Design and Field Application of Flexible Excitation System Damping Controllers

Nowadays a strong ability of stability control is required in the increasingly complex power system. The flexible excitation system of the synchronous generator is a novel structure with full-controlled devices, which has two damping channels to provide more stable and flexible control potential compared with the conventional excitation system with silicon-controlled rectifier. It is necessary to coordinate the two damping channel controllers, i.e., power system stabilizer (PSS) and reactive power damping controller (RPDC), to effectively improve the power system stability. A novel coordinated optimization method of PSS and RPDC is proposed in this article: the phase compensation method based on the derived electromagnetic torque is employed to design the time constants of PSS and RPDC; and an optimization method considering the interactions of the oscillation modes is proposed to design the proportional gains of PSS and RPDC. The simulations and the field tests with a 55-MW hydropower generator are carried out to compare the flexible excitation system with the conventional excitation system. The comparisons of the damping ratio, steady time and peak-to-peak value of the active power demonstrate that the flexible excitation system based on the proposed method can provide more ability of stability control with satisfactory dynamic performance.