Performance of IBR Power Oscillations Damper according to power system operating conditions

This paper analyses the performance of a Power Oscillations Damping (POD) controller through small-signal stability analysis. The POD is installed in a photovoltaic (PV) power plant controlled in conventional grid-following (GFL) mode. During frequency transients, the POD modifies the reactive power reference of the GFL control, in order to damp electromechanical power system oscillations. The transmission power grid IEEE 9-bus benchmark has been analysed in DIgSILENT PowerFactory software. The PV plant capacity, its location in the network, and the power system operating conditions are considered. Particularly, the analysis of a few specific consumption and generation conditions shows that the electromechanical oscillatory modes of the system are more critical in case of peak load, as it happens for 100 % synchronous generation. The main results are twofold: (i) the significant contribution of the POD to damping electromechanical modes in the scenario of winter evening peak consumption, when the PV plant does not inject active power to the grid, which coincides with the most poorly damped electromechanical modes; and (ii) the lack of negative interaction between PSS and POD controllers.