Suppression strategy of coupled oscillation and power anti-regulation of variable speed pumped storage unit with full size converter

The ultra-low frequency oscillation and poor speed regulation performance caused by the fast power control decrease the stability and efficiency of the variable speed pumped storage unit with a full size converter (FSC-VSPSU). This paper presents a fast frequency control strategy to solve this problem. The small-signal model of the FSC-VSPSU in fast frequency mode is established, and the key parameters for the system stability are studied by the eigenvalue method. Aiming at the coupling oscillation mode caused by the governor and generator side converter (GSC), the corresponding control parameters optimisation method is proposed. In order to solve the power anti-regulation problem, the strategy of combining rotor kinetic energy release, power slope adjustment, and delay acceleration control is proposed. PSCAD and RTDS simulation results show that the proposed strategy can effectively avoid the ultra-low frequency oscillation caused by the fast power control and significantly improves the frequency and power control performance.