Enhanced oscillation damping in power systems by extending the VSI control

In this paper, a control scheme is proposed aiming to further support the task of the synchronous generator’s power system stabilizer (PSS) to damp frequency oscillations. The proposed control law is applied as an additional loop to the classical control scheme of the grid-side power converter modelled in thedqsynchronously rotating frame. The main concept is based on suitably varying the dc-link capacitor voltage in order to quickly compensate the oscillating power of the grid. The control method is analysed by deploying a power balance technique which considers both the PSS and the proposed controller main tasks. Inserting the proposed controller into the whole control scheme, the system performance is evaluated through extended simulations on a system consisting of a conventional synchronous generator and a converter powered by a wind turbine, connected to inject power into a local load and the main grid through a transmission line. The examined cases include sudden disturbances occurring in different parts of the system, indicating the enhancement of the oscillations damping and the validity of the method.