Dynamic Interaction of Distribution-Connected DER_A with Transmission System Via Co-Simulation Analysis

A coupled load flow algorithm is developed to perform transmission and distribution (T&D) co-simulation. Subsequently, the effects of distributed energy resources (DERs) on the dynamics of power systems are studied by extending the T&D load flow algorithm to T&D dynamic co-simulation. The detailed distribution and transmission systems are modeled separately and are coupled at the substation nodes at each time step. Dynamics of the DER_A mechanisms are modeled separately downstream of the distribution substation using the North American Electric Reliability Corporation model (NERC-2018). The effects of the DER_A settings are examined on the dynamics of the transmission system and DER operation. In addition, lumped and distributed induction motor load models are compared at the distribution level. The results of the study show that under high DER penetration excessive operation may occur at the distribution load tap changers. Also, the effect of reactive power on voltage recovery is significant under DER high fault-ride-through capability and DER reactive current injections. Moreover, it is observed that DER frequency control may adversely affect the DER operation keeping the active and reactive currents at high levels due to frequency deviations. Finally, distributed induction motor loads stimulate more DER reactive power injection causing voltage overshoots