An improved power system stabilizer for higher critical gain

Recently, power system stabilizer (PSS) is widely used in the power system in China. However, PSS may have some shortcomings. That is, the gain of PSS may not satisfy both the damping ratio and the principle that it must be lower than 1/3 gain margin as the Guide for setting test of power system stabilizer required. After careful analysis, it was found that the gain margin is limited by exciter mode when using the self-excited excitation system. Exciter mode was formed by the natural characteristic of exciter-PSS loop. Therefore, a novel PSS with a parallel sector by introducing a soft feedback on the outer loop of exciter system was proposed. By improving the phase characteristics of the loop, the gain margin of PSS was increased effectively and the problem above was solved. Finally, case studies were undertaken based on the Ximeng thermal power centralized delivery simulation system. Simulation results validate the effectiveness of the proposed PSS. © 2015 Chin. Soc. for Elec. Eng.