Stability and multi-frequency dynamic characteristics of nonlinear grid-connected pumped storage-wind power interconnection system

This paper researches the stability and multi-frequency dynamic characteristics of nonlinear grid-connected pumped storage-wind power interconnection system (PS-WPIS). Firstly, a nonlinear model of grid-connected PS-WPIS is established. Then, the system stability and multi-frequency characteristics are revealed through stable domain and dynamic response analysis. Furthermore, the coupling mechanism of grid-connected PS-WPIS is explained, and the effect of capacity ratio on system stability is studied. Finally, the effect of hydraulic, mechanical and electrical parameters on grid-connected PS-WPIS is revealed. The results show that the stable domain of grid-connected PS-WPIS consists of two horizontal bifurcation lines and one curving bifurcation line. The former is related to wind power subsystem, and the latter is related to pumped storage subsystem. The grid-connected PS-WPIS contains the phenomenon of multi-frequency oscillations. The multi-frequency oscillations are generated by the coupling effect of pumped storage subsystem and wind power subsystem. The capacity increase of pumped storage or wind power worsens the stability and dynamic response of grid-connected PS-WPIS. The regulation performance of grid-connected PS-WPIS can be significantly improved by selecting smaller values of flow inertia time constant of penstock and time constant of wind turbine shafting.