Attenuation of power system oscillations by using virtual damper windings

We propose a modification of the virtual synchronous machine (VSM) control algorithm in order to better dampen oscillations in a power system comprising VSMs. The change is to add a virtual damper winding (VDW) to the control algorithm. The effect of the damper winding on the rotor of a real synchronous generator is similar to the presence of an asynchronous machine on the same axis. Its full theoretical analysis is complicated and requires several additional state variables. Instead, we derive the damper winding torque Tw from the existing state variables of the fourth-order VSM model and its terminal voltages. We assume that the damping torque is proportional to the power angle derivative. The decrease of the oscillations is verified by simulations.