  Ultra low frequency oscillation (ULFO) is significantly threatening the power
system stability. Its unstable mechanism is mostly studied via generalized
damping torque analysis method (GDTA). However, the analysis still adopts the
framework established for low frequency oscillation. Hence, this letter
proposes a GDTA approach in the jerk space for ULFO. A multi-information
variable is constructed to transform the system into a new state space, where
it is found that the jerk dynamics of the turbine-generator cascaded system is
a second-order differential equation. Benefiting from this characteristic, we
propose a new form for GDTA using jerk dynamics, which is established in the
frequency-frequency acceleration phase space. Then, analytical expressions of
all damping torque are provided. Finally, test results verified the proposed
theoretical results. The negative damping mechanism is revealed, and parameter
adjustment measures are concluded.
