Approach to dynamic voltage stability analysis for DFIG wind parks integration

In this study, an improved voltage stability index that can evaluate the unstable behaviour of the power system with doubly-fed induction generator (DFIG) wind parks integration is presented. Accordingly, voltage stability constrained optimal power flow (VSC-OPF) is studied including an improved impedance-based (IB) index. In particular, this study has two main contributions. First, it proposes an IB index with consideration of DFIG capability curve limits and on-load tap changer (OLTC) behaviour. The proposed voltage stability index can detect precisely the voltage collapse, especially after the occurrence of a given contingency due to the dynamic elements of the system. In this study, a model is proposed for DFIG capability curve limits that can be integrated to the internal circuit of the generator. In particular, the proposed model can be appended to impedance matching theory. Furthermore, the OLTC model is added to this index. The index uses the concept of the coupled single-port circuit. The second contribution proposes a VSCOPF with an improved IB index that is also compared with three existing VSC-OPF methods in stressed and single line outage conditions. These approaches are tested and validated on modified WSCC test system, IEEE 39-bus, IEEE 57-bus and Polish 2746-bus systems.