Time Response of the Frequency of Hydroelectric Generator Unit with Surge Tank Under Isolated Operation Based on Turbine Regulating Modes

Aiming at studying the regulation quality of isolated turbine regulating systems under load disturbance and different regulation modes, the complete mathematical model of a turbine regulating system under three regulation modes is established. Then, based on dominant poles and null points, the method of order reduction for a high-order system of time response of the frequency is proposed. By this method, the complete high-order systems are solved and the regulation quality for time response of the frequency is studied. The results indicate that (1) the tail wave, which is the main body of time response of the frequency and the principal factor that determines the regulation quality, is mainly determined by the dominant poles; (2) for the three regulation modes, by deleting the high-order terms, the three equivalent overall transfer functions are fourth order, third order, and third order, respectively, and can be solved; (3) the analytical fluctuation equations of time response of the frequency solved from low-order equivalent overall transfer functions accurately simulate the fluctuation characteristics of time response; and (4) based on damped vibrations decomposed from analytical fluctuation equations, the regulation qualities of three regulation modes are analyzed.