Voltage stability assessment of distribution systems with fixed speed wind generating systems

This paper proposes a simple voltage stability index (VSI) to assess static voltage stability of a radial distribution system integrated with fixed speed wind generators. The proposed VSI guarantees existence of positive real solutions of bus voltage magnitude. All generators parameters are carefully incorporated into its equivalent circuit by retaining two internal buses in addition to terminal bus of the generator. For a given wind speed, the turbine power is represented by a negative load at one of the internal buses of the generator. The above representation of a wind generating system preserves the property of radial network configuration with a single feeding node and that allows evaluating the load flow solutions of the system using a set of recursive equations. The proposed method of assessing voltage stability is then tested on a 12.66-kV, 32-bus radial distribution system with wind generators and the results found are systematically described.