A Novel Three-Phase Transmission and Unbalance Distribution Co-Simulation Power Flow Model For Long Term Voltage Stability Margin Assessment

The recent increasing deployment of distributed energy resources (DERs) is affecting many aspects of current power system operations including the coupling between distribution and transmission networks especially due to the dynamic and intermittent nature of DERs. An integrated grid modeling approach combining transmission and distribution (T&D) can help capture these unprecedented interactions between distribution and transmission systems. This paper proposes for the first time, a three-phase integrated T&D co-simulation power flow model and investigates various other co-simulation approaches for analyzing voltage stability of the power grid considering unbalances, and various load types. Results show that the proposed co-simulation approach can provide a weak phase voltage stability margin and thus provide the overall system stability considering each phase in the integrated T&D network.