Simulation research on the additional damping injection method of hydro turbine generating unit under multi-machine conditions

The relationship between the equivalent damping factor in motion equation and the electromagnetic torque of generator has been found in this paper by analyzing the motion equation of the generator. The transformation factor from excitation electromotive force to electromagnetic torque is defined. The indirect relation between the excitation electromotive force and the equivalent damping factor is established. Based on this, the supplementary excitation control signal is proposed by means of utilizing the deviation of the angular speed as an auxiliary signal, in which the dynamic damping is directly injected into the motion equation of the generator. Finally, the operation and simulation system of the hydro turbine generating sets is established and used for simulating two operation conditions, namely line fault and low frequency oscillation. Simulation results show that the proposed method can realize the purpose of injecting damping. The study reveals that there exist a relationship between the gain coefficient in additional input branch and the additional damping coefficient.