Assessment of wind power penetration level in distribution network with consideration of static, motor and composite loads

The complexity of power systems has increased in recent years due to the operation of existing wind generator closer to their limits, and also due to the diversity of load model. This changing nature of a power system has considerable effect on its dynamic behaviours resulting in dynamic interactions between different power system devices. This paper presents an assessment of wind power penetration in a distribution network, with consideration of a static load, exponential recovery load, motor load and a composite load. Motor loads are assessed with respect to their mechanical loads. The wind farm is represented by a variable-speed inductions generator based on doubly-fed induction generators. A differential algebraic representation is developed; and the study is based on the determination of bifurcation points and validated by time domain simulations. The bifurcation points indicated the load-generator dynamic interaction and the network permissible wind power penetration. A comparison is made in terms of permissible wind penetration. Various simulation results show that addition of exponential recovery load model improves the wind generation margin. However, the induction motor load and composite load model reduce the voltage stability of the wind integrated system. It has been established that the mechanical load of the induction motor which has a strong linear dependence on speed is the most critical load for the wind system.