Investigation of the dynamic oscillations of the Ludington pumped storage plant

Dynamic oscillations at a large pumped storage plant equipped with excitation systems of nominal voltage response ratio and connected to a tightly coupled transmission grid are investigated. The results of eigenvalue and transient stability investigations correlate well with the characteristics of the disturbance as interpreted from field measurements. However, the actual dynamic stability margin is somewhat higher than that determined analytically. The excitation control system is shown to be the practicable means for improving damping of the natural mechanical oscillations. Damping can be increased to desired margins during the critical maximum pumping condition by placing the automatic voltage regulators for some of the units at the multi-unit plant on manual control.