An analysis is made of the frequency characteristics of isolated grid operation of a regional power grid with high permeability of hydropower, and points out the problems of long operation time and low correct operation rate of substation standby automatic switching caused by hydropower residual voltage. It puts forward a scheme of a fast synchronous grid connection function of the regional power grid with high permeability hydropower, and points out the necessity of having increasing frequency change rate as the criterion of fast synchronous grid connection and the criterion of high-frequency protection of hydropower units. A calculation method of fast frequency and frequency change rate based on extended Kalman filter is proposed, and the algorithm flow of fast tracking fundamental frequency of power grid is given. From the knowledge that the initial frequency of a small hydropower isolated network cannot change suddenly, an improved standby automatic switching and high-frequency protection logic of hydropower units are proposed. PSCAD simulation is used to verify the analysis of the frequency characteristics of isolated network operation of a regional power grid with high permeability hydropower, and the proposed algorithm is implemented and verified in the self-developed standby automatic switching device. The effectiveness of the proposed automatic switching scheme is verified by practical engineering. The scheme proposed in this paper can significantly reduce the standby automatic switching time of a regional power grid with high permeability of hydropower and improve the power supply reliability of the power grid.

This work is supported by the National Natural Science Foundation of China (No. 51477057).