Abstract
The use of a Graph Trace Analysis (GTA)-based power flow for analyzing the voltage stability of integrated Transmission and Distribution (T&D) networks is discussed in the context of distributed Photovoltaic (PV) generation. The voltage stability of lines and the load carrying capability of buses is analyzed at various PV penetration levels. It is shown that as the PV generation levels increase, an increase in the steady state voltage stability of the system is observed. Moreover, within certain regions of stability margin changes, changes in voltage stability margins of transmission lines are shown to be linearly related to changes in the loading of the lines. Two case studies are presented, where one case study involves a model with eight voltage levels and 784,000 nodes. In one case study, a voltage-stability heat map is used to demonstrate the identification of weak lines and buses.
Highlights
Power transmission, and distribution networks have been modeled and solved separately
In the past, such modeling was justified using assumptions that the transmission system operates balanced, all generation lies in the transmission network, and the power flow is unidirectional from transmission to distribution
Recent studies have demonstrated phase imbalance in transmission systems for infrastructures with increased penetration of Distributed Energy Resources (DERs), and bi-directional power flows between transmission and distribution [1]
Summary
Power transmission, and distribution networks have been modeled and solved separately. Legacy transmission system power flows and tools model distribution systems as a single-phase bulk load on a transmission bus. Recent studies have demonstrated phase imbalance in transmission systems for infrastructures with increased penetration of DERs, and bi-directional power flows between transmission and distribution [1]. There is a need to model integrated Transmission and Distribution (T&D) networks and study voltage stability of the combined system. It is necessary to develop power flow analysis techniques to solve such integrated systems [7,8,9,10,11,12,13,14,15,16,17,18,19]. (DEW) [29] powered by the GTA power flow solver
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