Dynamical Behavior Comparison Between Variable Speed and Synchronous Machines With PSS

The dynamic performances of variable speed and fixed speed units are compared in the case of 2 × 320 MW pumped storage power plant. The case study of the pumped storage power plant with standard synchronous machine with PSS is presented and, then, the corresponding variable speed system is designed for this case. Unsteady numerical simulations of both architectures enable to demonstrate that the variable speed architecture improves the power system stability characteristics for both the local and the inter-area modes of oscillation. Moreover, the damping of active power oscillations originated by the part load operation of the pump-turbine in generating mode is investigated as well.