Research on the Self-excitation Characteristics and Practical Criterion in Isolated Hydropower Group

Group hydropower plants may form an isolated grid with the outgoing of their transmission line. In this special situation, the characteristics of high-frequency and over-voltage of the isolated hydropower group have great influence on the self-excitation boundary conditions and transient control of the hydropower generators. This paper studies the self-excitation characteristics of generators in isolated hydropower group. The emphasis is placed on the great influence on self-excitation boundary conditions and transient process by the characteristics of high-frequency and over-voltage of the isolated hydropower group. To avoid self-excitation, two practical criterions are derived respectively in the form of impedance and capacity. Furthermore, simulation of the self-excitation transient process is carried out in an isolated hydropower group in Sichuan Power Grid. The results validate the conclusions of the research.