A novel unified approach for analysis of small-signal stability of power systems

Small-signal stability analysis is generally carried out in the frequency domain and by the eigenvalue analysis method. This paper proposes a novel approach to analyze small-signal stability in the time domain, including low frequency oscillation (LFO) and subsynchronous oscillation (SSO). The characteristic of the small-signal eigenvalue analysis method is reviewed and compared with the complex torque coefficient method. It is pointed out that the complex torque coefficient method has unique strong points when used to analyze the SSO problems, caused by HVDC or FACTS, if the method is realized by time domain simulation. The concept of mechanical admittance is introduced to analyze the LFO problem, and its realization by time domain simulation is established in the paper