Multi-port network equivalent considering generator dynamics and mid-long term voltage stability monitoring

During the mid-long term voltage stability, the generator may, due to reactive power shortages, start its over-excitation limiter (OXL), leading the conventional approach that keeps the generator as PV node faces some problems. This paper improved the traditional multi-port network equivalent method by applying the generator model which can describe the action of OXL to the multi-port network, and provided an approach for online identification of OXL startup, thus the dynamic conversion of generator OXL can be considered in the improved multi-port equivalent network. Further, a voltage stability index was, based on the proposed multi-port equivalent network, derived to identify the maximum load power point. Simulation results show that the proposed method can provide a good early warning for the impending mid-long term voltage collapse.