Research on Coordinated Optimization of Cascaded Hydro–Photovoltaic Complement Power Stations for Ultra–Low Frequency Oscillation Suppression

Based on the phenomenon of ultra–low frequency oscillation after asynchronous interconnection of Yunnan power grid, this paper proposes a method to suppress ultra–low frequency oscillation by renewable energy base with hydropower units and grid connected photovoltaic. Firstly, the linear model of the system including grid connected photovoltaic power station and hydropower unit is established, and the ultra–low frequency oscillation mode of the system is analyzed according to the eigenvalue analysis method. Then, an supplementary damping controller (SDC) is added to the grid connected photovoltaic active power control channel side, and a power system stabilizer is added to the turbine governor side of the hydropower unit (GPSS). The particle swarm optimization algorithm is used to coordinate and optimize the parameters of GPSS and SDC. Finally, the simulation results in the four-machines and two-areas system show that the proposed method can significantly suppress the ultra–low frequency oscillation of the system and reduce the output fluctuation of hydropower units.