Optimal Design Method of Flexible Excitation System for Improving Power System Stability

Providing sufficient damping over the full frequency range of low-frequency oscillation (LFO) is a challenge in modern power systems. The flexible excitation system with two damping channels, controlled by the power system stabilizer (PSS) and the reactive power damping controller (RPDC), respectively, provides a new way to solve this problem. The controller structures of the flexible excitation system are studied, in which a novel structure is adopted in RPDC to enhance the damping over the lower frequency range of LFO. The controller parameters design method of the flexible excitation system is also proposed: the phase compensation method is employed to design the time constants of PSS and RPDC; and the gains of them are adjusted based on their critical values. A single machine-infinite bus system in a real-time digital system and a system considering the doubly-fed wind generator are simulated to verify the effectiveness of the flexible excitation system on improving the power system stability.