Parallel Studies Of The Power System Stabilizer

Starting with actual situation of PSS used in domestic and abroad, the paper discusses the producing mechanism of low-frequency oscillations and the working principium of PSS on power system, and furthermore, points out that PSS is an important method to damp low-frequency oscillations. Advantage and shortcomings of existing PSS models are introduced . The problem which existing PSS meets in wide frequency range and improvement measure under the fast-speed development of power system and the appearance of super-scale power system are mainly analyzed. Oscillations in very low-frequency have been produced on power system along with the enhancement of power system network. Washout time constants of PSS need to be high enough to assure PSS producing enough phase displacement at low frequency band (approximately between 0. 1 and 0. 2 Hz) . But too high washout time constant maybe result in much difference of amplitude frequency characteristics at low frequenciy band and high one (between 0. 2 and 2 Hz). Assuring damp effect at high frequencies band by increasing the gain of PSS may result in too high amplitude frequency characteristics at low frequencies band. Furthermore, such status can produce reactive fluctuate of dynamotor. However, if washout time constant is too low, amplitude frequency characteristics at low frequencies band aren' t enough to offer adequate compensatory angle of phase. So maximal positive damp cann' t be offered.Aiming at the insistent demand of improving amplitude frequency characteristics and phase frequency characteristics , paper put forward a new parallel PSS model by the concept of parallel PSS. Finished its design. Compared it with existing PSS models on platform of power system digital simulation (PSASP), and concluded that the new parallel PSS model can offer better amplitude frequency characteristics and phase frequency ones than existing PSS models.