Stability monitoring device and method

A stability monitoring device of a power system, comprising:

• a simple stability calculation unit that calculates an angular velocity and an internal phase angle of a generator in each fault case based on fault conditions and a system configuration of the power system;
• a severity indicator calculation unit that calculates a severity indicator representing a degree of system instability based on the angular velocity and the internal phase angle of the generator;
• a PCS power supply severe parallel-off condition extracting unit that calculates a parallel-off severity indicator of a PCS power supply based on a parallel-off sensitivity indicator representing a degree of influence of parallel-off of the PCS power supply on a degree of instability of a generator and the severity indicator, and that extracts fault cases corresponding to the parallel-off severity indicator exceeding a prescribed threshold;
• and
• a detailed stability calculation unit that performs a detailed stability calculation for each extracted fault case based on the severity indicator or the parallel-off severity indicator.