LAUSR

Summary Low-frequency oscillation occurs easily in a hydropower system with weak connected grid. Some oscillation behaviors cannot be explained by linear analysis method. According to unexplained oscillation frequency of hydropower stations, second-order oscillation mode of complex hydropower stations with weak grid is studied based on linear elastic model and modal series analysis method in this paper. Firstly, detailed hydropower station models with hydro-mechanical-electrical coupling are introduced. Especially, a new linear elastic model is used to model hydraulic conduit system. Secondly, hydro-mechanical-electrical coupling characteristics of hydropower stations are studied based on the whole model. Finally, the second-order oscillation mode and associated index of hydropower stations are calculated and studied by modal series method. Through numerical simulation of a single unit finite bus system, some useful results are achieved. Copyright © 2016 John Wiley & Sons, Ltd.