Validity range of stability assessments based on quasi-static phasor calculus in power systems with high levels of converter interfaced generation

Abstract

Power system stability is widely assessed by tools that model the network and the connected machine stators through algebraic equations and synchronous generators through differential equations, meaning that quasi-static phasor calculus (QPC) is used. In QPC, fast transients are neglected. However, the nature of the dynamic response of power systems is changing due to the increase in converter-interfaced generation (CIG). Therefore, the reliance on QPC must be questioned. In this thesis, the validity range of stability assessments based on QPC models is identified, verified, and investigated. Dynamic phasor calculus (DPC) is considered as an alternative. A systematic methodology is proposed to compare QPC and DPC. It includes frequency response, modal, and sensitivity analyses. Furthermore, common CIG models based on QPC are compared with DPC to investigate and identify the appropriate level of detail required for stability studies. In these comparisons, modal analysis is performed. The studies are performed in an IEEE test network considering up to 100% CIG levels. The results show that the QPC is suitable for stability assessments when low bandwidths of the converter controls are given. On the contrary, DPC is suitable and applicable to generic power system stability studies of networks with high penetration of CIG.