Dynamic Transmission and Distribution Analysis for Asymmetrical Networks in the Presence of Distribution-Connected DER Units

This paper investigates the dynamic impacts of distributed energy resources (DERs) by utilization of symmetrical and asymmetrical analyses on the power system. In the proposed transmission and distribution (T&D) co-simulation framework, the transmission network is modeled using sequence networks, while the distribution network is modeled in a full three-phase manner. Also, the North American Electric Reliability Corporation DER model (NERC-2018) is utilized to model the dynamics of the DER-A control scheme. DER-A mechanism is modeled downstream of the distribution substation. Here, the transmission system is modeled using the IEEE 118-bus test system.In this paper, the impacts of the DER-A control parameters on the DER operation and the dynamics of the transmission system are examined in the balanced and unbalanced power systems. It is shown that the DER-A control mechanism injects more reactive power during a fault in an asymmetrical system than in a symmetrical one initiating voltage overshoot.