A Characteristic Loci Method for Power Systems Small-signal Stability Analysis

A Nyquist characteristic loci based method is proposed to analyze small-signal stability. It is shown that the minimum characteristic loci of the loop frequency response matrix can be viewed a measure of stability margin. An approximate closed-form expression of the minimum characteristic loci is derived. Using this expression, the contributions of prime-mover and governor loop, PSS loop to stability margin are conveniently quantified. Several numerical examples are provided to demonstrate the versatile utility of the introduced results.