Mechanism of active-power PSS low-frequency oscillation suppression and characteristic of anti-regulation

This paper introduces the principle of MEC5220-type exciter regulator, elaborates the reasons of producing low-frequency oscillation in system, and describes the damping characteristics of excitation regulator. By studying the active-type power system stabilizer (PSS), it finds that although PSS can inhibit the oscillations, the merit-based PSS is used on the premise that mechanical power changes much slower than the electrical power changes. When the adjustment is made in generating the original motivation, signal power of PSS received is much larger than that of its required, resulting in excitation voltage and reactive power substantially change, that is anti-regulation. Anti-regulation characteristics of active-power PSS is demonstrated with an example and countermeasures to prevent the harm are proposed.