Contribution to System Frequency Stability and Resilience from PV Plants: A Closed-loop System Identification Approach

The rapid uptake of renewable energy resources and displacement of synchronous generators may pose threats to system frequency stability and resilience. Starting from the August 2018 separation event in Australia, this work models and discusses how utility-scale PV plants could contribute to frequency stability and resilience of islanded areas following separation events. In this regard, a converter-based dynamic equivalent of aggregated PV power plants is proposed which takes into account possible practical issues such as measurement and coordination delays. The unknown parameters of the proposed model are identified through a novel closed-loop identification process based on least-square minimization. Also, a simplified model is constructed to reproduce the system frequency during the event under study, thereby capturing continuous impact of PV response on the frequency. The proposed aggregated model can considerably reduce the complexity of frequency stability analysis as well as its processing time while capturing with good fidelity the frequency response from PV farms.