between VSWTs and electrical grids (EGs) will be missing, thus increasing penetration of such units in power systems (PSs) will result in reducing of the overall inertia and increasing of rate of change of frequency (RoCoF) and consequently will lead to frequency deviation upon power balance change. In the paper issues of inertia response and RoCoF with increased penetration of VSWTs within PSs are considered. RoCoF is determined with different penetration of power generation by VSWTs, without and with their constant inertia, with the same/different numbers and different power of synchronous generators (SGs) and with varying percentage of power balance change. The obtained results allow to analyze the maximum power of VSWTs that will not affect frequency of PS and evaluate their possible contribution to inertia of PS and decreasing of RoCoF.