Out-of-step detection using Zubov´s approximation stability boundaries

This paper presents a new out-of-step detection method for multi-machine power systems based on approximate stability boundaries. The boundaries are constructed based on Zubov´s method of stability analysis. The proposed out-of-step detection method first constructs a series of boundaries in power angle - frequency (δ-ω) plane, and tracks the trajectory of each generator in the δ-ω plane after the disturbance to differentiate out-of-step from stable power swings. The electrical parameters needed to construct approximate stability boundaries are obtained directly from Phasor Measurement Units (PMUs) located at the generator´s terminal. The effectiveness of the proposed method is tested in a Single Machine Infinite Bus (SMIB) and the IEEE 3-machine 9-bus system. Simulation results show that the proposed algorithm is capable of detecting out-of-step conditions in multi-machine power systems without using network reduction techniques.