An Adaptive Under Frequency Load Shedding Scheme for a Small Island Power System

An adaptive under-frequency load shedding scheme for an island power system is presented. This scheme monitors the frequency at the each generation bus in the system and employs a modified swing equation to estimate the power imbalance in the system following a disturbance and shed load accordingly at the feeder level. A reduced order system frequency response model was also developed and used to study the transient performance of the proposed scheme. The results presented illustrate this adaptive scheme is predictable and effective at curtailing the frequency deviation following the loss of the largest infeed on the Trinidad & Tobago power system. In all the cases studied, the power imbalance was found to be within 2% of the actual and the frequency recovered to within 99.5% of nominal in less than 8 seconds.