Oscillation damping: A comparison of wind and photovoltaic power plant capabilities

This paper investigates the potential for wind power plants (WPPs) and photovoltaic power plants (PVPs) to damp inter-area oscillations. Inter-area oscillations may be the result of a single or a group of generators oscillating against another group of generators across a weak transmission link. If poorly damped, these power system oscillations can cause system instability and potentially lead to blackouts. Power conversion devices, particularly megawatt-scale converters that connect wind turbines and photovoltaic power plants to the grid, could be used to damp these oscillations by injecting power into the system out of phase with the potentially unstable mode. Over time, the net energy injection is near zero; therefore, providing this “static damping” capability is not expected to affect annual energy production. However, WPPs and PVPs have different capabilities due to the inherent physical nature of these plants. WPPs have some energy stored in the rotating masses of the turbines, while PVPs have no such stored energy. Thus the challenge of providing oscillation damping services will have to be approached differently for WPPs and PVPPs. In this work strategies for providing oscillation damping services from WPPs and PVPs are compared and contrasted. Kundur´s well-known two-area, four-generator system is modeled in PSCAD/EMTDC. The WPP and PVP models are based on the Western Electricity Coordination Council (WECC) standard models. Controllers to damp inter-area oscillations are developed and added to the WECC WPP and PVP models, and their effects are studied. Analysis is performed on the data generated by the simulations.