Dynamic interactions in large scale photovoltaic power plants with frequency and voltage support

The increasing penetration of Large-Scale Photovoltaic Power Plants in the power system is raising the concern of potential stability issues due to dynamic interactions of power electronics components. In particular, Power Plant Controllers are starting to provide a fast dynamic response for specific services, such as fast frequency response, which could trigger unexpected unstable interactions with the PV inverters or other grid components. Also, an eventual reduction of synchronous generation in the grid could lead to a power system with high penetration of power electronics, which presents unexplored stability problems. This paper presents an interaction and stability study of a Photovoltaic Power Plant connected to the grid. This study is based on a small-signal analysis employing eigenvalues and participation factors to identify potential unstable modes. A linear model of the Photovoltaic Power Plant is implemented to apply a small-signal analysis. This linear model is validated with the equivalent non-linear model based on time-domain simulations in Matlab Simulink.